Use Pion's Setting Engine to reduce Multicast DNS noise

https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/issues/40123

The purpose of the patch is to prevent Pion from opening the mDNS port,
thus preventing snowflake from directly leaking .local candidates.

What this doesn't prevent is the resolution of .local candidates
once they are passed on to the system DNS.

.gitignore

@@ -6,19 +6,14 @@
 datadir/
 broker/broker
 client/client
-server-webrtc/server-webrtc
 server/server
-proxy-go/proxy-go
+proxy/proxy
+probetest/probetest
 snowflake.log
-proxy/test
-proxy/build
-proxy/node_modules
-proxy/spec/support
-proxy/webext/snowflake.js
-proxy/webext/popup.js
-proxy/webext/embed.html
-proxy/webext/embed.css
-proxy/webext/assets/
-proxy/webext/_locales/
 ignore/
-npm-debug.log
+
+# from running the vagrant setup
+/.vagrant/
+/sdk-tools-linux-*.zip*
+/android-ndk-*
+/tools/

.gitlab-ci.yml

@@ -1,29 +1,205 @@
-image: golang:1.10-stretch
 
-cache:
-  paths:
-    - .gradle/wrapper
-    - .gradle/caches
+variables:
+  DEBIAN_FRONTEND: noninteractive
+  REPRODUCIBLE_FLAGS: -trimpath -ldflags=-buildid=
 
-before_script:
-  # Create symbolic links under $GOPATH, this is needed for local build
-  - export src=$GOPATH/src
-  - mkdir -p $src/git.torproject.org/pluggable-transports
-  - mkdir -p $src/gitlab.com/$CI_PROJECT_NAMESPACE
-  - ln -s $CI_PROJECT_DIR $src/git.torproject.org/pluggable-transports/snowflake.git
-  - ln -s $CI_PROJECT_DIR $src/gitlab.com/$CI_PROJECT_PATH
+# set up apt for automated use
+.apt-template: &apt-template
+- export LC_ALL=C.UTF-8
+- export DEBIAN_FRONTEND=noninteractive
+- echo Etc/UTC > /etc/timezone
+- echo 'quiet "1";'
+       'APT::Install-Recommends "0";'
+       'APT::Install-Suggests "0";'
+       'APT::Acquire::Retries "20";'
+       'APT::Get::Assume-Yes "true";'
+       'Dpkg::Use-Pty "0";'
+      > /etc/apt/apt.conf.d/99gitlab
+- apt-get update
+- apt-get dist-upgrade
 
-build:
-  script:
-    - apt-get -qy update
-    - apt-get -qy install libx11-dev
-    - cd $src/gitlab.com/$CI_PROJECT_PATH/client
-    - go get ./...
-    - go build ./...
-    - go vet ./...
-    - go test -v -race ./...
 
-after_script:
+# Set things up to use the OS-native packages for Go.  Anything that
+# is downloaded by go during the `go fmt` stage is not coming from the
+# Debian/Ubuntu repo. So those would need to be packaged for this to
+# make it into Debian and/or Ubuntu.
+.debian-native-template: &debian-native-template
+  variables:
+    GOPATH: /usr/share/gocode
+  before_script:
+    - apt-get update
+    - apt-get -qy install --no-install-recommends
+        build-essential
+        ca-certificates
+        git
+        golang
+        golang-github-cheekybits-genny-dev
+        golang-github-jtolds-gls-dev
+        golang-github-klauspost-reedsolomon-dev
+        golang-github-lucas-clemente-quic-go-dev
+        golang-github-smartystreets-assertions-dev
+        golang-github-smartystreets-goconvey-dev
+        golang-github-tjfoc-gmsm-dev
+        golang-github-xtaci-kcp-dev
+        golang-github-xtaci-smux-dev
+        golang-golang-x-crypto-dev
+        golang-golang-x-net-dev
+        golang-goptlib-dev
+        golang-golang-x-sys-dev
+        golang-golang-x-text-dev
+        golang-golang-x-xerrors-dev
+        lbzip2
+
+# use Go installed as part of the official, Debian-based Docker images
+.golang-docker-debian-template: &golang-docker-debian-template
+  before_script:
+    - apt-get update
+    - apt-get -qy install --no-install-recommends
+        ca-certificates
+        git
+        lbzip2
+
+.go-test: &go-test
+  - test -z "$(go fmt ./...)"
+  - go vet ./...
+  - go test -v -race ./...
+
+  - cd $CI_PROJECT_DIR/client/
+  - go get
+  - go build $REPRODUCIBLE_FLAGS
+
+.test-template: &test-template
+  artifacts:
+    name: "${CI_PROJECT_PATH}_${CI_JOB_STAGE}_${CI_JOB_ID}_${CI_COMMIT_REF_NAME}_${CI_COMMIT_SHA}"
+    paths:
+      - client/*.aar
+      - client/*.jar
+      - client/client
+    expire_in: 1 week
+    when: on_success
+  after_script:
+    - echo "Download debug artifacts from https://gitlab.com/${CI_PROJECT_PATH}/-/jobs"
     # this file changes every time but should not be cached
     - rm -f $GRADLE_USER_HOME/caches/modules-2/modules-2.lock
-    - rm -fr $GRADLE_USER_HOME/caches/*/plugin-resolution/
+    - rm -rf $GRADLE_USER_HOME/caches/*/plugin-resolution/
+
+# -- jobs ------------------------------------------------------------
+
+android:
+  image: debian:bullseye-backports
+  variables:
+    ANDROID_HOME: /usr/lib/android-sdk
+    GOPATH: "/go"
+    LANG: C.UTF-8
+    PATH: "/go/bin:/usr/lib/go-1.16/bin:/usr/bin:/bin"
+  cache:
+    paths:
+      - .gradle/wrapper
+      - .gradle/caches
+  <<: *test-template
+  before_script:
+    - *apt-template
+    - apt-get install
+        android-sdk-platform-23
+        android-sdk-platform-tools
+        build-essential
+        curl
+        default-jdk-headless
+        git
+        gnupg
+        unzip
+        wget
+    - apt-get install -t bullseye-backports golang-1.16
+
+    - ndk=android-ndk-r21e-linux-x86_64.zip
+    - wget --continue --no-verbose https://dl.google.com/android/repository/$ndk
+    - echo "ad7ce5467e18d40050dc51b8e7affc3e635c85bd8c59be62de32352328ed467e  $ndk" > $ndk.sha256
+    - sha256sum -c $ndk.sha256
+    - unzip -q $ndk
+    - rm ${ndk}*
+    - mv android-ndk-* $ANDROID_HOME/ndk-bundle/
+
+    - chmod -R a+rX $ANDROID_HOME
+
+  script:
+    - *go-test
+    - export GRADLE_USER_HOME=$CI_PROJECT_DIR/.gradle
+    - go version
+    - go env
+
+    - go get golang.org/x/mobile/cmd/gomobile
+    - go get golang.org/x/mobile/cmd/gobind
+    - go install golang.org/x/mobile/cmd/gobind
+    - go install golang.org/x/mobile/cmd/gomobile
+    - gomobile init
+
+    - cd $CI_PROJECT_DIR/client
+    # gomobile builds a shared library not a CLI executable
+    - sed -i 's,^package main$,package snowflakeclient,' *.go
+    - go get golang.org/x/mobile/bind
+    - gomobile bind -v -target=android $REPRODUCIBLE_FLAGS .
+
+go-1.16:
+  image: golang:1.16-stretch
+  <<: *golang-docker-debian-template
+  <<: *test-template
+  script:
+    - *go-test
+
+go-1.17:
+  image: golang:1.17-stretch
+  <<: *golang-docker-debian-template
+  <<: *test-template
+  script:
+    - *go-test
+
+go-1.18:
+  image: golang:1.18-stretch
+  <<: *golang-docker-debian-template
+  <<: *test-template
+  script:
+    - *go-test
+
+debian-testing:
+  image: debian:testing
+  <<: *debian-native-template
+  <<: *test-template
+  script:
+    - *go-test
+
+generate_tarball:
+  stage: deploy
+  image: golang:1.17-stretch
+  rules:
+    - if: $CI_COMMIT_TAG
+  script:
+    - go mod vendor
+    - tar czf ${CI_PROJECT_NAME}-${CI_COMMIT_TAG#v}.tar.gz --transform "s,^,${CI_PROJECT_NAME}-${CI_COMMIT_TAG#v}/," *
+  after_script:
+    - echo TAR_JOB_ID=$CI_JOB_ID >> generate_tarball.env
+  artifacts:
+    paths:
+      - ${CI_PROJECT_NAME}-${CI_COMMIT_TAG#v}.tar.gz
+    reports:
+      dotenv: generate_tarball.env
+
+release-job:
+  stage: deploy
+  image: registry.gitlab.com/gitlab-org/release-cli:latest
+  rules:
+    - if: $CI_COMMIT_TAG
+  needs:
+    - job: generate_tarball
+      artifacts: true
+  script:
+    - echo "running release_job"
+  release:
+    name: 'Release $CI_COMMIT_TAG'
+    description: 'Created using the release-cli'
+    tag_name: '$CI_COMMIT_TAG'
+    ref: '$CI_COMMIT_TAG'
+    assets:
+      links:
+        - name: '${CI_PROJECT_NAME}-${CI_COMMIT_TAG#v}.tar.gz'
+          url: '${CI_PROJECT_URL}/-/jobs/${TAR_JOB_ID}/artifacts/file/${CI_PROJECT_NAME}-${CI_COMMIT_TAG#v}.tar.gz'
+ 

.gitmodules

@@ -1,4 +0,0 @@
-[submodule "proxy/translation"]
-	path = proxy/translation
-	url = https://git.torproject.org/translation.git
-	branch = snowflakeaddon-messages.json_completed

.travis.yml

@@ -2,43 +2,12 @@ language: go
 
 dist: xenial
 
-go_import_path: git.torproject.org/pluggable-transports/snowflake.git
-
-addons:
-    apt:
-        sources:
-            - ubuntu-toolchain-r-test
-        packages:
-            - g++-5
-            - gcc-5
+go_import_path: git.torproject.org/pluggable-transports/snowflake.git/v2
 
 go:
-    - 1.10.x
-
-env:
-    - TRAVIS_NODE_VERSION="8" CC="gcc-5" CXX="g++-5"
-
-before_install:
-    - nvm install $TRAVIS_NODE_VERSION
-
-install:
-    - go get -u github.com/smartystreets/goconvey
-    - go get -u github.com/keroserene/go-webrtc
-    - go get -u github.com/pion/webrtc
-    - go get -u github.com/dchest/uniuri
-    - go get -u git.torproject.org/pluggable-transports/goptlib.git
-    - go get -u git.torproject.org/pluggable-transports/websocket.git/websocket
-    - go get -u google.golang.org/appengine
-    - go get -u golang.org/x/crypto/acme/autocert
-    - go get -u golang.org/x/net/http2
-    - pushd proxy
-    - npm install
-    - popd
+    - 1.13.x
 
 script:
     - test -z "$(go fmt ./...)"
     - go vet ./...
     - go test -v -race ./...
-    - cd proxy
-    - npm run lint
-    - npm test

ChangeLog

@@ -0,0 +1,65 @@
+Changes in version v2.3.0 - 2022-06-23
+- Issue 40146: Avoid performing two NAT probe tests at startup
+- Issue 40134: Log messages from client NAT check failures are confusing
+- Issue 34075: Implement metrics to measure snowflake churn
+- Issue 28651: Prepare all pieces of the snowflake pipeline for a second snowflake bridge
+- Issue 40129: Distributed Snowflake Server Support
+
+Changes in version v2.2.0 - 2022-05-25
+
+- Issue 40099: Initialize SnowflakeListener.closed
+- Add connection failure events for proxy timeouts
+- Issue 40103: Fix proxy logging verb tense
+- Fix up and downstream metrics output for proxy
+- Issue 40095: uTLS for broker negotiation
+- Forward bridge fingerprint from client to broker (WIP, Issue 28651)
+- Issue 40104: Make it easier to configure proxy type
+- Remove version from ClientPollRequest
+- Issue 40124: Move tor-specific code out of library
+- Issue 40115: Scrub pt event logs
+- Issue 40127: Bump webrtc and dtls library versions
+- Bump version of webrtc and dtls to fix dtls CVEs
+- Issue 40141: Ensure library calls of events can be scrubbed
+
+Changes in version v2.1.0 - 2022-02-08
+
+- Issue 40098: Remove support for legacy one shot mode
+- Issue 40079: Make connection summary at proxy privacy preserving
+- Issue 40076: Add snowflake event API for notifications of connection events
+- Issue 40084: Increase capacity of client address map at the server
+- Issue 40060: Further clean up snowflake server logs
+- Issue 40089: Validate proxy and client supplied strings at broker
+- Issue 40014: Update version of DTLS library to include fingerprinting fixes
+- Issue 40075: Support recurring NAT type check in standalone proxy
+
+
+Changes in version v2.0.0 - 2021-11-04
+
+- Turn the standalone snowflake proxy code into a library
+- Clean up and reworked the snowflake client and server library code
+- Unify broker/bridge domains to *.torproject.net
+- Updates to the snowflake library documentation
+- New package functions to define and set a rendezvous method with the
+broker
+- Factor out the broker geoip code into its own external library
+- Bug fix to check error calls in preparePeerConnection
+- Bug fixes in snowflake tests
+- Issue 40059: add the ability to pass in snowflake arguments through SOCKS
+- Increase buffer sizes for sending and receiving snowflake data
+- Issue 25985: rendezvous with the broker using AMP cache
+- Issue 40055: wait for the full poll interval between proxy polls
+
+Changes in version v1.1.0 - 2021-07-13
+
+- Refactors of the Snowflake broker code
+- Refactors of the Snowflake proxy code
+- Issue 40048: assign proxies based on self-reported client load
+- Issue 40052: fixed a memory leak in the server accept loop
+- Version bump of kcp and smux libraries
+- Bug fix to pass the correct client address to the Snowflake bridge metrics
+counter
+- Bug fixes to prevent race conditions in the Snowflake client 
+
+Changes in version v1.0.0 - 2021-06-07
+
+- Initial release.

LICENSE

@@ -3,7 +3,7 @@
 
 ================================================================================
 Copyright (c) 2016, Serene Han, Arlo Breault
-All rights reserved.
+Copyright (c) 2019-2020, The Tor Project, Inc
 
 Redistribution and use in source and binary forms, with or without modification,
 are permitted provided that the following conditions are met:

README.md

@@ -8,95 +8,47 @@ Pluggable Transport using WebRTC, inspired by Flashproxy.
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 **Table of Contents**
 
+- [Structure of this Repository](#structure-of-this-repository)
 - [Usage](#usage)
-  - [Dependencies](#dependencies)
-  - [More Info](#more-info)
-  - [Building](#building)
-  - [Test Environment](#test-environment)
+  - [Using Snowflake with Tor](#using-snowflake-with-tor)
+  - [Running a Snowflake Proxy](#running-a-snowflake-proxy)
+  - [Using the Snowflake Library with Other Applications](#using-the-snowflake-library-with-other-applications)
+- [Test Environment](#test-environment)
 - [FAQ](#faq)
-- [Appendix](#appendix)
-    - [-- Testing directly via WebRTC Server --](#---testing-directly-via-webrtc-server---)
+- [More info and links](#more-info-and-links)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
+### Structure of this Repository
+
+- `broker/` contains code for the Snowflake broker
+- `doc/` contains Snowflake documentation and manpages
+- `client/` contains the Tor pluggable transport client and client library code
+- `common/` contains generic libraries used by multiple pieces of Snowflake
+- `proxy/` contains code for the Go standalone Snowflake proxy
+- `probetest/` contains code for a NAT probetesting service
+- `server/` contains the Tor pluggable transport server and server library code
+
 ### Usage
 
-```
-cd client/
-go get
-go build
-tor -f torrc
-```
-This should start the client plugin, bootstrapping to 100% using WebRTC.
+Snowflake is currently deployed as a pluggable transport for Tor.
 
-#### Dependencies
+#### Using Snowflake with Tor
 
-Client:
-- [pion/webrtc](https://github.com/pion/webrtc)
-- Go 1.10+
+To use the Snowflake client with Tor, you will need to add the appropriate `Bridge` and `ClientTransportPlugin` lines to your [torrc](https://2019.www.torproject.org/docs/tor-manual.html.en) file. See the [client README](client) for more information on building and running the Snowflake client.
 
-Proxy:
-- JavaScript
+#### Running a Snowflake Proxy
 
----
+You can contribute to Snowflake by running a Snowflake proxy. We have the option to run a proxy in your browser or as a standalone Go program. See our [community documentation](https://community.torproject.org/relay/setup/snowflake/) for more details. 
 
-#### More Info
+#### Using the Snowflake Library with Other Applications
 
-Tor can plug in the Snowflake client via a correctly configured `torrc`.
-For example:
+Snowflake can be used as a Go API, and adheres to the [v2.1 pluggable transports specification](). For more information on using the Snowflake Go library, see the [Snowflake library documentation](doc/using-the-snowflake-library.md).
 
-```
-ClientTransportPlugin snowflake exec ./client \
--url https://snowflake-broker.azureedge.net/ \
--front ajax.aspnetcdn.com \
--ice stun:stun.l.google.com:19302
--max 3
-```
-
-The flags `-url` and `-front` allow the Snowflake client to speak to the Broker,
-in order to get connected with some volunteer's browser proxy. `-ice` is a
-comma-separated list of ICE servers, which are required for NAT traversal.
-
-For logging, run `tail -F snowflake.log` in a second terminal.
-
-You can modify the `torrc` to use your own broker:
-
-```
-ClientTransportPlugin snowflake exec ./client --meek
-```
-
-
-#### Building
-
-This describes how to build the in-browser snowflake. For the client, see Usage,
-above.
-
-The client will only work if there are browser snowflakes available.
-To run your own:
-
-```
-cd proxy/
-npm run build
-```
-
-Then, start a local http server in the `proxy/build/` in any way you like.
-For instance:
-
-```
-cd build/
-python -m http.server
-```
-
-Then, open a browser tab to `http://127.0.0.1:8000/embed.html` to view
-the debug-console of the snowflake.,
-So long as that tab is open, you are an ephemeral Tor bridge.
-
-
-#### Test Environment
+### Test Environment
 
 There is a Docker-based test environment at https://github.com/cohosh/snowbox.
 
-
 ### FAQ
 
 **Q: How does it work?**
@@ -132,22 +84,16 @@ manual port forwarding!
 It utilizes the "ICE" negotiation via WebRTC, and also involves a great
 abundance of ephemeral and short-lived (and special!) volunteer proxies...
 
-### Appendix
+### More info and links
 
-##### -- Testing with Standalone Proxy --
+We have more documentation in the [Snowflake wiki](https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/wikis/home) and at https://snowflake.torproject.org/.
 
-```
-cd proxy-go
-go build
-./proxy-go
-```
 
-##### -- Testing directly via WebRTC Server --
+##### -- Android AAR Reproducible Build Setup  --
 
-See server-webrtc/README.md for information on connecting directly to a
-WebRTC server transport plugin, bypassing the Broker and browser proxy.
-
-More documentation on the way.
-
-Also available at:
-[torproject.org/pluggable-transports/snowflake](https://gitweb.torproject.org/pluggable-transports/snowflake.git/)
+Using `gomobile` it is possible to build snowflake as shared libraries for all
+the architectures supported by Android.  This is in the _.gitlab-ci.yml_, which
+runs in GitLab CI.  It is also possible to run this setup in a Virtual Machine
+using [vagrant](https://www.vagrantup.com/).  Just run `vagrant up` and it will
+create and provision the VM.  `vagrant ssh` to get into the VM to use it as a
+development environment.

Vagrantfile

@@ -0,0 +1,67 @@
+require 'pathname'
+require 'tempfile'
+require 'yaml'
+
+srvpath = Pathname.new(File.dirname(__FILE__)).realpath
+configfile = YAML.load_file(File.join(srvpath, "/.gitlab-ci.yml"))
+remote_url = 'https://git.torproject.org/pluggable-transports/snowflake.git'
+
+# set up essential environment variables
+env = configfile['variables']
+env = env.merge(configfile['android']['variables'])
+env['CI_PROJECT_DIR'] = '/builds/tpo/anti-censorship/pluggable-transports/snowflake'
+env_file = Tempfile.new('env')
+File.chmod(0644, env_file.path)
+env.each do |k,v|
+    env_file.write("export #{k}='#{v}'\n")
+end
+env_file.rewind
+
+sourcepath = '/etc/profile.d/env.sh'
+header = "#!/bin/bash -ex\nsource #{sourcepath}\ncd $CI_PROJECT_DIR\n"
+
+before_script_file = Tempfile.new('before_script')
+File.chmod(0755, before_script_file.path)
+before_script_file.write(header)
+configfile['android']['before_script'].flatten.each do |line|
+    before_script_file.write(line)
+    before_script_file.write("\n")
+end
+before_script_file.rewind
+
+script_file = Tempfile.new('script')
+File.chmod(0755, script_file.path)
+script_file.write(header)
+configfile['android']['script'].flatten.each do |line|
+    script_file.write(line)
+    script_file.write("\n")
+end
+script_file.rewind
+
+Vagrant.configure("2") do |config|
+  config.vm.box = "debian/bullseye64"
+  config.vm.synced_folder '.', '/vagrant', disabled: true
+  config.vm.provision "file", source: env_file.path, destination: 'env.sh'
+  config.vm.provision :shell, inline: <<-SHELL
+    set -ex
+    mv ~vagrant/env.sh #{sourcepath}
+    source #{sourcepath}
+    test -d /go || mkdir /go
+    mkdir -p $(dirname $CI_PROJECT_DIR)
+    chown -R vagrant.vagrant $(dirname $CI_PROJECT_DIR)
+    apt-get update
+    apt-get -qy install --no-install-recommends git
+    git clone #{remote_url} $CI_PROJECT_DIR
+    chmod -R a+rX,u+w /go $CI_PROJECT_DIR
+    chown -R vagrant.vagrant /go $CI_PROJECT_DIR
+SHELL
+  config.vm.provision "file", source: before_script_file.path, destination: 'before_script.sh'
+  config.vm.provision "file", source: script_file.path, destination: 'script.sh'
+  config.vm.provision :shell, inline: '/home/vagrant/before_script.sh'
+  config.vm.provision :shell, privileged: false, inline: '/home/vagrant/script.sh'
+
+  # remove this or comment it out to use VirtualBox instead of libvirt
+  config.vm.provider :libvirt do |libvirt|
+    libvirt.memory = 1536
+  end
+end

appengine/README

@@ -1,28 +0,0 @@
-This component runs on Google App Engine. It reflects domain-fronted
-requests from a client to the Snowflake broker.
-
-You need the Go App Engine SDK in order to deploy the app.
-	https://cloud.google.com/sdk/docs/#linux
-After unpacking, install the app-engine-go component:
-	google-cloud-sdk/bin/gcloud components install app-engine-go
-
-To test locally, run
-	google-cloud-sdk/bin/dev_appserver.py app.yaml
-The app will be running at http://127.0.0.1:8080/.
-
-To deploy to App Engine, first create a new project and app. You have to
-think of a unique name (marked as "<appname>" in the commands). You only
-have to do the "create" step once; subsequent times you can go straight
-to the "deploy" step. The "gcloud auth login" command will open a
-browser window so you can log in to a Google account.
-	google-cloud-sdk/bin/gcloud auth login
-	google-cloud-sdk/bin/gcloud projects create <appname>
-	google-cloud-sdk/bin/gcloud app create --project=<appname>
-Then to deploy the project, run:
-	google-cloud-sdk/bin/gcloud app deploy --project=<appname>
-
-To configure the Snowflake client to talk to the App Engine app, provide
-"https://<appname>.appspot.com/" as the --url option.
-	UseBridges 1
-	Bridge snowflake 0.0.2.0:1
-	ClientTransportPlugin snowflake exec ./client -url https://<appname>.appspot.com/ -front www.google.com

appengine/app.yaml

@@ -1,7 +0,0 @@
-runtime: go
-api_version: go1
-
-handlers:
-- url: /.*
-  script: _go_app
-  secure: always

appengine/reflect.go

@@ -1,111 +0,0 @@
-// A web app for Google App Engine that proxies HTTP requests and responses to
-// the Snowflake broker.
-package reflect
-
-import (
-	"context"
-	"io"
-	"net/http"
-	"net/url"
-	"time"
-
-	"google.golang.org/appengine"
-	"google.golang.org/appengine/log"
-	"google.golang.org/appengine/urlfetch"
-)
-
-const (
-	forwardURL = "https://snowflake-broker.bamsoftware.com/"
-	// A timeout of 0 means to use the App Engine default (5 seconds).
-	urlFetchTimeout = 20 * time.Second
-)
-
-var ctx context.Context
-
-// Join two URL paths.
-func pathJoin(a, b string) string {
-	if len(a) > 0 && a[len(a)-1] == '/' {
-		a = a[:len(a)-1]
-	}
-	if len(b) == 0 || b[0] != '/' {
-		b = "/" + b
-	}
-	return a + b
-}
-
-// We reflect only a whitelisted set of header fields. Otherwise, we may copy
-// headers like Transfer-Encoding that interfere with App Engine's own
-// hop-by-hop headers.
-var reflectedHeaderFields = []string{
-	"Content-Type",
-	"X-Session-Id",
-}
-
-// Make a copy of r, with the URL being changed to be relative to forwardURL,
-// and including only the headers in reflectedHeaderFields.
-func copyRequest(r *http.Request) (*http.Request, error) {
-	u, err := url.Parse(forwardURL)
-	if err != nil {
-		return nil, err
-	}
-	// Append the requested path to the path in forwardURL, so that
-	// forwardURL can be something like "https://example.com/reflect".
-	u.Path = pathJoin(u.Path, r.URL.Path)
-	c, err := http.NewRequest(r.Method, u.String(), r.Body)
-	if err != nil {
-		return nil, err
-	}
-	for _, key := range reflectedHeaderFields {
-		values, ok := r.Header[key]
-		if ok {
-			for _, value := range values {
-				c.Header.Add(key, value)
-			}
-		}
-	}
-	return c, nil
-}
-
-func handler(w http.ResponseWriter, r *http.Request) {
-	ctx = appengine.NewContext(r)
-	fr, err := copyRequest(r)
-	if err != nil {
-		log.Errorf(ctx, "copyRequest: %s", err)
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
-	}
-	if urlFetchTimeout != 0 {
-		var cancel context.CancelFunc
-		ctx, cancel = context.WithTimeout(ctx, urlFetchTimeout)
-		defer cancel()
-	}
-	// Use urlfetch.Transport directly instead of urlfetch.Client because we
-	// want only a single HTTP transaction, not following redirects.
-	transport := urlfetch.Transport{
-		Context: ctx,
-	}
-	resp, err := transport.RoundTrip(fr)
-	if err != nil {
-		log.Errorf(ctx, "RoundTrip: %s", err)
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
-	}
-	defer resp.Body.Close()
-	for _, key := range reflectedHeaderFields {
-		values, ok := resp.Header[key]
-		if ok {
-			for _, value := range values {
-				w.Header().Add(key, value)
-			}
-		}
-	}
-	w.WriteHeader(resp.StatusCode)
-	n, err := io.Copy(w, resp.Body)
-	if err != nil {
-		log.Errorf(ctx, "io.Copy after %d bytes: %s", n, err)
-	}
-}
-
-func init() {
-	http.HandleFunc("/", handler)
-}

broker/README.md

@@ -1,3 +1,12 @@
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of Contents**
+
+- [Overview](#overview)
+- [Running your own](#running-your-own)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
 This is the Broker component of Snowflake.
 
 ### Overview

broker/amp.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"strings"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/amp"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+)
+
+// ampClientOffers is the AMP-speaking endpoint for client poll messages,
+// intended for access via an AMP cache. In contrast to the other clientOffers,
+// the client's encoded poll message is stored in the URL path rather than the
+// HTTP request body (because an AMP cache does not support POST), and the
+// encoded client poll response is sent back as AMP-armored HTML.
+func ampClientOffers(i *IPC, w http.ResponseWriter, r *http.Request) {
+	// The encoded client poll message immediately follows the /amp/client/
+	// path prefix, so this function unfortunately needs to be aware of and
+	// remote its own routing prefix.
+	path := strings.TrimPrefix(r.URL.Path, "/amp/client/")
+	if path == r.URL.Path {
+		// The path didn't start with the expected prefix. This probably
+		// indicates an internal bug.
+		log.Println("ampClientOffers: unexpected prefix in path")
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	var encPollReq []byte
+	var response []byte
+	var err error
+
+	encPollReq, err = amp.DecodePath(path)
+	if err == nil {
+		arg := messages.Arg{
+			Body:       encPollReq,
+			RemoteAddr: "",
+		}
+		err = i.ClientOffers(arg, &response)
+	} else {
+		response, err = (&messages.ClientPollResponse{
+			Error: "cannot decode URL path",
+		}).EncodePollResponse()
+	}
+
+	if err != nil {
+		// We couldn't even construct a JSON object containing an error
+		// message :( Nothing to do but signal an error at the HTTP
+		// layer. The AMP cache will translate this 500 status into a
+		// 404 status.
+		// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#redirect-%26-error-handling
+		log.Printf("ampClientOffers: %v", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/html")
+	// Attempt to hint to an AMP cache not to waste resources caching this
+	// document. "The Google AMP Cache considers any document fresh for at
+	// least 15 seconds."
+	// https://developers.google.com/amp/cache/overview#google-amp-cache-updates
+	w.Header().Set("Cache-Control", "max-age=15")
+	w.WriteHeader(http.StatusOK)
+
+	enc, err := amp.NewArmorEncoder(w)
+	if err != nil {
+		log.Printf("amp.NewArmorEncoder: %v", err)
+		return
+	}
+	defer enc.Close()
+
+	if _, err := enc.Write(response); err != nil {
+		log.Printf("ampClientOffers: unable to write answer: %v", err)
+	}
+}

broker/bridge-list.go

@@ -0,0 +1,94 @@
+/* (*BridgeListHolderFileBased).LoadBridgeInfo loads a Snowflake Server bridge info description file,
+   its format is as follows:
+
+   This file should be in newline-delimited JSON format(https://jsonlines.org/).
+   For each line, the format of json data should be in the format of:
+   {"displayName":"default", "webSocketAddress":"wss://snowflake.torproject.net/", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80A72"}
+
+   displayName:string is the name of this bridge. This value is not currently used programmatically.
+
+   webSocketAddress:string is the WebSocket URL of this bridge.
+   This will be the address proxy used to connect to this snowflake server.
+
+   fingerprint:string is the identifier of the bridge.
+   This will be used by a client to identify the bridge it wishes to connect to.
+
+   The existence of ANY other fields is NOT permitted.
+
+   The file will be considered invalid if there is at least one invalid json record.
+   In this case, an error will be returned, and none of the records will be loaded.
+*/
+
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/json"
+	"errors"
+	"io"
+	"sync"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/bridgefingerprint"
+)
+
+var ErrBridgeNotFound = errors.New("bridge not found")
+
+func NewBridgeListHolder() BridgeListHolderFileBased {
+	return &bridgeListHolder{}
+}
+
+type bridgeListHolder struct {
+	bridgeInfo       map[bridgefingerprint.Fingerprint]BridgeInfo
+	accessBridgeInfo sync.RWMutex
+}
+
+type BridgeListHolder interface {
+	GetBridgeInfo(bridgefingerprint.Fingerprint) (BridgeInfo, error)
+}
+
+type BridgeListHolderFileBased interface {
+	BridgeListHolder
+	LoadBridgeInfo(reader io.Reader) error
+}
+
+type BridgeInfo struct {
+	DisplayName      string `json:"displayName"`
+	WebSocketAddress string `json:"webSocketAddress"`
+	Fingerprint      string `json:"fingerprint"`
+}
+
+func (h *bridgeListHolder) GetBridgeInfo(fingerprint bridgefingerprint.Fingerprint) (BridgeInfo, error) {
+	h.accessBridgeInfo.RLock()
+	defer h.accessBridgeInfo.RUnlock()
+	if bridgeInfo, ok := h.bridgeInfo[fingerprint]; ok {
+		return bridgeInfo, nil
+	}
+	return BridgeInfo{}, ErrBridgeNotFound
+}
+
+func (h *bridgeListHolder) LoadBridgeInfo(reader io.Reader) error {
+	bridgeInfoMap := map[bridgefingerprint.Fingerprint]BridgeInfo{}
+	inputScanner := bufio.NewScanner(reader)
+	for inputScanner.Scan() {
+		inputLine := inputScanner.Bytes()
+		bridgeInfo := BridgeInfo{}
+		decoder := json.NewDecoder(bytes.NewReader(inputLine))
+		decoder.DisallowUnknownFields()
+		if err := decoder.Decode(&bridgeInfo); err != nil {
+			return err
+		}
+
+		var bridgeFingerprint bridgefingerprint.Fingerprint
+		var err error
+		if bridgeFingerprint, err = bridgefingerprint.FingerprintFromHexString(bridgeInfo.Fingerprint); err != nil {
+			return err
+		}
+
+		bridgeInfoMap[bridgeFingerprint] = bridgeInfo
+	}
+	h.accessBridgeInfo.Lock()
+	defer h.accessBridgeInfo.Unlock()
+	h.bridgeInfo = bridgeInfoMap
+	return nil
+}

broker/bridge-list_test.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"bytes"
+	"encoding/hex"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/bridgefingerprint"
+	. "github.com/smartystreets/goconvey/convey"
+	"testing"
+)
+
+const DefaultBridges = `{"displayName":"default", "webSocketAddress":"wss://snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80A72"}
+`
+
+const ImaginaryBridges = `{"displayName":"default", "webSocketAddress":"wss://snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80A72"}
+{"displayName":"imaginary-1", "webSocketAddress":"wss://imaginary-1-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B00"}
+{"displayName":"imaginary-2", "webSocketAddress":"wss://imaginary-2-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B01"}
+{"displayName":"imaginary-3", "webSocketAddress":"wss://imaginary-3-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B02"}
+{"displayName":"imaginary-4", "webSocketAddress":"wss://imaginary-4-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B03"}
+{"displayName":"imaginary-5", "webSocketAddress":"wss://imaginary-5-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B04"}
+{"displayName":"imaginary-6", "webSocketAddress":"wss://imaginary-6-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B05"}
+{"displayName":"imaginary-7", "webSocketAddress":"wss://imaginary-7-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B06"}
+{"displayName":"imaginary-8", "webSocketAddress":"wss://imaginary-8-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B07"}
+{"displayName":"imaginary-9", "webSocketAddress":"wss://imaginary-9-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B08"}
+{"displayName":"imaginary-10", "webSocketAddress":"wss://imaginary-10-snowflake.torproject.org", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80B09"}
+`
+
+func TestBridgeLoad(t *testing.T) {
+	Convey("load default list", t, func() {
+		bridgeList := NewBridgeListHolder()
+		So(bridgeList.LoadBridgeInfo(bytes.NewReader([]byte(DefaultBridges))), ShouldBeNil)
+		{
+			bridgeFingerprint := [20]byte{}
+			{
+				n, err := hex.Decode(bridgeFingerprint[:], []byte("2B280B23E1107BB62ABFC40DDCC8824814F80A72"))
+				So(n, ShouldEqual, 20)
+				So(err, ShouldBeNil)
+			}
+			Fingerprint, err := bridgefingerprint.FingerprintFromBytes(bridgeFingerprint[:])
+			So(err, ShouldBeNil)
+			bridgeInfo, err := bridgeList.GetBridgeInfo(Fingerprint)
+			So(err, ShouldBeNil)
+			So(bridgeInfo.DisplayName, ShouldEqual, "default")
+			So(bridgeInfo.WebSocketAddress, ShouldEqual, "wss://snowflake.torproject.org")
+		}
+	})
+	Convey("load imaginary list", t, func() {
+		bridgeList := NewBridgeListHolder()
+		So(bridgeList.LoadBridgeInfo(bytes.NewReader([]byte(ImaginaryBridges))), ShouldBeNil)
+		{
+			bridgeFingerprint := [20]byte{}
+			{
+				n, err := hex.Decode(bridgeFingerprint[:], []byte("2B280B23E1107BB62ABFC40DDCC8824814F80B07"))
+				So(n, ShouldEqual, 20)
+				So(err, ShouldBeNil)
+			}
+			Fingerprint, err := bridgefingerprint.FingerprintFromBytes(bridgeFingerprint[:])
+			So(err, ShouldBeNil)
+			bridgeInfo, err := bridgeList.GetBridgeInfo(Fingerprint)
+			So(err, ShouldBeNil)
+			So(bridgeInfo.DisplayName, ShouldEqual, "imaginary-8")
+			So(bridgeInfo.WebSocketAddress, ShouldEqual, "wss://imaginary-8-snowflake.torproject.org")
+		}
+	})
+}

broker/broker.go

@@ -6,43 +6,56 @@ SessionDescriptions in order to negotiate a WebRTC connection.
 package main
 
 import (
+	"bytes"
 	"container/heap"
 	"crypto/tls"
 	"flag"
-	"fmt"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/bridgefingerprint"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/ipsetsink"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/ipsetsink/sinkcluster"
 	"io"
-	"io/ioutil"
 	"log"
-	"net"
 	"net/http"
 	"os"
 	"os/signal"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 
-	"git.torproject.org/pluggable-transports/snowflake.git/common/safelog"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/namematcher"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/safelog"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"golang.org/x/crypto/acme/autocert"
 )
 
-const (
-	ClientTimeout = 10
-	ProxyTimeout  = 10
-	readLimit     = 100000 //Maximum number of bytes to be read from an HTTP request
-)
-
 type BrokerContext struct {
-	snowflakes *SnowflakeHeap
-	// Map keeping track of snowflakeIDs required to match SDP answers from
-	// the second http POST.
+	snowflakes           *SnowflakeHeap
+	restrictedSnowflakes *SnowflakeHeap
+	// Maps keeping track of snowflakeIDs required to match SDP answers from
+	// the second http POST. Restricted snowflakes can only be matched up with
+	// clients behind an unrestricted NAT.
 	idToSnowflake map[string]*Snowflake
+	// Synchronization for the snowflake map and heap
+	snowflakeLock sync.Mutex
 	proxyPolls    chan *ProxyPoll
 	metrics       *Metrics
+
+	bridgeList                     BridgeListHolderFileBased
+	allowedRelayPattern            string
+	presumedPatternForLegacyClient string
+}
+
+func (ctx *BrokerContext) GetBridgeInfo(fingerprint bridgefingerprint.Fingerprint) (BridgeInfo, error) {
+	return ctx.bridgeList.GetBridgeInfo(fingerprint)
 }
 
 func NewBrokerContext(metricsLogger *log.Logger) *BrokerContext {
 	snowflakes := new(SnowflakeHeap)
 	heap.Init(snowflakes)
+	rSnowflakes := new(SnowflakeHeap)
+	heap.Init(rSnowflakes)
 	metrics, err := NewMetrics(metricsLogger)
 
 	if err != nil {
@@ -53,58 +66,40 @@ func NewBrokerContext(metricsLogger *log.Logger) *BrokerContext {
 		panic("Failed to create metrics")
 	}
 
+	bridgeListHolder := NewBridgeListHolder()
+
+	const DefaultBridges = `{"displayName":"default", "webSocketAddress":"wss://snowflake.torproject.net/", "fingerprint":"2B280B23E1107BB62ABFC40DDCC8824814F80A72"}
+`
+	bridgeListHolder.LoadBridgeInfo(bytes.NewReader([]byte(DefaultBridges)))
+
 	return &BrokerContext{
-		snowflakes:    snowflakes,
-		idToSnowflake: make(map[string]*Snowflake),
-		proxyPolls:    make(chan *ProxyPoll),
-		metrics:       metrics,
+		snowflakes:           snowflakes,
+		restrictedSnowflakes: rSnowflakes,
+		idToSnowflake:        make(map[string]*Snowflake),
+		proxyPolls:           make(chan *ProxyPoll),
+		metrics:              metrics,
+		bridgeList:           bridgeListHolder,
 	}
 }
 
-// Implements the http.Handler interface
-type SnowflakeHandler struct {
-	*BrokerContext
-	handle func(*BrokerContext, http.ResponseWriter, *http.Request)
-}
-
-// Implements the http.Handler interface
-type MetricsHandler struct {
-	logFilename string
-	handle      func(string, http.ResponseWriter, *http.Request)
-}
-
-func (sh SnowflakeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	w.Header().Set("Access-Control-Allow-Origin", "*")
-	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
-	// Return early if it's CORS preflight.
-	if "OPTIONS" == r.Method {
-		return
-	}
-	sh.handle(sh.BrokerContext, w, r)
-}
-
-func (mh MetricsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	w.Header().Set("Access-Control-Allow-Origin", "*")
-	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
-	// Return early if it's CORS preflight.
-	if "OPTIONS" == r.Method {
-		return
-	}
-	mh.handle(mh.logFilename, w, r)
-}
-
 // Proxies may poll for client offers concurrently.
 type ProxyPoll struct {
 	id           string
-	offerChannel chan []byte
+	proxyType    string
+	natType      string
+	clients      int
+	offerChannel chan *ClientOffer
 }
 
 // Registers a Snowflake and waits for some Client to send an offer,
 // as part of the polling logic of the proxy handler.
-func (ctx *BrokerContext) RequestOffer(id string) []byte {
+func (ctx *BrokerContext) RequestOffer(id string, proxyType string, natType string, clients int) *ClientOffer {
 	request := new(ProxyPoll)
 	request.id = id
-	request.offerChannel = make(chan []byte)
+	request.proxyType = proxyType
+	request.natType = natType
+	request.clients = clients
+	request.offerChannel = make(chan *ClientOffer)
 	ctx.proxyPolls <- request
 	// Block until an offer is available, or timeout which sends a nil offer.
 	offer := <-request.offerChannel
@@ -116,7 +111,7 @@ func (ctx *BrokerContext) RequestOffer(id string) []byte {
 // client offer or nil on timeout / none are available.
 func (ctx *BrokerContext) Broker() {
 	for request := range ctx.proxyPolls {
-		snowflake := ctx.AddSnowflake(request.id)
+		snowflake := ctx.AddSnowflake(request.id, request.proxyType, request.natType, request.clients)
 		// Wait for a client to avail an offer to the snowflake.
 		go func(request *ProxyPoll) {
 			select {
@@ -124,10 +119,18 @@ func (ctx *BrokerContext) Broker() {
 				request.offerChannel <- offer
 			case <-time.After(time.Second * ProxyTimeout):
 				// This snowflake is no longer available to serve clients.
-				// TODO: Fix race using a delete channel
-				heap.Remove(ctx.snowflakes, snowflake.index)
-				delete(ctx.idToSnowflake, snowflake.id)
-				request.offerChannel <- nil
+				ctx.snowflakeLock.Lock()
+				defer ctx.snowflakeLock.Unlock()
+				if snowflake.index != -1 {
+					if request.natType == NATUnrestricted {
+						heap.Remove(ctx.snowflakes, snowflake.index)
+					} else {
+						heap.Remove(ctx.restrictedSnowflakes, snowflake.index)
+					}
+					ctx.metrics.promMetrics.AvailableProxies.With(prometheus.Labels{"nat": request.natType, "type": request.proxyType}).Dec()
+					delete(ctx.idToSnowflake, snowflake.id)
+					close(request.offerChannel)
+				}
 			}
 		}(request)
 	}
@@ -136,165 +139,49 @@ func (ctx *BrokerContext) Broker() {
 // Create and add a Snowflake to the heap.
 // Required to keep track of proxies between providing them
 // with an offer and awaiting their second POST with an answer.
-func (ctx *BrokerContext) AddSnowflake(id string) *Snowflake {
+func (ctx *BrokerContext) AddSnowflake(id string, proxyType string, natType string, clients int) *Snowflake {
 	snowflake := new(Snowflake)
 	snowflake.id = id
-	snowflake.clients = 0
-	snowflake.offerChannel = make(chan []byte)
-	snowflake.answerChannel = make(chan []byte)
-	heap.Push(ctx.snowflakes, snowflake)
+	snowflake.clients = clients
+	snowflake.proxyType = proxyType
+	snowflake.natType = natType
+	snowflake.offerChannel = make(chan *ClientOffer)
+	snowflake.answerChannel = make(chan string)
+	ctx.snowflakeLock.Lock()
+	if natType == NATUnrestricted {
+		heap.Push(ctx.snowflakes, snowflake)
+	} else {
+		heap.Push(ctx.restrictedSnowflakes, snowflake)
+	}
+	ctx.metrics.promMetrics.AvailableProxies.With(prometheus.Labels{"nat": natType, "type": proxyType}).Inc()
 	ctx.idToSnowflake[id] = snowflake
+	ctx.snowflakeLock.Unlock()
 	return snowflake
 }
 
-/*
-For snowflake proxies to request a client from the Broker.
-*/
-func proxyPolls(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
-	id := r.Header.Get("X-Session-ID")
-	body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
-	if nil != err {
-		log.Println("Invalid data.")
-		w.WriteHeader(http.StatusBadRequest)
-		return
-	}
-	if string(body) != id {
-		log.Println("Mismatched IDs!")
-		w.WriteHeader(http.StatusBadRequest)
-		return
-	}
-
-	// Log geoip stats
-	remoteIP, _, err := net.SplitHostPort(r.RemoteAddr)
-	if err != nil {
-		log.Println("Error processing proxy IP: ", err.Error())
-	} else {
-		ctx.metrics.UpdateCountryStats(remoteIP)
-	}
-
-	// Wait for a client to avail an offer to the snowflake, or timeout if nil.
-	offer := ctx.RequestOffer(id)
-	if nil == offer {
-		ctx.metrics.proxyIdleCount++
-		w.WriteHeader(http.StatusGatewayTimeout)
-		return
-	}
-	log.Println("Passing client offer to snowflake.")
-	if _, err := w.Write(offer); err != nil {
-		log.Printf("proxyPolls unable to write offer with error: %v", err)
+func (ctx *BrokerContext) InstallBridgeListProfile(reader io.Reader, relayPattern, presumedPatternForLegacyClient string) error {
+	if err := ctx.bridgeList.LoadBridgeInfo(reader); err != nil {
+		return err
 	}
+	ctx.allowedRelayPattern = relayPattern
+	ctx.presumedPatternForLegacyClient = presumedPatternForLegacyClient
+	return nil
 }
 
-/*
-Expects a WebRTC SDP offer in the Request to give to an assigned
-snowflake proxy, which responds with the SDP answer to be sent in
-the HTTP response back to the client.
-*/
-func clientOffers(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
-	startTime := time.Now()
-	offer, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
-	if nil != err {
-		log.Println("Invalid data.")
-		w.WriteHeader(http.StatusBadRequest)
-		return
-	}
-	// Immediately fail if there are no snowflakes available.
-	if ctx.snowflakes.Len() <= 0 {
-		ctx.metrics.clientDeniedCount++
-		w.WriteHeader(http.StatusServiceUnavailable)
-		return
-	}
-	// Otherwise, find the most available snowflake proxy, and pass the offer to it.
-	// Delete must be deferred in order to correctly process answer request later.
-	snowflake := heap.Pop(ctx.snowflakes).(*Snowflake)
-	defer delete(ctx.idToSnowflake, snowflake.id)
-	snowflake.offerChannel <- offer
-
-	// Wait for the answer to be returned on the channel or timeout.
-	select {
-	case answer := <-snowflake.answerChannel:
-		ctx.metrics.clientProxyMatchCount++
-		if _, err := w.Write(answer); err != nil {
-			log.Printf("unable to write answer with error: %v", err)
-		}
-		// Initial tracking of elapsed time.
-		ctx.metrics.clientRoundtripEstimate = time.Since(startTime) /
-			time.Millisecond
-	case <-time.After(time.Second * ClientTimeout):
-		log.Println("Client: Timed out.")
-		w.WriteHeader(http.StatusGatewayTimeout)
-		if _, err := w.Write([]byte("timed out waiting for answer!")); err != nil {
-			log.Printf("unable to write timeout error, failed with error: %v", err)
-		}
+func (ctx *BrokerContext) CheckProxyRelayPattern(pattern string, nonSupported bool) bool {
+	if nonSupported {
+		pattern = ctx.presumedPatternForLegacyClient
 	}
+	proxyPattern := namematcher.NewNameMatcher(pattern)
+	brokerPattern := namematcher.NewNameMatcher(ctx.allowedRelayPattern)
+	return proxyPattern.IsSupersetOf(brokerPattern)
 }
 
-/*
-Expects snowflake proxes which have previously successfully received
-an offer from proxyHandler to respond with an answer in an HTTP POST,
-which the broker will pass back to the original client.
-*/
-func proxyAnswers(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
-	id := r.Header.Get("X-Session-ID")
-	snowflake, ok := ctx.idToSnowflake[id]
-	if !ok || nil == snowflake {
-		// The snowflake took too long to respond with an answer, so its client
-		// disappeared / the snowflake is no longer recognized by the Broker.
-		w.WriteHeader(http.StatusGone)
-		return
-	}
-	body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
-	if nil != err || nil == body || len(body) <= 0 {
-		log.Println("Invalid data.")
-		w.WriteHeader(http.StatusBadRequest)
-		return
-	}
-
-	snowflake.answerChannel <- body
-}
-
-func debugHandler(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
-	s := fmt.Sprintf("current snowflakes available: %d\n", ctx.snowflakes.Len())
-
-	var browsers, standalones int
-	for _, snowflake := range ctx.idToSnowflake {
-		if len(snowflake.id) < 16 {
-			browsers++
-		} else {
-			standalones++
-		}
-	}
-	s += fmt.Sprintf("\tstandalone proxies: %d", standalones)
-	s += fmt.Sprintf("\n\tbrowser proxies: %d", browsers)
-	if _, err := w.Write([]byte(s)); err != nil {
-		log.Printf("writing proxy information returned error: %v ", err)
-	}
-}
-
-func robotsTxtHandler(w http.ResponseWriter, r *http.Request) {
-	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
-	if _, err := w.Write([]byte("User-agent: *\nDisallow: /\n")); err != nil {
-		log.Printf("robotsTxtHandler unable to write, with this error: %v", err)
-	}
-}
-
-func metricsHandler(metricsFilename string, w http.ResponseWriter, r *http.Request) {
-	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
-
-	if metricsFilename == "" {
-		http.NotFound(w, r)
-		return
-	}
-	metricsFile, err := os.OpenFile(metricsFilename, os.O_RDONLY, 0644)
-	if err != nil {
-		log.Println("Error opening metrics file for reading")
-		http.NotFound(w, r)
-		return
-	}
-
-	if _, err := io.Copy(w, metricsFile); err != nil {
-		log.Printf("copying metricsFile returned error: %v", err)
-	}
+// Client offer contains an SDP, bridge fingerprint and the NAT type of the client
+type ClientOffer struct {
+	natType     string
+	sdp         []byte
+	fingerprint []byte
 }
 
 func main() {
@@ -304,10 +191,14 @@ func main() {
 	var addr string
 	var geoipDatabase string
 	var geoip6Database string
+	var bridgeListFilePath, allowedRelayPattern, presumedPatternForLegacyClient string
 	var disableTLS bool
 	var certFilename, keyFilename string
 	var disableGeoip bool
 	var metricsFilename string
+	var ipCountFilename, ipCountMaskingKey string
+	var ipCountInterval time.Duration
+	var unsafeLogging bool
 
 	flag.StringVar(&acmeEmail, "acme-email", "", "optional contact email for Let's Encrypt notifications")
 	flag.StringVar(&acmeHostnamesCommas, "acme-hostnames", "", "comma-separated hostnames for TLS certificate")
@@ -317,16 +208,27 @@ func main() {
 	flag.StringVar(&addr, "addr", ":443", "address to listen on")
 	flag.StringVar(&geoipDatabase, "geoipdb", "/usr/share/tor/geoip", "path to correctly formatted geoip database mapping IPv4 address ranges to country codes")
 	flag.StringVar(&geoip6Database, "geoip6db", "/usr/share/tor/geoip6", "path to correctly formatted geoip database mapping IPv6 address ranges to country codes")
+	flag.StringVar(&bridgeListFilePath, "bridge-list-path", "", "file path for bridgeListFile")
+	flag.StringVar(&allowedRelayPattern, "allowed-relay-pattern", "", "allowed pattern for relay host name")
+	flag.StringVar(&presumedPatternForLegacyClient, "default-relay-pattern", "", "presumed pattern for legacy client")
 	flag.BoolVar(&disableTLS, "disable-tls", false, "don't use HTTPS")
 	flag.BoolVar(&disableGeoip, "disable-geoip", false, "don't use geoip for stats collection")
 	flag.StringVar(&metricsFilename, "metrics-log", "", "path to metrics logging output")
+	flag.StringVar(&ipCountFilename, "ip-count-log", "", "path to ip count logging output")
+	flag.StringVar(&ipCountMaskingKey, "ip-count-mask", "", "masking key for ip count logging")
+	flag.DurationVar(&ipCountInterval, "ip-count-interval", time.Hour, "time interval between each chunk")
+	flag.BoolVar(&unsafeLogging, "unsafe-logging", false, "prevent logs from being scrubbed")
 	flag.Parse()
 
 	var err error
 	var metricsFile io.Writer
 	var logOutput io.Writer = os.Stderr
-	//We want to send the log output through our scrubber first
-	log.SetOutput(&safelog.LogScrubber{Output: logOutput})
+	if unsafeLogging {
+		log.SetOutput(logOutput)
+	} else {
+		// We want to send the log output through our scrubber first
+		log.SetOutput(&safelog.LogScrubber{Output: logOutput})
+	}
 
 	log.SetFlags(log.LstdFlags | log.LUTC)
 
@@ -344,6 +246,17 @@ func main() {
 
 	ctx := NewBrokerContext(metricsLogger)
 
+	if bridgeListFilePath != "" {
+		bridgeListFile, err := os.Open(bridgeListFilePath)
+		if err != nil {
+			log.Fatal(err.Error())
+		}
+		err = ctx.InstallBridgeListProfile(bridgeListFile, allowedRelayPattern, presumedPatternForLegacyClient)
+		if err != nil {
+			log.Fatal(err.Error())
+		}
+	}
+
 	if !disableGeoip {
 		err = ctx.metrics.LoadGeoipDatabases(geoipDatabase, geoip6Database)
 		if err != nil {
@@ -351,15 +264,30 @@ func main() {
 		}
 	}
 
+	if ipCountFilename != "" {
+		ipCountFile, err := os.OpenFile(ipCountFilename, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+
+		if err != nil {
+			log.Fatal(err.Error())
+		}
+		ipSetSink := ipsetsink.NewIPSetSink(ipCountMaskingKey)
+		ctx.metrics.distinctIPWriter = sinkcluster.NewClusterWriter(ipCountFile, ipCountInterval, ipSetSink)
+	}
+
 	go ctx.Broker()
 
+	i := &IPC{ctx}
+
 	http.HandleFunc("/robots.txt", robotsTxtHandler)
 
-	http.Handle("/proxy", SnowflakeHandler{ctx, proxyPolls})
-	http.Handle("/client", SnowflakeHandler{ctx, clientOffers})
-	http.Handle("/answer", SnowflakeHandler{ctx, proxyAnswers})
-	http.Handle("/debug", SnowflakeHandler{ctx, debugHandler})
+	http.Handle("/proxy", SnowflakeHandler{i, proxyPolls})
+	http.Handle("/client", SnowflakeHandler{i, clientOffers})
+	http.Handle("/answer", SnowflakeHandler{i, proxyAnswers})
+	http.Handle("/debug", SnowflakeHandler{i, debugHandler})
 	http.Handle("/metrics", MetricsHandler{metricsFilename, metricsHandler})
+	http.Handle("/prometheus", promhttp.HandlerFor(ctx.metrics.promMetrics.registry, promhttp.HandlerOpts{}))
+
+	http.Handle("/amp/client/", SnowflakeHandler{i, ampClientOffers})
 
 	server := http.Server{
 		Addr: addr,

broker/geoip.go

@@ -1,240 +0,0 @@
-/*
-This code is for loading database data that maps ip addresses to countries
-for collecting and presenting statistics on snowflake use that might alert us
-to censorship events.
-
-The functions here are heavily based off of how tor maintains and searches their
-geoip database
-
-The tables used for geoip data must be structured as follows:
-
-Recognized line format for IPv4 is:
-    INTIPLOW,INTIPHIGH,CC
-        where INTIPLOW and INTIPHIGH are IPv4 addresses encoded as big-endian 4-byte unsigned
-        integers, and CC is a country code.
-
-Note that the IPv4 line format
-    "INTIPLOW","INTIPHIGH","CC","CC3","COUNTRY NAME"
-is not currently supported.
-
-Recognized line format for IPv6 is:
-    IPV6LOW,IPV6HIGH,CC
-        where IPV6LOW and IPV6HIGH are IPv6 addresses and CC is a country code.
-
-It also recognizes, and skips over, blank lines and lines that start
-with '#' (comments).
-
-*/
-package main
-
-import (
-	"bufio"
-	"bytes"
-	"crypto/sha1"
-	"encoding/hex"
-	"fmt"
-	"io"
-	"log"
-	"net"
-	"os"
-	"sort"
-	"strconv"
-	"strings"
-	"sync"
-)
-
-type GeoIPTable interface {
-	parseEntry(string) (*GeoIPEntry, error)
-	Len() int
-	Append(GeoIPEntry)
-	ElementAt(int) GeoIPEntry
-	Lock()
-	Unlock()
-}
-
-type GeoIPEntry struct {
-	ipLow   net.IP
-	ipHigh  net.IP
-	country string
-}
-
-type GeoIPv4Table struct {
-	table []GeoIPEntry
-
-	lock sync.Mutex // synchronization for geoip table accesses and reloads
-}
-
-type GeoIPv6Table struct {
-	table []GeoIPEntry
-
-	lock sync.Mutex // synchronization for geoip table accesses and reloads
-}
-
-func (table *GeoIPv4Table) Len() int { return len(table.table) }
-func (table *GeoIPv6Table) Len() int { return len(table.table) }
-
-func (table *GeoIPv4Table) Append(entry GeoIPEntry) {
-	(*table).table = append(table.table, entry)
-}
-func (table *GeoIPv6Table) Append(entry GeoIPEntry) {
-	(*table).table = append(table.table, entry)
-}
-
-func (table *GeoIPv4Table) ElementAt(i int) GeoIPEntry { return table.table[i] }
-func (table *GeoIPv6Table) ElementAt(i int) GeoIPEntry { return table.table[i] }
-
-func (table *GeoIPv4Table) Lock() { (*table).lock.Lock() }
-func (table *GeoIPv6Table) Lock() { (*table).lock.Lock() }
-
-func (table *GeoIPv4Table) Unlock() { (*table).lock.Unlock() }
-func (table *GeoIPv6Table) Unlock() { (*table).lock.Unlock() }
-
-// Convert a geoip IP address represented as a big-endian unsigned integer to net.IP
-func geoipStringToIP(ipStr string) (net.IP, error) {
-	ip, err := strconv.ParseUint(ipStr, 10, 32)
-	if err != nil {
-		return net.IPv4(0, 0, 0, 0), fmt.Errorf("error parsing IP %s", ipStr)
-	}
-	var bytes [4]byte
-	bytes[0] = byte(ip & 0xFF)
-	bytes[1] = byte((ip >> 8) & 0xFF)
-	bytes[2] = byte((ip >> 16) & 0xFF)
-	bytes[3] = byte((ip >> 24) & 0xFF)
-
-	return net.IPv4(bytes[3], bytes[2], bytes[1], bytes[0]), nil
-}
-
-//Parses a line in the provided geoip file that corresponds
-//to an address range and a two character country code
-func (table *GeoIPv4Table) parseEntry(candidate string) (*GeoIPEntry, error) {
-
-	if candidate[0] == '#' {
-		return nil, nil
-	}
-
-	parsedCandidate := strings.Split(candidate, ",")
-
-	if len(parsedCandidate) != 3 {
-		return nil, fmt.Errorf("provided geoip file is incorrectly formatted. Could not parse line:\n%s", parsedCandidate)
-	}
-
-	low, err := geoipStringToIP(parsedCandidate[0])
-	if err != nil {
-		return nil, err
-	}
-	high, err := geoipStringToIP(parsedCandidate[1])
-	if err != nil {
-		return nil, err
-	}
-
-	geoipEntry := &GeoIPEntry{
-		ipLow:   low,
-		ipHigh:  high,
-		country: parsedCandidate[2],
-	}
-
-	return geoipEntry, nil
-}
-
-//Parses a line in the provided geoip file that corresponds
-//to an address range and a two character country code
-func (table *GeoIPv6Table) parseEntry(candidate string) (*GeoIPEntry, error) {
-
-	if candidate[0] == '#' {
-		return nil, nil
-	}
-
-	parsedCandidate := strings.Split(candidate, ",")
-
-	if len(parsedCandidate) != 3 {
-		return nil, fmt.Errorf("")
-	}
-
-	low := net.ParseIP(parsedCandidate[0])
-	if low == nil {
-		return nil, fmt.Errorf("")
-	}
-	high := net.ParseIP(parsedCandidate[1])
-	if high == nil {
-		return nil, fmt.Errorf("")
-	}
-
-	geoipEntry := &GeoIPEntry{
-		ipLow:   low,
-		ipHigh:  high,
-		country: parsedCandidate[2],
-	}
-
-	return geoipEntry, nil
-}
-
-//Loads provided geoip file into our tables
-//Entries are stored in a table
-func GeoIPLoadFile(table GeoIPTable, pathname string) error {
-	//open file
-	geoipFile, err := os.Open(pathname)
-	if err != nil {
-		return err
-	}
-	defer geoipFile.Close()
-
-	hash := sha1.New()
-
-	table.Lock()
-	defer table.Unlock()
-
-	hashedFile := io.TeeReader(geoipFile, hash)
-
-	//read in strings and call parse function
-	scanner := bufio.NewScanner(hashedFile)
-	for scanner.Scan() {
-		entry, err := table.parseEntry(scanner.Text())
-		if err != nil {
-			return fmt.Errorf("provided geoip file is incorrectly formatted. Line is: %+q", scanner.Text())
-		}
-
-		if entry != nil {
-			table.Append(*entry)
-		}
-
-	}
-	if err := scanner.Err(); err != nil {
-		return err
-	}
-
-	sha1Hash := hex.EncodeToString(hash.Sum(nil))
-	log.Println("Using geoip file ", pathname, " with checksum", sha1Hash)
-	log.Println("Loaded ", table.Len(), " entries into table")
-
-	return nil
-}
-
-//Returns the country location of an IPv4 or IPv6 address, and a boolean value
-//that indicates whether the IP address was present in the geoip database
-func GetCountryByAddr(table GeoIPTable, ip net.IP) (string, bool) {
-
-	table.Lock()
-	defer table.Unlock()
-
-	//look IP up in database
-	index := sort.Search(table.Len(), func(i int) bool {
-		entry := table.ElementAt(i)
-		return (bytes.Compare(ip.To16(), entry.ipHigh.To16()) <= 0)
-	})
-
-	if index == table.Len() {
-		return "", false
-	}
-
-	// check to see if addr is in the range specified by the returned index
-	// search on IPs in invalid ranges (e.g., 127.0.0.0/8) will return the
-	//country code of the next highest range
-	entry := table.ElementAt(index)
-	if !(bytes.Compare(ip.To16(), entry.ipLow.To16()) >= 0 &&
-		bytes.Compare(ip.To16(), entry.ipHigh.To16()) <= 0) {
-		return "", false
-	}
-
-	return table.ElementAt(index).country, true
-
-}

broker/http.go

@@ -0,0 +1,235 @@
+package main
+
+import (
+	"errors"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+)
+
+const (
+	readLimit = 100000 // Maximum number of bytes to be read from an HTTP request
+)
+
+// Implements the http.Handler interface
+type SnowflakeHandler struct {
+	*IPC
+	handle func(*IPC, http.ResponseWriter, *http.Request)
+}
+
+func (sh SnowflakeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
+	// Return early if it's CORS preflight.
+	if "OPTIONS" == r.Method {
+		return
+	}
+	sh.handle(sh.IPC, w, r)
+}
+
+// Implements the http.Handler interface
+type MetricsHandler struct {
+	logFilename string
+	handle      func(string, http.ResponseWriter, *http.Request)
+}
+
+func (mh MetricsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
+	// Return early if it's CORS preflight.
+	if "OPTIONS" == r.Method {
+		return
+	}
+	mh.handle(mh.logFilename, w, r)
+}
+
+func robotsTxtHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	if _, err := w.Write([]byte("User-agent: *\nDisallow: /\n")); err != nil {
+		log.Printf("robotsTxtHandler unable to write, with this error: %v", err)
+	}
+}
+
+func metricsHandler(metricsFilename string, w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+
+	if metricsFilename == "" {
+		http.NotFound(w, r)
+		return
+	}
+	metricsFile, err := os.OpenFile(metricsFilename, os.O_RDONLY, 0644)
+	if err != nil {
+		log.Println("Error opening metrics file for reading")
+		http.NotFound(w, r)
+		return
+	}
+
+	if _, err := io.Copy(w, metricsFile); err != nil {
+		log.Printf("copying metricsFile returned error: %v", err)
+	}
+}
+
+func debugHandler(i *IPC, w http.ResponseWriter, r *http.Request) {
+	var response string
+
+	err := i.Debug(new(interface{}), &response)
+	if err != nil {
+		log.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if _, err := w.Write([]byte(response)); err != nil {
+		log.Printf("writing proxy information returned error: %v ", err)
+	}
+}
+
+/*
+For snowflake proxies to request a client from the Broker.
+*/
+func proxyPolls(i *IPC, w http.ResponseWriter, r *http.Request) {
+	body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
+	if err != nil {
+		log.Println("Invalid data.", err.Error())
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	arg := messages.Arg{
+		Body:       body,
+		RemoteAddr: r.RemoteAddr,
+	}
+
+	var response []byte
+	err = i.ProxyPolls(arg, &response)
+	switch {
+	case err == nil:
+	case errors.Is(err, messages.ErrBadRequest):
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	case errors.Is(err, messages.ErrInternal):
+		fallthrough
+	default:
+		log.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if _, err := w.Write(response); err != nil {
+		log.Printf("proxyPolls unable to write offer with error: %v", err)
+	}
+}
+
+/*
+Expects a WebRTC SDP offer in the Request to give to an assigned
+snowflake proxy, which responds with the SDP answer to be sent in
+the HTTP response back to the client.
+*/
+func clientOffers(i *IPC, w http.ResponseWriter, r *http.Request) {
+	body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
+	if err != nil {
+		log.Printf("Error reading client request: %s", err.Error())
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	// Handle the legacy version
+	//
+	// We support two client message formats. The legacy format is for backwards
+	// combatability and relies heavily on HTTP headers and status codes to convey
+	// information.
+	isLegacy := false
+	if len(body) > 0 && body[0] == '{' {
+		isLegacy = true
+		req := messages.ClientPollRequest{
+			Offer: string(body),
+			NAT:   r.Header.Get("Snowflake-NAT-Type"),
+		}
+		body, err = req.EncodeClientPollRequest()
+		if err != nil {
+			log.Printf("Error shimming the legacy request: %s", err.Error())
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+	}
+
+	arg := messages.Arg{
+		Body:       body,
+		RemoteAddr: "",
+	}
+
+	var response []byte
+	err = i.ClientOffers(arg, &response)
+	if err != nil {
+		log.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if isLegacy {
+		resp, err := messages.DecodeClientPollResponse(response)
+		if err != nil {
+			log.Println(err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		switch resp.Error {
+		case "":
+			response = []byte(resp.Answer)
+		case messages.StrNoProxies:
+			w.WriteHeader(http.StatusServiceUnavailable)
+			return
+		case messages.StrTimedOut:
+			w.WriteHeader(http.StatusGatewayTimeout)
+			return
+		default:
+			panic("unknown error")
+		}
+	}
+
+	if _, err := w.Write(response); err != nil {
+		log.Printf("clientOffers unable to write answer with error: %v", err)
+	}
+}
+
+/*
+Expects snowflake proxes which have previously successfully received
+an offer from proxyHandler to respond with an answer in an HTTP POST,
+which the broker will pass back to the original client.
+*/
+func proxyAnswers(i *IPC, w http.ResponseWriter, r *http.Request) {
+	body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
+	if err != nil {
+		log.Println("Invalid data.", err.Error())
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	arg := messages.Arg{
+		Body:       body,
+		RemoteAddr: "",
+	}
+
+	var response []byte
+	err = i.ProxyAnswers(arg, &response)
+	switch {
+	case err == nil:
+	case errors.Is(err, messages.ErrBadRequest):
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	case errors.Is(err, messages.ErrInternal):
+		fallthrough
+	default:
+		log.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if _, err := w.Write(response); err != nil {
+		log.Printf("proxyAnswers unable to write answer response with error: %v", err)
+	}
+}

broker/ipc.go

@@ -0,0 +1,282 @@
+package main
+
+import (
+	"container/heap"
+	"encoding/hex"
+	"fmt"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/bridgefingerprint"
+	"log"
+	"net"
+	"time"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+	ClientTimeout = 10
+	ProxyTimeout  = 10
+
+	NATUnknown      = "unknown"
+	NATRestricted   = "restricted"
+	NATUnrestricted = "unrestricted"
+)
+
+type IPC struct {
+	ctx *BrokerContext
+}
+
+func (i *IPC) Debug(_ interface{}, response *string) error {
+	var unknowns int
+	var natRestricted, natUnrestricted, natUnknown int
+	proxyTypes := make(map[string]int)
+
+	i.ctx.snowflakeLock.Lock()
+	s := fmt.Sprintf("current snowflakes available: %d\n", len(i.ctx.idToSnowflake))
+	for _, snowflake := range i.ctx.idToSnowflake {
+		if messages.KnownProxyTypes[snowflake.proxyType] {
+			proxyTypes[snowflake.proxyType]++
+		} else {
+			unknowns++
+		}
+
+		switch snowflake.natType {
+		case NATRestricted:
+			natRestricted++
+		case NATUnrestricted:
+			natUnrestricted++
+		default:
+			natUnknown++
+		}
+
+	}
+	i.ctx.snowflakeLock.Unlock()
+
+	for pType, num := range proxyTypes {
+		s += fmt.Sprintf("\t%s proxies: %d\n", pType, num)
+	}
+	s += fmt.Sprintf("\tunknown proxies: %d", unknowns)
+
+	s += fmt.Sprintf("\nNAT Types available:")
+	s += fmt.Sprintf("\n\trestricted: %d", natRestricted)
+	s += fmt.Sprintf("\n\tunrestricted: %d", natUnrestricted)
+	s += fmt.Sprintf("\n\tunknown: %d", natUnknown)
+
+	*response = s
+	return nil
+}
+
+func (i *IPC) ProxyPolls(arg messages.Arg, response *[]byte) error {
+	sid, proxyType, natType, clients, relayPattern, relayPatternSupported, err := messages.DecodeProxyPollRequestWithRelayPrefix(arg.Body)
+	if err != nil {
+		return messages.ErrBadRequest
+	}
+
+	if !relayPatternSupported {
+		i.ctx.metrics.lock.Lock()
+		i.ctx.metrics.proxyPollWithoutRelayURLExtension++
+		i.ctx.metrics.promMetrics.ProxyPollWithoutRelayURLExtensionTotal.With(prometheus.Labels{"nat": natType, "type": proxyType}).Inc()
+		i.ctx.metrics.lock.Unlock()
+	} else {
+		i.ctx.metrics.lock.Lock()
+		i.ctx.metrics.proxyPollWithRelayURLExtension++
+		i.ctx.metrics.promMetrics.ProxyPollWithRelayURLExtensionTotal.With(prometheus.Labels{"nat": natType, "type": proxyType}).Inc()
+		i.ctx.metrics.lock.Unlock()
+	}
+
+	if !i.ctx.CheckProxyRelayPattern(relayPattern, !relayPatternSupported) {
+		i.ctx.metrics.lock.Lock()
+		i.ctx.metrics.proxyPollRejectedWithRelayURLExtension++
+		i.ctx.metrics.promMetrics.ProxyPollRejectedForRelayURLExtensionTotal.With(prometheus.Labels{"nat": natType, "type": proxyType}).Inc()
+		i.ctx.metrics.lock.Unlock()
+
+		log.Printf("bad request: rejected relay pattern from proxy = %v", messages.ErrBadRequest)
+		b, err := messages.EncodePollResponseWithRelayURL("", false, "", "", "incorrect relay pattern")
+		*response = b
+		if err != nil {
+			return messages.ErrInternal
+		}
+		return nil
+	}
+
+	// Log geoip stats
+	remoteIP, _, err := net.SplitHostPort(arg.RemoteAddr)
+	if err != nil {
+		log.Println("Error processing proxy IP: ", err.Error())
+	} else {
+		i.ctx.metrics.lock.Lock()
+		i.ctx.metrics.UpdateCountryStats(remoteIP, proxyType, natType)
+		i.ctx.metrics.RecordIPAddress(remoteIP)
+		i.ctx.metrics.lock.Unlock()
+	}
+
+	var b []byte
+
+	// Wait for a client to avail an offer to the snowflake, or timeout if nil.
+	offer := i.ctx.RequestOffer(sid, proxyType, natType, clients)
+
+	if offer == nil {
+		i.ctx.metrics.lock.Lock()
+		i.ctx.metrics.proxyIdleCount++
+		i.ctx.metrics.promMetrics.ProxyPollTotal.With(prometheus.Labels{"nat": natType, "status": "idle"}).Inc()
+		i.ctx.metrics.lock.Unlock()
+
+		b, err = messages.EncodePollResponse("", false, "")
+		if err != nil {
+			return messages.ErrInternal
+		}
+
+		*response = b
+		return nil
+	}
+
+	i.ctx.metrics.promMetrics.ProxyPollTotal.With(prometheus.Labels{"nat": natType, "status": "matched"}).Inc()
+	var relayURL string
+	bridgeFingerprint, err := bridgefingerprint.FingerprintFromBytes(offer.fingerprint)
+	if err != nil {
+		return messages.ErrBadRequest
+	}
+	if info, err := i.ctx.bridgeList.GetBridgeInfo(bridgeFingerprint); err != nil {
+		return err
+	} else {
+		relayURL = info.WebSocketAddress
+	}
+	b, err = messages.EncodePollResponseWithRelayURL(string(offer.sdp), true, offer.natType, relayURL, "")
+	if err != nil {
+		return messages.ErrInternal
+	}
+	*response = b
+
+	return nil
+}
+
+func sendClientResponse(resp *messages.ClientPollResponse, response *[]byte) error {
+	data, err := resp.EncodePollResponse()
+	if err != nil {
+		log.Printf("error encoding answer")
+		return messages.ErrInternal
+	} else {
+		*response = []byte(data)
+		return nil
+	}
+}
+
+func (i *IPC) ClientOffers(arg messages.Arg, response *[]byte) error {
+	startTime := time.Now()
+
+	req, err := messages.DecodeClientPollRequest(arg.Body)
+	if err != nil {
+		return sendClientResponse(&messages.ClientPollResponse{Error: err.Error()}, response)
+	}
+
+	offer := &ClientOffer{
+		natType: req.NAT,
+		sdp:     []byte(req.Offer),
+	}
+
+	fingerprint, err := hex.DecodeString(req.Fingerprint)
+	if err != nil {
+		return sendClientResponse(&messages.ClientPollResponse{Error: err.Error()}, response)
+	}
+
+	BridgeFingerprint, err := bridgefingerprint.FingerprintFromBytes(fingerprint)
+	if err != nil {
+		return sendClientResponse(&messages.ClientPollResponse{Error: err.Error()}, response)
+	}
+
+	if _, err := i.ctx.GetBridgeInfo(BridgeFingerprint); err != nil {
+		return err
+	}
+
+	offer.fingerprint = BridgeFingerprint.ToBytes()
+
+	snowflake := i.matchSnowflake(offer.natType)
+	if snowflake != nil {
+		snowflake.offerChannel <- offer
+	} else {
+		i.ctx.metrics.lock.Lock()
+		i.ctx.metrics.clientDeniedCount++
+		i.ctx.metrics.promMetrics.ClientPollTotal.With(prometheus.Labels{"nat": offer.natType, "status": "denied"}).Inc()
+		if offer.natType == NATUnrestricted {
+			i.ctx.metrics.clientUnrestrictedDeniedCount++
+		} else {
+			i.ctx.metrics.clientRestrictedDeniedCount++
+		}
+		i.ctx.metrics.lock.Unlock()
+		resp := &messages.ClientPollResponse{Error: messages.StrNoProxies}
+		return sendClientResponse(resp, response)
+	}
+
+	// Wait for the answer to be returned on the channel or timeout.
+	select {
+	case answer := <-snowflake.answerChannel:
+		i.ctx.metrics.lock.Lock()
+		i.ctx.metrics.clientProxyMatchCount++
+		i.ctx.metrics.promMetrics.ClientPollTotal.With(prometheus.Labels{"nat": offer.natType, "status": "matched"}).Inc()
+		i.ctx.metrics.lock.Unlock()
+		resp := &messages.ClientPollResponse{Answer: answer}
+		err = sendClientResponse(resp, response)
+		// Initial tracking of elapsed time.
+		i.ctx.metrics.clientRoundtripEstimate = time.Since(startTime) / time.Millisecond
+	case <-time.After(time.Second * ClientTimeout):
+		log.Println("Client: Timed out.")
+		resp := &messages.ClientPollResponse{Error: messages.StrTimedOut}
+		err = sendClientResponse(resp, response)
+	}
+
+	i.ctx.snowflakeLock.Lock()
+	i.ctx.metrics.promMetrics.AvailableProxies.With(prometheus.Labels{"nat": snowflake.natType, "type": snowflake.proxyType}).Dec()
+	delete(i.ctx.idToSnowflake, snowflake.id)
+	i.ctx.snowflakeLock.Unlock()
+
+	return err
+}
+
+func (i *IPC) matchSnowflake(natType string) *Snowflake {
+	// Only hand out known restricted snowflakes to unrestricted clients
+	var snowflakeHeap *SnowflakeHeap
+	if natType == NATUnrestricted {
+		snowflakeHeap = i.ctx.restrictedSnowflakes
+	} else {
+		snowflakeHeap = i.ctx.snowflakes
+	}
+
+	i.ctx.snowflakeLock.Lock()
+	defer i.ctx.snowflakeLock.Unlock()
+
+	if snowflakeHeap.Len() > 0 {
+		return heap.Pop(snowflakeHeap).(*Snowflake)
+	} else {
+		return nil
+	}
+}
+
+func (i *IPC) ProxyAnswers(arg messages.Arg, response *[]byte) error {
+	answer, id, err := messages.DecodeAnswerRequest(arg.Body)
+	if err != nil || answer == "" {
+		return messages.ErrBadRequest
+	}
+
+	var success = true
+	i.ctx.snowflakeLock.Lock()
+	snowflake, ok := i.ctx.idToSnowflake[id]
+	i.ctx.snowflakeLock.Unlock()
+	if !ok || snowflake == nil {
+		// The snowflake took too long to respond with an answer, so its client
+		// disappeared / the snowflake is no longer recognized by the Broker.
+		success = false
+	}
+
+	b, err := messages.EncodeAnswerResponse(success)
+	if err != nil {
+		log.Printf("Error encoding answer: %s", err.Error())
+		return messages.ErrInternal
+	}
+	*response = b
+
+	if success {
+		snowflake.answerChannel <- answer
+	}
+
+	return nil
+}

broker/metrics.go

@@ -1,84 +1,93 @@
 /*
-We export metrics in the following format:
-
-    "snowflake-stats-end" YYYY-MM-DD HH:MM:SS (NSEC s) NL
-        [At most once.]
-
-        YYYY-MM-DD HH:MM:SS defines the end of the included measurement
-        interval of length NSEC seconds (86400 seconds by default).
-
-    "snowflake-ips" CC=NUM,CC=NUM,... NL
-        [At most once.]
-
-        List of mappings from two-letter country codes to the number of
-        unique IP addresses of snowflake proxies that have polled.
-
-    "snowflake-ips-total" NUM NL
-        [At most once.]
-
-        A count of the total number of unique IP addresses of snowflake
-        proxies that have polled.
-
-    "snowflake-idle-count" NUM NL
-        [At most once.]
-
-        A count of the number of times a proxy has polled but received
-        no client offer, rounded up to the nearest multiple of 8.
-
-    "client-denied-count" NUM NL
-        [At most once.]
-
-        A count of the number of times a client has requested a proxy
-        from the broker but no proxies were available, rounded up to
-        the nearest multiple of 8.
-
-    "client-snowflake-match-count" NUM NL
-        [At most once.]
-
-        A count of the number of times a client successfully received a
-        proxy from the broker, rounded up to the nearest multiple of 8.
+We export metrics in the format specified in our broker spec:
+https://gitweb.torproject.org/pluggable-transports/snowflake.git/tree/doc/broker-spec.txt
 */
 
 package main
 
 import (
-	// "golang.org/x/net/internal/timeseries"
 	"fmt"
 	"log"
 	"math"
 	"net"
+	"sort"
 	"sync"
 	"time"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/ipsetsink/sinkcluster"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+	"github.com/prometheus/client_golang/prometheus"
+	"gitlab.torproject.org/tpo/anti-censorship/geoip"
 )
 
-var (
-	once sync.Once
+const (
+	prometheusNamespace = "snowflake"
+	metricsResolution   = 60 * 60 * 24 * time.Second //86400 seconds
 )
 
-const metricsResolution = 60 * 60 * 24 * time.Second //86400 seconds
-
 type CountryStats struct {
-	addrs  map[string]bool
+	// map[proxyType][address]bool
+	proxies map[string]map[string]bool
+	unknown map[string]bool
+
+	natRestricted   map[string]bool
+	natUnrestricted map[string]bool
+	natUnknown      map[string]bool
+
 	counts map[string]int
 }
 
 // Implements Observable
 type Metrics struct {
 	logger  *log.Logger
-	tablev4 *GeoIPv4Table
-	tablev6 *GeoIPv6Table
+	geoipdb *geoip.Geoip
 
-	countryStats            CountryStats
-	clientRoundtripEstimate time.Duration
-	proxyIdleCount          uint
-	clientDeniedCount       uint
-	clientProxyMatchCount   uint
+	distinctIPWriter *sinkcluster.ClusterWriter
+
+	countryStats                  CountryStats
+	clientRoundtripEstimate       time.Duration
+	proxyIdleCount                uint
+	clientDeniedCount             uint
+	clientRestrictedDeniedCount   uint
+	clientUnrestrictedDeniedCount uint
+	clientProxyMatchCount         uint
+
+	proxyPollWithRelayURLExtension         uint
+	proxyPollWithoutRelayURLExtension      uint
+	proxyPollRejectedWithRelayURLExtension uint
+
+	// synchronization for access to snowflake metrics
+	lock sync.Mutex
+
+	promMetrics *PromMetrics
+}
+
+type record struct {
+	cc    string
+	count int
+}
+type records []record
+
+func (r records) Len() int      { return len(r) }
+func (r records) Swap(i, j int) { r[i], r[j] = r[j], r[i] }
+func (r records) Less(i, j int) bool {
+	if r[i].count == r[j].count {
+		return r[i].cc > r[j].cc
+	}
+	return r[i].count < r[j].count
 }
 
 func (s CountryStats) Display() string {
 	output := ""
+
+	// Use the records struct to sort our counts map by value.
+	rs := records{}
 	for cc, count := range s.counts {
-		output += fmt.Sprintf("%s=%d,", cc, count)
+		rs = append(rs, record{cc: cc, count: count})
+	}
+	sort.Sort(sort.Reverse(rs))
+	for _, r := range rs {
+		output += fmt.Sprintf("%s=%d,", r.cc, r.count)
 	}
 
 	// cut off trailing ","
@@ -89,73 +98,80 @@ func (s CountryStats) Display() string {
 	return output
 }
 
-func (m *Metrics) UpdateCountryStats(addr string) {
+func (m *Metrics) UpdateCountryStats(addr string, proxyType string, natType string) {
 
 	var country string
 	var ok bool
 
-	if m.countryStats.addrs[addr] {
-		return
+	addresses, ok := m.countryStats.proxies[proxyType]
+	if !ok {
+		if m.countryStats.unknown[addr] {
+			return
+		}
+		m.countryStats.unknown[addr] = true
+	} else {
+		if addresses[addr] {
+			return
+		}
+		addresses[addr] = true
 	}
 
 	ip := net.ParseIP(addr)
-	if ip.To4() != nil {
-		//This is an IPv4 address
-		if m.tablev4 == nil {
-			return
-		}
-		country, ok = GetCountryByAddr(m.tablev4, ip)
-	} else {
-		if m.tablev6 == nil {
-			return
-		}
-		country, ok = GetCountryByAddr(m.tablev6, ip)
+	if m.geoipdb == nil {
+		return
 	}
-
+	country, ok = m.geoipdb.GetCountryByAddr(ip)
 	if !ok {
 		country = "??"
 	}
-
-	//update map of unique ips and counts
 	m.countryStats.counts[country]++
-	m.countryStats.addrs[addr] = true
+
+	m.promMetrics.ProxyTotal.With(prometheus.Labels{
+		"nat":  natType,
+		"type": proxyType,
+		"cc":   country,
+	}).Inc()
+
+	switch natType {
+	case NATRestricted:
+		m.countryStats.natRestricted[addr] = true
+	case NATUnrestricted:
+		m.countryStats.natUnrestricted[addr] = true
+	default:
+		m.countryStats.natUnknown[addr] = true
+	}
 
 }
 
 func (m *Metrics) LoadGeoipDatabases(geoipDB string, geoip6DB string) error {
 
 	// Load geoip databases
+	var err error
 	log.Println("Loading geoip databases")
-	tablev4 := new(GeoIPv4Table)
-	err := GeoIPLoadFile(tablev4, geoipDB)
-	if err != nil {
-		m.tablev4 = nil
-		return err
-	}
-	m.tablev4 = tablev4
-
-	tablev6 := new(GeoIPv6Table)
-	err = GeoIPLoadFile(tablev6, geoip6DB)
-	if err != nil {
-		m.tablev6 = nil
-		return err
-	}
-	m.tablev6 = tablev6
-	return nil
+	m.geoipdb, err = geoip.New(geoipDB, geoip6DB)
+	return err
 }
 
 func NewMetrics(metricsLogger *log.Logger) (*Metrics, error) {
 	m := new(Metrics)
 
 	m.countryStats = CountryStats{
-		counts: make(map[string]int),
-		addrs:  make(map[string]bool),
+		counts:          make(map[string]int),
+		proxies:         make(map[string]map[string]bool),
+		unknown:         make(map[string]bool),
+		natRestricted:   make(map[string]bool),
+		natUnrestricted: make(map[string]bool),
+		natUnknown:      make(map[string]bool),
+	}
+	for pType := range messages.KnownProxyTypes {
+		m.countryStats.proxies[pType] = make(map[string]bool)
 	}
 
 	m.logger = metricsLogger
+	m.promMetrics = initPrometheus()
 
-	// Write to log file every hour with updated metrics
-	go once.Do(m.logMetrics)
+	// Write to log file every day with updated metrics
+	go m.logMetrics()
 
 	return m, nil
 }
@@ -170,24 +186,154 @@ func (m *Metrics) logMetrics() {
 }
 
 func (m *Metrics) printMetrics() {
+	m.lock.Lock()
 	m.logger.Println("snowflake-stats-end", time.Now().UTC().Format("2006-01-02 15:04:05"), fmt.Sprintf("(%d s)", int(metricsResolution.Seconds())))
 	m.logger.Println("snowflake-ips", m.countryStats.Display())
-	m.logger.Println("snowflake-ips-total", len(m.countryStats.addrs))
+	total := len(m.countryStats.unknown)
+	for pType, addresses := range m.countryStats.proxies {
+		m.logger.Printf("snowflake-ips-%s %d\n", pType, len(addresses))
+		total += len(addresses)
+	}
+	m.logger.Println("snowflake-ips-total", total)
 	m.logger.Println("snowflake-idle-count", binCount(m.proxyIdleCount))
+	m.logger.Println("snowflake-proxy-poll-with-relay-url-count", binCount(m.proxyPollWithRelayURLExtension))
+	m.logger.Println("snowflake-proxy-poll-without-relay-url-count", binCount(m.proxyPollWithoutRelayURLExtension))
+	m.logger.Println("snowflake-proxy-rejected-for-relay-url-count", binCount(m.proxyPollRejectedWithRelayURLExtension))
 	m.logger.Println("client-denied-count", binCount(m.clientDeniedCount))
+	m.logger.Println("client-restricted-denied-count", binCount(m.clientRestrictedDeniedCount))
+	m.logger.Println("client-unrestricted-denied-count", binCount(m.clientUnrestrictedDeniedCount))
 	m.logger.Println("client-snowflake-match-count", binCount(m.clientProxyMatchCount))
+	m.logger.Println("snowflake-ips-nat-restricted", len(m.countryStats.natRestricted))
+	m.logger.Println("snowflake-ips-nat-unrestricted", len(m.countryStats.natUnrestricted))
+	m.logger.Println("snowflake-ips-nat-unknown", len(m.countryStats.natUnknown))
+	m.lock.Unlock()
 }
 
 // Restores all metrics to original values
 func (m *Metrics) zeroMetrics() {
 	m.proxyIdleCount = 0
 	m.clientDeniedCount = 0
+	m.clientRestrictedDeniedCount = 0
+	m.clientUnrestrictedDeniedCount = 0
+	m.proxyPollRejectedWithRelayURLExtension = 0
+	m.proxyPollWithRelayURLExtension = 0
+	m.proxyPollWithoutRelayURLExtension = 0
 	m.clientProxyMatchCount = 0
 	m.countryStats.counts = make(map[string]int)
-	m.countryStats.addrs = make(map[string]bool)
+	for pType := range m.countryStats.proxies {
+		m.countryStats.proxies[pType] = make(map[string]bool)
+	}
+	m.countryStats.unknown = make(map[string]bool)
+	m.countryStats.natRestricted = make(map[string]bool)
+	m.countryStats.natUnrestricted = make(map[string]bool)
+	m.countryStats.natUnknown = make(map[string]bool)
 }
 
 // Rounds up a count to the nearest multiple of 8.
 func binCount(count uint) uint {
 	return uint((math.Ceil(float64(count) / 8)) * 8)
 }
+
+type PromMetrics struct {
+	registry         *prometheus.Registry
+	ProxyTotal       *prometheus.CounterVec
+	ProxyPollTotal   *RoundedCounterVec
+	ClientPollTotal  *RoundedCounterVec
+	AvailableProxies *prometheus.GaugeVec
+
+	ProxyPollWithRelayURLExtensionTotal    *RoundedCounterVec
+	ProxyPollWithoutRelayURLExtensionTotal *RoundedCounterVec
+
+	ProxyPollRejectedForRelayURLExtensionTotal *RoundedCounterVec
+}
+
+// Initialize metrics for prometheus exporter
+func initPrometheus() *PromMetrics {
+	promMetrics := &PromMetrics{}
+
+	promMetrics.registry = prometheus.NewRegistry()
+
+	promMetrics.ProxyTotal = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: prometheusNamespace,
+			Name:      "proxy_total",
+			Help:      "The number of unique snowflake IPs",
+		},
+		[]string{"type", "nat", "cc"},
+	)
+
+	promMetrics.AvailableProxies = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: prometheusNamespace,
+			Name:      "available_proxies",
+			Help:      "The number of currently available snowflake proxies",
+		},
+		[]string{"type", "nat"},
+	)
+
+	promMetrics.ProxyPollTotal = NewRoundedCounterVec(
+		prometheus.CounterOpts{
+			Namespace: prometheusNamespace,
+			Name:      "rounded_proxy_poll_total",
+			Help:      "The number of snowflake proxy polls, rounded up to a multiple of 8",
+		},
+		[]string{"nat", "status"},
+	)
+
+	promMetrics.ProxyPollWithRelayURLExtensionTotal = NewRoundedCounterVec(
+		prometheus.CounterOpts{
+			Namespace: prometheusNamespace,
+			Name:      "rounded_proxy_poll_with_relay_url_extension_total",
+			Help:      "The number of snowflake proxy polls with Relay URL Extension, rounded up to a multiple of 8",
+		},
+		[]string{"nat", "type"},
+	)
+
+	promMetrics.ProxyPollWithoutRelayURLExtensionTotal = NewRoundedCounterVec(
+		prometheus.CounterOpts{
+			Namespace: prometheusNamespace,
+			Name:      "rounded_proxy_poll_without_relay_url_extension_total",
+			Help:      "The number of snowflake proxy polls without Relay URL Extension, rounded up to a multiple of 8",
+		},
+		[]string{"nat", "type"},
+	)
+
+	promMetrics.ProxyPollRejectedForRelayURLExtensionTotal = NewRoundedCounterVec(
+		prometheus.CounterOpts{
+			Namespace: prometheusNamespace,
+			Name:      "rounded_proxy_poll_rejected_relay_url_extension_total",
+			Help:      "The number of snowflake proxy polls rejected by Relay URL Extension, rounded up to a multiple of 8",
+		},
+		[]string{"nat", "type"},
+	)
+
+	promMetrics.ClientPollTotal = NewRoundedCounterVec(
+		prometheus.CounterOpts{
+			Namespace: prometheusNamespace,
+			Name:      "rounded_client_poll_total",
+			Help:      "The number of snowflake client polls, rounded up to a multiple of 8",
+		},
+		[]string{"nat", "status"},
+	)
+
+	// We need to register our metrics so they can be exported.
+	promMetrics.registry.MustRegister(
+		promMetrics.ClientPollTotal, promMetrics.ProxyPollTotal,
+		promMetrics.ProxyTotal, promMetrics.AvailableProxies,
+		promMetrics.ProxyPollWithRelayURLExtensionTotal,
+		promMetrics.ProxyPollWithoutRelayURLExtensionTotal,
+		promMetrics.ProxyPollRejectedForRelayURLExtensionTotal,
+	)
+
+	return promMetrics
+}
+
+func (m *Metrics) RecordIPAddress(ip string) {
+	if m.distinctIPWriter != nil {
+		m.distinctIPWriter.AddIPToSet(ip)
+	}
+}
+
+func (m *Metrics) SetIPAddressRecorder(recorder *sinkcluster.ClusterWriter) {
+	m.distinctIPWriter = recorder
+}

broker/prometheus.go

@@ -0,0 +1,83 @@
+/*
+Implements some additional prometheus metrics that we need for privacy preserving
+counts of users and proxies
+*/
+
+package main
+
+import (
+	"sync/atomic"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"google.golang.org/protobuf/proto"
+)
+
+// New Prometheus counter type that produces rounded counts of metrics
+// for privacy preserving reasons
+type RoundedCounter interface {
+	prometheus.Metric
+
+	Inc()
+}
+
+type roundedCounter struct {
+	total uint64 //reflects the true count
+	value uint64 //reflects the rounded count
+
+	desc       *prometheus.Desc
+	labelPairs []*dto.LabelPair
+}
+
+// Implements the RoundedCounter interface
+func (c *roundedCounter) Inc() {
+	atomic.AddUint64(&c.total, 1)
+	if c.total > c.value {
+		atomic.AddUint64(&c.value, 8)
+	}
+}
+
+// Implements the prometheus.Metric interface
+func (c *roundedCounter) Desc() *prometheus.Desc {
+	return c.desc
+}
+
+// Implements the prometheus.Metric interface
+func (c *roundedCounter) Write(m *dto.Metric) error {
+	m.Label = c.labelPairs
+
+	m.Counter = &dto.Counter{Value: proto.Float64(float64(c.value))}
+	return nil
+}
+
+// New prometheus vector type that will track RoundedCounter metrics
+// accross multiple labels
+type RoundedCounterVec struct {
+	*prometheus.MetricVec
+}
+
+func NewRoundedCounterVec(opts prometheus.CounterOpts, labelNames []string) *RoundedCounterVec {
+	desc := prometheus.NewDesc(
+		prometheus.BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
+		opts.Help,
+		labelNames,
+		opts.ConstLabels,
+	)
+	return &RoundedCounterVec{
+		MetricVec: prometheus.NewMetricVec(desc, func(lvs ...string) prometheus.Metric {
+			if len(lvs) != len(labelNames) {
+				panic("inconsistent cardinality")
+			}
+			return &roundedCounter{desc: desc, labelPairs: prometheus.MakeLabelPairs(desc, lvs)}
+		}),
+	}
+}
+
+// Helper function to return the underlying RoundedCounter metric from MetricVec
+func (v *RoundedCounterVec) With(labels prometheus.Labels) RoundedCounter {
+	metric, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return metric.(RoundedCounter)
+}

broker/snowflake-broker_test.go

@@ -3,15 +3,18 @@ package main
 import (
 	"bytes"
 	"container/heap"
+	"encoding/hex"
+	"io"
 	"io/ioutil"
 	"log"
-	"net"
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"sync"
 	"testing"
 	"time"
 
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/amp"
 	. "github.com/smartystreets/goconvey/convey"
 )
 
@@ -21,15 +24,31 @@ func NullLogger() *log.Logger {
 	return logger
 }
 
+var promOnce sync.Once
+
+func decodeAMPArmorToString(r io.Reader) (string, error) {
+	dec, err := amp.NewArmorDecoder(r)
+	if err != nil {
+		return "", err
+	}
+	p, err := ioutil.ReadAll(dec)
+	return string(p), err
+}
+
 func TestBroker(t *testing.T) {
 
+	defaultBridgeValue, _ := hex.DecodeString("2B280B23E1107BB62ABFC40DDCC8824814F80A72")
+	var defaultBridge [20]byte
+	copy(defaultBridge[:], defaultBridgeValue)
+
 	Convey("Context", t, func() {
 		ctx := NewBrokerContext(NullLogger())
+		i := &IPC{ctx}
 
 		Convey("Adds Snowflake", func() {
 			So(ctx.snowflakes.Len(), ShouldEqual, 0)
 			So(len(ctx.idToSnowflake), ShouldEqual, 0)
-			ctx.AddSnowflake("foo")
+			ctx.AddSnowflake("foo", "", NATUnrestricted, 0)
 			So(ctx.snowflakes.Len(), ShouldEqual, 1)
 			So(len(ctx.idToSnowflake), ShouldEqual, 1)
 		})
@@ -37,7 +56,8 @@ func TestBroker(t *testing.T) {
 		Convey("Broker goroutine matches clients with proxies", func() {
 			p := new(ProxyPoll)
 			p.id = "test"
-			p.offerChannel = make(chan []byte)
+			p.natType = "unrestricted"
+			p.offerChannel = make(chan *ClientOffer)
 			go func(ctx *BrokerContext) {
 				ctx.proxyPolls <- p
 				close(ctx.proxyPolls)
@@ -45,33 +65,82 @@ func TestBroker(t *testing.T) {
 			ctx.Broker()
 			So(ctx.snowflakes.Len(), ShouldEqual, 1)
 			snowflake := heap.Pop(ctx.snowflakes).(*Snowflake)
-			snowflake.offerChannel <- []byte("test offer")
+			snowflake.offerChannel <- &ClientOffer{sdp: []byte("test offer")}
 			offer := <-p.offerChannel
 			So(ctx.idToSnowflake["test"], ShouldNotBeNil)
-			So(offer, ShouldResemble, []byte("test offer"))
+			So(offer.sdp, ShouldResemble, []byte("test offer"))
 			So(ctx.snowflakes.Len(), ShouldEqual, 0)
 		})
 
 		Convey("Request an offer from the Snowflake Heap", func() {
-			done := make(chan []byte)
+			done := make(chan *ClientOffer)
 			go func() {
-				offer := ctx.RequestOffer("test")
+				offer := ctx.RequestOffer("test", "", NATUnrestricted, 0)
 				done <- offer
 			}()
 			request := <-ctx.proxyPolls
-			request.offerChannel <- []byte("test offer")
+			request.offerChannel <- &ClientOffer{sdp: []byte("test offer")}
 			offer := <-done
-			So(offer, ShouldResemble, []byte("test offer"))
+			So(offer.sdp, ShouldResemble, []byte("test offer"))
 		})
 
-		Convey("Responds to client offers...", func() {
+		Convey("Responds to HTTP client offers...", func() {
 			w := httptest.NewRecorder()
-			data := bytes.NewReader([]byte("test"))
+			data := bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
 			r, err := http.NewRequest("POST", "snowflake.broker/client", data)
 			So(err, ShouldBeNil)
 
+			Convey("with error when no snowflakes are available.", func() {
+				clientOffers(i, w, r)
+				So(w.Code, ShouldEqual, http.StatusOK)
+				So(w.Body.String(), ShouldEqual, `{"error":"no snowflake proxies currently available"}`)
+			})
+
+			Convey("with a proxy answer if available.", func() {
+				done := make(chan bool)
+				// Prepare a fake proxy to respond with.
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
+				go func() {
+					clientOffers(i, w, r)
+					done <- true
+				}()
+				offer := <-snowflake.offerChannel
+				So(offer.sdp, ShouldResemble, []byte("fake"))
+				snowflake.answerChannel <- "fake answer"
+				<-done
+				So(w.Body.String(), ShouldEqual, `{"answer":"fake answer"}`)
+				So(w.Code, ShouldEqual, http.StatusOK)
+			})
+
+			Convey("Times out when no proxy responds.", func() {
+				if testing.Short() {
+					return
+				}
+				done := make(chan bool)
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
+				go func() {
+					clientOffers(i, w, r)
+					// Takes a few seconds here...
+					done <- true
+				}()
+				offer := <-snowflake.offerChannel
+				So(offer.sdp, ShouldResemble, []byte("fake"))
+				<-done
+				So(w.Code, ShouldEqual, http.StatusOK)
+				So(w.Body.String(), ShouldEqual, `{"error":"timed out waiting for answer!"}`)
+			})
+		})
+
+		Convey("Responds to HTTP legacy client offers...", func() {
+			w := httptest.NewRecorder()
+			data := bytes.NewReader([]byte("{test}"))
+			r, err := http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			r.Header.Set("Snowflake-NAT-TYPE", "restricted")
+
 			Convey("with 503 when no snowflakes are available.", func() {
-				clientOffers(ctx, w, r)
+				clientOffers(i, w, r)
 				So(w.Code, ShouldEqual, http.StatusServiceUnavailable)
 				So(w.Body.String(), ShouldEqual, "")
 			})
@@ -79,14 +148,14 @@ func TestBroker(t *testing.T) {
 			Convey("with a proxy answer if available.", func() {
 				done := make(chan bool)
 				// Prepare a fake proxy to respond with.
-				snowflake := ctx.AddSnowflake("fake")
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
 				go func() {
-					clientOffers(ctx, w, r)
+					clientOffers(i, w, r)
 					done <- true
 				}()
 				offer := <-snowflake.offerChannel
-				So(offer, ShouldResemble, []byte("test"))
-				snowflake.answerChannel <- []byte("fake answer")
+				So(offer.sdp, ShouldResemble, []byte("{test}"))
+				snowflake.answerChannel <- "fake answer"
 				<-done
 				So(w.Body.String(), ShouldEqual, "fake answer")
 				So(w.Code, ShouldEqual, http.StatusOK)
@@ -97,154 +166,271 @@ func TestBroker(t *testing.T) {
 					return
 				}
 				done := make(chan bool)
-				snowflake := ctx.AddSnowflake("fake")
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
 				go func() {
-					clientOffers(ctx, w, r)
+					clientOffers(i, w, r)
 					// Takes a few seconds here...
 					done <- true
 				}()
 				offer := <-snowflake.offerChannel
-				So(offer, ShouldResemble, []byte("test"))
+				So(offer.sdp, ShouldResemble, []byte("{test}"))
 				<-done
 				So(w.Code, ShouldEqual, http.StatusGatewayTimeout)
 			})
+
+		})
+
+		Convey("Responds to AMP client offers...", func() {
+			w := httptest.NewRecorder()
+			encPollReq := []byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}")
+			r, err := http.NewRequest("GET", "/amp/client/"+amp.EncodePath(encPollReq), nil)
+			So(err, ShouldBeNil)
+
+			Convey("with status 200 when request is badly formatted.", func() {
+				r, err := http.NewRequest("GET", "/amp/client/bad", nil)
+				So(err, ShouldBeNil)
+				ampClientOffers(i, w, r)
+				body, err := decodeAMPArmorToString(w.Body)
+				So(err, ShouldBeNil)
+				So(body, ShouldEqual, `{"error":"cannot decode URL path"}`)
+			})
+
+			Convey("with error when no snowflakes are available.", func() {
+				ampClientOffers(i, w, r)
+				So(w.Code, ShouldEqual, http.StatusOK)
+				body, err := decodeAMPArmorToString(w.Body)
+				So(err, ShouldBeNil)
+				So(body, ShouldEqual, `{"error":"no snowflake proxies currently available"}`)
+			})
+
+			Convey("with a proxy answer if available.", func() {
+				done := make(chan bool)
+				// Prepare a fake proxy to respond with.
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
+				go func() {
+					ampClientOffers(i, w, r)
+					done <- true
+				}()
+				offer := <-snowflake.offerChannel
+				So(offer.sdp, ShouldResemble, []byte("fake"))
+				snowflake.answerChannel <- "fake answer"
+				<-done
+				body, err := decodeAMPArmorToString(w.Body)
+				So(err, ShouldBeNil)
+				So(body, ShouldEqual, `{"answer":"fake answer"}`)
+				So(w.Code, ShouldEqual, http.StatusOK)
+			})
+
+			Convey("Times out when no proxy responds.", func() {
+				if testing.Short() {
+					return
+				}
+				done := make(chan bool)
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
+				go func() {
+					ampClientOffers(i, w, r)
+					// Takes a few seconds here...
+					done <- true
+				}()
+				offer := <-snowflake.offerChannel
+				So(offer.sdp, ShouldResemble, []byte("fake"))
+				<-done
+				So(w.Code, ShouldEqual, http.StatusOK)
+				body, err := decodeAMPArmorToString(w.Body)
+				So(err, ShouldBeNil)
+				So(body, ShouldEqual, `{"error":"timed out waiting for answer!"}`)
+			})
+
 		})
 
 		Convey("Responds to proxy polls...", func() {
 			done := make(chan bool)
 			w := httptest.NewRecorder()
-			data := bytes.NewReader([]byte("test"))
+			data := bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0"}`))
 			r, err := http.NewRequest("POST", "snowflake.broker/proxy", data)
-			r.Header.Set("X-Session-ID", "test")
 			So(err, ShouldBeNil)
 
 			Convey("with a client offer if available.", func() {
-				go func(ctx *BrokerContext) {
-					proxyPolls(ctx, w, r)
+				go func(i *IPC) {
+					proxyPolls(i, w, r)
 					done <- true
-				}(ctx)
+				}(i)
 				// Pass a fake client offer to this proxy
 				p := <-ctx.proxyPolls
-				So(p.id, ShouldEqual, "test")
-				p.offerChannel <- []byte("fake offer")
+				So(p.id, ShouldEqual, "ymbcCMto7KHNGYlp")
+				p.offerChannel <- &ClientOffer{sdp: []byte("fake offer"), fingerprint: defaultBridge[:]}
 				<-done
 				So(w.Code, ShouldEqual, http.StatusOK)
-				So(w.Body.String(), ShouldEqual, "fake offer")
+				So(w.Body.String(), ShouldEqual, `{"Status":"client match","Offer":"fake offer","NAT":"","RelayURL":"wss://snowflake.torproject.net/"}`)
 			})
 
-			Convey("times out when no client offer is available.", func() {
-				go func(ctx *BrokerContext) {
-					proxyPolls(ctx, w, r)
+			Convey("return empty 200 OK when no client offer is available.", func() {
+				go func(i *IPC) {
+					proxyPolls(i, w, r)
 					done <- true
-				}(ctx)
+				}(i)
 				p := <-ctx.proxyPolls
-				So(p.id, ShouldEqual, "test")
+				So(p.id, ShouldEqual, "ymbcCMto7KHNGYlp")
 				// nil means timeout
 				p.offerChannel <- nil
 				<-done
-				So(w.Body.String(), ShouldEqual, "")
-				So(w.Code, ShouldEqual, http.StatusGatewayTimeout)
+				So(w.Body.String(), ShouldEqual, `{"Status":"no match","Offer":"","NAT":"","RelayURL":""}`)
+				So(w.Code, ShouldEqual, http.StatusOK)
 			})
 		})
 
 		Convey("Responds to proxy answers...", func() {
-			s := ctx.AddSnowflake("test")
+			done := make(chan bool)
+			s := ctx.AddSnowflake("test", "", NATUnrestricted, 0)
 			w := httptest.NewRecorder()
-			data := bytes.NewReader([]byte("fake answer"))
+			data := bytes.NewReader([]byte(`{"Version":"1.0","Sid":"test","Answer":"test"}`))
 
 			Convey("by passing to the client if valid.", func() {
 				r, err := http.NewRequest("POST", "snowflake.broker/answer", data)
 				So(err, ShouldBeNil)
-				r.Header.Set("X-Session-ID", "test")
-				go func(ctx *BrokerContext) {
-					proxyAnswers(ctx, w, r)
-				}(ctx)
+				go func(i *IPC) {
+					proxyAnswers(i, w, r)
+					done <- true
+				}(i)
 				answer := <-s.answerChannel
+				<-done
 				So(w.Code, ShouldEqual, http.StatusOK)
-				So(answer, ShouldResemble, []byte("fake answer"))
+				So(answer, ShouldResemble, "test")
 			})
 
-			Convey("with error if the proxy is not recognized", func() {
-				r, err := http.NewRequest("POST", "snowflake.broker/answer", nil)
+			Convey("with client gone status if the proxy is not recognized", func() {
+				data = bytes.NewReader([]byte(`{"Version":"1.0","Sid":"invalid","Answer":"test"}`))
+				r, err := http.NewRequest("POST", "snowflake.broker/answer", data)
 				So(err, ShouldBeNil)
-				r.Header.Set("X-Session-ID", "invalid")
-				proxyAnswers(ctx, w, r)
-				So(w.Code, ShouldEqual, http.StatusGone)
+				proxyAnswers(i, w, r)
+				So(w.Code, ShouldEqual, http.StatusOK)
+				b, err := ioutil.ReadAll(w.Body)
+				So(err, ShouldBeNil)
+				So(b, ShouldResemble, []byte(`{"Status":"client gone"}`))
+
 			})
 
 			Convey("with error if the proxy gives invalid answer", func() {
 				data := bytes.NewReader(nil)
 				r, err := http.NewRequest("POST", "snowflake.broker/answer", data)
-				r.Header.Set("X-Session-ID", "test")
 				So(err, ShouldBeNil)
-				proxyAnswers(ctx, w, r)
+				proxyAnswers(i, w, r)
 				So(w.Code, ShouldEqual, http.StatusBadRequest)
 			})
 
 			Convey("with error if the proxy writes too much data", func() {
 				data := bytes.NewReader(make([]byte, 100001))
 				r, err := http.NewRequest("POST", "snowflake.broker/answer", data)
-				r.Header.Set("X-Session-ID", "test")
 				So(err, ShouldBeNil)
-				proxyAnswers(ctx, w, r)
+				proxyAnswers(i, w, r)
 				So(w.Code, ShouldEqual, http.StatusBadRequest)
 			})
 
 		})
+
 	})
 
 	Convey("End-To-End", t, func() {
-		done := make(chan bool)
-		polled := make(chan bool)
 		ctx := NewBrokerContext(NullLogger())
+		i := &IPC{ctx}
 
-		// Proxy polls with its ID first...
-		dataP := bytes.NewReader([]byte("test"))
-		wP := httptest.NewRecorder()
-		rP, err := http.NewRequest("POST", "snowflake.broker/proxy", dataP)
-		So(err, ShouldBeNil)
-		rP.Header.Set("X-Session-ID", "test")
-		go func() {
-			proxyPolls(ctx, wP, rP)
-			polled <- true
-		}()
+		Convey("Check for client/proxy data race", func() {
+			proxy_done := make(chan bool)
+			client_done := make(chan bool)
 
-		// Manually do the Broker goroutine action here for full control.
-		p := <-ctx.proxyPolls
-		So(p.id, ShouldEqual, "test")
-		s := ctx.AddSnowflake(p.id)
-		go func() {
-			offer := <-s.offerChannel
-			p.offerChannel <- offer
-		}()
-		So(ctx.idToSnowflake["test"], ShouldNotBeNil)
+			go ctx.Broker()
 
-		// Client request blocks until proxy answer arrives.
-		dataC := bytes.NewReader([]byte("fake offer"))
-		wC := httptest.NewRecorder()
-		rC, err := http.NewRequest("POST", "snowflake.broker/client", dataC)
-		So(err, ShouldBeNil)
-		go func() {
-			clientOffers(ctx, wC, rC)
-			done <- true
-		}()
+			// Make proxy poll
+			wp := httptest.NewRecorder()
+			datap := bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0"}`))
+			rp, err := http.NewRequest("POST", "snowflake.broker/proxy", datap)
+			So(err, ShouldBeNil)
 
-		<-polled
-		So(wP.Code, ShouldEqual, http.StatusOK)
-		So(wP.Body.String(), ShouldResemble, "fake offer")
-		So(ctx.idToSnowflake["test"], ShouldNotBeNil)
-		// Follow up with the answer request afterwards
-		wA := httptest.NewRecorder()
-		dataA := bytes.NewReader([]byte("fake answer"))
-		rA, err := http.NewRequest("POST", "snowflake.broker/proxy", dataA)
-		So(err, ShouldBeNil)
-		rA.Header.Set("X-Session-ID", "test")
-		proxyAnswers(ctx, wA, rA)
-		So(wA.Code, ShouldEqual, http.StatusOK)
+			go func(i *IPC) {
+				proxyPolls(i, wp, rp)
+				proxy_done <- true
+			}(i)
 
-		<-done
-		So(wC.Code, ShouldEqual, http.StatusOK)
-		So(wC.Body.String(), ShouldEqual, "fake answer")
+			// Client offer
+			wc := httptest.NewRecorder()
+			datac := bytes.NewReader([]byte("test"))
+			rc, err := http.NewRequest("POST", "snowflake.broker/client", datac)
+			So(err, ShouldBeNil)
+
+			go func() {
+				clientOffers(i, wc, rc)
+				client_done <- true
+			}()
+
+			<-proxy_done
+			So(wp.Code, ShouldEqual, http.StatusOK)
+
+			// Proxy answers
+			wp = httptest.NewRecorder()
+			datap = bytes.NewReader([]byte(`{"Version":"1.0","Sid":"ymbcCMto7KHNGYlp","Answer":"test"}`))
+			rp, err = http.NewRequest("POST", "snowflake.broker/answer", datap)
+			So(err, ShouldBeNil)
+			go func(i *IPC) {
+				proxyAnswers(i, wp, rp)
+				proxy_done <- true
+			}(i)
+
+			<-proxy_done
+			<-client_done
+
+		})
+
+		Convey("Ensure correct snowflake brokering", func() {
+			done := make(chan bool)
+			polled := make(chan bool)
+
+			// Proxy polls with its ID first...
+			dataP := bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0"}`))
+			wP := httptest.NewRecorder()
+			rP, err := http.NewRequest("POST", "snowflake.broker/proxy", dataP)
+			So(err, ShouldBeNil)
+			go func() {
+				proxyPolls(i, wP, rP)
+				polled <- true
+			}()
+
+			// Manually do the Broker goroutine action here for full control.
+			p := <-ctx.proxyPolls
+			So(p.id, ShouldEqual, "ymbcCMto7KHNGYlp")
+			s := ctx.AddSnowflake(p.id, "", NATUnrestricted, 0)
+			go func() {
+				offer := <-s.offerChannel
+				p.offerChannel <- offer
+			}()
+			So(ctx.idToSnowflake["ymbcCMto7KHNGYlp"], ShouldNotBeNil)
+
+			// Client request blocks until proxy answer arrives.
+			dataC := bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
+			wC := httptest.NewRecorder()
+			rC, err := http.NewRequest("POST", "snowflake.broker/client", dataC)
+			So(err, ShouldBeNil)
+			go func() {
+				clientOffers(i, wC, rC)
+				done <- true
+			}()
+
+			<-polled
+			So(wP.Code, ShouldEqual, http.StatusOK)
+			So(wP.Body.String(), ShouldResemble, `{"Status":"client match","Offer":"fake","NAT":"unknown","RelayURL":"wss://snowflake.torproject.net/"}`)
+			So(ctx.idToSnowflake["ymbcCMto7KHNGYlp"], ShouldNotBeNil)
+			// Follow up with the answer request afterwards
+			wA := httptest.NewRecorder()
+			dataA := bytes.NewReader([]byte(`{"Version":"1.0","Sid":"ymbcCMto7KHNGYlp","Answer":"test"}`))
+			rA, err := http.NewRequest("POST", "snowflake.broker/answer", dataA)
+			So(err, ShouldBeNil)
+			proxyAnswers(i, wA, rA)
+			So(wA.Code, ShouldEqual, http.StatusOK)
+
+			<-done
+			So(wC.Code, ShouldEqual, http.StatusOK)
+			So(wC.Body.String(), ShouldEqual, `{"answer":"test"}`)
+		})
 	})
 }
 
@@ -291,116 +477,25 @@ func TestSnowflakeHeap(t *testing.T) {
 	})
 }
 
-func TestGeoip(t *testing.T) {
+func TestInvalidGeoipFile(t *testing.T) {
 	Convey("Geoip", t, func() {
-		tv4 := new(GeoIPv4Table)
-		err := GeoIPLoadFile(tv4, "test_geoip")
-		So(err, ShouldEqual, nil)
-		tv6 := new(GeoIPv6Table)
-		err = GeoIPLoadFile(tv6, "test_geoip6")
-		So(err, ShouldEqual, nil)
-
-		Convey("IPv4 Country Mapping Tests", func() {
-			for _, test := range []struct {
-				addr, cc string
-				ok       bool
-			}{
-				{
-					"129.97.208.23", //uwaterloo
-					"CA",
-					true,
-				},
-				{
-					"127.0.0.1",
-					"",
-					false,
-				},
-				{
-					"255.255.255.255",
-					"",
-					false,
-				},
-				{
-					"0.0.0.0",
-					"",
-					false,
-				},
-				{
-					"223.252.127.255", //test high end of range
-					"JP",
-					true,
-				},
-				{
-					"223.252.127.255", //test low end of range
-					"JP",
-					true,
-				},
-			} {
-				country, ok := GetCountryByAddr(tv4, net.ParseIP(test.addr))
-				So(country, ShouldEqual, test.cc)
-				So(ok, ShouldResemble, test.ok)
-			}
-		})
-
-		Convey("IPv6 Country Mapping Tests", func() {
-			for _, test := range []struct {
-				addr, cc string
-				ok       bool
-			}{
-				{
-					"2620:101:f000:0:250:56ff:fe80:168e", //uwaterloo
-					"CA",
-					true,
-				},
-				{
-					"fd00:0:0:0:0:0:0:1",
-					"",
-					false,
-				},
-				{
-					"0:0:0:0:0:0:0:0",
-					"",
-					false,
-				},
-				{
-					"ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff",
-					"",
-					false,
-				},
-				{
-					"2a07:2e47:ffff:ffff:ffff:ffff:ffff:ffff", //test high end of range
-					"FR",
-					true,
-				},
-				{
-					"2a07:2e40::", //test low end of range
-					"FR",
-					true,
-				},
-			} {
-				country, ok := GetCountryByAddr(tv6, net.ParseIP(test.addr))
-				So(country, ShouldEqual, test.cc)
-				So(ok, ShouldResemble, test.ok)
-			}
-		})
-
 		// Make sure things behave properly if geoip file fails to load
 		ctx := NewBrokerContext(NullLogger())
 		if err := ctx.metrics.LoadGeoipDatabases("invalid_filename", "invalid_filename6"); err != nil {
 			log.Printf("loading geo ip databases returned error: %v", err)
 		}
-		ctx.metrics.UpdateCountryStats("127.0.0.1")
-		So(ctx.metrics.tablev4, ShouldEqual, nil)
+		ctx.metrics.UpdateCountryStats("127.0.0.1", "", NATUnrestricted)
+		So(ctx.metrics.geoipdb, ShouldEqual, nil)
 
 	})
 }
 
 func TestMetrics(t *testing.T) {
-
 	Convey("Test metrics...", t, func() {
 		done := make(chan bool)
 		buf := new(bytes.Buffer)
 		ctx := NewBrokerContext(log.New(buf, "", 0))
+		i := &IPC{ctx}
 
 		err := ctx.metrics.LoadGeoipDatabases("test_geoip", "test_geoip6")
 		So(err, ShouldEqual, nil)
@@ -408,120 +503,299 @@ func TestMetrics(t *testing.T) {
 		//Test addition of proxy polls
 		Convey("for proxy polls", func() {
 			w := httptest.NewRecorder()
-			data := bytes.NewReader([]byte("test"))
+			data := bytes.NewReader([]byte("{\"Sid\":\"ymbcCMto7KHNGYlp\",\"Version\":\"1.0\"}"))
 			r, err := http.NewRequest("POST", "snowflake.broker/proxy", data)
-			r.Header.Set("X-Session-ID", "test")
 			r.RemoteAddr = "129.97.208.23:8888" //CA geoip
 			So(err, ShouldBeNil)
-			go func(ctx *BrokerContext) {
-				proxyPolls(ctx, w, r)
+			go func(i *IPC) {
+				proxyPolls(i, w, r)
 				done <- true
-			}(ctx)
+			}(i)
 			p := <-ctx.proxyPolls //manually unblock poll
 			p.offerChannel <- nil
 			<-done
 
+			w = httptest.NewRecorder()
+			data = bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0","Type":"standalone"}`))
+			r, err = http.NewRequest("POST", "snowflake.broker/proxy", data)
+			r.RemoteAddr = "129.97.208.23:8888" //CA geoip
+			So(err, ShouldBeNil)
+			go func(i *IPC) {
+				proxyPolls(i, w, r)
+				done <- true
+			}(i)
+			p = <-ctx.proxyPolls //manually unblock poll
+			p.offerChannel <- nil
+			<-done
+
+			w = httptest.NewRecorder()
+			data = bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0","Type":"badge"}`))
+			r, err = http.NewRequest("POST", "snowflake.broker/proxy", data)
+			r.RemoteAddr = "129.97.208.23:8888" //CA geoip
+			So(err, ShouldBeNil)
+			go func(i *IPC) {
+				proxyPolls(i, w, r)
+				done <- true
+			}(i)
+			p = <-ctx.proxyPolls //manually unblock poll
+			p.offerChannel <- nil
+			<-done
+
+			w = httptest.NewRecorder()
+			data = bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0","Type":"webext"}`))
+			r, err = http.NewRequest("POST", "snowflake.broker/proxy", data)
+			r.RemoteAddr = "129.97.208.23:8888" //CA geoip
+			So(err, ShouldBeNil)
+			go func(i *IPC) {
+				proxyPolls(i, w, r)
+				done <- true
+			}(i)
+			p = <-ctx.proxyPolls //manually unblock poll
+			p.offerChannel <- nil
+			<-done
 			ctx.metrics.printMetrics()
-			So(buf.String(), ShouldResemble, "snowflake-stats-end "+time.Now().UTC().Format("2006-01-02 15:04:05")+" (86400 s)\nsnowflake-ips CA=1\nsnowflake-ips-total 1\nsnowflake-idle-count 8\nclient-denied-count 0\nclient-snowflake-match-count 0\n")
+
+			metricsStr := buf.String()
+			So(metricsStr, ShouldStartWith, "snowflake-stats-end "+time.Now().UTC().Format("2006-01-02 15:04:05")+" (86400 s)\nsnowflake-ips CA=4\n")
+			So(metricsStr, ShouldContainSubstring, "\nsnowflake-ips-standalone 1\n")
+			So(metricsStr, ShouldContainSubstring, "\nsnowflake-ips-badge 1\n")
+			So(metricsStr, ShouldContainSubstring, "\nsnowflake-ips-webext 1\n")
+			So(metricsStr, ShouldEndWith, "\nsnowflake-ips-total 4\nsnowflake-idle-count 8\nsnowflake-proxy-poll-with-relay-url-count 0\nsnowflake-proxy-poll-without-relay-url-count 8\nsnowflake-proxy-rejected-for-relay-url-count 0\nclient-denied-count 0\nclient-restricted-denied-count 0\nclient-unrestricted-denied-count 0\nclient-snowflake-match-count 0\nsnowflake-ips-nat-restricted 0\nsnowflake-ips-nat-unrestricted 0\nsnowflake-ips-nat-unknown 1\n")
 		})
 
 		//Test addition of client failures
 		Convey("for no proxies available", func() {
 			w := httptest.NewRecorder()
-			data := bytes.NewReader([]byte("test"))
+			data := bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
 			r, err := http.NewRequest("POST", "snowflake.broker/client", data)
 			So(err, ShouldBeNil)
 
-			clientOffers(ctx, w, r)
+			clientOffers(i, w, r)
 
 			ctx.metrics.printMetrics()
-			So(buf.String(), ShouldResemble, "snowflake-stats-end "+time.Now().UTC().Format("2006-01-02 15:04:05")+" (86400 s)\nsnowflake-ips \nsnowflake-ips-total 0\nsnowflake-idle-count 0\nclient-denied-count 8\nclient-snowflake-match-count 0\n")
+			So(buf.String(), ShouldContainSubstring, "client-denied-count 8\nclient-restricted-denied-count 8\nclient-unrestricted-denied-count 0\nclient-snowflake-match-count 0")
 
 			// Test reset
 			buf.Reset()
 			ctx.metrics.zeroMetrics()
 			ctx.metrics.printMetrics()
-			So(buf.String(), ShouldResemble, "snowflake-stats-end "+time.Now().UTC().Format("2006-01-02 15:04:05")+" (86400 s)\nsnowflake-ips \nsnowflake-ips-total 0\nsnowflake-idle-count 0\nclient-denied-count 0\nclient-snowflake-match-count 0\n")
+			So(buf.String(), ShouldContainSubstring, "\nsnowflake-ips \n")
+			So(buf.String(), ShouldContainSubstring, "\nsnowflake-ips-standalone 0\n")
+			So(buf.String(), ShouldContainSubstring, "\nsnowflake-ips-badge 0\n")
+			So(buf.String(), ShouldContainSubstring, "\nsnowflake-ips-webext 0\n")
+			So(buf.String(), ShouldContainSubstring, "\nsnowflake-ips-total 0\nsnowflake-idle-count 0\nsnowflake-proxy-poll-with-relay-url-count 0\nsnowflake-proxy-poll-without-relay-url-count 0\nsnowflake-proxy-rejected-for-relay-url-count 0\nclient-denied-count 0\nclient-restricted-denied-count 0\nclient-unrestricted-denied-count 0\nclient-snowflake-match-count 0\nsnowflake-ips-nat-restricted 0\nsnowflake-ips-nat-unrestricted 0\nsnowflake-ips-nat-unknown 0\n")
 		})
 		//Test addition of client matches
 		Convey("for client-proxy match", func() {
 			w := httptest.NewRecorder()
-			data := bytes.NewReader([]byte("test"))
+			data := bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
 			r, err := http.NewRequest("POST", "snowflake.broker/client", data)
 			So(err, ShouldBeNil)
 
 			// Prepare a fake proxy to respond with.
-			snowflake := ctx.AddSnowflake("fake")
+			snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
 			go func() {
-				clientOffers(ctx, w, r)
+				clientOffers(i, w, r)
 				done <- true
 			}()
 			offer := <-snowflake.offerChannel
-			So(offer, ShouldResemble, []byte("test"))
-			snowflake.answerChannel <- []byte("fake answer")
+			So(offer.sdp, ShouldResemble, []byte("fake"))
+			snowflake.answerChannel <- "fake answer"
 			<-done
 
 			ctx.metrics.printMetrics()
-			So(buf.String(), ShouldResemble, "snowflake-stats-end "+time.Now().UTC().Format("2006-01-02 15:04:05")+" (86400 s)\nsnowflake-ips \nsnowflake-ips-total 0\nsnowflake-idle-count 0\nclient-denied-count 0\nclient-snowflake-match-count 8\n")
+			So(buf.String(), ShouldContainSubstring, "client-denied-count 0\nclient-restricted-denied-count 0\nclient-unrestricted-denied-count 0\nclient-snowflake-match-count 8")
 		})
 		//Test rounding boundary
 		Convey("binning boundary", func() {
 			w := httptest.NewRecorder()
-			data := bytes.NewReader([]byte("test"))
+			data := bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
 			r, err := http.NewRequest("POST", "snowflake.broker/client", data)
 			So(err, ShouldBeNil)
 
-			clientOffers(ctx, w, r)
-			clientOffers(ctx, w, r)
-			clientOffers(ctx, w, r)
-			clientOffers(ctx, w, r)
-			clientOffers(ctx, w, r)
-			clientOffers(ctx, w, r)
-			clientOffers(ctx, w, r)
-			clientOffers(ctx, w, r)
+			clientOffers(i, w, r)
+			w = httptest.NewRecorder()
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			clientOffers(i, w, r)
+			w = httptest.NewRecorder()
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			clientOffers(i, w, r)
+			w = httptest.NewRecorder()
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			clientOffers(i, w, r)
+			w = httptest.NewRecorder()
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			clientOffers(i, w, r)
+			w = httptest.NewRecorder()
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			clientOffers(i, w, r)
+			w = httptest.NewRecorder()
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			clientOffers(i, w, r)
+			w = httptest.NewRecorder()
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			clientOffers(i, w, r)
 
 			ctx.metrics.printMetrics()
-			So(buf.String(), ShouldResemble, "snowflake-stats-end "+time.Now().UTC().Format("2006-01-02 15:04:05")+" (86400 s)\nsnowflake-ips \nsnowflake-ips-total 0\nsnowflake-idle-count 0\nclient-denied-count 8\nclient-snowflake-match-count 0\n")
+			So(buf.String(), ShouldContainSubstring, "client-denied-count 8\nclient-restricted-denied-count 8\nclient-unrestricted-denied-count 0\n")
 
-			clientOffers(ctx, w, r)
+			w = httptest.NewRecorder()
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+			clientOffers(i, w, r)
 			buf.Reset()
 			ctx.metrics.printMetrics()
-			So(buf.String(), ShouldResemble, "snowflake-stats-end "+time.Now().UTC().Format("2006-01-02 15:04:05")+" (86400 s)\nsnowflake-ips \nsnowflake-ips-total 0\nsnowflake-idle-count 0\nclient-denied-count 16\nclient-snowflake-match-count 0\n")
+			So(buf.String(), ShouldContainSubstring, "client-denied-count 16\nclient-restricted-denied-count 16\nclient-unrestricted-denied-count 0\n")
 		})
 
 		//Test unique ip
 		Convey("proxy counts by unique ip", func() {
 			w := httptest.NewRecorder()
-			data := bytes.NewReader([]byte("test"))
+			data := bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0"}`))
 			r, err := http.NewRequest("POST", "snowflake.broker/proxy", data)
-			r.Header.Set("X-Session-ID", "test")
 			r.RemoteAddr = "129.97.208.23:8888" //CA geoip
 			So(err, ShouldBeNil)
-			go func(ctx *BrokerContext) {
-				proxyPolls(ctx, w, r)
+			go func(i *IPC) {
+				proxyPolls(i, w, r)
 				done <- true
-			}(ctx)
+			}(i)
 			p := <-ctx.proxyPolls //manually unblock poll
 			p.offerChannel <- nil
 			<-done
 
-			data = bytes.NewReader([]byte("test"))
+			data = bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0"}`))
 			r, err = http.NewRequest("POST", "snowflake.broker/proxy", data)
 			if err != nil {
 				log.Printf("unable to get NewRequest with error: %v", err)
 			}
-			r.Header.Set("X-Session-ID", "test")
 			r.RemoteAddr = "129.97.208.23:8888" //CA geoip
-			go func(ctx *BrokerContext) {
-				proxyPolls(ctx, w, r)
+			go func(i *IPC) {
+				proxyPolls(i, w, r)
 				done <- true
-			}(ctx)
+			}(i)
 			p = <-ctx.proxyPolls //manually unblock poll
 			p.offerChannel <- nil
 			<-done
 
 			ctx.metrics.printMetrics()
-			So(buf.String(), ShouldResemble, "snowflake-stats-end "+time.Now().UTC().Format("2006-01-02 15:04:05")+" (86400 s)\nsnowflake-ips CA=1\nsnowflake-ips-total 1\nsnowflake-idle-count 8\nclient-denied-count 0\nclient-snowflake-match-count 0\n")
+			metricsStr := buf.String()
+			So(metricsStr, ShouldContainSubstring, "snowflake-ips CA=1\n")
+			So(metricsStr, ShouldContainSubstring, "snowflake-ips-total 1\n")
+		})
+		//Test NAT types
+		Convey("proxy counts by NAT type", func() {
+			w := httptest.NewRecorder()
+			data := bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.2","Type":"unknown","NAT":"restricted"}`))
+			r, err := http.NewRequest("POST", "snowflake.broker/proxy", data)
+			r.RemoteAddr = "129.97.208.23:8888" //CA geoip
+			So(err, ShouldBeNil)
+			go func(i *IPC) {
+				proxyPolls(i, w, r)
+				done <- true
+			}(i)
+			p := <-ctx.proxyPolls //manually unblock poll
+			p.offerChannel <- nil
+			<-done
+
+			ctx.metrics.printMetrics()
+			So(buf.String(), ShouldContainSubstring, "snowflake-ips-nat-restricted 1\nsnowflake-ips-nat-unrestricted 0\nsnowflake-ips-nat-unknown 0")
+
+			data = bytes.NewReader([]byte(`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.2","Type":"unknown","NAT":"unrestricted"}`))
+			r, err = http.NewRequest("POST", "snowflake.broker/proxy", data)
+			if err != nil {
+				log.Printf("unable to get NewRequest with error: %v", err)
+			}
+			r.RemoteAddr = "129.97.208.24:8888" //CA geoip
+			go func(i *IPC) {
+				proxyPolls(i, w, r)
+				done <- true
+			}(i)
+			p = <-ctx.proxyPolls //manually unblock poll
+			p.offerChannel <- nil
+			<-done
+
+			ctx.metrics.printMetrics()
+			So(buf.String(), ShouldContainSubstring, "snowflake-ips-nat-restricted 1\nsnowflake-ips-nat-unrestricted 1\nsnowflake-ips-nat-unknown 0")
+		})
+		//Test client failures by NAT type
+		Convey("client failures by NAT type", func() {
+			w := httptest.NewRecorder()
+			data := bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"restricted\"}"))
+			r, err := http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+
+			clientOffers(i, w, r)
+
+			ctx.metrics.printMetrics()
+			So(buf.String(), ShouldContainSubstring, "client-denied-count 8\nclient-restricted-denied-count 8\nclient-unrestricted-denied-count 0\nclient-snowflake-match-count 0")
+
+			buf.Reset()
+			ctx.metrics.zeroMetrics()
+
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unrestricted\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+
+			clientOffers(i, w, r)
+
+			ctx.metrics.printMetrics()
+			So(buf.String(), ShouldContainSubstring, "client-denied-count 8\nclient-restricted-denied-count 0\nclient-unrestricted-denied-count 8\nclient-snowflake-match-count 0")
+
+			buf.Reset()
+			ctx.metrics.zeroMetrics()
+
+			data = bytes.NewReader(
+				[]byte("1.0\n{\"offer\": \"fake\", \"nat\": \"unknown\"}"))
+			r, err = http.NewRequest("POST", "snowflake.broker/client", data)
+			So(err, ShouldBeNil)
+
+			clientOffers(i, w, r)
+
+			ctx.metrics.printMetrics()
+			So(buf.String(), ShouldContainSubstring, "client-denied-count 8\nclient-restricted-denied-count 8\nclient-unrestricted-denied-count 0\nclient-snowflake-match-count 0")
+		})
+		Convey("for country stats order", func() {
+
+			stats := map[string]int{
+				"IT": 50,
+				"FR": 200,
+				"TZ": 100,
+				"CN": 250,
+				"RU": 150,
+				"CA": 1,
+				"BE": 1,
+				"PH": 1,
+			}
+			ctx.metrics.countryStats.counts = stats
+			So(ctx.metrics.countryStats.Display(), ShouldEqual, "CN=250,FR=200,RU=150,TZ=100,IT=50,BE=1,CA=1,PH=1")
 		})
 	})
 }

broker/snowflake-heap.go

@@ -10,8 +10,10 @@ over the offer and answer channels.
 */
 type Snowflake struct {
 	id            string
-	offerChannel  chan []byte
-	answerChannel chan []byte
+	proxyType     string
+	natType       string
+	offerChannel  chan *ClientOffer
+	answerChannel chan string
 	clients       int
 	index         int
 }

client/README.md

@@ -1,20 +1,110 @@
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of Contents**
+
+- [Dependencies](#dependencies)
+- [Building the Snowflake client](#building-the-snowflake-client)
+- [Running the Snowflake client with Tor](#running-the-snowflake-client-with-tor)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
 This is the Tor client component of Snowflake.
 
-It is based on goptlib.
+It is based on the [goptlib](https://gitweb.torproject.org/pluggable-transports/goptlib.git/) pluggable transports library for Tor.
 
-### Flags
 
-The client uses these following `torrc` options by default:
+### Dependencies
+
+- Go 1.13+
+- We use the [pion/webrtc](https://github.com/pion/webrtc) library for WebRTC communication with Snowflake proxies. Note: running `go get` will fetch this dependency automatically during the build process.
+
+### Building the Snowflake client
+
+To build the Snowflake client, make sure you are in the `client/` directory, and then run:
+
 ```
+go get
+go build
+```
+
+### Running the Snowflake client with Tor
+
+The Snowflake client can be configured with either command line options or SOCKS options. We have a few example `torrc` files in this directory. We recommend the following `torrc` options by default:
+```
+UseBridges 1
+
 ClientTransportPlugin snowflake exec ./client \
--url https://snowflake-broker.azureedge.net/ \
--front ajax.aspnetcdn.com \
--ice stun:stun.l.google.com:19302
+-url https://snowflake-broker.torproject.net.global.prod.fastly.net/ \
+-front cdn.sstatic.net \
+-ice stun:stun.voip.blackberry.com:3478,stun:stun.altar.com.pl:3478,stun:stun.antisip.com:3478,stun:stun.bluesip.net:3478,stun:stun.dus.net:3478,stun:stun.epygi.com:3478,stun:stun.sonetel.com:3478,stun:stun.sonetel.net:3478,stun:stun.stunprotocol.org:3478,stun:stun.uls.co.za:3478,stun:stun.voipgate.com:3478,stun:stun.voys.nl:3478
+
+Bridge snowflake 192.0.2.3:1
 ```
 
-`-url` should be the URL of a Broker instance.
+`-url` is the URL of a broker instance. If you would like to try out Snowflake with your own broker, simply provide the URL of your broker instance with this option.
 
-`-front` is an optional front domain for the Broker request.
+`-front` is an optional front domain for the broker request.
 
-`-ice` is a comma-separated list of ICE servers. These can be STUN or TURN
-servers.
+`-ice` is a comma-separated list of ICE servers. These can be STUN or TURN servers. We recommend using servers that have implemented NAT discovery. See our wiki page on [NAT traversal](https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/wikis/NAT-matching) for more information.
+
+To bootstrap Tor, run:
+```
+tor -f torrc
+```
+This should start the client plugin, bootstrapping to 100% using WebRTC.
+
+### Registration methods
+
+The Snowflake client supports a few different ways of communicating with the broker.
+This initial step is sometimes called rendezvous.
+
+#### Domain fronting HTTPS
+
+For domain fronting rendezvous, use the `-url` and `-front` command-line options together.
+[Domain fronting](https://www.bamsoftware.com/papers/fronting/)
+hides the externally visible domain name from an external observer,
+making it appear that the Snowflake client is communicating with some server
+other than the Snowflake broker.
+
+* `-url` is the HTTPS URL of a forwarder to the broker, on some service that supports domain fronting, such as a CDN.
+* `-front` is the domain name to show externally. It must be another domain on the same service.
+
+Example:
+```
+-url https://snowflake-broker.torproject.net.global.prod.fastly.net/ \
+-front cdn.sstatic.net \
+```
+
+#### AMP cache
+
+For AMP cache rendezvous, use the `-url`, `-ampcache`, and `-front` command-line options together.
+[AMP](https://amp.dev/documentation/) is a standard for web pages for mobile computers.
+An [AMP cache](https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/how_amp_pages_are_cached/)
+is a cache and proxy specialized for AMP pages.
+The Snowflake broker has the ability to make its client registration responses look like AMP pages,
+so it can be accessed through an AMP cache.
+When you use AMP cache rendezvous, it appears to an observer that the Snowflake client
+is accessing an AMP cache, or some other domain operated by the same organization.
+You still need to use the `-front` command-line option, because the
+[format of AMP cache URLs](https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/)
+would otherwise reveal the domain name of the broker.
+
+There is only one AMP cache that works with this option,
+the Google AMP cache at https://cdn.ampproject.org/.
+
+* `-url` is the HTTPS URL of the broker.
+* `-ampcache` is `https://cdn.ampproject.org/`.
+* `-front` is any Google domain, such as `www.google.com`.
+
+Example:
+```
+-url https://snowflake-broker.torproject.net/ \
+-ampcache https://cdn.ampproject.org/ \
+-front www.google.com \
+```
+
+#### Direct access
+
+It is also possible to access the broker directly using HTTPS, without domain fronting,
+for testing purposes. This mode is not suitable for circumvention, because the
+broker is easily blocked by its address.

client/lib/interfaces.go

@@ -1,56 +1,24 @@
-package lib
+package snowflake_client
 
-import (
-	"io"
-	"net"
-)
-
-type Connector interface {
-	Connect() error
-}
-
-type Resetter interface {
-	Reset()
-	WaitForReset()
-}
-
-// Interface for a single remote WebRTC peer.
-// In the Client context, "Snowflake" refers to the remote browser proxy.
-type Snowflake interface {
-	io.ReadWriteCloser
-	Resetter
-	Connector
-}
-
-// Interface for catching Snowflakes. (aka the remote dialer)
+// Tongue is an interface for catching Snowflakes. (aka the remote dialer)
 type Tongue interface {
-	Catch() (Snowflake, error)
+	// Catch makes a connection to a new snowflake.
+	Catch() (*WebRTCPeer, error)
+
+	// GetMax returns the maximum number of snowflakes a client can have.
+	GetMax() int
 }
 
-// Interface for collecting some number of Snowflakes, for passing along
-// ultimately to the SOCKS handler.
+// SnowflakeCollector is an interface for managing a client's collection of snowflakes.
 type SnowflakeCollector interface {
+	// Collect adds a snowflake to the collection.
+	// The implementation of Collect should decide how to connect to and maintain
+	// the connection to the WebRTCPeer.
+	Collect() (*WebRTCPeer, error)
 
-	// Add a Snowflake to the collection.
-	// Implementation should decide how to connect and maintain the webRTCConn.
-	Collect() (Snowflake, error)
+	// Pop removes and returns the most available snowflake from the collection.
+	Pop() *WebRTCPeer
 
-	// Remove and return the most available Snowflake from the collection.
-	Pop() Snowflake
-
-	// Signal when the collector has stopped collecting.
+	// Melted returns a channel that will signal when the collector has stopped.
 	Melted() <-chan struct{}
 }
-
-// Interface to adapt to goptlib's SocksConn struct.
-type SocksConnector interface {
-	Grant(*net.TCPAddr) error
-	Reject() error
-	net.Conn
-}
-
-// Interface for the Snowflake's transport. (Typically just webrtc.DataChannel)
-type SnowflakeDataChannel interface {
-	io.Closer
-	Send([]byte) error
-}

client/lib/lib_test.go

@@ -1,58 +1,26 @@
-package lib
+package snowflake_client
 
 import (
-	"bytes"
 	"fmt"
-	"io/ioutil"
 	"net"
-	"net/http"
 	"testing"
+	"time"
 
-	"github.com/pion/webrtc"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/event"
 	. "github.com/smartystreets/goconvey/convey"
 )
 
-type MockDataChannel struct {
-	destination bytes.Buffer
-	done        chan bool
+type FakeDialer struct {
+	max int
 }
 
-func (m *MockDataChannel) Send(data []byte) error {
-	m.destination.Write(data)
-	m.done <- true
-	return nil
-}
-
-func (*MockDataChannel) Close() error { return nil }
-
-type MockResponse struct{}
-
-func (m *MockResponse) Read(p []byte) (int, error) {
-	p = []byte(`{"type":"answer","sdp":"fake"}`)
-	return 0, nil
-}
-func (m *MockResponse) Close() error { return nil }
-
-type MockTransport struct {
-	statusOverride int
-	body           []byte
-}
-
-// Just returns a response with fake SDP answer.
-func (m *MockTransport) RoundTrip(req *http.Request) (*http.Response, error) {
-	s := ioutil.NopCloser(bytes.NewReader(m.body))
-	r := &http.Response{
-		StatusCode: m.statusOverride,
-		Body:       s,
-	}
-	return r, nil
-}
-
-type FakeDialer struct{}
-
-func (w FakeDialer) Catch() (Snowflake, error) {
+func (w FakeDialer) Catch() (*WebRTCPeer, error) {
 	fmt.Println("Caught a dummy snowflake.")
-	return &WebRTCPeer{}, nil
+	return &WebRTCPeer{closed: make(chan struct{})}, nil
+}
+
+func (w FakeDialer) GetMax() int {
+	return w.max
 }
 
 type FakeSocksConn struct {
@@ -66,29 +34,23 @@ func (f FakeSocksConn) Reject() error {
 }
 func (f FakeSocksConn) Grant(addr *net.TCPAddr) error { return nil }
 
-type FakePeers struct{ toRelease *WebRTCPeer }
-
-func (f FakePeers) Collect() (Snowflake, error) { return &WebRTCPeer{}, nil }
-func (f FakePeers) Pop() Snowflake              { return nil }
-func (f FakePeers) Melted() <-chan struct{}     { return nil }
-
 func TestSnowflakeClient(t *testing.T) {
 
 	Convey("Peers", t, func() {
 		Convey("Can construct", func() {
-			p := NewPeers(1)
-			So(p.capacity, ShouldEqual, 1)
+			d := &FakeDialer{max: 1}
+			p, _ := NewPeers(d)
+			So(p.Tongue.GetMax(), ShouldEqual, 1)
 			So(p.snowflakeChan, ShouldNotBeNil)
 			So(cap(p.snowflakeChan), ShouldEqual, 1)
 		})
 
 		Convey("Collecting a Snowflake requires a Tongue.", func() {
-			p := NewPeers(1)
-			_, err := p.Collect()
+			p, err := NewPeers(nil)
 			So(err, ShouldNotBeNil)
-			So(p.Count(), ShouldEqual, 0)
 			// Set the dialer so that collection is possible.
-			p.Tongue = FakeDialer{}
+			d := &FakeDialer{max: 1}
+			p, err = NewPeers(d)
 			_, err = p.Collect()
 			So(err, ShouldBeNil)
 			So(p.Count(), ShouldEqual, 1)
@@ -98,8 +60,7 @@ func TestSnowflakeClient(t *testing.T) {
 
 		Convey("Collection continues until capacity.", func() {
 			c := 5
-			p := NewPeers(c)
-			p.Tongue = FakeDialer{}
+			p, _ := NewPeers(FakeDialer{max: c})
 			// Fill up to capacity.
 			for i := 0; i < c; i++ {
 				fmt.Println("Adding snowflake ", i)
@@ -113,7 +74,7 @@ func TestSnowflakeClient(t *testing.T) {
 			So(err, ShouldNotBeNil)
 			So(p.Count(), ShouldEqual, c)
 
-			// But popping and closing allows it to continue.
+			// But popping allows it to continue.
 			s := p.Pop()
 			s.Close()
 			So(s, ShouldNotBeNil)
@@ -125,8 +86,7 @@ func TestSnowflakeClient(t *testing.T) {
 		})
 
 		Convey("Count correctly purges peers marked for deletion.", func() {
-			p := NewPeers(4)
-			p.Tongue = FakeDialer{}
+			p, _ := NewPeers(FakeDialer{max: 5})
 			p.Collect()
 			p.Collect()
 			p.Collect()
@@ -142,9 +102,9 @@ func TestSnowflakeClient(t *testing.T) {
 
 		Convey("End Closes all peers.", func() {
 			cnt := 5
-			p := NewPeers(cnt)
+			p, _ := NewPeers(FakeDialer{max: cnt})
 			for i := 0; i < cnt; i++ {
-				p.activePeers.PushBack(&WebRTCPeer{})
+				p.activePeers.PushBack(&WebRTCPeer{closed: make(chan struct{})})
 			}
 			So(p.Count(), ShouldEqual, cnt)
 			p.End()
@@ -153,8 +113,7 @@ func TestSnowflakeClient(t *testing.T) {
 		})
 
 		Convey("Pop skips over closed peers.", func() {
-			p := NewPeers(4)
-			p.Tongue = FakeDialer{}
+			p, _ := NewPeers(FakeDialer{max: 4})
 			wc1, _ := p.Collect()
 			wc2, _ := p.Collect()
 			wc3, _ := p.Collect()
@@ -172,162 +131,95 @@ func TestSnowflakeClient(t *testing.T) {
 			So(r, ShouldEqual, wc4)
 		})
 
-	})
+		Convey("Terminate Connect() loop", func() {
+			p, _ := NewPeers(FakeDialer{max: 4})
+			go func() {
+				for {
+					p.Collect()
+					select {
+					case <-p.Melted():
+						return
+					default:
+					}
+				}
+			}()
+			<-time.After(10 * time.Second)
 
-	Convey("Snowflake", t, func() {
-
-		SkipConvey("Handler Grants correctly", func() {
-			socks := &FakeSocksConn{}
-			snowflakes := &FakePeers{}
-
-			So(socks.rejected, ShouldEqual, false)
-			snowflakes.toRelease = nil
-			Handler(socks, snowflakes)
-			So(socks.rejected, ShouldEqual, true)
+			p.End()
+			<-p.Melted()
+			So(p.Count(), ShouldEqual, 0)
 		})
 
-		Convey("WebRTC Connection", func() {
-			c := NewWebRTCPeer(nil, nil)
-			So(c.buffer.Bytes(), ShouldEqual, nil)
-
-			Convey("Can construct a WebRTCConn", func() {
-				s := NewWebRTCPeer(nil, nil)
-				So(s, ShouldNotBeNil)
-				So(s.offerChannel, ShouldNotBeNil)
-				So(s.answerChannel, ShouldNotBeNil)
-				s.Close()
-			})
-
-			Convey("Write buffers when datachannel is nil", func() {
-				c.Write([]byte("test"))
-				c.transport = nil
-				So(c.buffer.Bytes(), ShouldResemble, []byte("test"))
-			})
-
-			Convey("Write sends to datachannel when not nil", func() {
-				mock := new(MockDataChannel)
-				c.transport = mock
-				mock.done = make(chan bool, 1)
-				c.Write([]byte("test"))
-				<-mock.done
-				So(c.buffer.Bytes(), ShouldEqual, nil)
-				So(mock.destination.Bytes(), ShouldResemble, []byte("test"))
-			})
-
-			Convey("Exchange SDP sets remote description", func() {
-				c.offerChannel = make(chan *webrtc.SessionDescription, 1)
-				c.answerChannel = make(chan *webrtc.SessionDescription, 1)
-
-				c.config = &webrtc.Configuration{}
-				c.preparePeerConnection()
-
-				c.offerChannel <- nil
-				answer := deserializeSessionDescription(
-					`{"type":"answer","sdp":""}`)
-				c.answerChannel <- answer
-				c.exchangeSDP()
-			})
-
-			SkipConvey("Exchange SDP fails on nil answer", func() {
-				c.reset = make(chan struct{})
-				c.offerChannel = make(chan *webrtc.SessionDescription, 1)
-				c.answerChannel = make(chan *webrtc.SessionDescription, 1)
-				c.offerChannel <- nil
-				c.answerChannel <- nil
-				c.exchangeSDP()
-				<-c.reset
-			})
-
-		})
 	})
 
 	Convey("Dialers", t, func() {
 		Convey("Can construct WebRTCDialer.", func() {
-			broker := &BrokerChannel{Host: "test"}
-			d := NewWebRTCDialer(broker, nil)
+			broker := &BrokerChannel{}
+			d := NewWebRTCDialer(broker, nil, 1)
 			So(d, ShouldNotBeNil)
 			So(d.BrokerChannel, ShouldNotBeNil)
-			So(d.BrokerChannel.Host, ShouldEqual, "test")
-		})
-		Convey("WebRTCDialer cannot Catch a snowflake with nil broker.", func() {
-			d := NewWebRTCDialer(nil, nil)
-			conn, err := d.Catch()
-			So(conn, ShouldBeNil)
-			So(err, ShouldNotBeNil)
 		})
 		SkipConvey("WebRTCDialer can Catch a snowflake.", func() {
-			broker := &BrokerChannel{Host: "test"}
-			d := NewWebRTCDialer(broker, nil)
+			broker := &BrokerChannel{}
+			d := NewWebRTCDialer(broker, nil, 1)
 			conn, err := d.Catch()
 			So(conn, ShouldBeNil)
 			So(err, ShouldNotBeNil)
 		})
 	})
 
-	Convey("Rendezvous", t, func() {
-		transport := &MockTransport{
-			http.StatusOK,
-			[]byte(`{"type":"answer","sdp":"fake"}`),
-		}
-		fakeOffer := deserializeSessionDescription(`{"type":"offer","sdp":"test"}`)
+}
 
-		Convey("Construct BrokerChannel with no front domain", func() {
-			b := NewBrokerChannel("test.broker", "", transport)
-			So(b.url, ShouldNotBeNil)
-			So(b.url.Path, ShouldResemble, "test.broker")
-			So(b.transport, ShouldNotBeNil)
-		})
-
-		Convey("Construct BrokerChannel *with* front domain", func() {
-			b := NewBrokerChannel("test.broker", "front", transport)
-			So(b.url, ShouldNotBeNil)
-			So(b.url.Path, ShouldResemble, "test.broker")
-			So(b.url.Host, ShouldResemble, "front")
-			So(b.transport, ShouldNotBeNil)
-		})
-
-		Convey("BrokerChannel.Negotiate responds with answer", func() {
-			b := NewBrokerChannel("test.broker", "", transport)
-			answer, err := b.Negotiate(fakeOffer)
-			So(err, ShouldBeNil)
-			So(answer, ShouldNotBeNil)
-			So(answer.SDP, ShouldResemble, "fake")
-		})
-
-		Convey("BrokerChannel.Negotiate fails with 503", func() {
-			b := NewBrokerChannel("test.broker", "",
-				&MockTransport{http.StatusServiceUnavailable, []byte("\n")})
-			answer, err := b.Negotiate(fakeOffer)
-			So(err, ShouldNotBeNil)
-			So(answer, ShouldBeNil)
-			So(err.Error(), ShouldResemble, BrokerError503)
-		})
-
-		Convey("BrokerChannel.Negotiate fails with 400", func() {
-			b := NewBrokerChannel("test.broker", "",
-				&MockTransport{http.StatusBadRequest, []byte("\n")})
-			answer, err := b.Negotiate(fakeOffer)
-			So(err, ShouldNotBeNil)
-			So(answer, ShouldBeNil)
-			So(err.Error(), ShouldResemble, BrokerError400)
-		})
-
-		Convey("BrokerChannel.Negotiate fails with large read", func() {
-			b := NewBrokerChannel("test.broker", "",
-				&MockTransport{http.StatusOK, make([]byte, 100001, 100001)})
-			answer, err := b.Negotiate(fakeOffer)
-			So(err, ShouldNotBeNil)
-			So(answer, ShouldBeNil)
-			So(err.Error(), ShouldResemble, "unexpected EOF")
-		})
-
-		Convey("BrokerChannel.Negotiate fails with unexpected error", func() {
-			b := NewBrokerChannel("test.broker", "",
-				&MockTransport{123, []byte("")})
-			answer, err := b.Negotiate(fakeOffer)
-			So(err, ShouldNotBeNil)
-			So(answer, ShouldBeNil)
-			So(err.Error(), ShouldResemble, BrokerErrorUnexpected)
+func TestWebRTCPeer(t *testing.T) {
+	Convey("WebRTCPeer", t, func(c C) {
+		p := &WebRTCPeer{closed: make(chan struct{}),
+			eventsLogger: event.NewSnowflakeEventDispatcher()}
+		Convey("checks for staleness", func() {
+			go p.checkForStaleness(time.Second)
+			<-time.After(2 * time.Second)
+			So(p.Closed(), ShouldEqual, true)
 		})
 	})
 }
+
+func TestICEServerParser(t *testing.T) {
+	Convey("Test parsing of ICE servers", t, func() {
+		for _, test := range []struct {
+			input  []string
+			urls   [][]string
+			length int
+		}{
+			{
+				[]string{"stun:stun.l.google.com:19302"},
+				[][]string{[]string{"stun:stun.l.google.com:19302"}},
+				1,
+			},
+			{
+				[]string{"stun:stun.l.google.com:19302", "stun.ekiga.net"},
+				[][]string{[]string{"stun:stun.l.google.com:19302"}, []string{"stun.ekiga.net"}},
+				2,
+			},
+			{
+				[]string{"stun:stun.l.google.com:19302", "stun.ekiga.net"},
+				[][]string{[]string{"stun:stun.l.google.com:19302"}, []string{"stun.ekiga.net"}},
+				2,
+			},
+		} {
+			servers := parseIceServers(test.input)
+
+			if test.urls == nil {
+				So(servers, ShouldBeNil)
+			} else {
+				So(servers, ShouldNotBeNil)
+			}
+
+			So(len(servers), ShouldEqual, test.length)
+
+			for _, server := range servers {
+				So(test.urls, ShouldContain, server.URLs)
+			}
+
+		}
+
+	})
+}

client/lib/peers.go

@@ -1,13 +1,14 @@
-package lib
+package snowflake_client
 
 import (
 	"container/list"
 	"errors"
 	"fmt"
 	"log"
+	"sync"
 )
 
-// Container which keeps track of multiple WebRTC remote peers.
+// Peers is a container that keeps track of multiple WebRTC remote peers.
 // Implements |SnowflakeCollector|.
 //
 // Maintaining a set of pre-connected Peers with fresh but inactive datachannels
@@ -20,38 +21,50 @@ import (
 // version of Snowflake)
 type Peers struct {
 	Tongue
-	BytesLogger
+	bytesLogger bytesLogger
 
-	snowflakeChan chan Snowflake
+	snowflakeChan chan *WebRTCPeer
 	activePeers   *list.List
-	capacity      int
 
 	melt chan struct{}
+
+	collectLock sync.Mutex
 }
 
-// Construct a fresh container of remote peers.
-func NewPeers(max int) *Peers {
-	p := &Peers{capacity: max}
+// NewPeers constructs a fresh container of remote peers.
+func NewPeers(tongue Tongue) (*Peers, error) {
+	p := &Peers{}
 	// Use buffered go channel to pass snowflakes onwards to the SOCKS handler.
-	p.snowflakeChan = make(chan Snowflake, max)
+	if tongue == nil {
+		return nil, errors.New("missing Tongue to catch Snowflakes with")
+	}
+	p.snowflakeChan = make(chan *WebRTCPeer, tongue.GetMax())
 	p.activePeers = list.New()
-	p.melt = make(chan struct{}, 1)
-	return p
+	p.melt = make(chan struct{})
+	p.Tongue = tongue
+	return p, nil
 }
 
-// As part of |SnowflakeCollector| interface.
-func (p *Peers) Collect() (Snowflake, error) {
-	cnt := p.Count()
-	s := fmt.Sprintf("Currently at [%d/%d]", cnt, p.capacity)
-	if cnt >= p.capacity {
-		s = fmt.Sprintf("At capacity [%d/%d]", cnt, p.capacity)
-		return nil, errors.New(s)
-	}
-	log.Println("WebRTC: Collecting a new Snowflake.", s)
+// Collect connects to and adds a new remote peer as part of |SnowflakeCollector| interface.
+func (p *Peers) Collect() (*WebRTCPeer, error) {
 	// Engage the Snowflake Catching interface, which must be available.
+	p.collectLock.Lock()
+	defer p.collectLock.Unlock()
+	select {
+	case <-p.melt:
+		return nil, fmt.Errorf("Snowflakes have melted")
+	default:
+	}
 	if nil == p.Tongue {
 		return nil, errors.New("missing Tongue to catch Snowflakes with")
 	}
+	cnt := p.Count()
+	capacity := p.Tongue.GetMax()
+	s := fmt.Sprintf("Currently at [%d/%d]", cnt, capacity)
+	if cnt >= capacity {
+		return nil, fmt.Errorf("At capacity [%d/%d]", cnt, capacity)
+	}
+	log.Println("WebRTC: Collecting a new Snowflake.", s)
 	// BUG: some broker conflict here.
 	connection, err := p.Tongue.Catch()
 	if nil != err {
@@ -63,32 +76,30 @@ func (p *Peers) Collect() (Snowflake, error) {
 	return connection, nil
 }
 
-// As part of |SnowflakeCollector| interface.
-func (p *Peers) Pop() Snowflake {
-	// Blocks until an available, valid snowflake appears.
-	var snowflake Snowflake
-	var ok bool
-	for nil == snowflake {
-		snowflake, ok = <-p.snowflakeChan
-		conn := snowflake.(*WebRTCPeer)
+// Pop blocks until an available, valid snowflake appears.
+// Pop will return nil after End has been called.
+func (p *Peers) Pop() *WebRTCPeer {
+	for {
+		snowflake, ok := <-p.snowflakeChan
 		if !ok {
 			return nil
 		}
-		if conn.closed {
-			snowflake = nil
+		if snowflake.Closed() {
+			continue
 		}
+		// Set to use the same rate-limited traffic logger to keep consistency.
+		snowflake.bytesLogger = p.bytesLogger
+		return snowflake
 	}
-	// Set to use the same rate-limited traffic logger to keep consistency.
-	snowflake.(*WebRTCPeer).BytesLogger = p.BytesLogger
-	return snowflake
 }
 
-// As part of |SnowflakeCollector| interface.
+// Melted returns a channel that will close when peers stop being collected.
+// Melted is a necessary part of |SnowflakeCollector| interface.
 func (p *Peers) Melted() <-chan struct{} {
 	return p.melt
 }
 
-// Returns total available Snowflakes (including the active one)
+// Count returns the total available Snowflakes (including the active ones)
 // The count only reduces when connections themselves close, rather than when
 // they are popped.
 func (p *Peers) Count() int {
@@ -101,17 +112,20 @@ func (p *Peers) purgeClosedPeers() {
 		next := e.Next()
 		conn := e.Value.(*WebRTCPeer)
 		// Purge those marked for deletion.
-		if conn.closed {
+		if conn.Closed() {
 			p.activePeers.Remove(e)
 		}
 		e = next
 	}
 }
 
-// Close all Peers contained here.
+// End closes all active connections to Peers contained here, and stops the
+// collection of future Peers.
 func (p *Peers) End() {
+	close(p.melt)
+	p.collectLock.Lock()
+	defer p.collectLock.Unlock()
 	close(p.snowflakeChan)
-	p.melt <- struct{}{}
 	cnt := p.Count()
 	for e := p.activePeers.Front(); e != nil; {
 		next := e.Next()
@@ -120,5 +134,5 @@ func (p *Peers) End() {
 		p.activePeers.Remove(e)
 		e = next
 	}
-	log.Println("WebRTC: melted all", cnt, "snowflakes.")
+	log.Printf("WebRTC: melted all %d snowflakes.", cnt)
 }

client/lib/rendezvous.go

@@ -1,154 +1,195 @@
 // WebRTC rendezvous requires the exchange of SessionDescriptions between
 // peers in order to establish a PeerConnection.
-//
-// This file contains the one method currently available to Snowflake:
-//
-// - Domain-fronted HTTP signaling. The Broker automatically exchange offers
-//   and answers between this client and some remote WebRTC proxy.
 
-package lib
+package snowflake_client
 
 import (
-	"bytes"
 	"errors"
-	"io"
-	"io/ioutil"
+	"fmt"
+
 	"log"
 	"net/http"
-	"net/url"
+	"sync"
+	"time"
 
-	"github.com/pion/webrtc"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/event"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/nat"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/util"
+	utlsutil "git.torproject.org/pluggable-transports/snowflake.git/v2/common/utls"
+	"github.com/pion/webrtc/v3"
+	utls "github.com/refraction-networking/utls"
 )
 
 const (
-	BrokerError503        string = "No snowflake proxies currently available."
-	BrokerError400        string = "You sent an invalid offer in the request."
-	BrokerErrorUnexpected string = "Unexpected error, no answer."
+	brokerErrorUnexpected string = "Unexpected error, no answer."
 	readLimit                    = 100000 //Maximum number of bytes to be read from an HTTP response
 )
 
-// Signalling Channel to the Broker.
+// RendezvousMethod represents a way of communicating with the broker: sending
+// an encoded client poll request (SDP offer) and receiving an encoded client
+// poll response (SDP answer) in return. RendezvousMethod is used by
+// BrokerChannel, which is in charge of encoding and decoding, and all other
+// tasks that are independent of the rendezvous method.
+type RendezvousMethod interface {
+	Exchange([]byte) ([]byte, error)
+}
+
+// BrokerChannel uses a RendezvousMethod to communicate with the Snowflake broker.
+// The BrokerChannel is responsible for encoding and decoding SDP offers and answers;
+// RendezvousMethod is responsible for the exchange of encoded information.
 type BrokerChannel struct {
-	// The Host header to put in the HTTP request (optional and may be
-	// different from the host name in URL).
-	Host      string
-	url       *url.URL
-	transport http.RoundTripper // Used to make all requests.
+	Rendezvous         RendezvousMethod
+	keepLocalAddresses bool
+	natType            string
+	lock               sync.Mutex
+	BridgeFingerprint  string
 }
 
 // We make a copy of DefaultTransport because we want the default Dial
 // and TLSHandshakeTimeout settings. But we want to disable the default
 // ProxyFromEnvironment setting.
-func CreateBrokerTransport() http.RoundTripper {
+func createBrokerTransport() http.RoundTripper {
 	transport := http.DefaultTransport.(*http.Transport)
 	transport.Proxy = nil
+	transport.ResponseHeaderTimeout = 15 * time.Second
 	return transport
 }
 
-// Construct a new BrokerChannel, where:
-// |broker| is the full URL of the facilitating program which assigns proxies
-// to clients, and |front| is the option fronting domain.
-func NewBrokerChannel(broker string, front string, transport http.RoundTripper) *BrokerChannel {
-	targetURL, err := url.Parse(broker)
-	if nil != err {
-		return nil
-	}
-	log.Println("Rendezvous using Broker at:", broker)
-	bc := new(BrokerChannel)
-	bc.url = targetURL
-	if "" != front { // Optional front domain.
-		log.Println("Domain fronting using:", front)
-		bc.Host = bc.url.Host
-		bc.url.Host = front
+func newBrokerChannelFromConfig(config ClientConfig) (*BrokerChannel, error) {
+	log.Println("Rendezvous using Broker at:", config.BrokerURL)
+
+	if config.FrontDomain != "" {
+		log.Println("Domain fronting using:", config.FrontDomain)
 	}
 
-	bc.transport = transport
-	return bc
-}
+	brokerTransport := createBrokerTransport()
 
-func limitedRead(r io.Reader, limit int64) ([]byte, error) {
-	p, err := ioutil.ReadAll(&io.LimitedReader{R: r, N: limit + 1})
+	if config.UTLSClientID != "" {
+		utlsClientHelloID, err := utlsutil.NameToUTLSID(config.UTLSClientID)
+		if err != nil {
+			return nil, fmt.Errorf("unable to create broker channel: %v", err)
+		}
+		utlsConfig := &utls.Config{}
+		brokerTransport = utlsutil.NewUTLSHTTPRoundTripper(utlsClientHelloID, utlsConfig, brokerTransport, config.UTLSRemoveSNI)
+	}
+
+	var rendezvous RendezvousMethod
+	var err error
+	if config.AmpCacheURL != "" {
+		log.Println("Through AMP cache at:", config.AmpCacheURL)
+		rendezvous, err = newAMPCacheRendezvous(
+			config.BrokerURL, config.AmpCacheURL, config.FrontDomain,
+			brokerTransport)
+	} else {
+		rendezvous, err = newHTTPRendezvous(
+			config.BrokerURL, config.FrontDomain, brokerTransport)
+	}
 	if err != nil {
-		return p, err
-	} else if int64(len(p)) == limit+1 {
-		return p[0:limit], io.ErrUnexpectedEOF
+		return nil, err
 	}
-	return p, err
+
+	return &BrokerChannel{
+		Rendezvous:         rendezvous,
+		keepLocalAddresses: config.KeepLocalAddresses,
+		natType:            nat.NATUnknown,
+		BridgeFingerprint:  config.BridgeFingerprint,
+	}, nil
 }
 
-// Roundtrip HTTP POST using WebRTC SessionDescriptions.
-//
-// Send an SDP offer to the broker, which assigns a proxy and responds
-// with an SDP answer from a designated remote WebRTC peer.
+// Negotiate uses a RendezvousMethod to send the client's WebRTC SDP offer
+// and receive a snowflake proxy WebRTC SDP answer in return.
 func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
 	*webrtc.SessionDescription, error) {
-	log.Println("Negotiating via BrokerChannel...\nTarget URL: ",
-		bc.Host, "\nFront URL:  ", bc.url.Host)
-	data := bytes.NewReader([]byte(serializeSessionDescription(offer)))
-	// Suffix with broker's client registration handler.
-	clientURL := bc.url.ResolveReference(&url.URL{Path: "client"})
-	request, err := http.NewRequest("POST", clientURL.String(), data)
-	if nil != err {
-		return nil, err
-	}
-	if "" != bc.Host { // Set true host if necessary.
-		request.Host = bc.Host
-	}
-	resp, err := bc.transport.RoundTrip(request)
-	if nil != err {
-		return nil, err
-	}
-	defer resp.Body.Close()
-	log.Printf("BrokerChannel Response:\n%s\n\n", resp.Status)
-
-	switch resp.StatusCode {
-	case http.StatusOK:
-		body, err := limitedRead(resp.Body, readLimit)
-		if nil != err {
-			return nil, err
+	// Ideally, we could specify an `RTCIceTransportPolicy` that would handle
+	// this for us.  However, "public" was removed from the draft spec.
+	// See https://developer.mozilla.org/en-US/docs/Web/API/RTCConfiguration#RTCIceTransportPolicy_enum
+	if !bc.keepLocalAddresses {
+		offer = &webrtc.SessionDescription{
+			Type: offer.Type,
+			SDP:  util.StripLocalAddresses(offer.SDP),
 		}
-		answer := deserializeSessionDescription(string(body))
-		return answer, nil
-
-	case http.StatusServiceUnavailable:
-		return nil, errors.New(BrokerError503)
-	case http.StatusBadRequest:
-		return nil, errors.New(BrokerError400)
-	default:
-		return nil, errors.New(BrokerErrorUnexpected)
 	}
+	offerSDP, err := util.SerializeSessionDescription(offer)
+	if err != nil {
+		return nil, err
+	}
+
+	// Encode the client poll request.
+	bc.lock.Lock()
+	req := &messages.ClientPollRequest{
+		Offer:       offerSDP,
+		NAT:         bc.natType,
+		Fingerprint: bc.BridgeFingerprint,
+	}
+	encReq, err := req.EncodeClientPollRequest()
+	bc.lock.Unlock()
+	if err != nil {
+		return nil, err
+	}
+
+	// Do the exchange using our RendezvousMethod.
+	encResp, err := bc.Rendezvous.Exchange(encReq)
+	if err != nil {
+		return nil, err
+	}
+	log.Printf("Received answer: %s", string(encResp))
+
+	// Decode the client poll response.
+	resp, err := messages.DecodeClientPollResponse(encResp)
+	if err != nil {
+		return nil, err
+	}
+	if resp.Error != "" {
+		return nil, errors.New(resp.Error)
+	}
+	return util.DeserializeSessionDescription(resp.Answer)
 }
 
-// Implements the |Tongue| interface to catch snowflakes, using BrokerChannel.
+// SetNATType sets the NAT type of the client so we can send it to the WebRTC broker.
+func (bc *BrokerChannel) SetNATType(NATType string) {
+	bc.lock.Lock()
+	bc.natType = NATType
+	bc.lock.Unlock()
+	log.Printf("NAT Type: %s", NATType)
+}
+
+// WebRTCDialer implements the |Tongue| interface to catch snowflakes, using BrokerChannel.
 type WebRTCDialer struct {
 	*BrokerChannel
 	webrtcConfig *webrtc.Configuration
+	max          int
+
+	eventLogger event.SnowflakeEventReceiver
 }
 
-func NewWebRTCDialer(
-	broker *BrokerChannel, iceServers []webrtc.ICEServer) *WebRTCDialer {
-	var config webrtc.Configuration
-	if iceServers != nil {
-		config = webrtc.Configuration{
-			ICEServers: iceServers,
-		}
-	} else {
-		config = webrtc.Configuration{}
+func NewWebRTCDialer(broker *BrokerChannel, iceServers []webrtc.ICEServer, max int) *WebRTCDialer {
+	return NewWebRTCDialerWithEvents(broker, iceServers, max, nil)
+}
+
+// NewWebRTCDialerWithEvents constructs a new WebRTCDialer.
+func NewWebRTCDialerWithEvents(broker *BrokerChannel, iceServers []webrtc.ICEServer, max int, eventLogger event.SnowflakeEventReceiver) *WebRTCDialer {
+	config := webrtc.Configuration{
+		ICEServers: iceServers,
 	}
+
 	return &WebRTCDialer{
 		BrokerChannel: broker,
 		webrtcConfig:  &config,
+		max:           max,
+
+		eventLogger: eventLogger,
 	}
 }
 
-// Initialize a WebRTC Connection by signaling through the broker.
-func (w WebRTCDialer) Catch() (Snowflake, error) {
-	if nil == w.BrokerChannel {
-		return nil, errors.New("cannot Dial WebRTC without a BrokerChannel")
-	}
-	// TODO: [#3] Fetch ICE server information from Broker.
-	// TODO: [#18] Consider TURN servers here too.
-	connection := NewWebRTCPeer(w.webrtcConfig, w.BrokerChannel)
-	err := connection.Connect()
-	return connection, err
+// Catch initializes a WebRTC Connection by signaling through the BrokerChannel.
+func (w WebRTCDialer) Catch() (*WebRTCPeer, error) {
+	// TODO: [#25591] Fetch ICE server information from Broker.
+	// TODO: [#25596] Consider TURN servers here too.
+	return NewWebRTCPeerWithEvents(w.webrtcConfig, w.BrokerChannel, w.eventLogger)
+}
+
+// GetMax returns the maximum number of snowflakes to collect.
+func (w WebRTCDialer) GetMax() int {
+	return w.max
 }

client/lib/rendezvous_ampcache.go

@@ -0,0 +1,124 @@
+package snowflake_client
+
+import (
+	"errors"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/url"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/amp"
+)
+
+// ampCacheRendezvous is a RendezvousMethod that communicates with the
+// .../amp/client route of the broker, optionally over an AMP cache proxy, and
+// with optional domain fronting.
+type ampCacheRendezvous struct {
+	brokerURL *url.URL
+	cacheURL  *url.URL          // Optional AMP cache URL.
+	front     string            // Optional front domain to replace url.Host in requests.
+	transport http.RoundTripper // Used to make all requests.
+}
+
+// newAMPCacheRendezvous creates a new ampCacheRendezvous that contacts the
+// broker at the given URL, optionally proxying through an AMP cache, and with
+// an optional front domain. transport is the http.RoundTripper used to make all
+// requests.
+func newAMPCacheRendezvous(broker, cache, front string, transport http.RoundTripper) (*ampCacheRendezvous, error) {
+	brokerURL, err := url.Parse(broker)
+	if err != nil {
+		return nil, err
+	}
+	var cacheURL *url.URL
+	if cache != "" {
+		var err error
+		cacheURL, err = url.Parse(cache)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return &ampCacheRendezvous{
+		brokerURL: brokerURL,
+		cacheURL:  cacheURL,
+		front:     front,
+		transport: transport,
+	}, nil
+}
+
+func (r *ampCacheRendezvous) Exchange(encPollReq []byte) ([]byte, error) {
+	log.Println("Negotiating via AMP cache rendezvous...")
+	log.Println("Broker URL:", r.brokerURL)
+	log.Println("AMP cache URL:", r.cacheURL)
+	log.Println("Front domain:", r.front)
+
+	// We cannot POST a body through an AMP cache, so instead we GET and
+	// encode the client poll request message into the URL.
+	reqURL := r.brokerURL.ResolveReference(&url.URL{
+		Path: "amp/client/" + amp.EncodePath(encPollReq),
+	})
+
+	if r.cacheURL != nil {
+		// Rewrite reqURL to its AMP cache version.
+		var err error
+		reqURL, err = amp.CacheURL(reqURL, r.cacheURL, "c")
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	req, err := http.NewRequest("GET", reqURL.String(), nil)
+	if err != nil {
+		return nil, err
+	}
+
+	if r.front != "" {
+		// Do domain fronting. Replace the domain in the URL's with the
+		// front, and store the original domain the HTTP Host header.
+		req.Host = req.URL.Host
+		req.URL.Host = r.front
+	}
+
+	resp, err := r.transport.RoundTrip(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	log.Printf("AMP cache rendezvous response: %s", resp.Status)
+	if resp.StatusCode != http.StatusOK {
+		// A non-200 status indicates an error:
+		// * If the broker returns a page with invalid AMP, then the AMP
+		//   cache returns a redirect that would bypass the cache.
+		// * If the broker returns a 5xx status, the AMP cache
+		//   translates it to a 404.
+		// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#redirect-%26-error-handling
+		return nil, errors.New(brokerErrorUnexpected)
+	}
+	if _, err := resp.Location(); err == nil {
+		// The Google AMP Cache may return a "silent redirect" with
+		// status 200, a Location header set, and a JavaScript redirect
+		// in the body. The redirect points directly at the origin
+		// server for the request (bypassing the AMP cache). We do not
+		// follow redirects nor execute JavaScript, but in any case we
+		// cannot extract information from this response and can only
+		// treat it as an error.
+		return nil, errors.New(brokerErrorUnexpected)
+	}
+
+	lr := io.LimitReader(resp.Body, readLimit+1)
+	dec, err := amp.NewArmorDecoder(lr)
+	if err != nil {
+		return nil, err
+	}
+	encPollResp, err := ioutil.ReadAll(dec)
+	if err != nil {
+		return nil, err
+	}
+	if lr.(*io.LimitedReader).N == 0 {
+		// We hit readLimit while decoding AMP armor, that's an error.
+		return nil, io.ErrUnexpectedEOF
+	}
+
+	return encPollResp, err
+}

client/lib/rendezvous_http.go

@@ -0,0 +1,77 @@
+package snowflake_client
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/url"
+)
+
+// httpRendezvous is a RendezvousMethod that communicates with the .../client
+// route of the broker over HTTP or HTTPS, with optional domain fronting.
+type httpRendezvous struct {
+	brokerURL *url.URL
+	front     string            // Optional front domain to replace url.Host in requests.
+	transport http.RoundTripper // Used to make all requests.
+}
+
+// newHTTPRendezvous creates a new httpRendezvous that contacts the broker at
+// the given URL, with an optional front domain. transport is the
+// http.RoundTripper used to make all requests.
+func newHTTPRendezvous(broker, front string, transport http.RoundTripper) (*httpRendezvous, error) {
+	brokerURL, err := url.Parse(broker)
+	if err != nil {
+		return nil, err
+	}
+	return &httpRendezvous{
+		brokerURL: brokerURL,
+		front:     front,
+		transport: transport,
+	}, nil
+}
+
+func (r *httpRendezvous) Exchange(encPollReq []byte) ([]byte, error) {
+	log.Println("Negotiating via HTTP rendezvous...")
+	log.Println("Target URL: ", r.brokerURL.Host)
+	log.Println("Front URL:  ", r.front)
+
+	// Suffix the path with the broker's client registration handler.
+	reqURL := r.brokerURL.ResolveReference(&url.URL{Path: "client"})
+	req, err := http.NewRequest("POST", reqURL.String(), bytes.NewReader(encPollReq))
+	if err != nil {
+		return nil, err
+	}
+
+	if r.front != "" {
+		// Do domain fronting. Replace the domain in the URL's with the
+		// front, and store the original domain the HTTP Host header.
+		req.Host = req.URL.Host
+		req.URL.Host = r.front
+	}
+
+	resp, err := r.transport.RoundTrip(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	log.Printf("HTTP rendezvous response: %s", resp.Status)
+	if resp.StatusCode != http.StatusOK {
+		return nil, errors.New(brokerErrorUnexpected)
+	}
+
+	return limitedRead(resp.Body, readLimit)
+}
+
+func limitedRead(r io.Reader, limit int64) ([]byte, error) {
+	p, err := ioutil.ReadAll(&io.LimitedReader{R: r, N: limit + 1})
+	if err != nil {
+		return p, err
+	} else if int64(len(p)) == limit+1 {
+		return p[0:limit], io.ErrUnexpectedEOF
+	}
+	return p, err
+}

client/lib/rendezvous_test.go

@@ -0,0 +1,273 @@
+package snowflake_client
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"testing"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/amp"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/nat"
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+// mockTransport's RoundTrip method returns a response with a fake status and
+// body.
+type mockTransport struct {
+	statusCode int
+	body       []byte
+}
+
+func (t *mockTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	return &http.Response{
+		Status:     fmt.Sprintf("%d %s", t.statusCode, http.StatusText(t.statusCode)),
+		StatusCode: t.statusCode,
+		Body:       ioutil.NopCloser(bytes.NewReader(t.body)),
+	}, nil
+}
+
+// errorTransport's RoundTrip method returns an error.
+type errorTransport struct {
+	err error
+}
+
+func (t errorTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	return nil, t.err
+}
+
+// makeEncPollReq returns an encoded client poll request containing a given
+// offer.
+func makeEncPollReq(offer string) []byte {
+	encPollReq, err := (&messages.ClientPollRequest{
+		Offer: offer,
+		NAT:   nat.NATUnknown,
+	}).EncodeClientPollRequest()
+	if err != nil {
+		panic(err)
+	}
+	return encPollReq
+}
+
+// makeEncPollResp returns an encoded client poll response with given answer and
+// error strings.
+func makeEncPollResp(answer, errorStr string) []byte {
+	encPollResp, err := (&messages.ClientPollResponse{
+		Answer: answer,
+		Error:  errorStr,
+	}).EncodePollResponse()
+	if err != nil {
+		panic(err)
+	}
+	return encPollResp
+}
+
+var fakeEncPollReq = makeEncPollReq(`{"type":"offer","sdp":"test"}`)
+
+func TestHTTPRendezvous(t *testing.T) {
+	Convey("HTTP rendezvous", t, func() {
+		Convey("Construct httpRendezvous with no front domain", func() {
+			transport := &mockTransport{http.StatusOK, []byte{}}
+			rend, err := newHTTPRendezvous("http://test.broker", "", transport)
+			So(err, ShouldBeNil)
+			So(rend.brokerURL, ShouldNotBeNil)
+			So(rend.brokerURL.Host, ShouldResemble, "test.broker")
+			So(rend.front, ShouldResemble, "")
+			So(rend.transport, ShouldEqual, transport)
+		})
+
+		Convey("Construct httpRendezvous *with* front domain", func() {
+			transport := &mockTransport{http.StatusOK, []byte{}}
+			rend, err := newHTTPRendezvous("http://test.broker", "front", transport)
+			So(err, ShouldBeNil)
+			So(rend.brokerURL, ShouldNotBeNil)
+			So(rend.brokerURL.Host, ShouldResemble, "test.broker")
+			So(rend.front, ShouldResemble, "front")
+			So(rend.transport, ShouldEqual, transport)
+		})
+
+		Convey("httpRendezvous.Exchange responds with answer", func() {
+			fakeEncPollResp := makeEncPollResp(
+				`{"answer": "{\"type\":\"answer\",\"sdp\":\"fake\"}" }`,
+				"",
+			)
+			rend, err := newHTTPRendezvous("http://test.broker", "",
+				&mockTransport{http.StatusOK, fakeEncPollResp})
+			So(err, ShouldBeNil)
+			answer, err := rend.Exchange(fakeEncPollReq)
+			So(err, ShouldBeNil)
+			So(answer, ShouldResemble, fakeEncPollResp)
+		})
+
+		Convey("httpRendezvous.Exchange responds with no answer", func() {
+			fakeEncPollResp := makeEncPollResp(
+				"",
+				`{"error": "no snowflake proxies currently available"}`,
+			)
+			rend, err := newHTTPRendezvous("http://test.broker", "",
+				&mockTransport{http.StatusOK, fakeEncPollResp})
+			So(err, ShouldBeNil)
+			answer, err := rend.Exchange(fakeEncPollReq)
+			So(err, ShouldBeNil)
+			So(answer, ShouldResemble, fakeEncPollResp)
+		})
+
+		Convey("httpRendezvous.Exchange fails with unexpected HTTP status code", func() {
+			rend, err := newHTTPRendezvous("http://test.broker", "",
+				&mockTransport{http.StatusInternalServerError, []byte{}})
+			So(err, ShouldBeNil)
+			answer, err := rend.Exchange(fakeEncPollReq)
+			So(err, ShouldNotBeNil)
+			So(answer, ShouldBeNil)
+			So(err.Error(), ShouldResemble, brokerErrorUnexpected)
+		})
+
+		Convey("httpRendezvous.Exchange fails with error", func() {
+			transportErr := errors.New("error")
+			rend, err := newHTTPRendezvous("http://test.broker", "",
+				&errorTransport{err: transportErr})
+			So(err, ShouldBeNil)
+			answer, err := rend.Exchange(fakeEncPollReq)
+			So(err, ShouldEqual, transportErr)
+			So(answer, ShouldBeNil)
+		})
+
+		Convey("httpRendezvous.Exchange fails with large read", func() {
+			rend, err := newHTTPRendezvous("http://test.broker", "",
+				&mockTransport{http.StatusOK, make([]byte, readLimit+1)})
+			So(err, ShouldBeNil)
+			_, err = rend.Exchange(fakeEncPollReq)
+			So(err, ShouldEqual, io.ErrUnexpectedEOF)
+		})
+	})
+}
+
+func ampArmorEncode(p []byte) []byte {
+	var buf bytes.Buffer
+	enc, err := amp.NewArmorEncoder(&buf)
+	if err != nil {
+		panic(err)
+	}
+	_, err = enc.Write(p)
+	if err != nil {
+		panic(err)
+	}
+	err = enc.Close()
+	if err != nil {
+		panic(err)
+	}
+	return buf.Bytes()
+}
+
+func TestAMPCacheRendezvous(t *testing.T) {
+	Convey("AMP cache rendezvous", t, func() {
+		Convey("Construct ampCacheRendezvous with no cache and no front domain", func() {
+			transport := &mockTransport{http.StatusOK, []byte{}}
+			rend, err := newAMPCacheRendezvous("http://test.broker", "", "", transport)
+			So(err, ShouldBeNil)
+			So(rend.brokerURL, ShouldNotBeNil)
+			So(rend.brokerURL.String(), ShouldResemble, "http://test.broker")
+			So(rend.cacheURL, ShouldBeNil)
+			So(rend.front, ShouldResemble, "")
+			So(rend.transport, ShouldEqual, transport)
+		})
+
+		Convey("Construct ampCacheRendezvous with cache and no front domain", func() {
+			transport := &mockTransport{http.StatusOK, []byte{}}
+			rend, err := newAMPCacheRendezvous("http://test.broker", "https://amp.cache/", "", transport)
+			So(err, ShouldBeNil)
+			So(rend.brokerURL, ShouldNotBeNil)
+			So(rend.brokerURL.String(), ShouldResemble, "http://test.broker")
+			So(rend.cacheURL, ShouldNotBeNil)
+			So(rend.cacheURL.String(), ShouldResemble, "https://amp.cache/")
+			So(rend.front, ShouldResemble, "")
+			So(rend.transport, ShouldEqual, transport)
+		})
+
+		Convey("Construct ampCacheRendezvous with no cache and front domain", func() {
+			transport := &mockTransport{http.StatusOK, []byte{}}
+			rend, err := newAMPCacheRendezvous("http://test.broker", "", "front", transport)
+			So(err, ShouldBeNil)
+			So(rend.brokerURL, ShouldNotBeNil)
+			So(rend.brokerURL.String(), ShouldResemble, "http://test.broker")
+			So(rend.cacheURL, ShouldBeNil)
+			So(rend.front, ShouldResemble, "front")
+			So(rend.transport, ShouldEqual, transport)
+		})
+
+		Convey("Construct ampCacheRendezvous with cache and front domain", func() {
+			transport := &mockTransport{http.StatusOK, []byte{}}
+			rend, err := newAMPCacheRendezvous("http://test.broker", "https://amp.cache/", "front", transport)
+			So(err, ShouldBeNil)
+			So(rend.brokerURL, ShouldNotBeNil)
+			So(rend.brokerURL.String(), ShouldResemble, "http://test.broker")
+			So(rend.cacheURL, ShouldNotBeNil)
+			So(rend.cacheURL.String(), ShouldResemble, "https://amp.cache/")
+			So(rend.front, ShouldResemble, "front")
+			So(rend.transport, ShouldEqual, transport)
+		})
+
+		Convey("ampCacheRendezvous.Exchange responds with answer", func() {
+			fakeEncPollResp := makeEncPollResp(
+				`{"answer": "{\"type\":\"answer\",\"sdp\":\"fake\"}" }`,
+				"",
+			)
+			rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
+				&mockTransport{http.StatusOK, ampArmorEncode(fakeEncPollResp)})
+			So(err, ShouldBeNil)
+			answer, err := rend.Exchange(fakeEncPollReq)
+			So(err, ShouldBeNil)
+			So(answer, ShouldResemble, fakeEncPollResp)
+		})
+
+		Convey("ampCacheRendezvous.Exchange responds with no answer", func() {
+			fakeEncPollResp := makeEncPollResp(
+				"",
+				`{"error": "no snowflake proxies currently available"}`,
+			)
+			rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
+				&mockTransport{http.StatusOK, ampArmorEncode(fakeEncPollResp)})
+			So(err, ShouldBeNil)
+			answer, err := rend.Exchange(fakeEncPollReq)
+			So(err, ShouldBeNil)
+			So(answer, ShouldResemble, fakeEncPollResp)
+		})
+
+		Convey("ampCacheRendezvous.Exchange fails with unexpected HTTP status code", func() {
+			rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
+				&mockTransport{http.StatusInternalServerError, []byte{}})
+			So(err, ShouldBeNil)
+			answer, err := rend.Exchange(fakeEncPollReq)
+			So(err, ShouldNotBeNil)
+			So(answer, ShouldBeNil)
+			So(err.Error(), ShouldResemble, brokerErrorUnexpected)
+		})
+
+		Convey("ampCacheRendezvous.Exchange fails with error", func() {
+			transportErr := errors.New("error")
+			rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
+				&errorTransport{err: transportErr})
+			So(err, ShouldBeNil)
+			answer, err := rend.Exchange(fakeEncPollReq)
+			So(err, ShouldEqual, transportErr)
+			So(answer, ShouldBeNil)
+		})
+
+		Convey("ampCacheRendezvous.Exchange fails with large read", func() {
+			// readLimit should apply to the raw HTTP body, not the
+			// encoded bytes. Encode readLimit bytes—the encoded
+			// size will be larger—and try to read the body. It
+			// should fail.
+			rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
+				&mockTransport{http.StatusOK, ampArmorEncode(make([]byte, readLimit))})
+			So(err, ShouldBeNil)
+			_, err = rend.Exchange(fakeEncPollReq)
+			// We may get io.ErrUnexpectedEOF here, or something
+			// like "missing </pre> tag".
+			So(err, ShouldNotBeNil)
+		})
+	})
+}

client/lib/snowflake.go

@@ -1,68 +1,368 @@
-package lib
+/*
+Package snowflake_client implements functionality necessary for a client to establish a connection
+to a server using Snowflake.
+
+Included in the package is a Transport type that implements the Pluggable Transports v2.1 Go API
+specification. To use Snowflake, you must first create a client from a configuration:
+
+	config := snowflake_client.ClientConfig{
+		BrokerURL:   "https://snowflake-broker.example.com",
+		FrontDomain: "https://friendlyfrontdomain.net",
+		// ...
+	}
+	transport, err := snowflake_client.NewSnowflakeClient(config)
+	if err != nil {
+		// handle error
+	}
+
+The Dial function connects to a Snowflake server:
+
+	conn, err := transport.Dial()
+	if err != nil {
+		// handle error
+	}
+	defer conn.Close()
+
+*/
+package snowflake_client
 
 import (
+	"context"
 	"errors"
-	"io"
 	"log"
+	"math/rand"
 	"net"
-	"sync"
+	"strings"
+	"time"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/event"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/nat"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/turbotunnel"
+	"github.com/pion/webrtc/v3"
+	"github.com/xtaci/kcp-go/v5"
+	"github.com/xtaci/smux"
 )
 
 const (
-	ReconnectTimeout = 10
-	SnowflakeTimeout = 30
+	// ReconnectTimeout is the time a Snowflake client will wait before collecting
+	// more snowflakes.
+	ReconnectTimeout = 10 * time.Second
+	// SnowflakeTimeout is the time a Snowflake client will wait before determining that
+	// a remote snowflake has been disconnected. If no new messages are sent or received
+	// in this time period, the client will terminate the connection with the remote
+	// peer and collect a new snowflake.
+	SnowflakeTimeout = 20 * time.Second
+	// DataChannelTimeout is how long the client will wait for the OnOpen callback
+	// on a newly created DataChannel.
+	DataChannelTimeout = 10 * time.Second
+
+	// WindowSize is the number of packets in the send and receive window of a KCP connection.
+	WindowSize = 65535
+	// StreamSize controls the maximum amount of in flight data between a client and server.
+	StreamSize = 1048576 //1MB
 )
 
-// Given an accepted SOCKS connection, establish a WebRTC connection to the
-// remote peer and exchange traffic.
-func Handler(socks SocksConnector, snowflakes SnowflakeCollector) error {
-	// Obtain an available WebRTC remote. May block.
-	snowflake := snowflakes.Pop()
-	if nil == snowflake {
-		if err := socks.Reject(); err != nil {
-			log.Printf("socks.Reject returned error: %v", err)
-		}
+type dummyAddr struct{}
 
-		return errors.New("handler: Received invalid Snowflake")
+func (addr dummyAddr) Network() string { return "dummy" }
+func (addr dummyAddr) String() string  { return "dummy" }
+
+// Transport is a structure with methods that conform to the Go PT v2.1 API
+// https://github.com/Pluggable-Transports/Pluggable-Transports-spec/blob/master/releases/PTSpecV2.1/Pluggable%20Transport%20Specification%20v2.1%20-%20Go%20Transport%20API.pdf
+type Transport struct {
+	dialer *WebRTCDialer
+
+	// EventDispatcher is the event bus for snowflake events.
+	// When an important event happens, it will be distributed here.
+	eventDispatcher event.SnowflakeEventDispatcher
+}
+
+// ClientConfig defines how the SnowflakeClient will connect to the broker and Snowflake proxies.
+type ClientConfig struct {
+	// BrokerURL is the full URL of the Snowflake broker that the client will connect to.
+	BrokerURL string
+	// AmpCacheURL is the full URL of a valid AMP cache. A nonzero value indicates
+	// that AMP cache will be used as the rendezvous method with the broker.
+	AmpCacheURL string
+	// FrontDomain is a the full URL of an optional front domain that can be used with either
+	// the AMP cache or HTTP domain fronting rendezvous method.
+	FrontDomain string
+	// ICEAddresses are a slice of ICE server URLs that will be used for NAT traversal and
+	// the creation of the client's WebRTC SDP offer.
+	ICEAddresses []string
+	// KeepLocalAddresses is an optional setting that will prevent the removal of local or
+	// invalid addresses from the client's SDP offer. This is useful for local deployments
+	// and testing.
+	KeepLocalAddresses bool
+	// Max is the maximum number of snowflake proxy peers that the client should attempt to
+	// connect to. Defaults to 1.
+	Max int
+	// UTLSClientID is the type of user application that snowflake should imitate.
+	// If an empty value is provided, it will use Go's default TLS implementation
+	UTLSClientID string
+	// UTLSRemoveSNI is the flag to control whether SNI should be removed from Client Hello
+	// when uTLS is used.
+	UTLSRemoveSNI bool
+	// BridgeFingerprint is the fingerprint of the bridge that the client will eventually
+	// connect to, as specified in the Bridge line of the torrc.
+	BridgeFingerprint string
+}
+
+// NewSnowflakeClient creates a new Snowflake transport client that can spawn multiple
+// Snowflake connections.
+//
+// brokerURL and frontDomain are the urls for the broker host and domain fronting host
+// iceAddresses are the STUN/TURN urls needed for WebRTC negotiation
+// keepLocalAddresses is a flag to enable sending local network addresses (for testing purposes)
+// max is the maximum number of snowflakes the client should gather for each SOCKS connection
+func NewSnowflakeClient(config ClientConfig) (*Transport, error) {
+
+	log.Println("\n\n\n --- Starting Snowflake Client ---")
+
+	iceServers := parseIceServers(config.ICEAddresses)
+	// chooses a random subset of servers from inputs
+	rand.Seed(time.Now().UnixNano())
+	rand.Shuffle(len(iceServers), func(i, j int) {
+		iceServers[i], iceServers[j] = iceServers[j], iceServers[i]
+	})
+	if len(iceServers) > 2 {
+		iceServers = iceServers[:(len(iceServers)+1)/2]
 	}
-	defer socks.Close()
-	defer snowflake.Close()
-	log.Println("---- Handler: snowflake assigned ----")
-	err := socks.Grant(&net.TCPAddr{IP: net.IPv4zero, Port: 0})
+	log.Printf("Using ICE servers:")
+	for _, server := range iceServers {
+		log.Printf("url: %v", strings.Join(server.URLs, " "))
+	}
+
+	// Rendezvous with broker using the given parameters.
+	broker, err := newBrokerChannelFromConfig(config)
 	if err != nil {
-		return err
+		return nil, err
+	}
+	go updateNATType(iceServers, broker)
+
+	max := 1
+	if config.Max > max {
+		max = config.Max
+	}
+	eventsLogger := event.NewSnowflakeEventDispatcher()
+	transport := &Transport{dialer: NewWebRTCDialerWithEvents(broker, iceServers, max, eventsLogger), eventDispatcher: eventsLogger}
+
+	return transport, nil
+}
+
+// Dial creates a new Snowflake connection.
+// Dial starts the collection of snowflakes and returns a SnowflakeConn that is a
+// wrapper around a smux.Stream that will reliably deliver data to a Snowflake
+// server through one or more snowflake proxies.
+func (t *Transport) Dial() (net.Conn, error) {
+	// Cleanup functions to run before returning, in case of an error.
+	var cleanup []func()
+	defer func() {
+		// Run cleanup in reverse order, as defer does.
+		for i := len(cleanup) - 1; i >= 0; i-- {
+			cleanup[i]()
+		}
+	}()
+
+	// Prepare to collect remote WebRTC peers.
+	snowflakes, err := NewPeers(t.dialer)
+	if err != nil {
+		return nil, err
+	}
+	cleanup = append(cleanup, func() { snowflakes.End() })
+
+	// Use a real logger to periodically output how much traffic is happening.
+	snowflakes.bytesLogger = newBytesSyncLogger()
+
+	log.Printf("---- SnowflakeConn: begin collecting snowflakes ---")
+	go connectLoop(snowflakes)
+
+	// Create a new smux session
+	log.Printf("---- SnowflakeConn: starting a new session ---")
+	pconn, sess, err := newSession(snowflakes)
+	if err != nil {
+		return nil, err
+	}
+	cleanup = append(cleanup, func() {
+		pconn.Close()
+		sess.Close()
+	})
+
+	// On the smux session we overlay a stream.
+	stream, err := sess.OpenStream()
+	if err != nil {
+		return nil, err
+	}
+	// Begin exchanging data.
+	log.Printf("---- SnowflakeConn: begin stream %v ---", stream.ID())
+	cleanup = append(cleanup, func() { stream.Close() })
+
+	// All good, clear the cleanup list.
+	cleanup = nil
+	return &SnowflakeConn{Stream: stream, sess: sess, pconn: pconn, snowflakes: snowflakes}, nil
+}
+func (t *Transport) AddSnowflakeEventListener(receiver event.SnowflakeEventReceiver) {
+	t.eventDispatcher.AddSnowflakeEventListener(receiver)
+}
+
+func (t *Transport) RemoveSnowflakeEventListener(receiver event.SnowflakeEventReceiver) {
+	t.eventDispatcher.RemoveSnowflakeEventListener(receiver)
+}
+
+// SetRendezvousMethod sets the rendezvous method to the Snowflake broker.
+func (t *Transport) SetRendezvousMethod(r RendezvousMethod) {
+	t.dialer.Rendezvous = r
+}
+
+// SnowflakeConn is a reliable connection to a snowflake server that implements net.Conn.
+type SnowflakeConn struct {
+	*smux.Stream
+	sess       *smux.Session
+	pconn      net.PacketConn
+	snowflakes *Peers
+}
+
+// Close closes the connection.
+//
+// The collection of snowflake proxies for this connection is stopped.
+func (conn *SnowflakeConn) Close() error {
+	log.Printf("---- SnowflakeConn: closed stream %v ---", conn.ID())
+	conn.Stream.Close()
+	log.Printf("---- SnowflakeConn: end collecting snowflakes ---")
+	conn.snowflakes.End()
+	conn.pconn.Close()
+	log.Printf("---- SnowflakeConn: discarding finished session ---")
+	conn.sess.Close()
+	return nil //TODO: return errors if any of the above do
+}
+
+// loop through all provided STUN servers until we exhaust the list or find
+// one that is compatible with RFC 5780
+func updateNATType(servers []webrtc.ICEServer, broker *BrokerChannel) {
+
+	var restrictedNAT bool
+	var err error
+	for _, server := range servers {
+		addr := strings.TrimPrefix(server.URLs[0], "stun:")
+		restrictedNAT, err = nat.CheckIfRestrictedNAT(addr)
+
+		if err != nil {
+			log.Printf("Warning: NAT checking failed for server at %s: %s", addr, err)
+		} else {
+			if restrictedNAT {
+				broker.SetNATType(nat.NATRestricted)
+			} else {
+				broker.SetNATType(nat.NATUnrestricted)
+			}
+			break
+		}
+	}
+	if err != nil {
+		broker.SetNATType(nat.NATUnknown)
+	}
+}
+
+// Returns a slice of webrtc.ICEServer given a slice of addresses
+func parseIceServers(addresses []string) []webrtc.ICEServer {
+	var servers []webrtc.ICEServer
+	if len(addresses) == 0 {
+		return nil
+	}
+	for _, url := range addresses {
+		url = strings.TrimSpace(url)
+		servers = append(servers, webrtc.ICEServer{
+			URLs: []string{url},
+		})
+	}
+	return servers
+}
+
+// newSession returns a new smux.Session and the net.PacketConn it is running
+// over. The net.PacketConn successively connects through Snowflake proxies
+// pulled from snowflakes.
+func newSession(snowflakes SnowflakeCollector) (net.PacketConn, *smux.Session, error) {
+	clientID := turbotunnel.NewClientID()
+
+	// We build a persistent KCP session on a sequence of ephemeral WebRTC
+	// connections. This dialContext tells RedialPacketConn how to get a new
+	// WebRTC connection when the previous one dies. Inside each WebRTC
+	// connection, we use encapsulationPacketConn to encode packets into a
+	// stream.
+	dialContext := func(ctx context.Context) (net.PacketConn, error) {
+		log.Printf("redialing on same connection")
+		// Obtain an available WebRTC remote. May block.
+		conn := snowflakes.Pop()
+		if conn == nil {
+			return nil, errors.New("handler: Received invalid Snowflake")
+		}
+		log.Println("---- Handler: snowflake assigned ----")
+		// Send the magic Turbo Tunnel token.
+		_, err := conn.Write(turbotunnel.Token[:])
+		if err != nil {
+			return nil, err
+		}
+		// Send ClientID prefix.
+		_, err = conn.Write(clientID[:])
+		if err != nil {
+			return nil, err
+		}
+		return newEncapsulationPacketConn(dummyAddr{}, dummyAddr{}, conn), nil
+	}
+	pconn := turbotunnel.NewRedialPacketConn(dummyAddr{}, dummyAddr{}, dialContext)
+
+	// conn is built on the underlying RedialPacketConn—when one WebRTC
+	// connection dies, another one will be found to take its place. The
+	// sequence of packets across multiple WebRTC connections drives the KCP
+	// engine.
+	conn, err := kcp.NewConn2(dummyAddr{}, nil, 0, 0, pconn)
+	if err != nil {
+		pconn.Close()
+		return nil, nil, err
+	}
+	// Permit coalescing the payloads of consecutive sends.
+	conn.SetStreamMode(true)
+	// Set the maximum send and receive window sizes to a high number
+	// Removes KCP bottlenecks: https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/issues/40026
+	conn.SetWindowSize(WindowSize, WindowSize)
+	// Disable the dynamic congestion window (limit only by the
+	// maximum of local and remote static windows).
+	conn.SetNoDelay(
+		0, // default nodelay
+		0, // default interval
+		0, // default resend
+		1, // nc=1 => congestion window off
+	)
+	// On the KCP connection we overlay an smux session and stream.
+	smuxConfig := smux.DefaultConfig()
+	smuxConfig.Version = 2
+	smuxConfig.KeepAliveTimeout = 10 * time.Minute
+	smuxConfig.MaxStreamBuffer = StreamSize
+
+	sess, err := smux.Client(conn, smuxConfig)
+	if err != nil {
+		conn.Close()
+		pconn.Close()
+		return nil, nil, err
 	}
 
-	go func() {
-		// When WebRTC resets, close the SOCKS connection too.
-		snowflake.WaitForReset()
-		socks.Close()
-	}()
-
-	// Begin exchanging data. Either WebRTC or localhost SOCKS will close first.
-	// In eithercase, this closes the handler and induces a new handler.
-	copyLoop(socks, snowflake)
-	log.Println("---- Handler: closed ---")
-	return nil
+	return pconn, sess, err
 }
 
-// Exchanges bytes between two ReadWriters.
-// (In this case, between a SOCKS and WebRTC connection.)
-func copyLoop(WebRTC, SOCKS io.ReadWriter) {
-	var wg sync.WaitGroup
-	wg.Add(2)
-	go func() {
-		if _, err := io.Copy(SOCKS, WebRTC); err != nil {
-			log.Printf("copying WebRTC to SOCKS resulted in error: %v", err)
+// Maintain |SnowflakeCapacity| number of available WebRTC connections, to
+// transfer to the Tor SOCKS handler when needed.
+func connectLoop(snowflakes SnowflakeCollector) {
+	for {
+		timer := time.After(ReconnectTimeout)
+		_, err := snowflakes.Collect()
+		if err != nil {
+			log.Printf("WebRTC: %v  Retrying...", err)
 		}
-		wg.Done()
-	}()
-	go func() {
-		if _, err := io.Copy(WebRTC, SOCKS); err != nil {
-			log.Printf("copying SOCKS to WebRTC resulted in error: %v", err)
+		select {
+		case <-timer:
+			continue
+		case <-snowflakes.Melted():
+			log.Println("ConnectLoop: stopped.")
+			return
 		}
-		wg.Done()
-	}()
-	wg.Wait()
-	log.Println("copy loop ended")
+	}
 }

client/lib/turbotunnel.go

@@ -0,0 +1,68 @@
+package snowflake_client
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"net"
+	"time"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/encapsulation"
+)
+
+var errNotImplemented = errors.New("not implemented")
+
+// encapsulationPacketConn implements the net.PacketConn interface over an
+// io.ReadWriteCloser stream, using the encapsulation package to represent
+// packets in a stream.
+type encapsulationPacketConn struct {
+	io.ReadWriteCloser
+	localAddr  net.Addr
+	remoteAddr net.Addr
+	bw         *bufio.Writer
+}
+
+// NewEncapsulationPacketConn makes
+func newEncapsulationPacketConn(
+	localAddr, remoteAddr net.Addr,
+	conn io.ReadWriteCloser,
+) *encapsulationPacketConn {
+	return &encapsulationPacketConn{
+		ReadWriteCloser: conn,
+		localAddr:       localAddr,
+		remoteAddr:      remoteAddr,
+		bw:              bufio.NewWriter(conn),
+	}
+}
+
+// ReadFrom reads an encapsulated packet from the stream.
+func (c *encapsulationPacketConn) ReadFrom(p []byte) (int, net.Addr, error) {
+	data, err := encapsulation.ReadData(c.ReadWriteCloser)
+	if err != nil {
+		return 0, c.remoteAddr, err
+	}
+	return copy(p, data), c.remoteAddr, nil
+}
+
+// WriteTo writes an encapsulated packet to the stream.
+func (c *encapsulationPacketConn) WriteTo(p []byte, addr net.Addr) (int, error) {
+	// addr is ignored.
+	_, err := encapsulation.WriteData(c.bw, p)
+	if err == nil {
+		err = c.bw.Flush()
+	}
+	if err != nil {
+		return 0, err
+	}
+	return len(p), nil
+}
+
+// LocalAddr returns the localAddr value that was passed to
+// NewEncapsulationPacketConn.
+func (c *encapsulationPacketConn) LocalAddr() net.Addr {
+	return c.localAddr
+}
+
+func (c *encapsulationPacketConn) SetDeadline(t time.Time) error      { return errNotImplemented }
+func (c *encapsulationPacketConn) SetReadDeadline(t time.Time) error  { return errNotImplemented }
+func (c *encapsulationPacketConn) SetWriteDeadline(t time.Time) error { return errNotImplemented }

client/lib/util.go

@@ -1,137 +1,70 @@
-package lib
+package snowflake_client
 
 import (
-	"encoding/json"
 	"log"
 	"time"
-
-	"github.com/pion/webrtc"
 )
 
 const (
-	LogTimeInterval = 5
+	LogTimeInterval = 5 * time.Second
 )
 
-type BytesLogger interface {
-	Log()
-	AddOutbound(int)
-	AddInbound(int)
+type bytesLogger interface {
+	addOutbound(int)
+	addInbound(int)
 }
 
-// Default BytesLogger does nothing.
-type BytesNullLogger struct{}
+// Default bytesLogger does nothing.
+type bytesNullLogger struct{}
 
-func (b BytesNullLogger) Log()                   {}
-func (b BytesNullLogger) AddOutbound(amount int) {}
-func (b BytesNullLogger) AddInbound(amount int)  {}
+func (b bytesNullLogger) addOutbound(amount int) {}
+func (b bytesNullLogger) addInbound(amount int)  {}
 
-// BytesSyncLogger uses channels to safely log from multiple sources with output
+// bytesSyncLogger uses channels to safely log from multiple sources with output
 // occuring at reasonable intervals.
-type BytesSyncLogger struct {
-	OutboundChan chan int
-	InboundChan  chan int
-	Outbound     int
-	Inbound      int
-	OutEvents    int
-	InEvents     int
-	IsLogging    bool
+type bytesSyncLogger struct {
+	outboundChan chan int
+	inboundChan  chan int
 }
 
-func (b *BytesSyncLogger) Log() {
-	b.IsLogging = true
-	var amount int
-	output := func() {
-		log.Printf("Traffic Bytes (in|out): %d | %d -- (%d OnMessages, %d Sends)",
-			b.Inbound, b.Outbound, b.InEvents, b.OutEvents)
-		b.Outbound = 0
-		b.OutEvents = 0
-		b.Inbound = 0
-		b.InEvents = 0
+// newBytesSyncLogger returns a new bytesSyncLogger and starts it loggin.
+func newBytesSyncLogger() *bytesSyncLogger {
+	b := &bytesSyncLogger{
+		outboundChan: make(chan int, 5),
+		inboundChan:  make(chan int, 5),
 	}
-	last := time.Now()
+	go b.log()
+	return b
+}
+
+func (b *bytesSyncLogger) log() {
+	var outbound, inbound, outEvents, inEvents int
+	ticker := time.NewTicker(LogTimeInterval)
 	for {
 		select {
-		case amount = <-b.OutboundChan:
-			b.Outbound += amount
-			b.OutEvents++
-			if time.Since(last) > time.Second*LogTimeInterval {
-				last = time.Now()
-				output()
-			}
-		case amount = <-b.InboundChan:
-			b.Inbound += amount
-			b.InEvents++
-			if time.Since(last) > time.Second*LogTimeInterval {
-				last = time.Now()
-				output()
-			}
-		case <-time.After(time.Second * LogTimeInterval):
-			if b.InEvents > 0 || b.OutEvents > 0 {
-				output()
+		case <-ticker.C:
+			if outEvents > 0 || inEvents > 0 {
+				log.Printf("Traffic Bytes (in|out): %d | %d -- (%d OnMessages, %d Sends)",
+					inbound, outbound, inEvents, outEvents)
 			}
+			outbound = 0
+			outEvents = 0
+			inbound = 0
+			inEvents = 0
+		case amount := <-b.outboundChan:
+			outbound += amount
+			outEvents++
+		case amount := <-b.inboundChan:
+			inbound += amount
+			inEvents++
 		}
 	}
 }
 
-func (b *BytesSyncLogger) AddOutbound(amount int) {
-	if !b.IsLogging {
-		return
-	}
-	b.OutboundChan <- amount
+func (b *bytesSyncLogger) addOutbound(amount int) {
+	b.outboundChan <- amount
 }
 
-func (b *BytesSyncLogger) AddInbound(amount int) {
-	if !b.IsLogging {
-		return
-	}
-	b.InboundChan <- amount
-}
-func deserializeSessionDescription(msg string) *webrtc.SessionDescription {
-	var parsed map[string]interface{}
-	err := json.Unmarshal([]byte(msg), &parsed)
-	if nil != err {
-		log.Println(err)
-		return nil
-	}
-	if _, ok := parsed["type"]; !ok {
-		log.Println("Cannot deserialize SessionDescription without type field.")
-		return nil
-	}
-	if _, ok := parsed["sdp"]; !ok {
-		log.Println("Cannot deserialize SessionDescription without sdp field.")
-		return nil
-	}
-
-	var stype webrtc.SDPType
-	switch parsed["type"].(string) {
-	default:
-		log.Println("Unknown SDP type")
-		return nil
-	case "offer":
-		stype = webrtc.SDPTypeOffer
-	case "pranswer":
-		stype = webrtc.SDPTypePranswer
-	case "answer":
-		stype = webrtc.SDPTypeAnswer
-	case "rollback":
-		stype = webrtc.SDPTypeRollback
-	}
-
-	if err != nil {
-		log.Println(err)
-		return nil
-	}
-	return &webrtc.SessionDescription{
-		Type: stype,
-		SDP:  parsed["sdp"].(string),
-	}
-}
-
-func serializeSessionDescription(desc *webrtc.SessionDescription) string {
-	bytes, err := json.Marshal(*desc)
-	if nil != err {
-		log.Println(err)
-		return ""
-	}
-	return string(bytes)
+func (b *bytesSyncLogger) addInbound(amount int) {
+	b.inboundChan <- amount
 }

client/lib/webrtc.go

@@ -1,67 +1,82 @@
-package lib
+package snowflake_client
 
 import (
-	"bytes"
+	"crypto/rand"
+	"encoding/hex"
 	"errors"
 	"io"
 	"log"
 	"sync"
 	"time"
 
-	"github.com/dchest/uniuri"
-	"github.com/pion/webrtc"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/event"
+	"github.com/pion/ice/v2"
+	"github.com/pion/webrtc/v3"
 )
 
-// Remote WebRTC peer.
-// Implements the |Snowflake| interface, which includes
-// |io.ReadWriter|, |Resetter|, and |Connector|.
+// WebRTCPeer represents a WebRTC connection to a remote snowflake proxy.
 //
-// Handles preparation of go-webrtc PeerConnection. Only ever has
-// one DataChannel.
+// Each WebRTCPeer only ever has one DataChannel that is used as the peer's transport.
 type WebRTCPeer struct {
 	id        string
-	config    *webrtc.Configuration
 	pc        *webrtc.PeerConnection
-	transport SnowflakeDataChannel // Holds the WebRTC DataChannel.
-	broker    *BrokerChannel
+	transport *webrtc.DataChannel
 
-	offerChannel  chan *webrtc.SessionDescription
-	answerChannel chan *webrtc.SessionDescription
-	errorChannel  chan error
-	recvPipe      *io.PipeReader
-	writePipe     *io.PipeWriter
-	lastReceive   time.Time
-	buffer        bytes.Buffer
-	reset         chan struct{}
+	recvPipe  *io.PipeReader
+	writePipe *io.PipeWriter
 
-	closed bool
+	mu          sync.Mutex // protects the following:
+	lastReceive time.Time
 
-	lock sync.Mutex // Synchronization for DataChannel destruction
-	once sync.Once  // Synchronization for PeerConnection destruction
+	open   chan struct{} // Channel to notify when datachannel opens
+	closed chan struct{}
 
-	BytesLogger
+	once sync.Once // Synchronization for PeerConnection destruction
+
+	bytesLogger  bytesLogger
+	eventsLogger event.SnowflakeEventReceiver
 }
 
-// Construct a WebRTC PeerConnection.
 func NewWebRTCPeer(config *webrtc.Configuration,
-	broker *BrokerChannel) *WebRTCPeer {
+	broker *BrokerChannel) (*WebRTCPeer, error) {
+	return NewWebRTCPeerWithEvents(config, broker, nil)
+}
+
+// NewWebRTCPeerWithEvents constructs a WebRTC PeerConnection to a snowflake proxy.
+//
+// The creation of the peer handles the signaling to the Snowflake broker, including
+// the exchange of SDP information, the creation of a PeerConnection, and the establishment
+// of a DataChannel to the Snowflake proxy.
+func NewWebRTCPeerWithEvents(config *webrtc.Configuration,
+	broker *BrokerChannel, eventsLogger event.SnowflakeEventReceiver) (*WebRTCPeer, error) {
+	if eventsLogger == nil {
+		eventsLogger = event.NewSnowflakeEventDispatcher()
+	}
+
 	connection := new(WebRTCPeer)
-	connection.id = "snowflake-" + uniuri.New()
-	connection.config = config
-	connection.broker = broker
-	connection.offerChannel = make(chan *webrtc.SessionDescription, 1)
-	connection.answerChannel = make(chan *webrtc.SessionDescription, 1)
-	// Error channel is mostly for reporting during the initial SDP offer
-	// creation & local description setting, which happens asynchronously.
-	connection.errorChannel = make(chan error, 1)
-	connection.reset = make(chan struct{}, 1)
+	{
+		var buf [8]byte
+		if _, err := rand.Read(buf[:]); err != nil {
+			panic(err)
+		}
+		connection.id = "snowflake-" + hex.EncodeToString(buf[:])
+	}
+	connection.closed = make(chan struct{})
 
 	// Override with something that's not NullLogger to have real logging.
-	connection.BytesLogger = &BytesNullLogger{}
+	connection.bytesLogger = &bytesNullLogger{}
 
 	// Pipes remain the same even when DataChannel gets switched.
 	connection.recvPipe, connection.writePipe = io.Pipe()
-	return connection
+
+	connection.eventsLogger = eventsLogger
+
+	err := connection.connect(config, broker)
+	if err != nil {
+		connection.Close()
+		return nil, err
+	}
+	return connection, nil
 }
 
 // Read bytes from local SOCKS.
@@ -73,200 +88,145 @@ func (c *WebRTCPeer) Read(b []byte) (int, error) {
 // Writes bytes out to remote WebRTC.
 // As part of |io.ReadWriter|
 func (c *WebRTCPeer) Write(b []byte) (int, error) {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-	c.BytesLogger.AddOutbound(len(b))
-	// TODO: Buffering could be improved / separated out of WebRTCPeer.
-	if nil == c.transport {
-		log.Printf("Buffered %d bytes --> WebRTC", len(b))
-		c.buffer.Write(b)
-	} else {
-		c.transport.Send(b)
+	err := c.transport.Send(b)
+	if err != nil {
+		return 0, err
 	}
+	c.bytesLogger.addOutbound(len(b))
 	return len(b), nil
 }
 
-// As part of |Snowflake|
+// Closed returns a boolean indicated whether the peer is closed.
+func (c *WebRTCPeer) Closed() bool {
+	select {
+	case <-c.closed:
+		return true
+	default:
+	}
+	return false
+}
+
+// Close closes the connection the snowflake proxy.
 func (c *WebRTCPeer) Close() error {
 	c.once.Do(func() {
-		c.closed = true
+		close(c.closed)
 		c.cleanup()
-		c.Reset()
 		log.Printf("WebRTC: Closing")
 	})
 	return nil
 }
 
-// As part of |Resetter|
-func (c *WebRTCPeer) Reset() {
-	if nil == c.reset {
-		return
-	}
-	c.reset <- struct{}{}
-}
-
-// As part of |Resetter|
-func (c *WebRTCPeer) WaitForReset() { <-c.reset }
-
 // Prevent long-lived broken remotes.
 // Should also update the DataChannel in underlying go-webrtc's to make Closes
 // more immediate / responsive.
-func (c *WebRTCPeer) checkForStaleness() {
+func (c *WebRTCPeer) checkForStaleness(timeout time.Duration) {
+	c.mu.Lock()
 	c.lastReceive = time.Now()
+	c.mu.Unlock()
 	for {
-		if c.closed {
-			return
-		}
-		if time.Since(c.lastReceive).Seconds() > SnowflakeTimeout {
-			log.Println("WebRTC: No messages received for", SnowflakeTimeout,
-				"seconds -- closing stale connection.")
+		c.mu.Lock()
+		lastReceive := c.lastReceive
+		c.mu.Unlock()
+		if time.Since(lastReceive) > timeout {
+			log.Printf("WebRTC: No messages received for %v -- closing stale connection.",
+				timeout)
+			err := errors.New("no messages received, closing stale connection")
+			c.eventsLogger.OnNewSnowflakeEvent(event.EventOnSnowflakeConnectionFailed{Error: err})
 			c.Close()
 			return
 		}
-		<-time.After(time.Second)
+		select {
+		case <-c.closed:
+			return
+		case <-time.After(time.Second):
+		}
 	}
 }
 
-// As part of |Connector| interface.
-func (c *WebRTCPeer) Connect() error {
+func (c *WebRTCPeer) connect(config *webrtc.Configuration, broker *BrokerChannel) error {
 	log.Println(c.id, " connecting...")
 	// TODO: When go-webrtc is more stable, it's possible that a new
 	// PeerConnection won't need to be re-prepared each time.
-	err := c.preparePeerConnection()
+	err := c.preparePeerConnection(config)
+	localDescription := c.pc.LocalDescription()
+	c.eventsLogger.OnNewSnowflakeEvent(event.EventOnOfferCreated{
+		WebRTCLocalDescription: localDescription,
+		Error:                  err,
+	})
 	if err != nil {
 		return err
 	}
-	err = c.establishDataChannel()
-	if err != nil {
-		// nolint: golint
-		return errors.New("WebRTC: Could not establish DataChannel")
-	}
-	err = c.exchangeSDP()
+
+	answer, err := broker.Negotiate(localDescription)
+	c.eventsLogger.OnNewSnowflakeEvent(event.EventOnBrokerRendezvous{
+		WebRTCRemoteDescription: answer,
+		Error:                   err,
+	})
 	if err != nil {
 		return err
 	}
-	go c.checkForStaleness()
+	log.Printf("Received Answer.\n")
+	err = c.pc.SetRemoteDescription(*answer)
+	if nil != err {
+		log.Println("WebRTC: Unable to SetRemoteDescription:", err)
+		return err
+	}
+
+	// Wait for the datachannel to open or time out
+	select {
+	case <-c.open:
+	case <-time.After(DataChannelTimeout):
+		c.transport.Close()
+		err = errors.New("timeout waiting for DataChannel.OnOpen")
+		c.eventsLogger.OnNewSnowflakeEvent(event.EventOnSnowflakeConnectionFailed{Error: err})
+		return err
+	}
+
+	go c.checkForStaleness(SnowflakeTimeout)
 	return nil
 }
 
-// Create and prepare callbacks on a new WebRTC PeerConnection.
-func (c *WebRTCPeer) preparePeerConnection() error {
-	if nil != c.pc {
-		if err := c.pc.Close(); err != nil {
-			log.Printf("c.pc.Close returned error: %v", err)
-		}
-		c.pc = nil
-	}
-
+// preparePeerConnection creates a new WebRTC PeerConnection and returns it
+// after ICE candidate gathering is complete..
+func (c *WebRTCPeer) preparePeerConnection(config *webrtc.Configuration) error {
+	var err error
 	s := webrtc.SettingEngine{}
-	s.SetTrickle(true)
+	s.SetICEMulticastDNSMode(ice.MulticastDNSModeDisabled)
 	api := webrtc.NewAPI(webrtc.WithSettingEngine(s))
-	pc, err := api.NewPeerConnection(*c.config)
+	c.pc, err = api.NewPeerConnection(*config)
 	if err != nil {
 		log.Printf("NewPeerConnection ERROR: %s", err)
 		return err
 	}
-	// Prepare PeerConnection callbacks.
-	// Allow candidates to accumulate until ICEGatheringStateComplete.
-	pc.OnICECandidate(func(candidate *webrtc.ICECandidate) {
-		if candidate == nil {
-			log.Printf("WebRTC: Done gathering candidates")
-		} else {
-			log.Printf("WebRTC: Got ICE candidate: %s", candidate.String())
-		}
-	})
-	pc.OnICEGatheringStateChange(func(state webrtc.ICEGathererState) {
-		if state == webrtc.ICEGathererStateComplete {
-			log.Println("WebRTC: ICEGatheringStateComplete")
-			c.offerChannel <- pc.LocalDescription()
-		}
-	})
-	// This callback is not expected, as the Client initiates the creation
-	// of the data channel, not the remote peer.
-	pc.OnDataChannel(func(channel *webrtc.DataChannel) {
-		log.Println("OnDataChannel")
-		panic("Unexpected OnDataChannel!")
-	})
-	c.pc = pc
-	go func() {
-		offer, err := pc.CreateOffer(nil)
-		// TODO: Potentially timeout and retry if ICE isn't working.
-		if err != nil {
-			c.errorChannel <- err
-			return
-		}
-		log.Println("WebRTC: Created offer")
-		err = pc.SetLocalDescription(offer)
-		if err != nil {
-			c.errorChannel <- err
-			return
-		}
-		log.Println("WebRTC: Set local description")
-	}()
-	log.Println("WebRTC: PeerConnection created.")
-	return nil
-}
-
-// Create a WebRTC DataChannel locally.
-func (c *WebRTCPeer) establishDataChannel() error {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-	if c.transport != nil {
-		panic("Unexpected datachannel already exists!")
-	}
 	ordered := true
 	dataChannelOptions := &webrtc.DataChannelInit{
 		Ordered: &ordered,
 	}
+	// We must create the data channel before creating an offer
+	// https://github.com/pion/webrtc/wiki/Release-WebRTC@v3.0.0
 	dc, err := c.pc.CreateDataChannel(c.id, dataChannelOptions)
-	// Triggers "OnNegotiationNeeded" on the PeerConnection, which will prepare
-	// an SDP offer while other goroutines operating on this struct handle the
-	// signaling. Eventually fires "OnOpen".
 	if err != nil {
 		log.Printf("CreateDataChannel ERROR: %s", err)
 		return err
 	}
 	dc.OnOpen(func() {
-		c.lock.Lock()
-		defer c.lock.Unlock()
+		c.eventsLogger.OnNewSnowflakeEvent(event.EventOnSnowflakeConnected{})
 		log.Println("WebRTC: DataChannel.OnOpen")
-		if nil != c.transport {
-			panic("WebRTC: transport already exists.")
-		}
-		// Flush buffered outgoing SOCKS data if necessary.
-		if c.buffer.Len() > 0 {
-			dc.Send(c.buffer.Bytes())
-			log.Println("Flushed", c.buffer.Len(), "bytes.")
-			c.buffer.Reset()
-		}
-		// Then enable the datachannel.
-		c.transport = dc
+		close(c.open)
 	})
 	dc.OnClose(func() {
-		c.lock.Lock()
-		// Future writes will go to the buffer until a new DataChannel is available.
-		if nil == c.transport {
-			// Closed locally, as part of a reset.
-			log.Println("WebRTC: DataChannel.OnClose [locally]")
-			c.lock.Unlock()
-			return
-		}
-		// Closed remotely, need to reset everything.
-		// Disable the DataChannel as a write destination.
-		log.Println("WebRTC: DataChannel.OnClose [remotely]")
-		c.transport = nil
-		dc.Close()
-		// Unlock before Close'ing, since it calls cleanup and asks for the
-		// lock to check if the transport needs to be be deleted.
-		c.lock.Unlock()
+		log.Println("WebRTC: DataChannel.OnClose")
 		c.Close()
 	})
+	dc.OnError(func(err error) {
+		c.eventsLogger.OnNewSnowflakeEvent(event.EventOnSnowflakeConnectionFailed{Error: err})
+	})
 	dc.OnMessage(func(msg webrtc.DataChannelMessage) {
 		if len(msg.Data) <= 0 {
 			log.Println("0 length message---")
 		}
-		c.BytesLogger.AddInbound(len(msg.Data))
 		n, err := c.writePipe.Write(msg.Data)
+		c.bytesLogger.addInbound(n)
 		if err != nil {
 			// TODO: Maybe shouldn't actually close.
 			log.Println("Error writing to SOCKS pipe")
@@ -274,93 +234,46 @@ func (c *WebRTCPeer) establishDataChannel() error {
 				log.Printf("c.writePipe.CloseWithError returned error: %v", inerr)
 			}
 		}
-		if n != len(msg.Data) {
-			log.Println("Error: short write")
-			panic("short write")
-		}
+		c.mu.Lock()
 		c.lastReceive = time.Now()
+		c.mu.Unlock()
 	})
+	c.transport = dc
+	c.open = make(chan struct{})
 	log.Println("WebRTC: DataChannel created.")
-	return nil
-}
 
-func (c *WebRTCPeer) sendOfferToBroker() {
-	if nil == c.broker {
-		return
-	}
-	offer := c.pc.LocalDescription()
-	answer, err := c.broker.Negotiate(offer)
-	if nil != err || nil == answer {
-		log.Printf("BrokerChannel Error: %s", err)
-		answer = nil
-	}
-	c.answerChannel <- answer
-}
-
-// Block until an SDP offer is available, send it to either
-// the Broker or signal pipe, then await for the SDP answer.
-func (c *WebRTCPeer) exchangeSDP() error {
-	select {
-	case <-c.offerChannel:
-	case err := <-c.errorChannel:
+	// Allow candidates to accumulate until ICEGatheringStateComplete.
+	done := webrtc.GatheringCompletePromise(c.pc)
+	offer, err := c.pc.CreateOffer(nil)
+	// TODO: Potentially timeout and retry if ICE isn't working.
+	if err != nil {
 		log.Println("Failed to prepare offer", err)
-		c.Close()
+		c.pc.Close()
 		return err
 	}
-	// Keep trying the same offer until a valid answer arrives.
-	var ok bool
-	var answer *webrtc.SessionDescription
-	for nil == answer {
-		go c.sendOfferToBroker()
-		answer, ok = <-c.answerChannel // Blocks...
-		if !ok || nil == answer {
-			log.Printf("Failed to retrieve answer. Retrying in %d seconds", ReconnectTimeout)
-			<-time.After(time.Second * ReconnectTimeout)
-			answer = nil
-		}
-	}
-	log.Printf("Received Answer.\n")
-	err := c.pc.SetRemoteDescription(*answer)
-	if nil != err {
-		log.Println("WebRTC: Unable to SetRemoteDescription:", err)
+	log.Println("WebRTC: Created offer")
+	err = c.pc.SetLocalDescription(offer)
+	if err != nil {
+		log.Println("Failed to prepare offer", err)
+		c.pc.Close()
 		return err
 	}
+	log.Println("WebRTC: Set local description")
+
+	<-done // Wait for ICE candidate gathering to complete.
+	log.Println("WebRTC: PeerConnection created.")
 	return nil
 }
 
-// Close all channels and transports
+// cleanup closes all channels and transports
 func (c *WebRTCPeer) cleanup() {
-	if nil != c.offerChannel {
-		close(c.offerChannel)
-	}
-	if nil != c.answerChannel {
-		close(c.answerChannel)
-	}
-	if nil != c.errorChannel {
-		close(c.errorChannel)
-	}
 	// Close this side of the SOCKS pipe.
-	if nil != c.writePipe {
+	if c.writePipe != nil { // c.writePipe can be nil in tests.
 		c.writePipe.Close()
-		c.writePipe = nil
 	}
-	c.lock.Lock()
 	if nil != c.transport {
 		log.Printf("WebRTC: closing DataChannel")
-		dataChannel := c.transport
-		// Setting transport to nil *before* dc Close indicates to OnClose that
-		// this was locally triggered.
-		c.transport = nil
-		// Release the lock before calling DeleteDataChannel (which in turn
-		// calls Close on the dataChannel), but after nil'ing out the transport,
-		// since otherwise we'll end up in the onClose handler in a deadlock.
-		c.lock.Unlock()
-		if c.pc == nil {
-			panic("DataChannel w/o PeerConnection, not good.")
-		}
-		dataChannel.(*webrtc.DataChannel).Close()
-	} else {
-		c.lock.Unlock()
+		c.transport.Close()
 	}
 	if nil != c.pc {
 		log.Printf("WebRTC: closing PeerConnection")
@@ -368,6 +281,5 @@ func (c *WebRTCPeer) cleanup() {
 		if nil != err {
 			log.Printf("Error closing peerconnection...")
 		}
-		c.pc = nil
 	}
 }

client/snowflake.go

@@ -10,101 +10,170 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"strconv"
 	"strings"
+	"sync"
 	"syscall"
-	"time"
 
 	pt "git.torproject.org/pluggable-transports/goptlib.git"
-	sf "git.torproject.org/pluggable-transports/snowflake.git/client/lib"
-	"git.torproject.org/pluggable-transports/snowflake.git/common/safelog"
-	"github.com/pion/webrtc"
+	sf "git.torproject.org/pluggable-transports/snowflake.git/v2/client/lib"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/event"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/safelog"
 )
 
 const (
 	DefaultSnowflakeCapacity = 1
 )
 
-// Maintain |SnowflakeCapacity| number of available WebRTC connections, to
-// transfer to the Tor SOCKS handler when needed.
-func ConnectLoop(snowflakes sf.SnowflakeCollector) {
-	for {
-		// Check if ending is necessary.
-		_, err := snowflakes.Collect()
-		if nil != err {
-			log.Println("WebRTC:", err,
-				" Retrying in", sf.ReconnectTimeout, "seconds...")
-		}
-		select {
-		case <-time.After(time.Second * sf.ReconnectTimeout):
-			continue
-		case <-snowflakes.Melted():
-			log.Println("ConnectLoop: stopped.")
-			return
-		}
-	}
+type ptEventLogger struct {
 }
 
-// Accept local SOCKS connections and pass them to the handler.
-func socksAcceptLoop(ln *pt.SocksListener, snowflakes sf.SnowflakeCollector) {
+func NewPTEventLogger() event.SnowflakeEventReceiver {
+	return &ptEventLogger{}
+}
+
+func (p ptEventLogger) OnNewSnowflakeEvent(e event.SnowflakeEvent) {
+	pt.Log(pt.LogSeverityNotice, e.String())
+}
+
+// Exchanges bytes between two ReadWriters.
+// (In this case, between a SOCKS connection and a snowflake transport conn)
+func copyLoop(socks, sfconn io.ReadWriter) {
+	done := make(chan struct{}, 2)
+	go func() {
+		if _, err := io.Copy(socks, sfconn); err != nil {
+			log.Printf("copying Snowflake to SOCKS resulted in error: %v", err)
+		}
+		done <- struct{}{}
+	}()
+	go func() {
+		if _, err := io.Copy(sfconn, socks); err != nil {
+			log.Printf("copying SOCKS to Snowflake resulted in error: %v", err)
+		}
+		done <- struct{}{}
+	}()
+	<-done
+	log.Println("copy loop ended")
+}
+
+// Accept local SOCKS connections and connect to a Snowflake connection
+func socksAcceptLoop(ln *pt.SocksListener, config sf.ClientConfig, shutdown chan struct{}, wg *sync.WaitGroup) {
 	defer ln.Close()
-	log.Println("Started SOCKS listener.")
 	for {
-		log.Println("SOCKS listening...")
 		conn, err := ln.AcceptSocks()
 		if err != nil {
-			if e, ok := err.(net.Error); ok && e.Temporary() {
+			if err, ok := err.(net.Error); ok && err.Temporary() {
 				continue
 			}
 			log.Printf("SOCKS accept error: %s", err)
 			break
 		}
-		log.Println("SOCKS accepted: ", conn.Req)
-		err = sf.Handler(conn, snowflakes)
-		if err != nil {
-			log.Printf("handler error: %s", err)
-		}
-	}
-}
+		log.Printf("SOCKS accepted: %v", conn.Req)
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			defer conn.Close()
 
-//s is a comma-separated list of ICE server URLs
-func parseIceServers(s string) []webrtc.ICEServer {
-	var servers []webrtc.ICEServer
-	log.Println(s)
-	s = strings.TrimSpace(s)
-	if len(s) == 0 {
-		return nil
+			// Check to see if our command line options are overriden by SOCKS options
+			if arg, ok := conn.Req.Args.Get("ampcache"); ok {
+				config.AmpCacheURL = arg
+			}
+			if arg, ok := conn.Req.Args.Get("front"); ok {
+				config.FrontDomain = arg
+			}
+			if arg, ok := conn.Req.Args.Get("ice"); ok {
+				config.ICEAddresses = strings.Split(strings.TrimSpace(arg), ",")
+			}
+			if arg, ok := conn.Req.Args.Get("max"); ok {
+				max, err := strconv.Atoi(arg)
+				if err != nil {
+					conn.Reject()
+					log.Println("Invalid SOCKS arg: max=", arg)
+					return
+				}
+				config.Max = max
+			}
+			if arg, ok := conn.Req.Args.Get("url"); ok {
+				config.BrokerURL = arg
+			}
+			if arg, ok := conn.Req.Args.Get("utls-nosni"); ok {
+				switch strings.ToLower(arg) {
+				case "true":
+					fallthrough
+				case "yes":
+					config.UTLSRemoveSNI = true
+				}
+			}
+			if arg, ok := conn.Req.Args.Get("utls-imitate"); ok {
+				config.UTLSClientID = arg
+			}
+			if arg, ok := conn.Req.Args.Get("fingerprint"); ok {
+				config.BridgeFingerprint = arg
+			}
+			transport, err := sf.NewSnowflakeClient(config)
+			if err != nil {
+				conn.Reject()
+				log.Println("Failed to start snowflake transport: ", err)
+				return
+			}
+			transport.AddSnowflakeEventListener(NewPTEventLogger())
+			err = conn.Grant(&net.TCPAddr{IP: net.IPv4zero, Port: 0})
+			if err != nil {
+				log.Printf("conn.Grant error: %s", err)
+				return
+			}
+
+			handler := make(chan struct{})
+			go func() {
+				defer close(handler)
+				sconn, err := transport.Dial()
+				if err != nil {
+					log.Printf("dial error: %s", err)
+					return
+				}
+				defer sconn.Close()
+				// copy between the created Snowflake conn and the SOCKS conn
+				copyLoop(conn, sconn)
+			}()
+			select {
+			case <-shutdown:
+				log.Println("Received shutdown signal")
+			case <-handler:
+				log.Println("Handler ended")
+			}
+			return
+		}()
 	}
-	urls := strings.Split(s, ",")
-	log.Printf("Using ICE Servers:")
-	for _, url := range urls {
-		log.Printf("url: %s", url)
-		servers = append(servers, webrtc.ICEServer{
-			URLs: []string{url},
-		})
-	}
-	return servers
 }
 
 func main() {
 	iceServersCommas := flag.String("ice", "", "comma-separated list of ICE servers")
 	brokerURL := flag.String("url", "", "URL of signaling broker")
 	frontDomain := flag.String("front", "", "front domain")
+	ampCacheURL := flag.String("ampcache", "", "URL of AMP cache to use as a proxy for signaling")
 	logFilename := flag.String("log", "", "name of log file")
-	logToStateDir := flag.Bool("logToStateDir", false, "resolve the log file relative to tor's pt state dir")
+	logToStateDir := flag.Bool("log-to-state-dir", false, "resolve the log file relative to tor's pt state dir")
+	keepLocalAddresses := flag.Bool("keep-local-addresses", false, "keep local LAN address ICE candidates")
+	unsafeLogging := flag.Bool("unsafe-logging", false, "prevent logs from being scrubbed")
 	max := flag.Int("max", DefaultSnowflakeCapacity,
 		"capacity for number of multiplexed WebRTC peers")
+
+	// Deprecated
+	oldLogToStateDir := flag.Bool("logToStateDir", false, "use -log-to-state-dir instead")
+	oldKeepLocalAddresses := flag.Bool("keepLocalAddresses", false, "use -keep-local-addresses instead")
+
 	flag.Parse()
 
 	log.SetFlags(log.LstdFlags | log.LUTC)
 
-	// Don't write to stderr; versions of tor earlier than about
-	// 0.3.5.6 do not read from the pipe, and eventually we will
-	// deadlock because the buffer is full.
+	// Don't write to stderr; versions of tor earlier than about 0.3.5.6 do
+	// not read from the pipe, and eventually we will deadlock because the
+	// buffer is full.
 	// https://bugs.torproject.org/26360
 	// https://bugs.torproject.org/25600#comment:14
 	var logOutput = ioutil.Discard
 	if *logFilename != "" {
-		if *logToStateDir {
+		if *logToStateDir || *oldLogToStateDir {
 			stateDir, err := pt.MakeStateDir()
 			if err != nil {
 				log.Fatal(err)
@@ -119,36 +188,23 @@ func main() {
 		defer logFile.Close()
 		logOutput = logFile
 	}
-	//We want to send the log output through our scrubber first
-	log.SetOutput(&safelog.LogScrubber{Output: logOutput})
-
-	log.Println("\n\n\n --- Starting Snowflake Client ---")
-
-	iceServers := parseIceServers(*iceServersCommas)
-
-	// Prepare to collect remote WebRTC peers.
-	snowflakes := sf.NewPeers(*max)
-
-	// Use potentially domain-fronting broker to rendezvous.
-	broker := sf.NewBrokerChannel(*brokerURL, *frontDomain, sf.CreateBrokerTransport())
-	snowflakes.Tongue = sf.NewWebRTCDialer(broker, iceServers)
-
-	if nil == snowflakes.Tongue {
-		log.Fatal("Unable to prepare rendezvous method.")
-		return
+	if *unsafeLogging {
+		log.SetOutput(logOutput)
+	} else {
+		// We want to send the log output through our scrubber first
+		log.SetOutput(&safelog.LogScrubber{Output: logOutput})
 	}
-	// Use a real logger to periodically output how much traffic is happening.
-	snowflakes.BytesLogger = &sf.BytesSyncLogger{
-		InboundChan:  make(chan int, 5),
-		OutboundChan: make(chan int, 5),
-		Inbound:      0,
-		Outbound:     0,
-		InEvents:     0,
-		OutEvents:    0,
-	}
-	go snowflakes.BytesLogger.Log()
 
-	go ConnectLoop(snowflakes)
+	iceAddresses := strings.Split(strings.TrimSpace(*iceServersCommas), ",")
+
+	config := sf.ClientConfig{
+		BrokerURL:          *brokerURL,
+		AmpCacheURL:        *ampCacheURL,
+		FrontDomain:        *frontDomain,
+		ICEAddresses:       iceAddresses,
+		KeepLocalAddresses: *keepLocalAddresses || *oldKeepLocalAddresses,
+		Max:                *max,
+	}
 
 	// Begin goptlib client process.
 	ptInfo, err := pt.ClientSetup(nil)
@@ -156,30 +212,27 @@ func main() {
 		log.Fatal(err)
 	}
 	if ptInfo.ProxyURL != nil {
-		if err := pt.ProxyError("proxy is not supported"); err != nil {
-			log.Printf("call to pt.ProxyError generated error: %v", err)
-		}
+		pt.ProxyError("proxy is not supported")
 		os.Exit(1)
 	}
 	listeners := make([]net.Listener, 0)
+	shutdown := make(chan struct{})
+	var wg sync.WaitGroup
 	for _, methodName := range ptInfo.MethodNames {
 		switch methodName {
 		case "snowflake":
 			// TODO: Be able to recover when SOCKS dies.
 			ln, err := pt.ListenSocks("tcp", "127.0.0.1:0")
 			if err != nil {
-				if inerr := pt.CmethodError(methodName, err.Error()); inerr != nil {
-					log.Printf("handling error generated by pt.ListenSocks with pt.CmethodError generated error: %v", inerr)
-				}
+				pt.CmethodError(methodName, err.Error())
 				break
 			}
-			go socksAcceptLoop(ln, snowflakes)
+			log.Printf("Started SOCKS listener at %v.", ln.Addr())
+			go socksAcceptLoop(ln, config, shutdown, &wg)
 			pt.Cmethod(methodName, ln.Version(), ln.Addr())
 			listeners = append(listeners, ln)
 		default:
-			if err := pt.CmethodError(methodName, "no such method"); err != nil {
-				log.Printf("calling pt.CmethodError generated error: %v", err)
-			}
+			pt.CmethodError(methodName, "no such method")
 		}
 	}
 	pt.CmethodsDone()
@@ -199,13 +252,15 @@ func main() {
 		}()
 	}
 
-	// keep track of handlers and wait for a signal
+	// Wait for a signal.
 	<-sigChan
+	log.Println("stopping snowflake")
 
-	// signal received, shut down
+	// Signal received, shut down.
 	for _, ln := range listeners {
 		ln.Close()
 	}
-	snowflakes.End()
+	close(shutdown)
+	wg.Wait()
 	log.Println("snowflake is done.")
 }

client/torrc

@@ -1,10 +1,8 @@
 UseBridges 1
 DataDirectory datadir
 
-ClientTransportPlugin snowflake exec ./client \
--url https://snowflake-broker.azureedge.net/ \
--front ajax.aspnetcdn.com \
--ice stun:stun.l.google.com:19302 \
--max 3
+ClientTransportPlugin snowflake exec ./client -log snowflake.log
 
-Bridge snowflake 0.0.3.0:1
+Bridge snowflake 192.0.2.3:1 2B280B23E1107BB62ABFC40DDCC8824814F80A72 fingerprint=2B280B23E1107BB62ABFC40DDCC8824814F80A72 url=https://snowflake-broker.torproject.net.global.prod.fastly.net/ front=cdn.sstatic.net ice=stun:stun.voip.blackberry.com:3478,stun:stun.altar.com.pl:3478,stun:stun.antisip.com:3478,stun:stun.bluesip.net:3478,stun:stun.dus.net:3478,stun:stun.epygi.com:3478,stun:stun.sonetel.com:3478,stun:stun.sonetel.net:3478,stun:stun.stunprotocol.org:3478,stun:stun.uls.co.za:3478,stun:stun.voipgate.com:3478,stun:stun.voys.nl:3478
+
+SocksPort auto

client/torrc-localhost

@@ -1,7 +0,0 @@
-UseBridges 1
-DataDirectory datadir
-
-ClientTransportPlugin snowflake exec ./client \
--url http://localhost:8080/ \
-
-Bridge snowflake 0.0.3.0:1

client/torrc.localhost

@@ -0,0 +1,6 @@
+UseBridges 1
+DataDirectory datadir
+
+ClientTransportPlugin snowflake exec ./client -keep-local-addresses
+
+Bridge snowflake 192.0.2.3:1 url=http://localhost:8080/

common/amp/armor_decoder.go

@@ -0,0 +1,136 @@
+package amp
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/base64"
+	"fmt"
+	"io"
+
+	"golang.org/x/net/html"
+)
+
+// ErrUnknownVersion is the error returned when the first character inside the
+// element encoding (but outside the base64 encoding) is not '0'.
+type ErrUnknownVersion byte
+
+func (err ErrUnknownVersion) Error() string {
+	return fmt.Sprintf("unknown armor version indicator %+q", byte(err))
+}
+
+func isASCIIWhitespace(b byte) bool {
+	switch b {
+	// https://infra.spec.whatwg.org/#ascii-whitespace
+	case '\x09', '\x0a', '\x0c', '\x0d', '\x20':
+		return true
+	default:
+		return false
+	}
+}
+
+func splitASCIIWhitespace(data []byte, atEOF bool) (advance int, token []byte, err error) {
+	var i, j int
+	// Skip initial whitespace.
+	for i = 0; i < len(data); i++ {
+		if !isASCIIWhitespace(data[i]) {
+			break
+		}
+	}
+	// Look for next whitespace.
+	for j = i; j < len(data); j++ {
+		if isASCIIWhitespace(data[j]) {
+			return j + 1, data[i:j], nil
+		}
+	}
+	// We reached the end of data without finding more whitespace. Only
+	// consider it a token if we are at EOF.
+	if atEOF && i < j {
+		return j, data[i:j], nil
+	}
+	// Otherwise, request more data.
+	return i, nil, nil
+}
+
+func decodeToWriter(w io.Writer, r io.Reader) (int64, error) {
+	tokenizer := html.NewTokenizer(r)
+	// Set a memory limit on token sizes, otherwise the tokenizer will
+	// buffer text indefinitely if it is not broken up by other token types.
+	tokenizer.SetMaxBuf(elementSizeLimit)
+	active := false
+	total := int64(0)
+	for {
+		tt := tokenizer.Next()
+		switch tt {
+		case html.ErrorToken:
+			err := tokenizer.Err()
+			if err == io.EOF {
+				err = nil
+			}
+			if err == nil && active {
+				return total, fmt.Errorf("missing </pre> tag")
+			}
+			return total, err
+		case html.TextToken:
+			if active {
+				// Re-join the separate chunks of text and
+				// feed them to the decoder.
+				scanner := bufio.NewScanner(bytes.NewReader(tokenizer.Text()))
+				scanner.Split(splitASCIIWhitespace)
+				for scanner.Scan() {
+					n, err := w.Write(scanner.Bytes())
+					total += int64(n)
+					if err != nil {
+						return total, err
+					}
+				}
+				if err := scanner.Err(); err != nil {
+					return total, err
+				}
+			}
+		case html.StartTagToken:
+			tn, _ := tokenizer.TagName()
+			if string(tn) == "pre" {
+				if active {
+					// nesting not allowed
+					return total, fmt.Errorf("unexpected %s", tokenizer.Token())
+				}
+				active = true
+			}
+		case html.EndTagToken:
+			tn, _ := tokenizer.TagName()
+			if string(tn) == "pre" {
+				if !active {
+					// stray end tag
+					return total, fmt.Errorf("unexpected %s", tokenizer.Token())
+				}
+				active = false
+			}
+		}
+	}
+}
+
+// NewArmorDecoder returns a new AMP armor decoder.
+func NewArmorDecoder(r io.Reader) (io.Reader, error) {
+	pr, pw := io.Pipe()
+	go func() {
+		_, err := decodeToWriter(pw, r)
+		pw.CloseWithError(err)
+	}()
+
+	// The first byte inside the element encoding is a server–client
+	// protocol version indicator.
+	var version [1]byte
+	_, err := pr.Read(version[:])
+	if err != nil {
+		pr.CloseWithError(err)
+		return nil, err
+	}
+	switch version[0] {
+	case '0':
+		return base64.NewDecoder(base64.StdEncoding, pr), nil
+	default:
+		err := ErrUnknownVersion(version[0])
+		pr.CloseWithError(err)
+		return nil, err
+	}
+}

common/amp/armor_encoder.go

@@ -0,0 +1,176 @@
+package amp
+
+import (
+	"encoding/base64"
+	"io"
+)
+
+// https://amp.dev/boilerplate/
+// https://amp.dev/documentation/guides-and-tutorials/learn/spec/amp-boilerplate/?format=websites
+// https://amp.dev/documentation/guides-and-tutorials/learn/spec/amphtml/?format=websites#the-amp-html-format
+const (
+	boilerplateStart = `<!doctype html>
+<html amp>
+<head>
+<meta charset="utf-8">
+<script async src="https://cdn.ampproject.org/v0.js"></script>
+<link rel="canonical" href="#">
+<meta name="viewport" content="width=device-width">
+<style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style><noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>
+</head>
+<body>
+`
+	boilerplateEnd = `</body>
+</html>`
+)
+
+const (
+	// We restrict the amount of text may go inside an HTML element, in
+	// order to limit the amount a decoder may have to buffer.
+	elementSizeLimit = 32 * 1024
+
+	// The payload is conceptually a long base64-encoded string, but we
+	// break the string into short chunks separated by whitespace. This is
+	// to protect against modification by AMP caches, which reportedly may
+	// truncate long words in text:
+	// https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/25985#note_2592348
+	bytesPerChunk = 32
+
+	// We set the number of chunks per element so as to stay under
+	// elementSizeLimit. Here, we assume that there is 1 byte of whitespace
+	// after each chunk (with an additional whitespace byte at the beginning
+	// of the element).
+	chunksPerElement = (elementSizeLimit - 1) / (bytesPerChunk + 1)
+)
+
+// The AMP armor encoder is a chain of a base64 encoder (base64.NewEncoder) and
+// an HTML element encoder (elementEncoder). A top-level encoder (armorEncoder)
+// coordinates these two, and handles prepending and appending the AMP
+// boilerplate. armorEncoder's Write method writes data into the base64 encoder,
+// where it makes its way through the chain.
+
+// NewArmorEncoder returns a new AMP armor encoder. Anything written to the
+// returned io.WriteCloser will be encoded and written to w. The caller must
+// call Close to flush any partially written data and output the AMP boilerplate
+// trailer.
+func NewArmorEncoder(w io.Writer) (io.WriteCloser, error) {
+	// Immediately write the AMP boilerplate header.
+	_, err := w.Write([]byte(boilerplateStart))
+	if err != nil {
+		return nil, err
+	}
+
+	element := &elementEncoder{w: w}
+	// Write a server–client protocol version indicator, outside the base64
+	// layer.
+	_, err = element.Write([]byte{'0'})
+	if err != nil {
+		return nil, err
+	}
+
+	base64 := base64.NewEncoder(base64.StdEncoding, element)
+	return &armorEncoder{
+		w:       w,
+		element: element,
+		base64:  base64,
+	}, nil
+}
+
+type armorEncoder struct {
+	base64  io.WriteCloser
+	element *elementEncoder
+	w       io.Writer
+}
+
+func (enc *armorEncoder) Write(p []byte) (int, error) {
+	// Write into the chain base64 | element | w.
+	return enc.base64.Write(p)
+}
+
+func (enc *armorEncoder) Close() error {
+	// Close the base64 encoder first, to flush out any buffered data and
+	// the final padding.
+	err := enc.base64.Close()
+	if err != nil {
+		return err
+	}
+
+	// Next, close the element encoder, to close any open elements.
+	err = enc.element.Close()
+	if err != nil {
+		return err
+	}
+
+	// Finally, output the AMP boilerplate trailer.
+	_, err = enc.w.Write([]byte(boilerplateEnd))
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// elementEncoder arranges written data into pre elements, with the text within
+// separated into chunks. It does no HTML encoding, so data written must not
+// contain any bytes that are meaningful in HTML.
+type elementEncoder struct {
+	w              io.Writer
+	chunkCounter   int
+	elementCounter int
+}
+
+func (enc *elementEncoder) Write(p []byte) (n int, err error) {
+	total := 0
+	for len(p) > 0 {
+		if enc.elementCounter == 0 && enc.chunkCounter == 0 {
+			_, err := enc.w.Write([]byte("<pre>\n"))
+			if err != nil {
+				return total, err
+			}
+		}
+
+		n := bytesPerChunk - enc.chunkCounter
+		if n > len(p) {
+			n = len(p)
+		}
+		nn, err := enc.w.Write(p[:n])
+		if err != nil {
+			return total, err
+		}
+		total += nn
+		p = p[n:]
+
+		enc.chunkCounter += n
+		if enc.chunkCounter >= bytesPerChunk {
+			enc.chunkCounter = 0
+			enc.elementCounter += 1
+			nn, err = enc.w.Write([]byte("\n"))
+			if err != nil {
+				return total, err
+			}
+			total += nn
+		}
+
+		if enc.elementCounter >= chunksPerElement {
+			enc.elementCounter = 0
+			nn, err = enc.w.Write([]byte("</pre>\n"))
+			if err != nil {
+				return total, err
+			}
+			total += nn
+		}
+	}
+	return total, nil
+}
+
+func (enc *elementEncoder) Close() error {
+	var err error
+	if !(enc.elementCounter == 0 && enc.chunkCounter == 0) {
+		if enc.chunkCounter == 0 {
+			_, err = enc.w.Write([]byte("</pre>\n"))
+		} else {
+			_, err = enc.w.Write([]byte("\n</pre>\n"))
+		}
+	}
+	return err
+}

common/amp/armor_test.go

@@ -0,0 +1,227 @@
+package amp
+
+import (
+	"io"
+	"io/ioutil"
+	"math/rand"
+	"strings"
+	"testing"
+)
+
+func armorDecodeToString(src string) (string, error) {
+	dec, err := NewArmorDecoder(strings.NewReader(src))
+	if err != nil {
+		return "", err
+	}
+	p, err := ioutil.ReadAll(dec)
+	return string(p), err
+}
+
+func TestArmorDecoder(t *testing.T) {
+	for _, test := range []struct {
+		input          string
+		expectedOutput string
+		expectedErr    bool
+	}{
+		{`
+<pre>
+0
+</pre>
+`,
+			"",
+			false,
+		},
+		{`
+<pre>
+0aGVsbG8gd29ybGQK
+</pre>
+`,
+			"hello world\n",
+			false,
+		},
+		// bad version indicator
+		{`
+<pre>
+1aGVsbG8gd29ybGQK
+</pre>
+`,
+			"",
+			true,
+		},
+		// text outside <pre> elements
+		{`
+0aGVsbG8gd29ybGQK
+blah blah blah
+<pre>
+0aGVsbG8gd29ybGQK
+</pre>
+0aGVsbG8gd29ybGQK
+blah blah blah
+`,
+			"hello world\n",
+			false,
+		},
+		{`
+<pre>
+0QUJDREV
+GR0hJSkt
+MTU5PUFF
+SU1RVVld
+</pre>
+junk
+<pre>
+YWVowMTI
+zNDU2Nzg
+5Cg
+=
+</pre>
+<pre>
+=
+</pre>
+`,
+			"ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789\n",
+			false,
+		},
+		// no <pre> elements, hence no version indicator
+		{`
+aGVsbG8gd29ybGQK
+blah blah blah
+aGVsbG8gd29ybGQK
+aGVsbG8gd29ybGQK
+blah blah blah
+`,
+			"",
+			true,
+		},
+		// empty <pre> elements, hence no version indicator
+		{`
+aGVsbG8gd29ybGQK
+blah blah blah
+<pre>   </pre>
+aGVsbG8gd29ybGQK
+aGVsbG8gd29ybGQK<pre></pre>
+blah blah blah
+`,
+			"",
+			true,
+		},
+		// other elements inside <pre>
+		{
+			"blah <pre>0aGVsb<p>G8gd29</p>ybGQK</pre>",
+			"hello world\n",
+			false,
+		},
+		// HTML comment
+		{
+			"blah <!-- <pre>aGVsbG8gd29ybGQK</pre> -->",
+			"",
+			true,
+		},
+		// all kinds of ASCII whitespace
+		{
+			"blah <pre>\x200\x09aG\x0aV\x0csb\x0dG8\x20gd29ybGQK</pre>",
+			"hello world\n",
+			false,
+		},
+
+		// bad padding
+		{`
+<pre>
+0QUJDREV
+GR0hJSkt
+MTU5PUFF
+SU1RVVld
+</pre>
+junk
+<pre>
+YWVowMTI
+zNDU2Nzg
+5Cg
+=
+</pre>
+`,
+			"",
+			true,
+		},
+		/*
+			// per-chunk base64
+			// test disabled because Go stdlib handles this incorrectly:
+			// https://github.com/golang/go/issues/31626
+			{
+				"<pre>QQ==</pre><pre>Qg==</pre>",
+				"",
+				true,
+			},
+		*/
+		// missing </pre>
+		{
+			"blah <pre></pre><pre>0aGVsbG8gd29ybGQK",
+			"",
+			true,
+		},
+		// nested <pre>
+		{
+			"blah <pre>0aGVsb<pre>G8gd29</pre>ybGQK</pre>",
+			"",
+			true,
+		},
+	} {
+		output, err := armorDecodeToString(test.input)
+		if test.expectedErr && err == nil {
+			t.Errorf("%+q → (%+q, %v), expected error", test.input, output, err)
+			continue
+		}
+		if !test.expectedErr && err != nil {
+			t.Errorf("%+q → (%+q, %v), expected no error", test.input, output, err)
+			continue
+		}
+		if !test.expectedErr && output != test.expectedOutput {
+			t.Errorf("%+q → (%+q, %v), expected (%+q, %v)",
+				test.input, output, err, test.expectedOutput, nil)
+			continue
+		}
+	}
+}
+
+func armorRoundTrip(s string) (string, error) {
+	var encoded strings.Builder
+	enc, err := NewArmorEncoder(&encoded)
+	if err != nil {
+		return "", err
+	}
+	_, err = io.Copy(enc, strings.NewReader(s))
+	if err != nil {
+		return "", err
+	}
+	err = enc.Close()
+	if err != nil {
+		return "", err
+	}
+	return armorDecodeToString(encoded.String())
+}
+
+func TestArmorRoundTrip(t *testing.T) {
+	lengths := make([]int, 0)
+	// Test short strings and lengths around elementSizeLimit thresholds.
+	for i := 0; i < bytesPerChunk*2; i++ {
+		lengths = append(lengths, i)
+	}
+	for i := -10; i < +10; i++ {
+		lengths = append(lengths, elementSizeLimit+i)
+		lengths = append(lengths, 2*elementSizeLimit+i)
+	}
+	for _, n := range lengths {
+		buf := make([]byte, n)
+		rand.Read(buf)
+		input := string(buf)
+		output, err := armorRoundTrip(input)
+		if err != nil {
+			t.Errorf("length %d → error %v", n, err)
+			continue
+		}
+		if output != input {
+			t.Errorf("length %d → %+q", n, output)
+			continue
+		}
+	}
+}

common/amp/cache.go

@@ -0,0 +1,178 @@
+package amp
+
+import (
+	"crypto/sha256"
+	"encoding/base32"
+	"fmt"
+	"net"
+	"net/url"
+	"path"
+	"strings"
+
+	"golang.org/x/net/idna"
+)
+
+// domainPrefixBasic does the basic domain prefix conversion. Does not do any
+// IDNA mapping, such as https://www.unicode.org/reports/tr46/.
+//
+// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#basic-algorithm
+func domainPrefixBasic(domain string) (string, error) {
+	// 1. Punycode Decode the publisher domain.
+	prefix, err := idna.ToUnicode(domain)
+	if err != nil {
+		return "", err
+	}
+
+	// 2. Replace any "-" (hyphen) character in the output of step 1 with
+	//    "--" (two hyphens).
+	prefix = strings.Replace(prefix, "-", "--", -1)
+
+	// 3. Replace any "." (dot) character in the output of step 2 with "-"
+	//    (hyphen).
+	prefix = strings.Replace(prefix, ".", "-", -1)
+
+	// 4. If the output of step 3 has a "-" (hyphen) at both positions 3 and
+	//    4, then to the output of step 3, add a prefix of "0-" and add a
+	//    suffix of "-0".
+	if len(prefix) >= 4 && prefix[2] == '-' && prefix[3] == '-' {
+		prefix = "0-" + prefix + "-0"
+	}
+
+	// 5. Punycode Encode the output of step 3.
+	return idna.ToASCII(prefix)
+}
+
+// Lower-case base32 without padding.
+var fallbackBase32Encoding = base32.NewEncoding("abcdefghijklmnopqrstuvwxyz234567").WithPadding(base32.NoPadding)
+
+// domainPrefixFallback does the fallback domain prefix conversion. The returned
+// base32 domain uses lower-case letters.
+//
+// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#fallback-algorithm
+func domainPrefixFallback(domain string) string {
+	// The algorithm specification does not say what, exactly, we are to
+	// take the SHA-256 of. domain is notionally an abstract Unicode
+	// string, not a byte sequence. While
+	// https://github.com/ampproject/amp-toolbox/blob/84cb3057e5f6c54d64369ddd285db1cb36237ee8/packages/cache-url/lib/AmpCurlUrlGenerator.js#L62
+	// says "Take the SHA256 of the punycode view of the domain," in reality
+	// it hashes the UTF-8 encoding of the domain, without Punycode:
+	// https://github.com/ampproject/amp-toolbox/blob/84cb3057e5f6c54d64369ddd285db1cb36237ee8/packages/cache-url/lib/AmpCurlUrlGenerator.js#L141
+	// https://github.com/ampproject/amp-toolbox/blob/84cb3057e5f6c54d64369ddd285db1cb36237ee8/packages/cache-url/lib/browser/Sha256.js#L24
+	// We do the same here, hashing the raw bytes of domain, presumed to be
+	// UTF-8.
+
+	// 1. Hash the publisher's domain using SHA256.
+	h := sha256.Sum256([]byte(domain))
+
+	// 2. Base32 Escape the output of step 1.
+	// 3. Remove the last 4 characters from the output of step 2, which are
+	//    always "=" (equals) characters.
+	return fallbackBase32Encoding.EncodeToString(h[:])
+}
+
+// domainPrefix computes the domain prefix of an AMP cache URL.
+//
+// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#domain-name-prefix
+func domainPrefix(domain string) string {
+	// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#combined-algorithm
+	// 1. Run the Basic Algorithm. If the output is a valid DNS label,
+	//    [append the Cache domain suffix and] return. Otherwise continue to
+	//    step 2.
+	prefix, err := domainPrefixBasic(domain)
+	// "A domain prefix is not a valid DNS label if it is longer than 63
+	// characters"
+	if err == nil && len(prefix) <= 63 {
+		return prefix
+	}
+	// 2. Run the Fallback Algorithm. [Append the Cache domain suffix and]
+	//    return.
+	return domainPrefixFallback(domain)
+}
+
+// CacheURL computes the AMP cache URL for the publisher URL pubURL, using the
+// AMP cache at cacheURL. contentType is a string such as "c" or "i" that
+// indicates what type of serving the AMP cache is to perform. The Scheme of
+// pubURL must be "http" or "https". The Port of pubURL, if any, must match the
+// default for the scheme. cacheURL may not have RawQuery, Fragment, or
+// RawFragment set, because the resulting URL's query and fragment are taken
+// from the publisher URL.
+//
+// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/
+func CacheURL(pubURL, cacheURL *url.URL, contentType string) (*url.URL, error) {
+	// The cache URL subdomain, including the domain prefix corresponding to
+	// the publisher URL's domain.
+	resultHost := domainPrefix(pubURL.Hostname()) + "." + cacheURL.Hostname()
+	if cacheURL.Port() != "" {
+		resultHost = net.JoinHostPort(resultHost, cacheURL.Port())
+	}
+
+	// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#url-path
+	// The first part of the path is the cache URL's own path, if any.
+	pathComponents := []string{cacheURL.EscapedPath()}
+	// The next path component is the content type. We cannot encode an
+	// empty content type, because it would result in consecutive path
+	// separators, which would semantically combine into a single separator.
+	if contentType == "" {
+		return nil, fmt.Errorf("invalid content type %+q", contentType)
+	}
+	pathComponents = append(pathComponents, url.PathEscape(contentType))
+	// Then, we add an "s" path component, if the publisher URL scheme is
+	// "https".
+	switch pubURL.Scheme {
+	case "http":
+		// Do nothing.
+	case "https":
+		pathComponents = append(pathComponents, "s")
+	default:
+		return nil, fmt.Errorf("invalid scheme %+q in publisher URL", pubURL.Scheme)
+	}
+	// The next path component is the publisher URL's host. The AMP cache
+	// URL format specification is not clear about whether other
+	// subcomponents of the authority (namely userinfo and port) may appear
+	// here. We adopt a policy of forbidding userinfo, and requiring that
+	// the port be the default for the scheme (and then we omit the port
+	// entirely from the returned URL).
+	if pubURL.User != nil {
+		return nil, fmt.Errorf("publisher URL may not contain userinfo")
+	}
+	if port := pubURL.Port(); port != "" {
+		if !((pubURL.Scheme == "http" && port == "80") || (pubURL.Scheme == "https" && port == "443")) {
+			return nil, fmt.Errorf("publisher URL port %+q is not the default for scheme %+q", port, pubURL.Scheme)
+		}
+	}
+	// As with the content type, we cannot encode an empty host, because
+	// that would result in an empty path component.
+	if pubURL.Hostname() == "" {
+		return nil, fmt.Errorf("invalid host %+q in publisher URL", pubURL.Hostname())
+	}
+	pathComponents = append(pathComponents, url.PathEscape(pubURL.Hostname()))
+	// Finally, we append the remainder of the original escaped path from
+	// the publisher URL.
+	pathComponents = append(pathComponents, pubURL.EscapedPath())
+
+	resultRawPath := path.Join(pathComponents...)
+	resultPath, err := url.PathUnescape(resultRawPath)
+	if err != nil {
+		return nil, err
+	}
+
+	// The query and fragment of the returned URL always come from pubURL.
+	// Any query or fragment of cacheURL would be ignored. Return an error
+	// if either is set.
+	if cacheURL.RawQuery != "" {
+		return nil, fmt.Errorf("cache URL may not contain a query")
+	}
+	if cacheURL.Fragment != "" {
+		return nil, fmt.Errorf("cache URL may not contain a fragment")
+	}
+
+	return &url.URL{
+		Scheme:   cacheURL.Scheme,
+		User:     cacheURL.User,
+		Host:     resultHost,
+		Path:     resultPath,
+		RawPath:  resultRawPath,
+		RawQuery: pubURL.RawQuery,
+		Fragment: pubURL.Fragment,
+	}, nil
+}

common/amp/cache_test.go

@@ -0,0 +1,320 @@
+package amp
+
+import (
+	"bytes"
+	"net/url"
+	"testing"
+
+	"golang.org/x/net/idna"
+)
+
+func TestDomainPrefixBasic(t *testing.T) {
+	// Tests expecting no error.
+	for _, test := range []struct {
+		domain, expected string
+	}{
+		{"", ""},
+		{"xn--", ""},
+		{"...", "---"},
+
+		// Should not apply mappings such as case folding and
+		// normalization.
+		{"b\u00fccher.de", "xn--bcher-de-65a"},
+		{"B\u00fccher.de", "xn--Bcher-de-65a"},
+		{"bu\u0308cher.de", "xn--bucher-de-hkf"},
+
+		// Check some that differ between IDNA 2003 and IDNA 2008.
+		// https://unicode.org/reports/tr46/#Deviations
+		// https://util.unicode.org/UnicodeJsps/idna.jsp
+		{"faß.de", "xn--fa-de-mqa"},
+		{"βόλοσ.com", "xn---com-4ld8c2a6a8e"},
+
+		// Lengths of 63 and 64. 64 is too long for a DNS label, but
+		// domainPrefixBasic is not expected to check for that.
+		{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"},
+		{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"},
+
+		// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#basic-algorithm
+		{"example.com", "example-com"},
+		{"foo.example.com", "foo-example-com"},
+		{"foo-example.com", "foo--example-com"},
+		{"xn--57hw060o.com", "xn---com-p33b41770a"},
+		{"\u26a1\U0001f60a.com", "xn---com-p33b41770a"},
+		{"en-us.example.com", "0-en--us-example-com-0"},
+	} {
+		output, err := domainPrefixBasic(test.domain)
+		if err != nil || output != test.expected {
+			t.Errorf("%+q → (%+q, %v), expected (%+q, %v)",
+				test.domain, output, err, test.expected, nil)
+		}
+	}
+
+	// Tests expecting an error.
+	for _, domain := range []string{
+		"xn---",
+	} {
+		output, err := domainPrefixBasic(domain)
+		if err == nil || output != "" {
+			t.Errorf("%+q → (%+q, %v), expected (%+q, non-nil)",
+				domain, output, err, "")
+		}
+	}
+}
+
+func TestDomainPrefixFallback(t *testing.T) {
+	for _, test := range []struct {
+		domain, expected string
+	}{
+		{
+			"",
+			"4oymiquy7qobjgx36tejs35zeqt24qpemsnzgtfeswmrw6csxbkq",
+		},
+		{
+			"example.com",
+			"un42n5xov642kxrxrqiyanhcoupgql5lt4wtbkyt2ijflbwodfdq",
+		},
+
+		// These checked against the output of
+		// https://github.com/ampproject/amp-toolbox/tree/84cb3057e5f6c54d64369ddd285db1cb36237ee8/packages/cache-url,
+		// using the widget at
+		// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#url-format.
+		{
+			"000000000000000000000000000000000000000000000000000000000000.com",
+			"stejanx4hsijaoj4secyecy4nvqodk56kw72whwcmvdbtucibf5a",
+		},
+		{
+			"00000000000000000000000000000000000000000000000000000000000a.com",
+			"jdcvbsorpnc3hcjrhst56nfm6ymdpovlawdbm2efyxpvlt4cpbya",
+		},
+		{
+			"00000000000000000000000000000000000000000000000000000000000\u03bb.com",
+			"qhzqeumjkfpcpuic3vqruyjswcr7y7gcm3crqyhhywvn3xrhchfa",
+		},
+	} {
+		output := domainPrefixFallback(test.domain)
+		if output != test.expected {
+			t.Errorf("%+q → %+q, expected %+q",
+				test.domain, output, test.expected)
+		}
+	}
+}
+
+// Checks that domainPrefix chooses domainPrefixBasic or domainPrefixFallback as
+// appropriate; i.e., always returns string that is a valid DNS label and is
+// IDNA-decodable.
+func TestDomainPrefix(t *testing.T) {
+	// A validating IDNA profile, which checks label length and that the
+	// label contains only certain ASCII characters. It does not do the
+	// ValidateLabels check, because that depends on the input having
+	// certain properties.
+	profile := idna.New(
+		idna.VerifyDNSLength(true),
+		idna.StrictDomainName(true),
+	)
+	for _, domain := range []string{
+		"example.com",
+		"\u0314example.com",
+		"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",  // 63 bytes
+		"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", // 64 bytes
+		"xn--57hw060o.com",
+		"a b c",
+	} {
+		output := domainPrefix(domain)
+		if bytes.IndexByte([]byte(output), '.') != -1 {
+			t.Errorf("%+q → %+q contains a dot", domain, output)
+		}
+		_, err := profile.ToUnicode(output)
+		if err != nil {
+			t.Errorf("%+q → error %v", domain, err)
+		}
+	}
+}
+
+func mustParseURL(rawurl string) *url.URL {
+	u, err := url.Parse(rawurl)
+	if err != nil {
+		panic(err)
+	}
+	return u
+}
+
+func TestCacheURL(t *testing.T) {
+	// Tests expecting no error.
+	for _, test := range []struct {
+		pub         string
+		cache       string
+		contentType string
+		expected    string
+	}{
+		// With or without trailing slash on pubURL.
+		{
+			"http://example.com/",
+			"https://amp.cache/",
+			"c",
+			"https://example-com.amp.cache/c/example.com",
+		},
+		{
+			"http://example.com",
+			"https://amp.cache/",
+			"c",
+			"https://example-com.amp.cache/c/example.com",
+		},
+		// https pubURL.
+		{
+			"https://example.com/",
+			"https://amp.cache/",
+			"c",
+			"https://example-com.amp.cache/c/s/example.com",
+		},
+		// The content type should be escaped if necessary.
+		{
+			"http://example.com/",
+			"https://amp.cache/",
+			"/",
+			"https://example-com.amp.cache/%2F/example.com",
+		},
+		// Retain pubURL path, query, and fragment, including escaping.
+		{
+			"http://example.com/my%2Fpath/index.html?a=1#fragment",
+			"https://amp.cache/",
+			"c",
+			"https://example-com.amp.cache/c/example.com/my%2Fpath/index.html?a=1#fragment",
+		},
+		// Retain scheme, userinfo, port, and path of cacheURL, escaping
+		// whatever is necessary.
+		{
+			"http://example.com",
+			"http://cache%2Fuser:cache%40pass@amp.cache:123/with/../../path/..%2f../",
+			"c",
+			"http://cache%2Fuser:cache%40pass@example-com.amp.cache:123/path/..%2f../c/example.com",
+		},
+		// Port numbers in pubURL are allowed, if they're the default
+		// for scheme.
+		{
+			"http://example.com:80/",
+			"https://amp.cache/",
+			"c",
+			"https://example-com.amp.cache/c/example.com",
+		},
+		{
+			"https://example.com:443/",
+			"https://amp.cache/",
+			"c",
+			"https://example-com.amp.cache/c/s/example.com",
+		},
+		// "?" at the end of cacheURL is okay, as long as the query is
+		// empty.
+		{
+			"http://example.com/",
+			"https://amp.cache/?",
+			"c",
+			"https://example-com.amp.cache/c/example.com",
+		},
+
+		// https://developers.google.com/amp/cache/overview#example-requesting-document-using-tls
+		{
+			"https://example.com/amp_document.html",
+			"https://cdn.ampproject.org/",
+			"c",
+			"https://example-com.cdn.ampproject.org/c/s/example.com/amp_document.html",
+		},
+		// https://developers.google.com/amp/cache/overview#example-requesting-image-using-plain-http
+		{
+			"http://example.com/logo.png",
+			"https://cdn.ampproject.org/",
+			"i",
+			"https://example-com.cdn.ampproject.org/i/example.com/logo.png",
+		},
+		// https://developers.google.com/amp/cache/overview#query-parameter-example
+		{
+			"https://example.com/g?value=Hello%20World",
+			"https://cdn.ampproject.org/",
+			"c",
+			"https://example-com.cdn.ampproject.org/c/s/example.com/g?value=Hello%20World",
+		},
+	} {
+		pubURL := mustParseURL(test.pub)
+		cacheURL := mustParseURL(test.cache)
+		outputURL, err := CacheURL(pubURL, cacheURL, test.contentType)
+		if err != nil {
+			t.Errorf("%+q %+q %+q → error %v",
+				test.pub, test.cache, test.contentType, err)
+			continue
+		}
+		if outputURL.String() != test.expected {
+			t.Errorf("%+q %+q %+q → %+q, expected %+q",
+				test.pub, test.cache, test.contentType, outputURL, test.expected)
+			continue
+		}
+	}
+
+	// Tests expecting an error.
+	for _, test := range []struct {
+		pub         string
+		cache       string
+		contentType string
+	}{
+		// Empty content type.
+		{
+			"http://example.com/",
+			"https://amp.cache/",
+			"",
+		},
+		// Empty host.
+		{
+			"http:///index.html",
+			"https://amp.cache/",
+			"c",
+		},
+		// Empty scheme.
+		{
+			"//example.com/",
+			"https://amp.cache/",
+			"c",
+		},
+		// Unrecognized scheme.
+		{
+			"ftp://example.com/",
+			"https://amp.cache/",
+			"c",
+		},
+		// Wrong port number for scheme.
+		{
+			"http://example.com:443/",
+			"https://amp.cache/",
+			"c",
+		},
+		// userinfo in pubURL.
+		{
+			"http://user@example.com/",
+			"https://amp.cache/",
+			"c",
+		},
+		{
+			"http://user:pass@example.com/",
+			"https://amp.cache/",
+			"c",
+		},
+		// cacheURL may not contain a query.
+		{
+			"http://example.com/",
+			"https://amp.cache/?a=1",
+			"c",
+		},
+		// cacheURL may not contain a fragment.
+		{
+			"http://example.com/",
+			"https://amp.cache/#fragment",
+			"c",
+		},
+	} {
+		pubURL := mustParseURL(test.pub)
+		cacheURL := mustParseURL(test.cache)
+		outputURL, err := CacheURL(pubURL, cacheURL, test.contentType)
+		if err == nil {
+			t.Errorf("%+q %+q %+q → %+q, expected error",
+				test.pub, test.cache, test.contentType, outputURL)
+			continue
+		}
+	}
+}

common/amp/doc.go

@@ -0,0 +1,88 @@
+/*
+Package amp provides functions for working with the AMP (Accelerated Mobile
+Pages) subset of HTML, and conveying binary data through an AMP cache.
+
+AMP cache
+
+The CacheURL function takes a plain URL and converts it to be accessed through a
+given AMP cache.
+
+The EncodePath and DecodePath functions provide a way to encode data into the
+suffix of a URL path. AMP caches do not support HTTP POST, but encoding data
+into a URL path with GET is an alternative means of sending data to the server.
+The format of an encoded path is:
+	0<0 or more bytes, including slash>/<base64 of data>
+That is:
+* "0", a format version number, which controls the interpretation of the rest of
+the path. Only the first byte matters as a version indicator (not the whole
+first path component).
+* Any number of slash or non-slash bytes. These may be used as padding or to
+prevent cache collisions in the AMP cache.
+* A final slash.
+* base64 encoding of the data, using the URL-safe alphabet (which does not
+include slash).
+
+For example, an encoding of the string "This is path-encoded data." is the
+following. The "lgWHcwhXFjUm" following the format version number is random
+padding that will be ignored on decoding.
+	0lgWHcwhXFjUm/VGhpcyBpcyBwYXRoLWVuY29kZWQgZGF0YS4
+
+It is the caller's responsibility to add or remove any directory path prefix
+before calling EncodePath or DecodePath.
+
+AMP armor
+
+AMP armor is a data encoding scheme that that satisfies the requirements of the
+AMP (Accelerated Mobile Pages) subset of HTML, and survives modification by an
+AMP cache. For the requirements of AMP HTML, see
+https://amp.dev/documentation/guides-and-tutorials/learn/spec/amphtml/.
+For modifications that may be made by an AMP cache, see
+https://github.com/ampproject/amphtml/blob/main/docs/spec/amp-cache-modifications.md.
+
+The encoding is based on ones created by Ivan Markin. See codec/amp/ in
+https://github.com/nogoegst/amper and discussion at
+https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/25985.
+
+The encoding algorithm works as follows. Base64-encode the input. Prepend the
+input with the byte '0'; this is a protocol version indicator that the decoder
+can use to determine how to interpret the bytes that follow. Split the base64
+into fixed-size chunks separated by whitespace. Take up to 1024 chunks at a
+time, and wrap them in a pre element. Then, situate the markup so far within the
+body of the AMP HTML boilerplate. The decoding algorithm is to scan the HTML for
+pre elements, split their text contents on whitespace and concatenate, then
+base64 decode. The base64 encoding uses the standard alphabet, with normal "="
+padding (https://tools.ietf.org/html/rfc4648#section-4).
+
+The reason for splitting the base64 into chunks is that AMP caches reportedly
+truncate long strings that are not broken by whitespace:
+https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/25985#note_2592348.
+The characters that may separate the chunks are the ASCII whitespace characters
+(https://infra.spec.whatwg.org/#ascii-whitespace) "\x09", "\x0a", "\x0c",
+"\x0d", and "\x20". The reason for separating the chunks into pre elements is to
+limit the amount of text a decoder may have to buffer while parsing the HTML.
+Each pre element may contain at most 64 KB of text. pre elements may not be
+nested.
+
+Example
+
+The following is the result of encoding the string
+"This was encoded with AMP armor.":
+
+	<!doctype html>
+	<html amp>
+	<head>
+	<meta charset="utf-8">
+	<script async src="https://cdn.ampproject.org/v0.js"></script>
+	<link rel="canonical" href="#">
+	<meta name="viewport" content="width=device-width">
+	<style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style><noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>
+	</head>
+	<body>
+	<pre>
+	0VGhpcyB3YXMgZW5jb2RlZCB3aXRoIEF
+	NUCBhcm1vci4=
+	</pre>
+	</body>
+	</html>
+*/
+package amp

common/amp/path.go

@@ -0,0 +1,44 @@
+package amp
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"strings"
+)
+
+// EncodePath encodes data in a way that is suitable for the suffix of an AMP
+// cache URL.
+func EncodePath(data []byte) string {
+	var cacheBreaker [9]byte
+	_, err := rand.Read(cacheBreaker[:])
+	if err != nil {
+		panic(err)
+	}
+	b64 := base64.RawURLEncoding.EncodeToString
+	return "0" + b64(cacheBreaker[:]) + "/" + b64(data)
+}
+
+// DecodePath decodes data from a path suffix as encoded by EncodePath. The path
+// must have already been trimmed of any directory prefix (as might be present
+// in, e.g., an HTTP request). That is, the first character of path should be
+// the "0" message format indicator.
+func DecodePath(path string) ([]byte, error) {
+	if len(path) < 1 {
+		return nil, fmt.Errorf("missing format indicator")
+	}
+	version := path[0]
+	rest := path[1:]
+	switch version {
+	case '0':
+		// Ignore everything else up to and including the final slash
+		// (there must be at least one slash).
+		i := strings.LastIndexByte(rest, '/')
+		if i == -1 {
+			return nil, fmt.Errorf("missing data")
+		}
+		return base64.RawURLEncoding.DecodeString(rest[i+1:])
+	default:
+		return nil, fmt.Errorf("unknown format indicator %q", version)
+	}
+}

common/amp/path_test.go

@@ -0,0 +1,54 @@
+package amp
+
+import (
+	"testing"
+)
+
+func TestDecodePath(t *testing.T) {
+	for _, test := range []struct {
+		path           string
+		expectedData   string
+		expectedErrStr string
+	}{
+		{"", "", "missing format indicator"},
+		{"0", "", "missing data"},
+		{"0foobar", "", "missing data"},
+		{"/0/YWJj", "", "unknown format indicator '/'"},
+
+		{"0/", "", ""},
+		{"0foobar/", "", ""},
+		{"0/YWJj", "abc", ""},
+		{"0///YWJj", "abc", ""},
+		{"0foobar/YWJj", "abc", ""},
+		{"0/foobar/YWJj", "abc", ""},
+	} {
+		data, err := DecodePath(test.path)
+		if test.expectedErrStr != "" {
+			if err == nil || err.Error() != test.expectedErrStr {
+				t.Errorf("%+q expected error %+q, got %+q",
+					test.path, test.expectedErrStr, err)
+			}
+		} else if err != nil {
+			t.Errorf("%+q expected no error, got %+q", test.path, err)
+		} else if string(data) != test.expectedData {
+			t.Errorf("%+q expected data %+q, got %+q",
+				test.path, test.expectedData, data)
+		}
+	}
+}
+
+func TestPathRoundTrip(t *testing.T) {
+	for _, data := range []string{
+		"",
+		"\x00",
+		"/",
+		"hello world",
+	} {
+		decoded, err := DecodePath(EncodePath([]byte(data)))
+		if err != nil {
+			t.Errorf("%+q roundtripped with error %v", data, err)
+		} else if string(decoded) != data {
+			t.Errorf("%+q roundtripped to %+q", data, decoded)
+		}
+	}
+}

common/bridgefingerprint/fingerprint.go

@@ -0,0 +1,30 @@
+package bridgefingerprint
+
+import (
+	"encoding/hex"
+	"errors"
+)
+
+type Fingerprint string
+
+var ErrBridgeFingerprintInvalid = errors.New("bridge fingerprint invalid")
+
+func FingerprintFromBytes(bytes []byte) (Fingerprint, error) {
+	n := len(bytes)
+	if n != 20 && n != 32 {
+		return Fingerprint(""), ErrBridgeFingerprintInvalid
+	}
+	return Fingerprint(bytes), nil
+}
+
+func FingerprintFromHexString(hexString string) (Fingerprint, error) {
+	decoded, err := hex.DecodeString(hexString)
+	if err != nil {
+		return "", err
+	}
+	return FingerprintFromBytes(decoded)
+}
+
+func (f Fingerprint) ToBytes() []byte {
+	return []byte(f)
+}

common/encapsulation/encapsulation.go

@@ -0,0 +1,194 @@
+// Package encapsulation implements a way of encoding variable-size chunks of
+// data and padding into a byte stream.
+//
+// Each chunk of data or padding starts with a variable-size length prefix. One
+// bit ("d") in the first byte of the prefix indicates whether the chunk
+// represents data or padding (1=data, 0=padding). Another bit ("c" for
+// "continuation") is the indicates whether there are more bytes in the length
+// prefix. The remaining 6 bits ("x") encode part of the length value.
+// 	dcxxxxxx
+// If the continuation bit is set, then the next byte is also part of the length
+// prefix. It lacks the "d" bit, has its own "c" bit, and 7 value-carrying bits
+// ("y").
+// 	cyyyyyyy
+// The length is decoded by concatenating value-carrying bits, from left to
+// right, of all value-carrying bits, up to and including the first byte whose
+// "c" bit is 0. Although in principle this encoding would allow for length
+// prefixes of any size, length prefixes are arbitrarily limited to 3 bytes and
+// any attempt to read or write a longer one is an error. These are therefore
+// the only valid formats:
+// 	00xxxxxx			xxxxxx₂ bytes of padding
+// 	10xxxxxx			xxxxxx₂ bytes of data
+// 	01xxxxxx 0yyyyyyy		xxxxxxyyyyyyy₂ bytes of padding
+// 	11xxxxxx 0yyyyyyy		xxxxxxyyyyyyy₂ bytes of data
+// 	01xxxxxx 1yyyyyyy 0zzzzzzz	xxxxxxyyyyyyyzzzzzzz₂ bytes of padding
+// 	11xxxxxx 1yyyyyyy 0zzzzzzz	xxxxxxyyyyyyyzzzzzzz₂ bytes of data
+// The maximum encodable length is 11111111111111111111₂ = 0xfffff = 1048575.
+// There is no requirement to use a length prefix of minimum size; i.e. 00000100
+// and 01000000 00000100 are both valid encodings of the value 4.
+//
+// After the length prefix follow that many bytes of padding or data. There are
+// no restrictions on the value of bytes comprising padding.
+//
+// The idea for this encapsulation is sketched here:
+// https://github.com/net4people/bbs/issues/9#issuecomment-524095186
+package encapsulation
+
+import (
+	"errors"
+	"io"
+	"io/ioutil"
+)
+
+// ErrTooLong is the error returned when an encoded length prefix is longer than
+// 3 bytes, or when ReadData receives an input whose length is too large to
+// encode in a 3-byte length prefix.
+var ErrTooLong = errors.New("length prefix is too long")
+
+// ReadData returns a new slice with the contents of the next available data
+// chunk, skipping over any padding chunks that may come first. The returned
+// error value is nil if and only if a data chunk was present and was read in
+// its entirety. The returned error is io.EOF only if r ended before the first
+// byte of a length prefix. If r ended in the middle of a length prefix or
+// data/padding, the returned error is io.ErrUnexpectedEOF.
+func ReadData(r io.Reader) ([]byte, error) {
+	for {
+		var b [1]byte
+		_, err := r.Read(b[:])
+		if err != nil {
+			// This is the only place we may return a real io.EOF.
+			return nil, err
+		}
+		isData := (b[0] & 0x80) != 0
+		moreLength := (b[0] & 0x40) != 0
+		n := int(b[0] & 0x3f)
+		for i := 0; moreLength; i++ {
+			if i >= 2 {
+				return nil, ErrTooLong
+			}
+			_, err := r.Read(b[:])
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
+			if err != nil {
+				return nil, err
+			}
+			moreLength = (b[0] & 0x80) != 0
+			n = (n << 7) | int(b[0]&0x7f)
+		}
+		if isData {
+			p := make([]byte, n)
+			_, err := io.ReadFull(r, p)
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
+			if err != nil {
+				return nil, err
+			}
+			return p, err
+		} else {
+			_, err := io.CopyN(ioutil.Discard, r, int64(n))
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+}
+
+// dataPrefixForLength returns a length prefix for the given length, with the
+// "d" bit set to 1.
+func dataPrefixForLength(n int) ([]byte, error) {
+	switch {
+	case (n>>0)&0x3f == (n >> 0):
+		return []byte{0x80 | byte((n>>0)&0x3f)}, nil
+	case (n>>7)&0x3f == (n >> 7):
+		return []byte{0xc0 | byte((n>>7)&0x3f), byte((n >> 0) & 0x7f)}, nil
+	case (n>>14)&0x3f == (n >> 14):
+		return []byte{0xc0 | byte((n>>14)&0x3f), 0x80 | byte((n>>7)&0x7f), byte((n >> 0) & 0x7f)}, nil
+	default:
+		return nil, ErrTooLong
+	}
+}
+
+// WriteData encodes a data chunk into w. It returns the total number of bytes
+// written; i.e., including the length prefix. The error is ErrTooLong if the
+// length of data cannot fit into a length prefix.
+func WriteData(w io.Writer, data []byte) (int, error) {
+	prefix, err := dataPrefixForLength(len(data))
+	if err != nil {
+		return 0, err
+	}
+	total := 0
+	n, err := w.Write(prefix)
+	total += n
+	if err != nil {
+		return total, err
+	}
+	n, err = w.Write(data)
+	total += n
+	return total, err
+}
+
+var paddingBuffer = make([]byte, 1024)
+
+// WritePadding encodes padding chunks, whose total size (including their own
+// length prefixes) is n. Returns the total number of bytes written to w, which
+// will be exactly n unless there was an error. The error cannot be ErrTooLong
+// because this function will write multiple padding chunks if necessary to
+// reach the requested size. Panics if n is negative.
+func WritePadding(w io.Writer, n int) (int, error) {
+	if n < 0 {
+		panic("negative length")
+	}
+	total := 0
+	for n > 0 {
+		p := len(paddingBuffer)
+		if p > n {
+			p = n
+		}
+		n -= p
+		var prefix []byte
+		switch {
+		case ((p-1)>>0)&0x3f == ((p - 1) >> 0):
+			p = p - 1
+			prefix = []byte{byte((p >> 0) & 0x3f)}
+		case ((p-2)>>7)&0x3f == ((p - 2) >> 7):
+			p = p - 2
+			prefix = []byte{0x40 | byte((p>>7)&0x3f), byte((p >> 0) & 0x7f)}
+		case ((p-3)>>14)&0x3f == ((p - 3) >> 14):
+			p = p - 3
+			prefix = []byte{0x40 | byte((p>>14)&0x3f), 0x80 | byte((p>>7)&0x3f), byte((p >> 0) & 0x7f)}
+		}
+		nn, err := w.Write(prefix)
+		total += nn
+		if err != nil {
+			return total, err
+		}
+		nn, err = w.Write(paddingBuffer[:p])
+		total += nn
+		if err != nil {
+			return total, err
+		}
+	}
+	return total, nil
+}
+
+// MaxDataForSize returns the length of the longest slice that can pe passed to
+// WriteData, whose total encoded size (including length prefix) is no larger
+// than n. Call this to find out if a chunk of data will fit into a length
+// budget. Panics if n == 0.
+func MaxDataForSize(n int) int {
+	if n == 0 {
+		panic("zero length")
+	}
+	prefix, err := dataPrefixForLength(n)
+	if err == ErrTooLong {
+		return (1 << (6 + 7 + 7)) - 1 - 3
+	} else if err != nil {
+		panic(err)
+	}
+	return n - len(prefix)
+}

common/encapsulation/encapsulation_test.go

@@ -0,0 +1,330 @@
+package encapsulation
+
+import (
+	"bytes"
+	"io"
+	"math/rand"
+	"testing"
+)
+
+// Return a byte slice with non-trivial contents.
+func pseudorandomBuffer(n int) []byte {
+	source := rand.NewSource(0)
+	p := make([]byte, n)
+	for i := 0; i < len(p); i++ {
+		p[i] = byte(source.Int63() & 0xff)
+	}
+	return p
+}
+
+func mustWriteData(w io.Writer, p []byte) int {
+	n, err := WriteData(w, p)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
+
+func mustWritePadding(w io.Writer, n int) int {
+	n, err := WritePadding(w, n)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
+
+// Test that ReadData(WriteData()) recovers the original data.
+func TestRoundtrip(t *testing.T) {
+	// Test above and below interesting thresholds.
+	for _, i := range []int{
+		0x00, 0x01,
+		0x3e, 0x3f, 0x40, 0x41,
+		0xfe, 0xff, 0x100, 0x101,
+		0x1ffe, 0x1fff, 0x2000, 0x2001,
+		0xfffe, 0xffff, 0x10000, 0x10001,
+		0xffffe, 0xfffff,
+	} {
+		original := pseudorandomBuffer(i)
+		var enc bytes.Buffer
+		n, err := WriteData(&enc, original)
+		if err != nil {
+			t.Fatalf("size %d, WriteData returned error %v", i, err)
+		}
+		if enc.Len() != n {
+			t.Fatalf("size %d, returned length was %d, written length was %d",
+				i, n, enc.Len())
+		}
+		inverse, err := ReadData(&enc)
+		if err != nil {
+			t.Fatalf("size %d, ReadData returned error %v", i, err)
+		}
+		if !bytes.Equal(inverse, original) {
+			t.Fatalf("size %d, got <%x>, expected <%x>", i, inverse, original)
+		}
+	}
+}
+
+// Test that WritePadding writes exactly as much as requested.
+func TestPaddingLength(t *testing.T) {
+	// Test above and below interesting thresholds. WritePadding also gets
+	// values above 0xfffff, the maximum value of a single length prefix.
+	for _, i := range []int{
+		0x00, 0x01,
+		0x3f, 0x40, 0x41, 0x42,
+		0xff, 0x100, 0x101, 0x102,
+		0x2000, 0x2001, 0x2002, 0x2003,
+		0x10000, 0x10001, 0x10002, 0x10003,
+		0x100001, 0x100002, 0x100003, 0x100004,
+	} {
+		var enc bytes.Buffer
+		n, err := WritePadding(&enc, i)
+		if err != nil {
+			t.Fatalf("size %d, WritePadding returned error %v", i, err)
+		}
+		if n != i {
+			t.Fatalf("requested %d bytes, returned %d", i, n)
+		}
+		if enc.Len() != n {
+			t.Fatalf("requested %d bytes, wrote %d bytes", i, enc.Len())
+		}
+	}
+}
+
+// Test that ReadData skips over padding.
+func TestSkipPadding(t *testing.T) {
+	var data = [][]byte{{}, {}, []byte("hello"), {}, []byte("world")}
+	var enc bytes.Buffer
+	mustWritePadding(&enc, 10)
+	mustWritePadding(&enc, 100)
+	mustWriteData(&enc, data[0])
+	mustWriteData(&enc, data[1])
+	mustWritePadding(&enc, 10)
+	mustWriteData(&enc, data[2])
+	mustWriteData(&enc, data[3])
+	mustWritePadding(&enc, 10)
+	mustWriteData(&enc, data[4])
+	mustWritePadding(&enc, 10)
+	mustWritePadding(&enc, 10)
+	for i, expected := range data {
+		actual, err := ReadData(&enc)
+		if err != nil {
+			t.Fatalf("slice %d, got error %v, expected %v", i, err, nil)
+		}
+		if !bytes.Equal(actual, expected) {
+			t.Fatalf("slice %d, got <%x>, expected <%x>", i, actual, expected)
+		}
+	}
+	p, err := ReadData(&enc)
+	if p != nil || err != io.EOF {
+		t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, io.EOF)
+	}
+}
+
+// Test that EOF before a length prefix returns io.EOF.
+func TestEOF(t *testing.T) {
+	p, err := ReadData(bytes.NewReader(nil))
+	if p != nil || err != io.EOF {
+		t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, io.EOF)
+	}
+}
+
+// Test that an EOF while reading a length prefix, or while reading the
+// subsequent data/padding, returns io.ErrUnexpectedEOF.
+func TestUnexpectedEOF(t *testing.T) {
+	for _, test := range [][]byte{
+		{0x40},                  // expecting a second length byte
+		{0xc0},                  // expecting a second length byte
+		{0x41, 0x80},            // expecting a third length byte
+		{0xc1, 0x80},            // expecting a third length byte
+		{0x02},                  // expecting 2 bytes of padding
+		{0x82},                  // expecting 2 bytes of data
+		{0x02, 'X'},             // expecting 1 byte of padding
+		{0x82, 'X'},             // expecting 1 byte of data
+		{0x41, 0x00},            // expecting 128 bytes of padding
+		{0xc1, 0x00},            // expecting 128 bytes of data
+		{0x41, 0x00, 'X'},       // expecting 127 bytes of padding
+		{0xc1, 0x00, 'X'},       // expecting 127 bytes of data
+		{0x41, 0x80, 0x00},      // expecting 32768 bytes of padding
+		{0xc1, 0x80, 0x00},      // expecting 32768 bytes of data
+		{0x41, 0x80, 0x00, 'X'}, // expecting 32767 bytes of padding
+		{0xc1, 0x80, 0x00, 'X'}, // expecting 32767 bytes of data
+	} {
+		p, err := ReadData(bytes.NewReader(test))
+		if p != nil || err != io.ErrUnexpectedEOF {
+			t.Fatalf("<%x> got (<%x>, %v), expected (%v, %v)", test, p, err, nil, io.ErrUnexpectedEOF)
+		}
+	}
+}
+
+// Test that length encodings that are longer than they could be are still
+// interpreted.
+func TestNonMinimalLengthEncoding(t *testing.T) {
+	for _, test := range []struct {
+		enc      []byte
+		expected []byte
+	}{
+		{[]byte{0x81, 'X'}, []byte("X")},
+		{[]byte{0xc0, 0x01, 'X'}, []byte("X")},
+		{[]byte{0xc0, 0x80, 0x01, 'X'}, []byte("X")},
+	} {
+		p, err := ReadData(bytes.NewReader(test.enc))
+		if err != nil {
+			t.Fatalf("<%x> got error %v, expected %v", test.enc, err, nil)
+		}
+		if !bytes.Equal(p, test.expected) {
+			t.Fatalf("<%x> got <%x>, expected <%x>", test.enc, p, test.expected)
+		}
+	}
+}
+
+// Test that ReadData only reads up to 3 bytes of length prefix.
+func TestReadLimits(t *testing.T) {
+	// Test the maximum length that's possible with 3 bytes of length
+	// prefix.
+	maxLength := (0x3f << 14) | (0x7f << 7) | 0x7f
+	data := bytes.Repeat([]byte{'X'}, maxLength)
+	prefix := []byte{0xff, 0xff, 0x7f} // encodes 0xfffff
+	p, err := ReadData(bytes.NewReader(append(prefix, data...)))
+	if err != nil {
+		t.Fatalf("got error %v, expected %v", err, nil)
+	}
+	if !bytes.Equal(p, data) {
+		t.Fatalf("got %d bytes unequal to %d bytes", len(p), len(data))
+	}
+	// Test a 4-byte prefix.
+	prefix = []byte{0xc0, 0xc0, 0x80, 0x80} // encodes 0x100000
+	data = bytes.Repeat([]byte{'X'}, maxLength+1)
+	p, err = ReadData(bytes.NewReader(append(prefix, data...)))
+	if p != nil || err != ErrTooLong {
+		t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, ErrTooLong)
+	}
+	// Test that 4 bytes don't work, even when they encode an integer that
+	// would fix in 3 bytes.
+	prefix = []byte{0xc0, 0x80, 0x80, 0x80} // encodes 0x0
+	data = []byte{}
+	p, err = ReadData(bytes.NewReader(append(prefix, data...)))
+	if p != nil || err != ErrTooLong {
+		t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, ErrTooLong)
+	}
+
+	// Do the same tests with padding lengths.
+	data = []byte("hello")
+	prefix = []byte{0x7f, 0xff, 0x7f} // encodes 0xfffff
+	padding := bytes.Repeat([]byte{'X'}, maxLength)
+	enc := bytes.NewBuffer(append(prefix, padding...))
+	mustWriteData(enc, data)
+	p, err = ReadData(enc)
+	if err != nil {
+		t.Fatalf("got error %v, expected %v", err, nil)
+	}
+	if !bytes.Equal(p, data) {
+		t.Fatalf("got <%x>, expected <%x>", p, data)
+	}
+	prefix = []byte{0x40, 0xc0, 0x80, 0x80} // encodes 0x100000
+	padding = bytes.Repeat([]byte{'X'}, maxLength+1)
+	enc = bytes.NewBuffer(append(prefix, padding...))
+	mustWriteData(enc, data)
+	p, err = ReadData(enc)
+	if p != nil || err != ErrTooLong {
+		t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, ErrTooLong)
+	}
+	prefix = []byte{0x40, 0x80, 0x80, 0x80} // encodes 0x0
+	padding = []byte{}
+	enc = bytes.NewBuffer(append(prefix, padding...))
+	mustWriteData(enc, data)
+	p, err = ReadData(enc)
+	if p != nil || err != ErrTooLong {
+		t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, ErrTooLong)
+	}
+}
+
+// Test that WriteData and WritePadding only accept lengths that can be encoded
+// in up to 3 bytes of length prefix.
+func TestWriteLimits(t *testing.T) {
+	maxLength := (0x3f << 14) | (0x7f << 7) | 0x7f
+	var enc bytes.Buffer
+	n, err := WriteData(&enc, bytes.Repeat([]byte{'X'}, maxLength))
+	if n != maxLength+3 || err != nil {
+		t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength, nil)
+	}
+	enc.Reset()
+	n, err = WriteData(&enc, bytes.Repeat([]byte{'X'}, maxLength+1))
+	if n != 0 || err != ErrTooLong {
+		t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, 0, ErrTooLong)
+	}
+
+	// Padding gets an extra 3 bytes because the prefix is counted as part
+	// of the length.
+	enc.Reset()
+	n, err = WritePadding(&enc, maxLength+3)
+	if n != maxLength+3 || err != nil {
+		t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength+3, nil)
+	}
+	// Writing a too-long padding is okay because WritePadding will break it
+	// into smaller chunks.
+	enc.Reset()
+	n, err = WritePadding(&enc, maxLength+4)
+	if n != maxLength+4 || err != nil {
+		t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength+4, nil)
+	}
+}
+
+// Test that WritePadding panics when given a negative length.
+func TestNegativeLength(t *testing.T) {
+	for _, n := range []int{-1, ^0} {
+		var enc bytes.Buffer
+		panicked, nn, err := testNegativeLengthSub(t, &enc, n)
+		if !panicked {
+			t.Fatalf("WritePadding(%d) returned (%d, %v) instead of panicking", n, nn, err)
+		}
+	}
+}
+
+// Calls WritePadding(w, n) and augments the return value with a flag indicating
+// whether the call panicked.
+func testNegativeLengthSub(t *testing.T, w io.Writer, n int) (panicked bool, nn int, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			panicked = true
+		}
+	}()
+	t.Helper()
+	nn, err = WritePadding(w, n)
+	return false, n, err
+}
+
+// Test that MaxDataForSize panics when given a 0 length.
+func TestMaxDataForSizeZero(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatal("didn't panic")
+		}
+	}()
+	MaxDataForSize(0)
+}
+
+// Test thresholds of available sizes for MaxDataForSize.
+func TestMaxDataForSize(t *testing.T) {
+	for _, test := range []struct {
+		size     int
+		expected int
+	}{
+		{0x01, 0x00},
+		{0x02, 0x01},
+		{0x3f, 0x3e},
+		{0x40, 0x3e},
+		{0x41, 0x3f},
+		{0x1fff, 0x1ffd},
+		{0x2000, 0x1ffd},
+		{0x2001, 0x1ffe},
+		{0xfffff, 0xffffc},
+		{0x100000, 0xffffc},
+		{0x100001, 0xffffc},
+		{0x7fffffff, 0xffffc},
+	} {
+		max := MaxDataForSize(test.size)
+		if max != test.expected {
+			t.Fatalf("size %d, got %d, expected %d", test.size, max, test.expected)
+		}
+	}
+}

common/event/bus.go

@@ -0,0 +1,39 @@
+package event
+
+import "sync"
+
+func NewSnowflakeEventDispatcher() SnowflakeEventDispatcher {
+	return &eventBus{lock: &sync.Mutex{}}
+}
+
+type eventBus struct {
+	lock      *sync.Mutex
+	listeners []SnowflakeEventReceiver
+}
+
+func (e *eventBus) OnNewSnowflakeEvent(event SnowflakeEvent) {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+	for _, v := range e.listeners {
+		v.OnNewSnowflakeEvent(event)
+	}
+}
+
+func (e *eventBus) AddSnowflakeEventListener(receiver SnowflakeEventReceiver) {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+	e.listeners = append(e.listeners, receiver)
+}
+
+func (e *eventBus) RemoveSnowflakeEventListener(receiver SnowflakeEventReceiver) {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+	var newListeners []SnowflakeEventReceiver
+	for _, v := range e.listeners {
+		if v != receiver {
+			newListeners = append(newListeners, v)
+		}
+	}
+	e.listeners = newListeners
+	return
+}

common/event/bus_test.go

@@ -0,0 +1,32 @@
+package event
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+type stubReceiver struct {
+	counter int
+}
+
+func (s *stubReceiver) OnNewSnowflakeEvent(event SnowflakeEvent) {
+	s.counter++
+}
+
+func TestBusDispatch(t *testing.T) {
+	EventBus := NewSnowflakeEventDispatcher()
+	StubReceiverA := &stubReceiver{}
+	StubReceiverB := &stubReceiver{}
+	EventBus.AddSnowflakeEventListener(StubReceiverA)
+	EventBus.AddSnowflakeEventListener(StubReceiverB)
+	assert.Equal(t, 0, StubReceiverA.counter)
+	assert.Equal(t, 0, StubReceiverB.counter)
+	EventBus.OnNewSnowflakeEvent(EventOnSnowflakeConnected{})
+	assert.Equal(t, 1, StubReceiverA.counter)
+	assert.Equal(t, 1, StubReceiverB.counter)
+	EventBus.RemoveSnowflakeEventListener(StubReceiverB)
+	EventBus.OnNewSnowflakeEvent(EventOnSnowflakeConnected{})
+	assert.Equal(t, 2, StubReceiverA.counter)
+	assert.Equal(t, 1, StubReceiverB.counter)
+
+}

common/event/interface.go

@@ -0,0 +1,85 @@
+package event
+
+import (
+	"fmt"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/safelog"
+	"github.com/pion/webrtc/v3"
+)
+
+type SnowflakeEvent interface {
+	IsSnowflakeEvent()
+	String() string
+}
+
+type EventOnOfferCreated struct {
+	SnowflakeEvent
+	WebRTCLocalDescription *webrtc.SessionDescription
+	Error                  error
+}
+
+func (e EventOnOfferCreated) String() string {
+	if e.Error != nil {
+		scrubbed := safelog.Scrub([]byte(e.Error.Error()))
+		return fmt.Sprintf("offer creation failure %s", scrubbed)
+	}
+	return "offer created"
+}
+
+type EventOnBrokerRendezvous struct {
+	SnowflakeEvent
+	WebRTCRemoteDescription *webrtc.SessionDescription
+	Error                   error
+}
+
+func (e EventOnBrokerRendezvous) String() string {
+	if e.Error != nil {
+		scrubbed := safelog.Scrub([]byte(e.Error.Error()))
+		return fmt.Sprintf("broker failure %s", scrubbed)
+	}
+	return "broker rendezvous peer received"
+}
+
+type EventOnSnowflakeConnected struct {
+	SnowflakeEvent
+}
+
+func (e EventOnSnowflakeConnected) String() string {
+	return "connected"
+}
+
+type EventOnSnowflakeConnectionFailed struct {
+	SnowflakeEvent
+	Error error
+}
+
+func (e EventOnSnowflakeConnectionFailed) String() string {
+	scrubbed := safelog.Scrub([]byte(e.Error.Error()))
+	return fmt.Sprintf("trying a new proxy: %s", scrubbed)
+}
+
+type EventOnProxyConnectionOver struct {
+	SnowflakeEvent
+	InboundTraffic  int
+	OutboundTraffic int
+}
+
+func (e EventOnProxyConnectionOver) String() string {
+	return fmt.Sprintf("Proxy connection closed (↑ %d, ↓ %d)", e.InboundTraffic, e.OutboundTraffic)
+}
+
+type SnowflakeEventReceiver interface {
+	// OnNewSnowflakeEvent notify receiver about a new event
+	// This method MUST not block
+	OnNewSnowflakeEvent(event SnowflakeEvent)
+}
+
+type SnowflakeEventDispatcher interface {
+	SnowflakeEventReceiver
+	// AddSnowflakeEventListener allow receiver(s) to receive event notification
+	// when OnNewSnowflakeEvent is called on the dispatcher.
+	// Every event listener added will be called when an event is received by the dispatcher.
+	// The order each listener is called is undefined.
+	AddSnowflakeEventListener(receiver SnowflakeEventReceiver)
+	RemoveSnowflakeEventListener(receiver SnowflakeEventReceiver)
+}

common/ipsetsink/sink.go

@@ -0,0 +1,55 @@
+package ipsetsink
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"encoding/binary"
+	"hash"
+
+	"github.com/clarkduvall/hyperloglog"
+	"golang.org/x/crypto/sha3"
+)
+
+func NewIPSetSink(maskingKey string) *IPSetSink {
+	countDistinct, _ := hyperloglog.NewPlus(18)
+	return &IPSetSink{
+		ipMaskingKey:  maskingKey,
+		countDistinct: countDistinct,
+	}
+}
+
+type IPSetSink struct {
+	ipMaskingKey  string
+	countDistinct *hyperloglog.HyperLogLogPlus
+}
+
+func (s *IPSetSink) maskIPAddress(ipAddress string) []byte {
+	hmacIPMasker := hmac.New(func() hash.Hash {
+		return sha3.New256()
+	}, []byte(s.ipMaskingKey))
+	hmacIPMasker.Write([]byte(ipAddress))
+	return hmacIPMasker.Sum(nil)
+}
+
+func (s *IPSetSink) AddIPToSet(ipAddress string) {
+	s.countDistinct.Add(truncatedHash64FromBytes{hashValue(s.maskIPAddress(ipAddress))})
+}
+
+func (s *IPSetSink) Dump() ([]byte, error) {
+	return s.countDistinct.GobEncode()
+}
+
+func (s *IPSetSink) Reset() {
+	s.countDistinct.Clear()
+}
+
+type hashValue []byte
+type truncatedHash64FromBytes struct {
+	hashValue
+}
+
+func (c truncatedHash64FromBytes) Sum64() uint64 {
+	var value uint64
+	binary.Read(bytes.NewReader(c.hashValue), binary.BigEndian, &value)
+	return value
+}

common/ipsetsink/sink_test.go

@@ -0,0 +1,47 @@
+package ipsetsink
+
+import (
+	"fmt"
+	"github.com/clarkduvall/hyperloglog"
+	"testing"
+)
+import . "github.com/smartystreets/goconvey/convey"
+
+func TestSinkInit(t *testing.T) {
+	Convey("Context", t, func() {
+		sink := NewIPSetSink("demo")
+		sink.AddIPToSet("test1")
+		sink.AddIPToSet("test2")
+		data, err := sink.Dump()
+		So(err, ShouldBeNil)
+		structure, err := hyperloglog.NewPlus(18)
+		So(err, ShouldBeNil)
+		err = structure.GobDecode(data)
+		So(err, ShouldBeNil)
+		count := structure.Count()
+		So(count, ShouldBeBetweenOrEqual, 1, 3)
+	})
+}
+
+func TestSinkCounting(t *testing.T) {
+	Convey("Context", t, func() {
+		for itemCount := 300; itemCount <= 10000; itemCount += 200 {
+			sink := NewIPSetSink("demo")
+			for i := 0; i <= itemCount; i++ {
+				sink.AddIPToSet(fmt.Sprintf("demo%v", i))
+			}
+			for i := 0; i <= itemCount; i++ {
+				sink.AddIPToSet(fmt.Sprintf("demo%v", i))
+			}
+			data, err := sink.Dump()
+			So(err, ShouldBeNil)
+			structure, err := hyperloglog.NewPlus(18)
+			So(err, ShouldBeNil)
+			err = structure.GobDecode(data)
+			So(err, ShouldBeNil)
+			count := structure.Count()
+			So((float64(count)/float64(itemCount))-1.0, ShouldAlmostEqual, 0, 0.01)
+		}
+
+	})
+}

common/ipsetsink/sinkcluster/common.go

@@ -0,0 +1,24 @@
+package sinkcluster
+
+/* ClusterWriter, and (ClusterCountResult).Count output a streamed IP set journal file to remember distinct IP address
+
+   its format is as follows:
+
+   This file should be in newline-delimited JSON format(https://jsonlines.org/).
+   For each line, the format of json data should be in the format of:
+   {"recordingStart":"2022-05-30T14:38:44.678610091Z","recordingEnd":"2022-05-30T14:39:48.157630926Z","recorded":""}
+
+	recordingStart:datetime is the time this chunk of recording start.
+
+	recordingEnd:datetime is the time this chunk of recording end.
+
+	recorded is the checkpoint data generated by hyperloglog.
+*/
+
+import "time"
+
+type SinkEntry struct {
+	RecordingStart time.Time `json:"recordingStart"`
+	RecordingEnd   time.Time `json:"recordingEnd"`
+	Recorded       []byte    `json:"recorded"`
+}

common/ipsetsink/sinkcluster/reader.go

@@ -0,0 +1,60 @@
+package sinkcluster
+
+import (
+	"bufio"
+	"encoding/json"
+	"github.com/clarkduvall/hyperloglog"
+	"io"
+	"time"
+)
+
+func NewClusterCounter(from time.Time, to time.Time) *ClusterCounter {
+	return &ClusterCounter{from: from, to: to}
+}
+
+type ClusterCounter struct {
+	from time.Time
+	to   time.Time
+}
+
+type ClusterCountResult struct {
+	Sum           uint64
+	ChunkIncluded int64
+}
+
+func (c ClusterCounter) Count(reader io.Reader) (*ClusterCountResult, error) {
+	result := ClusterCountResult{}
+	counter, err := hyperloglog.NewPlus(18)
+	if err != nil {
+		return nil, err
+	}
+	inputScanner := bufio.NewScanner(reader)
+	for inputScanner.Scan() {
+		inputLine := inputScanner.Bytes()
+		sinkInfo := SinkEntry{}
+		if err := json.Unmarshal(inputLine, &sinkInfo); err != nil {
+			return nil, err
+		}
+
+		if (sinkInfo.RecordingStart.Before(c.from) && !sinkInfo.RecordingStart.Equal(c.from)) ||
+			sinkInfo.RecordingEnd.After(c.to) {
+			continue
+		}
+
+		restoredCounter, err := hyperloglog.NewPlus(18)
+		if err != nil {
+			return nil, err
+		}
+		err = restoredCounter.GobDecode(sinkInfo.Recorded)
+		if err != nil {
+			return nil, err
+		}
+		result.ChunkIncluded++
+		err = counter.Merge(restoredCounter)
+		if err != nil {
+			return nil, err
+		}
+	}
+	result.Sum = counter.Count()
+	return &result, nil
+}

common/ipsetsink/sinkcluster/writer.go

@@ -0,0 +1,68 @@
+package sinkcluster
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"log"
+	"time"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/ipsetsink"
+)
+
+func NewClusterWriter(writer WriteSyncer, writeInterval time.Duration, sink *ipsetsink.IPSetSink) *ClusterWriter {
+	c := &ClusterWriter{
+		writer:        writer,
+		lastWriteTime: time.Now(),
+		writeInterval: writeInterval,
+		current:       sink,
+	}
+	return c
+}
+
+type ClusterWriter struct {
+	writer        WriteSyncer
+	lastWriteTime time.Time
+	writeInterval time.Duration
+	current       *ipsetsink.IPSetSink
+}
+
+type WriteSyncer interface {
+	Sync() error
+	io.Writer
+}
+
+func (c *ClusterWriter) WriteIPSetToDisk() {
+	currentTime := time.Now()
+	data, err := c.current.Dump()
+	if err != nil {
+		log.Println("unable able to write ipset to file:", err)
+		return
+	}
+	entry := &SinkEntry{
+		RecordingStart: c.lastWriteTime,
+		RecordingEnd:   currentTime,
+		Recorded:       data,
+	}
+	jsonData, err := json.Marshal(entry)
+	if err != nil {
+		log.Println("unable able to write ipset to file:", err)
+		return
+	}
+	jsonData = append(jsonData, byte('\n'))
+	_, err = io.Copy(c.writer, bytes.NewReader(jsonData))
+	if err != nil {
+		log.Println("unable able to write ipset to file:", err)
+		return
+	}
+	c.writer.Sync()
+	c.lastWriteTime = currentTime
+	c.current.Reset()
+}
+
+func (c *ClusterWriter) AddIPToSet(ipAddress string) {
+	if c.lastWriteTime.Add(c.writeInterval).Before(time.Now()) {
+		c.WriteIPSetToDisk()
+	}
+	c.current.AddIPToSet(ipAddress)
+}

common/ipsetsink/sinkcluster/writer_test.go

@@ -0,0 +1,33 @@
+package sinkcluster
+
+import (
+	"bytes"
+	"io"
+	"testing"
+	"time"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/ipsetsink"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+type writerStub struct {
+	io.Writer
+}
+
+func (w writerStub) Sync() error {
+	return nil
+}
+
+func TestSinkWriter(t *testing.T) {
+
+	Convey("Context", t, func() {
+		buffer := bytes.NewBuffer(nil)
+		writerStubInst := &writerStub{buffer}
+		sink := ipsetsink.NewIPSetSink("demo")
+		clusterWriter := NewClusterWriter(writerStubInst, time.Minute, sink)
+		clusterWriter.AddIPToSet("1")
+		clusterWriter.WriteIPSetToDisk()
+		So(buffer.Bytes(), ShouldNotBeNil)
+	})
+}

common/messages/client.go

@@ -0,0 +1,151 @@
+//Package for communication with the snowflake broker
+
+//import "git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+package messages
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/bridgefingerprint"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/nat"
+)
+
+const ClientVersion = "1.0"
+
+/* Client--Broker protocol v1.x specification:
+
+All messages contain the version number
+followed by a new line and then the message body
+<message> := <version>\n<body>
+<version> := <digit>.<digit>
+<body> := <poll request>|<poll response>
+
+There are two different types of body messages,
+each encoded in JSON format
+
+== ClientPollRequest ==
+<poll request> :=
+{
+  offer: <sdp offer>
+  [nat: (unknown|restricted|unrestricted)]
+  [fingerprint: <fingerprint string>]
+}
+
+The NAT field is optional, and if it is missing a
+value of "unknown" will be assumed.  The fingerprint
+is also optional and, if absent, will be assigned the
+fingerprint of the default bridge.
+
+== ClientPollResponse ==
+<poll response> :=
+{
+  [answer: <sdp answer>]
+  [error: <error string>]
+}
+
+If the broker succeeded in matching the client with a proxy,
+the answer field MUST contain a valid SDP answer, and the
+error field MUST be empty. If the answer field is empty, the
+error field MUST contain a string explaining with a reason
+for the error.
+
+*/
+
+// The bridge fingerprint to assume, for client poll requests that do not
+// specify a fingerprint.  Before #28651, there was only one bridge with one
+// fingerprint, which all clients expected to be connected to implicitly.
+// If a client is old enough that it does not specify a fingerprint, this is
+// the fingerprint it expects.  Clients that do set a fingerprint in the
+// SOCKS params will also be assumed to want to connect to the default bridge.
+const defaultBridgeFingerprint = "2B280B23E1107BB62ABFC40DDCC8824814F80A72"
+
+type ClientPollRequest struct {
+	Offer       string `json:"offer"`
+	NAT         string `json:"nat"`
+	Fingerprint string `json:"fingerprint"`
+}
+
+// Encodes a poll message from a snowflake client
+func (req *ClientPollRequest) EncodeClientPollRequest() ([]byte, error) {
+	if req.Fingerprint == "" {
+		req.Fingerprint = defaultBridgeFingerprint
+	}
+	body, err := json.Marshal(req)
+	if err != nil {
+		return nil, err
+	}
+	return append([]byte(ClientVersion+"\n"), body...), nil
+}
+
+// Decodes a poll message from a snowflake client
+func DecodeClientPollRequest(data []byte) (*ClientPollRequest, error) {
+	parts := bytes.SplitN(data, []byte("\n"), 2)
+
+	if len(parts) < 2 {
+		// no version number found
+		return nil, fmt.Errorf("unsupported message version")
+	}
+
+	var message ClientPollRequest
+
+	if string(parts[0]) != ClientVersion {
+		return nil, fmt.Errorf("unsupported message version")
+	}
+
+	err := json.Unmarshal(parts[1], &message)
+	if err != nil {
+		return nil, err
+	}
+
+	if message.Offer == "" {
+		return nil, fmt.Errorf("no supplied offer")
+	}
+
+	if message.Fingerprint == "" {
+		message.Fingerprint = defaultBridgeFingerprint
+	}
+
+	if _, err := bridgefingerprint.FingerprintFromHexString(message.Fingerprint); err != nil {
+		return nil, fmt.Errorf("cannot decode fingerprint")
+	}
+
+	switch message.NAT {
+	case "":
+		message.NAT = nat.NATUnknown
+	case nat.NATUnknown:
+	case nat.NATRestricted:
+	case nat.NATUnrestricted:
+	default:
+		return nil, fmt.Errorf("invalid NAT type")
+	}
+
+	return &message, nil
+}
+
+type ClientPollResponse struct {
+	Answer string `json:"answer,omitempty"`
+	Error  string `json:"error,omitempty"`
+}
+
+// Encodes a poll response for a snowflake client
+func (resp *ClientPollResponse) EncodePollResponse() ([]byte, error) {
+	return json.Marshal(resp)
+}
+
+// Decodes a poll response for a snowflake client
+// If the Error field is empty, the Answer should be non-empty
+func DecodeClientPollResponse(data []byte) (*ClientPollResponse, error) {
+	var message ClientPollResponse
+
+	err := json.Unmarshal(data, &message)
+	if err != nil {
+		return nil, err
+	}
+	if message.Error == "" && message.Answer == "" {
+		return nil, fmt.Errorf("received empty broker response")
+	}
+
+	return &message, nil
+}

common/messages/ipc.go

@@ -0,0 +1,19 @@
+package messages
+
+import (
+	"errors"
+)
+
+type Arg struct {
+	Body       []byte
+	RemoteAddr string
+}
+
+var (
+	ErrBadRequest = errors.New("bad request")
+	ErrInternal   = errors.New("internal error")
+	ErrExtraInfo  = errors.New("client sent extra info")
+
+	StrTimedOut  = "timed out waiting for answer!"
+	StrNoProxies = "no snowflake proxies currently available"
+)

common/messages/messages_test.go

@@ -0,0 +1,472 @@
+package messages
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestDecodeProxyPollRequest(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			sid       string
+			proxyType string
+			natType   string
+			clients   int
+			data      string
+			err       error
+
+			acceptedRelayPattern string
+		}{
+			{
+				//Version 1.0 proxy message
+				sid:       "ymbcCMto7KHNGYlp",
+				proxyType: "unknown",
+				natType:   "unknown",
+				clients:   0,
+				data:      `{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0"}`,
+				err:       nil,
+			},
+			{
+				//Version 1.1 proxy message
+				sid:       "ymbcCMto7KHNGYlp",
+				proxyType: "standalone",
+				natType:   "unknown",
+				clients:   0,
+				data:      `{"Sid":"ymbcCMto7KHNGYlp","Version":"1.1","Type":"standalone"}`,
+				err:       nil,
+			},
+			{
+				//Version 1.2 proxy message
+				sid:       "ymbcCMto7KHNGYlp",
+				proxyType: "standalone",
+				natType:   "restricted",
+				clients:   0,
+				data:      `{"Sid":"ymbcCMto7KHNGYlp","Version":"1.2","Type":"standalone", "NAT":"restricted"}`,
+				err:       nil,
+			},
+			{
+				//Version 1.2 proxy message with clients
+				sid:       "ymbcCMto7KHNGYlp",
+				proxyType: "standalone",
+				natType:   "restricted",
+				clients:   24,
+				data:      `{"Sid":"ymbcCMto7KHNGYlp","Version":"1.2","Type":"standalone", "NAT":"restricted","Clients":24}`,
+				err:       nil,
+			},
+			{
+				//Version 1.3 proxy message with clients and proxyURL
+				sid:                  "ymbcCMto7KHNGYlp",
+				proxyType:            "standalone",
+				natType:              "restricted",
+				clients:              24,
+				acceptedRelayPattern: "snowfalke.torproject.org",
+				data:                 `{"Sid":"ymbcCMto7KHNGYlp","Version":"1.2","Type":"standalone", "NAT":"restricted","Clients":24, "AcceptedRelayPattern":"snowfalke.torproject.org"}`,
+				err:                  nil,
+			},
+			{
+				//Version 0.X proxy message:
+				sid:       "",
+				proxyType: "",
+				natType:   "",
+				clients:   0,
+				data:      "",
+				err:       &json.SyntaxError{},
+			},
+			{
+				sid:       "",
+				proxyType: "",
+				natType:   "",
+				clients:   0,
+				data:      `{"Sid":"ymbcCMto7KHNGYlp"}`,
+				err:       fmt.Errorf(""),
+			},
+			{
+				sid:       "",
+				proxyType: "",
+				natType:   "",
+				clients:   0,
+				data:      "{}",
+				err:       fmt.Errorf(""),
+			},
+			{
+				sid:       "",
+				proxyType: "",
+				natType:   "",
+				clients:   0,
+				data:      `{"Version":"1.0"}`,
+				err:       fmt.Errorf(""),
+			},
+			{
+				sid:       "",
+				proxyType: "",
+				natType:   "",
+				clients:   0,
+				data:      `{"Version":"2.0"}`,
+				err:       fmt.Errorf(""),
+			},
+		} {
+			sid, proxyType, natType, clients, relayPattern, _, err := DecodeProxyPollRequestWithRelayPrefix([]byte(test.data))
+			So(sid, ShouldResemble, test.sid)
+			So(proxyType, ShouldResemble, test.proxyType)
+			So(natType, ShouldResemble, test.natType)
+			So(clients, ShouldEqual, test.clients)
+			So(relayPattern, ShouldResemble, test.acceptedRelayPattern)
+			So(err, ShouldHaveSameTypeAs, test.err)
+		}
+
+	})
+}
+
+func TestEncodeProxyPollRequests(t *testing.T) {
+	Convey("Context", t, func() {
+		b, err := EncodeProxyPollRequest("ymbcCMto7KHNGYlp", "standalone", "unknown", 16)
+		So(err, ShouldEqual, nil)
+		sid, proxyType, natType, clients, err := DecodeProxyPollRequest(b)
+		So(sid, ShouldEqual, "ymbcCMto7KHNGYlp")
+		So(proxyType, ShouldEqual, "standalone")
+		So(natType, ShouldEqual, "unknown")
+		So(clients, ShouldEqual, 16)
+		So(err, ShouldEqual, nil)
+	})
+}
+
+func TestDecodeProxyPollResponse(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			offer    string
+			data     string
+			relayURL string
+			err      error
+		}{
+			{
+				offer: "fake offer",
+				data:  `{"Status":"client match","Offer":"fake offer","NAT":"unknown"}`,
+				err:   nil,
+			},
+			{
+				offer:    "fake offer",
+				data:     `{"Status":"client match","Offer":"fake offer","NAT":"unknown", "RelayURL":"wss://snowflake.torproject.org/proxy"}`,
+				relayURL: "wss://snowflake.torproject.org/proxy",
+				err:      nil,
+			},
+			{
+				offer: "",
+				data:  `{"Status":"no match"}`,
+				err:   nil,
+			},
+			{
+				offer: "",
+				data:  `{"Status":"client match"}`,
+				err:   fmt.Errorf("no supplied offer"),
+			},
+			{
+				offer: "",
+				data:  `{"Test":"test"}`,
+				err:   fmt.Errorf(""),
+			},
+		} {
+			offer, _, relayURL, err := DecodePollResponseWithRelayURL([]byte(test.data))
+			So(err, ShouldHaveSameTypeAs, test.err)
+			So(offer, ShouldResemble, test.offer)
+			So(relayURL, ShouldResemble, test.relayURL)
+		}
+
+	})
+}
+
+func TestEncodeProxyPollResponse(t *testing.T) {
+	Convey("Context", t, func() {
+		b, err := EncodePollResponse("fake offer", true, "restricted")
+		So(err, ShouldEqual, nil)
+		offer, natType, err := DecodePollResponse(b)
+		So(offer, ShouldEqual, "fake offer")
+		So(natType, ShouldEqual, "restricted")
+		So(err, ShouldEqual, nil)
+
+		b, err = EncodePollResponse("", false, "unknown")
+		So(err, ShouldEqual, nil)
+		offer, natType, err = DecodePollResponse(b)
+		So(offer, ShouldEqual, "")
+		So(natType, ShouldEqual, "unknown")
+		So(err, ShouldEqual, nil)
+	})
+}
+
+func TestEncodeProxyPollResponseWithProxyURL(t *testing.T) {
+	Convey("Context", t, func() {
+		b, err := EncodePollResponseWithRelayURL("fake offer", true, "restricted", "wss://test/", "")
+		So(err, ShouldBeNil)
+		offer, natType, err := DecodePollResponse(b)
+		So(err, ShouldNotBeNil)
+
+		offer, natType, relay, err := DecodePollResponseWithRelayURL(b)
+		So(offer, ShouldEqual, "fake offer")
+		So(natType, ShouldEqual, "restricted")
+		So(relay, ShouldEqual, "wss://test/")
+		So(err, ShouldBeNil)
+
+		b, err = EncodePollResponse("", false, "unknown")
+		So(err, ShouldBeNil)
+		offer, natType, relay, err = DecodePollResponseWithRelayURL(b)
+		So(offer, ShouldEqual, "")
+		So(natType, ShouldEqual, "unknown")
+		So(err, ShouldBeNil)
+
+		b, err = EncodePollResponseWithRelayURL("fake offer", false, "restricted", "wss://test/", "test error reason")
+		So(err, ShouldBeNil)
+		offer, natType, relay, err = DecodePollResponseWithRelayURL(b)
+		So(err, ShouldNotBeNil)
+		So(err.Error(), ShouldContainSubstring, "test error reason")
+	})
+}
+func TestDecodeProxyAnswerRequest(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			answer string
+			sid    string
+			data   string
+			err    error
+		}{
+			{
+				"test",
+				"test",
+				`{"Version":"1.0","Sid":"test","Answer":"test"}`,
+				nil,
+			},
+			{
+				"",
+				"",
+				`{"type":"offer","sdp":"v=0\r\no=- 4358805017720277108 2 IN IP4 [scrubbed]\r\ns=-\r\nt=0 0\r\na=group:BUNDLE data\r\na=msid-semantic: WMS\r\nm=application 56688 DTLS/SCTP 5000\r\nc=IN IP4 [scrubbed]\r\na=candidate:3769337065 1 udp 2122260223 [scrubbed] 56688 typ host generation 0 network-id 1 network-cost 50\r\na=candidate:2921887769 1 tcp 1518280447 [scrubbed] 35441 typ host tcptype passive generation 0 network-id 1 network-cost 50\r\na=ice-ufrag:aMAZ\r\na=ice-pwd:jcHb08Jjgrazp2dzjdrvPPvV\r\na=ice-options:trickle\r\na=fingerprint:sha-256 C8:88:EE:B9:E7:02:2E:21:37:ED:7A:D1:EB:2B:A3:15:A2:3B:5B:1C:3D:D4:D5:1F:06:CF:52:40:03:F8:DD:66\r\na=setup:actpass\r\na=mid:data\r\na=sctpmap:5000 webrtc-datachannel 1024\r\n"}`,
+				fmt.Errorf(""),
+			},
+			{
+				"",
+				"",
+				`{"Version":"1.0","Answer":"test"}`,
+				fmt.Errorf(""),
+			},
+			{
+				"",
+				"",
+				`{"Version":"1.0","Sid":"test"}`,
+				fmt.Errorf(""),
+			},
+		} {
+			answer, sid, err := DecodeAnswerRequest([]byte(test.data))
+			So(answer, ShouldResemble, test.answer)
+			So(sid, ShouldResemble, test.sid)
+			So(err, ShouldHaveSameTypeAs, test.err)
+		}
+
+	})
+}
+
+func TestEncodeProxyAnswerRequest(t *testing.T) {
+	Convey("Context", t, func() {
+		b, err := EncodeAnswerRequest("test answer", "test sid")
+		So(err, ShouldEqual, nil)
+		answer, sid, err := DecodeAnswerRequest(b)
+		So(answer, ShouldEqual, "test answer")
+		So(sid, ShouldEqual, "test sid")
+		So(err, ShouldEqual, nil)
+	})
+}
+
+func TestDecodeProxyAnswerResponse(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			success bool
+			data    string
+			err     error
+		}{
+			{
+				true,
+				`{"Status":"success"}`,
+				nil,
+			},
+			{
+				false,
+				`{"Status":"client gone"}`,
+				nil,
+			},
+			{
+				false,
+				`{"Test":"test"}`,
+				fmt.Errorf(""),
+			},
+		} {
+			success, err := DecodeAnswerResponse([]byte(test.data))
+			So(success, ShouldResemble, test.success)
+			So(err, ShouldHaveSameTypeAs, test.err)
+		}
+
+	})
+}
+
+func TestEncodeProxyAnswerResponse(t *testing.T) {
+	Convey("Context", t, func() {
+		b, err := EncodeAnswerResponse(true)
+		So(err, ShouldEqual, nil)
+		success, err := DecodeAnswerResponse(b)
+		So(success, ShouldEqual, true)
+		So(err, ShouldEqual, nil)
+
+		b, err = EncodeAnswerResponse(false)
+		So(err, ShouldEqual, nil)
+		success, err = DecodeAnswerResponse(b)
+		So(success, ShouldEqual, false)
+		So(err, ShouldEqual, nil)
+	})
+}
+
+func TestDecodeClientPollRequest(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			natType string
+			offer   string
+			data    string
+			err     error
+		}{
+			{
+				//version 1.0 client message
+				"unknown",
+				"fake",
+				`1.0
+{"nat":"unknown","offer":"fake"}`,
+				nil,
+			},
+			{
+				//version 1.0 client message
+				"unknown",
+				"fake",
+				`1.0
+{"offer":"fake"}`,
+				nil,
+			},
+			{
+				//unknown version
+				"",
+				"",
+				`{"version":"2.0"}`,
+				fmt.Errorf(""),
+			},
+			{
+				//no offer
+				"",
+				"",
+				`1.0
+{"nat":"unknown"}`,
+				fmt.Errorf(""),
+			},
+		} {
+			req, err := DecodeClientPollRequest([]byte(test.data))
+			So(err, ShouldHaveSameTypeAs, test.err)
+			if test.err == nil {
+				So(req.NAT, ShouldResemble, test.natType)
+				So(req.Offer, ShouldResemble, test.offer)
+			}
+		}
+
+	})
+}
+
+func TestEncodeClientPollRequests(t *testing.T) {
+	Convey("Context", t, func() {
+		for i, test := range []struct {
+			natType     string
+			offer       string
+			fingerprint string
+			err         error
+		}{
+			{
+				"unknown",
+				"fake",
+				"",
+				nil,
+			},
+			{
+				"unknown",
+				"fake",
+				defaultBridgeFingerprint,
+				nil,
+			},
+			{
+				"unknown",
+				"fake",
+				"123123",
+				fmt.Errorf(""),
+			},
+		} {
+			req1 := &ClientPollRequest{
+				NAT:         test.natType,
+				Offer:       test.offer,
+				Fingerprint: test.fingerprint,
+			}
+			b, err := req1.EncodeClientPollRequest()
+			So(err, ShouldEqual, nil)
+			req2, err := DecodeClientPollRequest(b)
+			So(err, ShouldHaveSameTypeAs, test.err)
+			if test.err == nil {
+				So(req2.Offer, ShouldEqual, req1.Offer)
+				So(req2.NAT, ShouldEqual, req1.NAT)
+				fingerprint := test.fingerprint
+				if i == 0 {
+					fingerprint = defaultBridgeFingerprint
+				}
+				So(req2.Fingerprint, ShouldEqual, fingerprint)
+			}
+		}
+	})
+}
+
+func TestDecodeClientPollResponse(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			answer string
+			msg    string
+			data   string
+		}{
+			{
+				"fake answer",
+				"",
+				`{"answer":"fake answer"}`,
+			},
+			{
+				"",
+				"no snowflakes",
+				`{"error":"no snowflakes"}`,
+			},
+		} {
+			resp, err := DecodeClientPollResponse([]byte(test.data))
+			So(err, ShouldBeNil)
+			So(resp.Answer, ShouldResemble, test.answer)
+			So(resp.Error, ShouldResemble, test.msg)
+		}
+
+	})
+}
+
+func TestEncodeClientPollResponse(t *testing.T) {
+	Convey("Context", t, func() {
+		resp1 := &ClientPollResponse{
+			Answer: "fake answer",
+		}
+		b, err := resp1.EncodePollResponse()
+		So(err, ShouldEqual, nil)
+		resp2, err := DecodeClientPollResponse(b)
+		So(err, ShouldEqual, nil)
+		So(resp1, ShouldResemble, resp2)
+
+		resp1 = &ClientPollResponse{
+			Error: "failed",
+		}
+		b, err = resp1.EncodePollResponse()
+		So(err, ShouldEqual, nil)
+		resp2, err = DecodeClientPollResponse(b)
+		So(err, ShouldEqual, nil)
+		So(resp1, ShouldResemble, resp2)
+	})
+}

common/messages/proxy.go

@@ -0,0 +1,310 @@
+//Package for communication with the snowflake broker
+
+//import "git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+package messages
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/nat"
+)
+
+const (
+	version      = "1.3"
+	ProxyUnknown = "unknown"
+)
+
+var KnownProxyTypes = map[string]bool{
+	"standalone": true,
+	"webext":     true,
+	"badge":      true,
+	"iptproxy":   true,
+}
+
+/* Version 1.3 specification:
+
+== ProxyPollRequest ==
+{
+  Sid: [generated session id of proxy],
+  Version: 1.3,
+  Type: ["badge"|"webext"|"standalone"],
+  NAT: ["unknown"|"restricted"|"unrestricted"],
+  Clients: [number of current clients, rounded down to multiples of 8],
+  AcceptedRelayPattern: [a pattern representing accepted set of relay domains]
+}
+
+== ProxyPollResponse ==
+1) If a client is matched:
+HTTP 200 OK
+{
+  Status: "client match",
+  {
+    type: offer,
+    sdp: [WebRTC SDP]
+  },
+  NAT: ["unknown"|"restricted"|"unrestricted"],
+  RelayURL: [the WebSocket URL proxy should connect to relay Snowflake traffic]
+}
+
+2) If a client is not matched:
+HTTP 200 OK
+
+{
+    Status: "no match"
+}
+
+3) If the request is malformed:
+HTTP 400 BadRequest
+
+== ProxyAnswerRequest ==
+{
+  Sid: [generated session id of proxy],
+  Version: 1.3,
+  Answer:
+  {
+    type: answer,
+    sdp: [WebRTC SDP]
+  }
+}
+
+== ProxyAnswerResponse ==
+1) If the client retrieved the answer:
+HTTP 200 OK
+
+{
+  Status: "success"
+}
+
+2) If the client left:
+HTTP 200 OK
+
+{
+  Status: "client gone"
+}
+
+3) If the request is malformed:
+HTTP 400 BadRequest
+
+*/
+
+type ProxyPollRequest struct {
+	Sid     string
+	Version string
+	Type    string
+	NAT     string
+	Clients int
+
+	AcceptedRelayPattern *string
+}
+
+func EncodeProxyPollRequest(sid string, proxyType string, natType string, clients int) ([]byte, error) {
+	return EncodeProxyPollRequestWithRelayPrefix(sid, proxyType, natType, clients, "")
+}
+
+func EncodeProxyPollRequestWithRelayPrefix(sid string, proxyType string, natType string, clients int, relayPattern string) ([]byte, error) {
+	return json.Marshal(ProxyPollRequest{
+		Sid:                  sid,
+		Version:              version,
+		Type:                 proxyType,
+		NAT:                  natType,
+		Clients:              clients,
+		AcceptedRelayPattern: &relayPattern,
+	})
+}
+
+func DecodeProxyPollRequest(data []byte) (sid string, proxyType string, natType string, clients int, err error) {
+	var relayPrefix string
+	sid, proxyType, natType, clients, relayPrefix, _, err = DecodeProxyPollRequestWithRelayPrefix(data)
+	if relayPrefix != "" {
+		return "", "", "", 0, ErrExtraInfo
+	}
+	return
+}
+
+// Decodes a poll message from a snowflake proxy and returns the
+// sid, proxy type, nat type and clients of the proxy on success
+// and an error if it failed
+func DecodeProxyPollRequestWithRelayPrefix(data []byte) (
+	sid string, proxyType string, natType string, clients int, relayPrefix string, relayPrefixAware bool, err error) {
+	var message ProxyPollRequest
+
+	err = json.Unmarshal(data, &message)
+	if err != nil {
+		return
+	}
+
+	majorVersion := strings.Split(message.Version, ".")[0]
+	if majorVersion != "1" {
+		err = fmt.Errorf("using unknown version")
+		return
+	}
+
+	// Version 1.x requires an Sid
+	if message.Sid == "" {
+		err = fmt.Errorf("no supplied session id")
+		return
+	}
+
+	switch message.NAT {
+	case "":
+		message.NAT = nat.NATUnknown
+	case nat.NATUnknown:
+	case nat.NATRestricted:
+	case nat.NATUnrestricted:
+	default:
+		err = fmt.Errorf("invalid NAT type")
+		return
+	}
+
+	// we don't reject polls with an unknown proxy type because we encourage
+	// projects that embed proxy code to include their own type
+	if !KnownProxyTypes[message.Type] {
+		message.Type = ProxyUnknown
+	}
+	var acceptedRelayPattern = ""
+	if message.AcceptedRelayPattern != nil {
+		acceptedRelayPattern = *message.AcceptedRelayPattern
+	}
+	return message.Sid, message.Type, message.NAT, message.Clients,
+		acceptedRelayPattern, message.AcceptedRelayPattern != nil, nil
+}
+
+type ProxyPollResponse struct {
+	Status string
+	Offer  string
+	NAT    string
+
+	RelayURL string
+}
+
+func EncodePollResponse(offer string, success bool, natType string) ([]byte, error) {
+	return EncodePollResponseWithRelayURL(offer, success, natType, "", "no match")
+}
+
+func EncodePollResponseWithRelayURL(offer string, success bool, natType, relayURL, failReason string) ([]byte, error) {
+	if success {
+		return json.Marshal(ProxyPollResponse{
+			Status:   "client match",
+			Offer:    offer,
+			NAT:      natType,
+			RelayURL: relayURL,
+		})
+
+	}
+	return json.Marshal(ProxyPollResponse{
+		Status: failReason,
+	})
+}
+func DecodePollResponse(data []byte) (string, string, error) {
+	offer, natType, relayURL, err := DecodePollResponseWithRelayURL(data)
+	if relayURL != "" {
+		return "", "", ErrExtraInfo
+	}
+	return offer, natType, err
+}
+
+// Decodes a poll response from the broker and returns an offer and the client's NAT type
+// If there is a client match, the returned offer string will be non-empty
+func DecodePollResponseWithRelayURL(data []byte) (string, string, string, error) {
+	var message ProxyPollResponse
+
+	err := json.Unmarshal(data, &message)
+	if err != nil {
+		return "", "", "", err
+	}
+	if message.Status == "" {
+		return "", "", "", fmt.Errorf("received invalid data")
+	}
+
+	err = nil
+	if message.Status == "client match" {
+		if message.Offer == "" {
+			return "", "", "", fmt.Errorf("no supplied offer")
+		}
+	} else {
+		message.Offer = ""
+		if message.Status != "no match" {
+			err = errors.New(message.Status)
+		}
+	}
+
+	natType := message.NAT
+	if natType == "" {
+		natType = "unknown"
+	}
+
+	return message.Offer, natType, message.RelayURL, err
+}
+
+type ProxyAnswerRequest struct {
+	Version string
+	Sid     string
+	Answer  string
+}
+
+func EncodeAnswerRequest(answer string, sid string) ([]byte, error) {
+	return json.Marshal(ProxyAnswerRequest{
+		Version: version,
+		Sid:     sid,
+		Answer:  answer,
+	})
+}
+
+// Returns the sdp answer and proxy sid
+func DecodeAnswerRequest(data []byte) (string, string, error) {
+	var message ProxyAnswerRequest
+
+	err := json.Unmarshal(data, &message)
+	if err != nil {
+		return "", "", err
+	}
+
+	majorVersion := strings.Split(message.Version, ".")[0]
+	if majorVersion != "1" {
+		return "", "", fmt.Errorf("using unknown version")
+	}
+
+	if message.Sid == "" || message.Answer == "" {
+		return "", "", fmt.Errorf("no supplied sid or answer")
+	}
+
+	return message.Answer, message.Sid, nil
+}
+
+type ProxyAnswerResponse struct {
+	Status string
+}
+
+func EncodeAnswerResponse(success bool) ([]byte, error) {
+	if success {
+		return json.Marshal(ProxyAnswerResponse{
+			Status: "success",
+		})
+
+	}
+	return json.Marshal(ProxyAnswerResponse{
+		Status: "client gone",
+	})
+}
+
+func DecodeAnswerResponse(data []byte) (bool, error) {
+	var message ProxyAnswerResponse
+	var success bool
+
+	err := json.Unmarshal(data, &message)
+	if err != nil {
+		return success, err
+	}
+	if message.Status == "" {
+		return success, fmt.Errorf("received invalid data")
+	}
+
+	if message.Status == "success" {
+		success = true
+	}
+
+	return success, nil
+}

common/namematcher/matcher.go

@@ -0,0 +1,31 @@
+package namematcher
+
+import "strings"
+
+func NewNameMatcher(rule string) NameMatcher {
+	rule = strings.TrimSuffix(rule, "$")
+	return NameMatcher{suffix: strings.TrimPrefix(rule, "^"), exact: strings.HasPrefix(rule, "^")}
+}
+
+func IsValidRule(rule string) bool {
+	return strings.HasSuffix(rule, "$")
+}
+
+type NameMatcher struct {
+	exact  bool
+	suffix string
+}
+
+func (m *NameMatcher) IsSupersetOf(matcher NameMatcher) bool {
+	if m.exact {
+		return matcher.exact && m.suffix == matcher.suffix
+	}
+	return strings.HasSuffix(matcher.suffix, m.suffix)
+}
+
+func (m *NameMatcher) IsMember(s string) bool {
+	if m.exact {
+		return s == m.suffix
+	}
+	return strings.HasSuffix(s, m.suffix)
+}

common/namematcher/matcher_test.go

@@ -0,0 +1,55 @@
+package namematcher
+
+import "testing"
+
+import . "github.com/smartystreets/goconvey/convey"
+
+func TestMatchMember(t *testing.T) {
+	testingVector := []struct {
+		matcher string
+		target  string
+		expects bool
+	}{
+		{matcher: "", target: "", expects: true},
+		{matcher: "^snowflake.torproject.net$", target: "snowflake.torproject.net", expects: true},
+		{matcher: "^snowflake.torproject.net$", target: "faketorproject.net", expects: false},
+		{matcher: "snowflake.torproject.net$", target: "faketorproject.net", expects: false},
+		{matcher: "snowflake.torproject.net$", target: "snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net$", target: "imaginary-01-snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net$", target: "imaginary-aaa-snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net$", target: "imaginary-aaa-snowflake.faketorproject.net", expects: false},
+	}
+	for _, v := range testingVector {
+		t.Run(v.matcher+"<>"+v.target, func(t *testing.T) {
+			Convey("test", t, func() {
+				matcher := NewNameMatcher(v.matcher)
+				So(matcher.IsMember(v.target), ShouldEqual, v.expects)
+			})
+		})
+	}
+}
+
+func TestMatchSubset(t *testing.T) {
+	testingVector := []struct {
+		matcher string
+		target  string
+		expects bool
+	}{
+		{matcher: "", target: "", expects: true},
+		{matcher: "^snowflake.torproject.net$", target: "^snowflake.torproject.net$", expects: true},
+		{matcher: "snowflake.torproject.net$", target: "^snowflake.torproject.net$", expects: true},
+		{matcher: "snowflake.torproject.net$", target: "snowflake.torproject.net$", expects: true},
+		{matcher: "snowflake.torproject.net$", target: "testing-snowflake.torproject.net$", expects: true},
+		{matcher: "snowflake.torproject.net$", target: "^testing-snowflake.torproject.net$", expects: true},
+		{matcher: "snowflake.torproject.net$", target: "", expects: false},
+	}
+	for _, v := range testingVector {
+		t.Run(v.matcher+"<>"+v.target, func(t *testing.T) {
+			Convey("test", t, func() {
+				matcher := NewNameMatcher(v.matcher)
+				target := NewNameMatcher(v.target)
+				So(matcher.IsSupersetOf(target), ShouldEqual, v.expects)
+			})
+		})
+	}
+}

common/nat/nat.go

@@ -0,0 +1,231 @@
+/*
+The majority of this code is taken from a utility I wrote for pion/stun
+https://github.com/pion/stun/blob/master/cmd/stun-nat-behaviour/main.go
+
+Copyright 2018 Pion LLC
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+package nat
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"net"
+	"time"
+
+	"github.com/pion/stun"
+)
+
+var ErrTimedOut = errors.New("timed out waiting for response")
+
+const (
+	NATUnknown      = "unknown"
+	NATRestricted   = "restricted"
+	NATUnrestricted = "unrestricted"
+)
+
+// This function checks the NAT mapping and filtering
+// behaviour and returns true if the NAT is restrictive
+// (address-dependent mapping and/or port-dependent filtering)
+// and false if the NAT is unrestrictive (meaning it
+// will work with most other NATs),
+func CheckIfRestrictedNAT(server string) (bool, error) {
+	return isRestrictedMapping(server)
+}
+
+// Performs two tests from RFC 5780 to determine whether the mapping type
+// of the client's NAT is address-independent or address-dependent
+// Returns true if the mapping is address-dependent and false otherwise
+func isRestrictedMapping(addrStr string) (bool, error) {
+	var xorAddr1 stun.XORMappedAddress
+	var xorAddr2 stun.XORMappedAddress
+
+	mapTestConn, err := connect(addrStr)
+	if err != nil {
+		return false, fmt.Errorf("Error creating STUN connection: %w", err)
+	}
+
+	defer mapTestConn.Close()
+
+	// Test I: Regular binding request
+	message := stun.MustBuild(stun.TransactionID, stun.BindingRequest)
+
+	resp, err := mapTestConn.RoundTrip(message, mapTestConn.PrimaryAddr)
+	if err != nil {
+		return false, fmt.Errorf("Error completing roundtrip map test: %w", err)
+	}
+
+	// Decoding XOR-MAPPED-ADDRESS attribute from message.
+	if err = xorAddr1.GetFrom(resp); err != nil {
+		return false, fmt.Errorf("Error retrieving XOR-MAPPED-ADDRESS resonse: %w", err)
+	}
+
+	// Decoding OTHER-ADDRESS attribute from message.
+	var otherAddr stun.OtherAddress
+	if err = otherAddr.GetFrom(resp); err != nil {
+		return false, fmt.Errorf("NAT discovery feature not supported: %w", err)
+	}
+
+	if err = mapTestConn.AddOtherAddr(otherAddr.String()); err != nil {
+		return false, fmt.Errorf("Error resolving address %s: %w", otherAddr.String(), err)
+	}
+
+	// Test II: Send binding request to other address
+	resp, err = mapTestConn.RoundTrip(message, mapTestConn.OtherAddr)
+	if err != nil {
+		return false, fmt.Errorf("Error retrieveing server response: %w", err)
+	}
+
+	// Decoding XOR-MAPPED-ADDRESS attribute from message.
+	if err = xorAddr2.GetFrom(resp); err != nil {
+		return false, fmt.Errorf("Error retrieving XOR-MAPPED-ADDRESS resonse: %w", err)
+	}
+
+	return xorAddr1.String() != xorAddr2.String(), nil
+
+}
+
+// Performs two tests from RFC 5780 to determine whether the filtering type
+// of the client's NAT is port-dependent.
+// Returns true if the filtering is port-dependent and false otherwise
+// Note: This function is no longer used because a client's NAT type is
+// determined only by their mapping type, but the functionality might
+// be useful in the future and remains here.
+func isRestrictedFiltering(addrStr string) (bool, error) {
+	var xorAddr stun.XORMappedAddress
+
+	mapTestConn, err := connect(addrStr)
+	if err != nil {
+		log.Printf("Error creating STUN connection: %s", err.Error())
+		return false, err
+	}
+
+	defer mapTestConn.Close()
+
+	// Test I: Regular binding request
+	message := stun.MustBuild(stun.TransactionID, stun.BindingRequest)
+
+	resp, err := mapTestConn.RoundTrip(message, mapTestConn.PrimaryAddr)
+	if err == ErrTimedOut {
+		log.Printf("Error: no response from server")
+		return false, err
+	}
+	if err != nil {
+		log.Printf("Error: %s", err.Error())
+		return false, err
+	}
+
+	// Decoding XOR-MAPPED-ADDRESS attribute from message.
+	if err = xorAddr.GetFrom(resp); err != nil {
+		log.Printf("Error retrieving XOR-MAPPED-ADDRESS from resonse: %s", err.Error())
+		return false, err
+	}
+
+	// Test III: Request port change
+	message.Add(stun.AttrChangeRequest, []byte{0x00, 0x00, 0x00, 0x02})
+
+	_, err = mapTestConn.RoundTrip(message, mapTestConn.PrimaryAddr)
+	if err != ErrTimedOut && err != nil {
+		// something else went wrong
+		log.Printf("Error reading response from server: %s", err.Error())
+		return false, err
+	}
+
+	return err == ErrTimedOut, nil
+}
+
+// Given an address string, returns a StunServerConn
+func connect(addrStr string) (*StunServerConn, error) {
+	// Creating a "connection" to STUN server.
+	addr, err := net.ResolveUDPAddr("udp4", addrStr)
+	if err != nil {
+		log.Printf("Error resolving address: %s\n", err.Error())
+		return nil, err
+	}
+
+	c, err := net.ListenUDP("udp4", nil)
+	if err != nil {
+		return nil, err
+	}
+
+	mChan := listen(c)
+
+	return &StunServerConn{
+		conn:        c,
+		PrimaryAddr: addr,
+		messageChan: mChan,
+	}, nil
+}
+
+type StunServerConn struct {
+	conn        net.PacketConn
+	PrimaryAddr *net.UDPAddr
+	OtherAddr   *net.UDPAddr
+	messageChan chan *stun.Message
+}
+
+func (c *StunServerConn) Close() {
+	c.conn.Close()
+}
+
+func (c *StunServerConn) RoundTrip(msg *stun.Message, addr net.Addr) (*stun.Message, error) {
+	_, err := c.conn.WriteTo(msg.Raw, addr)
+	if err != nil {
+		return nil, err
+	}
+
+	// Wait for response or timeout
+	select {
+	case m, ok := <-c.messageChan:
+		if !ok {
+			return nil, fmt.Errorf("error reading from messageChan")
+		}
+		return m, nil
+	case <-time.After(10 * time.Second):
+		return nil, ErrTimedOut
+	}
+}
+
+func (c *StunServerConn) AddOtherAddr(addrStr string) error {
+	addr2, err := net.ResolveUDPAddr("udp4", addrStr)
+	if err != nil {
+		return err
+	}
+	c.OtherAddr = addr2
+	return nil
+}
+
+// taken from https://github.com/pion/stun/blob/master/cmd/stun-traversal/main.go
+func listen(conn *net.UDPConn) chan *stun.Message {
+	messages := make(chan *stun.Message)
+	go func() {
+		for {
+			buf := make([]byte, 1024)
+
+			n, _, err := conn.ReadFromUDP(buf)
+			if err != nil {
+				close(messages)
+				return
+			}
+			buf = buf[:n]
+
+			m := new(stun.Message)
+			m.Raw = buf
+			err = m.Decode()
+			if err != nil {
+				close(messages)
+				return
+			}
+
+			messages <- m
+		}
+	}()
+	return messages
+}

common/safelog/log.go

@@ -1,6 +1,6 @@
 //Package for a safer logging wrapper around the standard logging package
 
-//import "git.torproject.org/pluggable-transports/snowflake.git/common/safelog"
+//import "git.torproject.org/pluggable-transports/snowflake.git/v2/common/safelog"
 package safelog
 
 import (
@@ -38,7 +38,7 @@ type LogScrubber struct {
 func (ls *LogScrubber) Lock()   { (*ls).lock.Lock() }
 func (ls *LogScrubber) Unlock() { (*ls).lock.Unlock() }
 
-func scrub(b []byte) []byte {
+func Scrub(b []byte) []byte {
 	scrubbedBytes := b
 	for _, pattern := range scrubberPatterns {
 		// this is a workaround since go does not yet support look ahead or look
@@ -62,7 +62,7 @@ func (ls *LogScrubber) Write(b []byte) (n int, err error) {
 			return
 		}
 		fullLines := ls.buffer[:i+1]
-		_, err = ls.Output.Write(scrub(fullLines))
+		_, err = ls.Output.Write(Scrub(fullLines))
 		if err != nil {
 			return
 		}

common/task/periodic.go

@@ -0,0 +1,116 @@
+// Package task
+// Reused from https://github.com/v2fly/v2ray-core/blob/784775f68922f07d40c9eead63015b2026af2ade/common/task/periodic.go
+/*
+The MIT License (MIT)
+
+Copyright (c) 2015-2021 V2Ray & V2Fly Community
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+package task
+
+import (
+	"sync"
+	"time"
+)
+
+// Periodic is a task that runs periodically.
+type Periodic struct {
+	// Interval of the task being run
+	Interval time.Duration
+	// Execute is the task function
+	Execute func() error
+
+	access  sync.Mutex
+	timer   *time.Timer
+	running bool
+}
+
+func (t *Periodic) hasClosed() bool {
+	t.access.Lock()
+	defer t.access.Unlock()
+
+	return !t.running
+}
+
+func (t *Periodic) checkedExecute() error {
+	if t.hasClosed() {
+		return nil
+	}
+
+	if err := t.Execute(); err != nil {
+		t.access.Lock()
+		t.running = false
+		t.access.Unlock()
+		return err
+	}
+
+	t.access.Lock()
+	defer t.access.Unlock()
+
+	if !t.running {
+		return nil
+	}
+
+	t.timer = time.AfterFunc(t.Interval, func() {
+		t.checkedExecute()
+	})
+
+	return nil
+}
+
+// Start implements common.Runnable.
+func (t *Periodic) Start() error {
+	t.access.Lock()
+	if t.running {
+		t.access.Unlock()
+		return nil
+	}
+	t.running = true
+	t.access.Unlock()
+
+	if err := t.checkedExecute(); err != nil {
+		t.access.Lock()
+		t.running = false
+		t.access.Unlock()
+		return err
+	}
+
+	return nil
+}
+
+func (t *Periodic) WaitThenStart() {
+	time.AfterFunc(t.Interval, func() {
+		t.Start()
+	})
+}
+
+// Close implements common.Closable.
+func (t *Periodic) Close() error {
+	t.access.Lock()
+	defer t.access.Unlock()
+
+	t.running = false
+	if t.timer != nil {
+		t.timer.Stop()
+		t.timer = nil
+	}
+
+	return nil
+}

common/turbotunnel/clientid.go

@@ -0,0 +1,28 @@
+package turbotunnel
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+)
+
+// ClientID is an abstract identifier that binds together all the communications
+// belonging to a single client session, even though those communications may
+// arrive from multiple IP addresses or over multiple lower-level connections.
+// It plays the same role that an (IP address, port number) tuple plays in a
+// net.UDPConn: it's the return address pertaining to a long-lived abstract
+// client session. The client attaches its ClientID to each of its
+// communications, enabling the server to disambiguate requests among its many
+// clients. ClientID implements the net.Addr interface.
+type ClientID [8]byte
+
+func NewClientID() ClientID {
+	var id ClientID
+	_, err := rand.Read(id[:])
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+func (id ClientID) Network() string { return "clientid" }
+func (id ClientID) String() string  { return hex.EncodeToString(id[:]) }

common/turbotunnel/clientmap.go

@@ -0,0 +1,145 @@
+package turbotunnel
+
+import (
+	"container/heap"
+	"net"
+	"sync"
+	"time"
+)
+
+// clientRecord is a record of a recently seen client, with the time it was last
+// seen and a send queue.
+type clientRecord struct {
+	Addr      net.Addr
+	LastSeen  time.Time
+	SendQueue chan []byte
+}
+
+// ClientMap manages a mapping of live clients (keyed by address, which will be
+// a ClientID) to their respective send queues. ClientMap's functions are safe
+// to call from multiple goroutines.
+type ClientMap struct {
+	// We use an inner structure to avoid exposing public heap.Interface
+	// functions to users of clientMap.
+	inner clientMapInner
+	// Synchronizes access to inner.
+	lock sync.Mutex
+}
+
+// NewClientMap creates a ClientMap that expires clients after a timeout.
+//
+// The timeout does not have to be kept in sync with QUIC's internal idle
+// timeout. If a client is removed from the client map while the QUIC session is
+// still live, the worst that can happen is a loss of whatever packets were in
+// the send queue at the time. If QUIC later decides to send more packets to the
+// same client, we'll instantiate a new send queue, and if the client ever
+// connects again with the proper client ID, we'll deliver them.
+func NewClientMap(timeout time.Duration) *ClientMap {
+	m := &ClientMap{
+		inner: clientMapInner{
+			byAge:  make([]*clientRecord, 0),
+			byAddr: make(map[net.Addr]int),
+		},
+	}
+	go func() {
+		for {
+			time.Sleep(timeout / 2)
+			now := time.Now()
+			m.lock.Lock()
+			m.inner.removeExpired(now, timeout)
+			m.lock.Unlock()
+		}
+	}()
+	return m
+}
+
+// SendQueue returns the send queue corresponding to addr, creating it if
+// necessary.
+func (m *ClientMap) SendQueue(addr net.Addr) chan []byte {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+	return m.inner.SendQueue(addr, time.Now())
+}
+
+// clientMapInner is the inner type of ClientMap, implementing heap.Interface.
+// byAge is the backing store, a heap ordered by LastSeen time, to facilitate
+// expiring old client records. byAddr is a map from addresses (i.e., ClientIDs)
+// to heap indices, to allow looking up by address. Unlike ClientMap,
+// clientMapInner requires external synchonization.
+type clientMapInner struct {
+	byAge  []*clientRecord
+	byAddr map[net.Addr]int
+}
+
+// removeExpired removes all client records whose LastSeen timestamp is more
+// than timeout in the past.
+func (inner *clientMapInner) removeExpired(now time.Time, timeout time.Duration) {
+	for len(inner.byAge) > 0 && now.Sub(inner.byAge[0].LastSeen) >= timeout {
+		heap.Pop(inner)
+	}
+}
+
+// SendQueue finds the existing client record corresponding to addr, or creates
+// a new one if none exists yet. It updates the client record's LastSeen time
+// and returns its SendQueue.
+func (inner *clientMapInner) SendQueue(addr net.Addr, now time.Time) chan []byte {
+	var record *clientRecord
+	i, ok := inner.byAddr[addr]
+	if ok {
+		// Found one, update its LastSeen.
+		record = inner.byAge[i]
+		record.LastSeen = now
+		heap.Fix(inner, i)
+	} else {
+		// Not found, create a new one.
+		record = &clientRecord{
+			Addr:      addr,
+			LastSeen:  now,
+			SendQueue: make(chan []byte, queueSize),
+		}
+		heap.Push(inner, record)
+	}
+	return record.SendQueue
+}
+
+// heap.Interface for clientMapInner.
+
+func (inner *clientMapInner) Len() int {
+	if len(inner.byAge) != len(inner.byAddr) {
+		panic("inconsistent clientMap")
+	}
+	return len(inner.byAge)
+}
+
+func (inner *clientMapInner) Less(i, j int) bool {
+	return inner.byAge[i].LastSeen.Before(inner.byAge[j].LastSeen)
+}
+
+func (inner *clientMapInner) Swap(i, j int) {
+	inner.byAge[i], inner.byAge[j] = inner.byAge[j], inner.byAge[i]
+	inner.byAddr[inner.byAge[i].Addr] = i
+	inner.byAddr[inner.byAge[j].Addr] = j
+}
+
+func (inner *clientMapInner) Push(x interface{}) {
+	record := x.(*clientRecord)
+	if _, ok := inner.byAddr[record.Addr]; ok {
+		panic("duplicate address in clientMap")
+	}
+	// Insert into byAddr map.
+	inner.byAddr[record.Addr] = len(inner.byAge)
+	// Insert into byAge slice.
+	inner.byAge = append(inner.byAge, record)
+}
+
+func (inner *clientMapInner) Pop() interface{} {
+	n := len(inner.byAddr)
+	// Remove from byAge slice.
+	record := inner.byAge[n-1]
+	inner.byAge[n-1] = nil
+	inner.byAge = inner.byAge[:n-1]
+	// Remove from byAddr map.
+	delete(inner.byAddr, record.Addr)
+	close(record.SendQueue)
+	return record
+}

common/turbotunnel/consts.go

@@ -0,0 +1,17 @@
+// Package turbotunnel provides support for overlaying a virtual net.PacketConn
+// on some other network carrier.
+//
+// https://github.com/net4people/bbs/issues/9
+package turbotunnel
+
+import "errors"
+
+// This magic prefix is how a client opts into turbo tunnel mode. It is just a
+// randomly generated byte string.
+var Token = [8]byte{0x12, 0x93, 0x60, 0x5d, 0x27, 0x81, 0x75, 0xf5}
+
+// The size of receive and send queues.
+const queueSize = 2048
+
+var errClosedPacketConn = errors.New("operation on closed connection")
+var errNotImplemented = errors.New("not implemented")

common/turbotunnel/queuepacketconn.go

@@ -0,0 +1,137 @@
+package turbotunnel
+
+import (
+	"net"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// taggedPacket is a combination of a []byte and a net.Addr, encapsulating the
+// return type of PacketConn.ReadFrom.
+type taggedPacket struct {
+	P    []byte
+	Addr net.Addr
+}
+
+// QueuePacketConn implements net.PacketConn by storing queues of packets. There
+// is one incoming queue (where packets are additionally tagged by the source
+// address of the client that sent them). There are many outgoing queues, one
+// for each client address that has been recently seen. The QueueIncoming method
+// inserts a packet into the incoming queue, to eventually be returned by
+// ReadFrom. WriteTo inserts a packet into an address-specific outgoing queue,
+// which can later by accessed through the OutgoingQueue method.
+type QueuePacketConn struct {
+	clients   *ClientMap
+	localAddr net.Addr
+	recvQueue chan taggedPacket
+	closeOnce sync.Once
+	closed    chan struct{}
+	// What error to return when the QueuePacketConn is closed.
+	err atomic.Value
+}
+
+// NewQueuePacketConn makes a new QueuePacketConn, set to track recent clients
+// for at least a duration of timeout.
+func NewQueuePacketConn(localAddr net.Addr, timeout time.Duration) *QueuePacketConn {
+	return &QueuePacketConn{
+		clients:   NewClientMap(timeout),
+		localAddr: localAddr,
+		recvQueue: make(chan taggedPacket, queueSize),
+		closed:    make(chan struct{}),
+	}
+}
+
+// QueueIncoming queues and incoming packet and its source address, to be
+// returned in a future call to ReadFrom.
+func (c *QueuePacketConn) QueueIncoming(p []byte, addr net.Addr) {
+	select {
+	case <-c.closed:
+		// If we're closed, silently drop it.
+		return
+	default:
+	}
+	// Copy the slice so that the caller may reuse it.
+	buf := make([]byte, len(p))
+	copy(buf, p)
+	select {
+	case c.recvQueue <- taggedPacket{buf, addr}:
+	default:
+		// Drop the incoming packet if the receive queue is full.
+	}
+}
+
+// OutgoingQueue returns the queue of outgoing packets corresponding to addr,
+// creating it if necessary. The contents of the queue will be packets that are
+// written to the address in question using WriteTo.
+func (c *QueuePacketConn) OutgoingQueue(addr net.Addr) <-chan []byte {
+	return c.clients.SendQueue(addr)
+}
+
+// ReadFrom returns a packet and address previously stored by QueueIncoming.
+func (c *QueuePacketConn) ReadFrom(p []byte) (int, net.Addr, error) {
+	select {
+	case <-c.closed:
+		return 0, nil, &net.OpError{Op: "read", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	default:
+	}
+	select {
+	case <-c.closed:
+		return 0, nil, &net.OpError{Op: "read", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	case packet := <-c.recvQueue:
+		return copy(p, packet.P), packet.Addr, nil
+	}
+}
+
+// WriteTo queues an outgoing packet for the given address. The queue can later
+// be retrieved using the OutgoingQueue method.
+func (c *QueuePacketConn) WriteTo(p []byte, addr net.Addr) (int, error) {
+	select {
+	case <-c.closed:
+		return 0, &net.OpError{Op: "write", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	default:
+	}
+	// Copy the slice so that the caller may reuse it.
+	buf := make([]byte, len(p))
+	copy(buf, p)
+	select {
+	case c.clients.SendQueue(addr) <- buf:
+		return len(buf), nil
+	default:
+		// Drop the outgoing packet if the send queue is full.
+		return len(buf), nil
+	}
+}
+
+// closeWithError unblocks pending operations and makes future operations fail
+// with the given error. If err is nil, it becomes errClosedPacketConn.
+func (c *QueuePacketConn) closeWithError(err error) error {
+	var newlyClosed bool
+	c.closeOnce.Do(func() {
+		newlyClosed = true
+		// Store the error to be returned by future PacketConn
+		// operations.
+		if err == nil {
+			err = errClosedPacketConn
+		}
+		c.err.Store(err)
+		close(c.closed)
+	})
+	if !newlyClosed {
+		return &net.OpError{Op: "close", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	}
+	return nil
+}
+
+// Close unblocks pending operations and makes future operations fail with a
+// "closed connection" error.
+func (c *QueuePacketConn) Close() error {
+	return c.closeWithError(nil)
+}
+
+// LocalAddr returns the localAddr value that was passed to NewQueuePacketConn.
+func (c *QueuePacketConn) LocalAddr() net.Addr { return c.localAddr }
+
+func (c *QueuePacketConn) SetDeadline(t time.Time) error      { return errNotImplemented }
+func (c *QueuePacketConn) SetReadDeadline(t time.Time) error  { return errNotImplemented }
+func (c *QueuePacketConn) SetWriteDeadline(t time.Time) error { return errNotImplemented }

common/turbotunnel/redialpacketconn.go

@@ -0,0 +1,204 @@
+package turbotunnel
+
+import (
+	"context"
+	"errors"
+	"net"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// RedialPacketConn implements a long-lived net.PacketConn atop a sequence of
+// other, transient net.PacketConns. RedialPacketConn creates a new
+// net.PacketConn by calling a provided dialContext function. Whenever the
+// net.PacketConn experiences a ReadFrom or WriteTo error, RedialPacketConn
+// calls the dialContext function again and starts sending and receiving packets
+// on the new net.PacketConn. RedialPacketConn's own ReadFrom and WriteTo
+// methods return an error only when the dialContext function returns an error.
+//
+// RedialPacketConn uses static local and remote addresses that are independent
+// of those of any dialed net.PacketConn.
+type RedialPacketConn struct {
+	localAddr   net.Addr
+	remoteAddr  net.Addr
+	dialContext func(context.Context) (net.PacketConn, error)
+	recvQueue   chan []byte
+	sendQueue   chan []byte
+	closed      chan struct{}
+	closeOnce   sync.Once
+	// The first dial error, which causes the clientPacketConn to be
+	// closed and is returned from future read/write operations. Compare to
+	// the rerr and werr in io.Pipe.
+	err atomic.Value
+}
+
+// NewQueuePacketConn makes a new RedialPacketConn, with the given static local
+// and remote addresses, and dialContext function.
+func NewRedialPacketConn(
+	localAddr, remoteAddr net.Addr,
+	dialContext func(context.Context) (net.PacketConn, error),
+) *RedialPacketConn {
+	c := &RedialPacketConn{
+		localAddr:   localAddr,
+		remoteAddr:  remoteAddr,
+		dialContext: dialContext,
+		recvQueue:   make(chan []byte, queueSize),
+		sendQueue:   make(chan []byte, queueSize),
+		closed:      make(chan struct{}),
+		err:         atomic.Value{},
+	}
+	go c.dialLoop()
+	return c
+}
+
+// dialLoop repeatedly calls c.dialContext and passes the resulting
+// net.PacketConn to c.exchange. It returns only when c is closed or dialContext
+// returns an error.
+func (c *RedialPacketConn) dialLoop() {
+	ctx, cancel := context.WithCancel(context.Background())
+	for {
+		select {
+		case <-c.closed:
+			cancel()
+			return
+		default:
+		}
+		conn, err := c.dialContext(ctx)
+		if err != nil {
+			c.closeWithError(err)
+			cancel()
+			return
+		}
+		c.exchange(conn)
+		conn.Close()
+	}
+}
+
+// exchange calls ReadFrom on the given net.PacketConn and places the resulting
+// packets in the receive queue, and takes packets from the send queue and calls
+// WriteTo on them, making the current net.PacketConn active.
+func (c *RedialPacketConn) exchange(conn net.PacketConn) {
+	readErrCh := make(chan error)
+	writeErrCh := make(chan error)
+
+	go func() {
+		defer close(readErrCh)
+		for {
+			select {
+			case <-c.closed:
+				return
+			case <-writeErrCh:
+				return
+			default:
+			}
+
+			var buf [1500]byte
+			n, _, err := conn.ReadFrom(buf[:])
+			if err != nil {
+				readErrCh <- err
+				return
+			}
+			p := make([]byte, n)
+			copy(p, buf[:])
+			select {
+			case c.recvQueue <- p:
+			default: // OK to drop packets.
+			}
+		}
+	}()
+
+	go func() {
+		defer close(writeErrCh)
+		for {
+			select {
+			case <-c.closed:
+				return
+			case <-readErrCh:
+				return
+			case p := <-c.sendQueue:
+				_, err := conn.WriteTo(p, c.remoteAddr)
+				if err != nil {
+					writeErrCh <- err
+					return
+				}
+			}
+		}
+	}()
+
+	select {
+	case <-readErrCh:
+	case <-writeErrCh:
+	}
+}
+
+// ReadFrom reads a packet from the currently active net.PacketConn. The
+// packet's original remote address is replaced with the RedialPacketConn's own
+// remote address.
+func (c *RedialPacketConn) ReadFrom(p []byte) (int, net.Addr, error) {
+	select {
+	case <-c.closed:
+		return 0, nil, &net.OpError{Op: "read", Net: c.LocalAddr().Network(), Source: c.LocalAddr(), Addr: c.remoteAddr, Err: c.err.Load().(error)}
+	default:
+	}
+	select {
+	case <-c.closed:
+		return 0, nil, &net.OpError{Op: "read", Net: c.LocalAddr().Network(), Source: c.LocalAddr(), Addr: c.remoteAddr, Err: c.err.Load().(error)}
+	case buf := <-c.recvQueue:
+		return copy(p, buf), c.remoteAddr, nil
+	}
+}
+
+// WriteTo writes a packet to the currently active net.PacketConn. The addr
+// argument is ignored and instead replaced with the RedialPacketConn's own
+// remote address.
+func (c *RedialPacketConn) WriteTo(p []byte, addr net.Addr) (int, error) {
+	// addr is ignored.
+	select {
+	case <-c.closed:
+		return 0, &net.OpError{Op: "write", Net: c.LocalAddr().Network(), Source: c.LocalAddr(), Addr: c.remoteAddr, Err: c.err.Load().(error)}
+	default:
+	}
+	buf := make([]byte, len(p))
+	copy(buf, p)
+	select {
+	case c.sendQueue <- buf:
+		return len(buf), nil
+	default:
+		// Drop the outgoing packet if the send queue is full.
+		return len(buf), nil
+	}
+}
+
+// closeWithError unblocks pending operations and makes future operations fail
+// with the given error. If err is nil, it becomes errClosedPacketConn.
+func (c *RedialPacketConn) closeWithError(err error) error {
+	var once bool
+	c.closeOnce.Do(func() {
+		// Store the error to be returned by future read/write
+		// operations.
+		if err == nil {
+			err = errors.New("operation on closed connection")
+		}
+		c.err.Store(err)
+		close(c.closed)
+		once = true
+	})
+	if !once {
+		return &net.OpError{Op: "close", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	}
+	return nil
+}
+
+// Close unblocks pending operations and makes future operations fail with a
+// "closed connection" error.
+func (c *RedialPacketConn) Close() error {
+	return c.closeWithError(nil)
+}
+
+// LocalAddr returns the localAddr value that was passed to NewRedialPacketConn.
+func (c *RedialPacketConn) LocalAddr() net.Addr { return c.localAddr }
+
+func (c *RedialPacketConn) SetDeadline(t time.Time) error      { return errNotImplemented }
+func (c *RedialPacketConn) SetReadDeadline(t time.Time) error  { return errNotImplemented }
+func (c *RedialPacketConn) SetWriteDeadline(t time.Time) error { return errNotImplemented }

common/util/util.go

@@ -0,0 +1,99 @@
+package util
+
+import (
+	"encoding/json"
+	"errors"
+	"net"
+
+	"github.com/pion/ice/v2"
+	"github.com/pion/sdp/v3"
+	"github.com/pion/webrtc/v3"
+)
+
+func SerializeSessionDescription(desc *webrtc.SessionDescription) (string, error) {
+	bytes, err := json.Marshal(*desc)
+	if err != nil {
+		return "", err
+	}
+	return string(bytes), nil
+}
+
+func DeserializeSessionDescription(msg string) (*webrtc.SessionDescription, error) {
+	var parsed map[string]interface{}
+	err := json.Unmarshal([]byte(msg), &parsed)
+	if err != nil {
+		return nil, err
+	}
+	if _, ok := parsed["type"]; !ok {
+		return nil, errors.New("cannot deserialize SessionDescription without type field")
+	}
+	if _, ok := parsed["sdp"]; !ok {
+		return nil, errors.New("cannot deserialize SessionDescription without sdp field")
+	}
+
+	var stype webrtc.SDPType
+	switch parsed["type"].(string) {
+	default:
+		return nil, errors.New("Unknown SDP type")
+	case "offer":
+		stype = webrtc.SDPTypeOffer
+	case "pranswer":
+		stype = webrtc.SDPTypePranswer
+	case "answer":
+		stype = webrtc.SDPTypeAnswer
+	case "rollback":
+		stype = webrtc.SDPTypeRollback
+	}
+
+	return &webrtc.SessionDescription{
+		Type: stype,
+		SDP:  parsed["sdp"].(string),
+	}, nil
+}
+
+// Stolen from https://github.com/golang/go/pull/30278
+func IsLocal(ip net.IP) bool {
+	if ip4 := ip.To4(); ip4 != nil {
+		// Local IPv4 addresses are defined in https://tools.ietf.org/html/rfc1918
+		return ip4[0] == 10 ||
+			(ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
+			(ip4[0] == 192 && ip4[1] == 168) ||
+			// Carrier-Grade NAT as per https://tools.ietf.org/htm/rfc6598
+			(ip4[0] == 100 && ip4[1]&0xc0 == 64) ||
+			// Dynamic Configuration as per https://tools.ietf.org/htm/rfc3927
+			(ip4[0] == 169 && ip4[1] == 254)
+	}
+	// Local IPv6 addresses are defined in https://tools.ietf.org/html/rfc4193
+	return len(ip) == net.IPv6len && ip[0]&0xfe == 0xfc
+}
+
+// Removes local LAN address ICE candidates
+func StripLocalAddresses(str string) string {
+	var desc sdp.SessionDescription
+	err := desc.Unmarshal([]byte(str))
+	if err != nil {
+		return str
+	}
+	for _, m := range desc.MediaDescriptions {
+		attrs := make([]sdp.Attribute, 0)
+		for _, a := range m.Attributes {
+			if a.IsICECandidate() {
+				c, err := ice.UnmarshalCandidate(a.Value)
+				if err == nil && c.Type() == ice.CandidateTypeHost {
+					ip := net.ParseIP(c.Address())
+					if ip != nil && (IsLocal(ip) || ip.IsUnspecified() || ip.IsLoopback()) {
+						/* no append in this case */
+						continue
+					}
+				}
+			}
+			attrs = append(attrs, a)
+		}
+		m.Attributes = attrs
+	}
+	bts, err := desc.Marshal()
+	if err != nil {
+		return str
+	}
+	return string(bts)
+}

common/util/util_test.go

@@ -0,0 +1,28 @@
+package util
+
+import (
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestUtil(t *testing.T) {
+	Convey("Strip", t, func() {
+		const offerStart = "v=0\r\no=- 4358805017720277108 2 IN IP4 8.8.8.8\r\ns=-\r\nt=0 0\r\na=group:BUNDLE data\r\na=msid-semantic: WMS\r\nm=application 56688 DTLS/SCTP 5000\r\nc=IN IP4 8.8.8.8\r\n"
+		const goodCandidate = "a=candidate:3769337065 1 udp 2122260223 8.8.8.8 56688 typ host generation 0 network-id 1 network-cost 50\r\n"
+		const offerEnd = "a=ice-ufrag:aMAZ\r\na=ice-pwd:jcHb08Jjgrazp2dzjdrvPPvV\r\na=ice-options:trickle\r\na=fingerprint:sha-256 C8:88:EE:B9:E7:02:2E:21:37:ED:7A:D1:EB:2B:A3:15:A2:3B:5B:1C:3D:D4:D5:1F:06:CF:52:40:03:F8:DD:66\r\na=setup:actpass\r\na=mid:data\r\na=sctpmap:5000 webrtc-datachannel 1024\r\n"
+
+		offer := offerStart + goodCandidate +
+			"a=candidate:3769337065 1 udp 2122260223 192.168.0.100 56688 typ host generation 0 network-id 1 network-cost 50\r\n" + // IsLocal IPv4
+			"a=candidate:3769337065 1 udp 2122260223 100.127.50.5 56688 typ host generation 0 network-id 1 network-cost 50\r\n" + // IsLocal IPv4
+			"a=candidate:3769337065 1 udp 2122260223 169.254.250.88 56688 typ host generation 0 network-id 1 network-cost 50\r\n" + // IsLocal IPv4
+			"a=candidate:3769337065 1 udp 2122260223 fdf8:f53b:82e4::53 56688 typ host generation 0 network-id 1 network-cost 50\r\n" + // IsLocal IPv6
+			"a=candidate:3769337065 1 udp 2122260223 0.0.0.0 56688 typ host generation 0 network-id 1 network-cost 50\r\n" + // IsUnspecified IPv4
+			"a=candidate:3769337065 1 udp 2122260223 :: 56688 typ host generation 0 network-id 1 network-cost 50\r\n" + // IsUnspecified IPv6
+			"a=candidate:3769337065 1 udp 2122260223 127.0.0.1 56688 typ host generation 0 network-id 1 network-cost 50\r\n" + // IsLoopback IPv4
+			"a=candidate:3769337065 1 udp 2122260223 ::1 56688 typ host generation 0 network-id 1 network-cost 50\r\n" + // IsLoopback IPv6
+			offerEnd
+
+		So(StripLocalAddresses(offer), ShouldEqual, offerStart+goodCandidate+offerEnd)
+	})
+}

common/utls/client_hello_id.go

@@ -0,0 +1,38 @@
+package utls
+
+import (
+	"errors"
+	utls "github.com/refraction-networking/utls"
+	"strings"
+)
+
+// ported from https://github.com/max-b/snowflake/commit/9dded063cb74c6941a16ad90b9dd0e06e618e55e
+var clientHelloIDMap = map[string]utls.ClientHelloID{
+	// No HelloCustom: not useful for external configuration.
+	// No HelloRandomized: doesn't negotiate consistent ALPN.
+	"hellorandomizedalpn":   utls.HelloRandomizedALPN,
+	"hellorandomizednoalpn": utls.HelloRandomizedNoALPN,
+	"hellofirefox_auto":     utls.HelloFirefox_Auto,
+	"hellofirefox_55":       utls.HelloFirefox_55,
+	"hellofirefox_56":       utls.HelloFirefox_56,
+	"hellofirefox_63":       utls.HelloFirefox_63,
+	"hellofirefox_65":       utls.HelloFirefox_65,
+	"hellochrome_auto":      utls.HelloChrome_Auto,
+	"hellochrome_58":        utls.HelloChrome_58,
+	"hellochrome_62":        utls.HelloChrome_62,
+	"hellochrome_70":        utls.HelloChrome_70,
+	"hellochrome_72":        utls.HelloChrome_72,
+	"helloios_auto":         utls.HelloIOS_Auto,
+	"helloios_11_1":         utls.HelloIOS_11_1,
+	"helloios_12_1":         utls.HelloIOS_12_1,
+}
+
+var errNameNotFound = errors.New("client hello name is unrecognized")
+
+func NameToUTLSID(name string) (utls.ClientHelloID, error) {
+	normalizedName := strings.ToLower(name)
+	if id, ok := clientHelloIDMap[normalizedName]; ok {
+		return id, nil
+	}
+	return utls.ClientHelloID{}, errNameNotFound
+}

common/utls/roundtripper.go

@@ -0,0 +1,238 @@
+package utls
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+
+	utls "github.com/refraction-networking/utls"
+	"golang.org/x/net/http2"
+)
+
+// NewUTLSHTTPRoundTripper creates an instance of RoundTripper that dial to remote HTTPS endpoint with
+// an alternative version of TLS implementation that attempts to imitate browsers' fingerprint.
+// clientHelloID is the clientHello that uTLS attempts to imitate
+// uTlsConfig is the TLS Configuration template
+// backdropTransport is the transport that will be used for non-https traffic
+// removeSNI indicates not to send Server Name Indication Extension
+// returns a RoundTripper: its behaviour is documented at
+// https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/merge_requests/76#note_2777161
+func NewUTLSHTTPRoundTripper(clientHelloID utls.ClientHelloID, uTlsConfig *utls.Config,
+	backdropTransport http.RoundTripper, removeSNI bool) http.RoundTripper {
+	rtImpl := &uTLSHTTPRoundTripperImpl{
+		clientHelloID:     clientHelloID,
+		config:            uTlsConfig,
+		connectWithH1:     map[string]bool{},
+		backdropTransport: backdropTransport,
+		pendingConn:       map[pendingConnKey]*unclaimedConnection{},
+		removeSNI:         removeSNI,
+	}
+	rtImpl.init()
+	return rtImpl
+}
+
+type uTLSHTTPRoundTripperImpl struct {
+	clientHelloID utls.ClientHelloID
+	config        *utls.Config
+
+	accessConnectWithH1 sync.Mutex
+	connectWithH1       map[string]bool
+
+	httpsH1Transport  http.RoundTripper
+	httpsH2Transport  http.RoundTripper
+	backdropTransport http.RoundTripper
+
+	accessDialingConnection sync.Mutex
+	pendingConn             map[pendingConnKey]*unclaimedConnection
+
+	removeSNI bool
+}
+
+type pendingConnKey struct {
+	isH2 bool
+	dest string
+}
+
+var errEAGAIN = errors.New("incorrect ALPN negotiated, try again with another ALPN")
+var errEAGAINTooMany = errors.New("incorrect ALPN negotiated")
+var errExpired = errors.New("connection have expired")
+
+func (r *uTLSHTTPRoundTripperImpl) RoundTrip(req *http.Request) (*http.Response, error) {
+	if req.URL.Scheme != "https" {
+		return r.backdropTransport.RoundTrip(req)
+	}
+	for retryCount := 0; retryCount < 5; retryCount++ {
+		if r.getShouldConnectWithH1(req.URL.Host) {
+			resp, err := r.httpsH1Transport.RoundTrip(req)
+			if errors.Is(err, errEAGAIN) {
+				continue
+			}
+			return resp, err
+		}
+		resp, err := r.httpsH2Transport.RoundTrip(req)
+		if errors.Is(err, errEAGAIN) {
+			continue
+		}
+		return resp, err
+	}
+	return nil, errEAGAINTooMany
+}
+
+func (r *uTLSHTTPRoundTripperImpl) getShouldConnectWithH1(domainName string) bool {
+	r.accessConnectWithH1.Lock()
+	defer r.accessConnectWithH1.Unlock()
+	if value, set := r.connectWithH1[domainName]; set {
+		return value
+	}
+	return false
+}
+
+func (r *uTLSHTTPRoundTripperImpl) setShouldConnectWithH1(domainName string) {
+	r.accessConnectWithH1.Lock()
+	defer r.accessConnectWithH1.Unlock()
+	r.connectWithH1[domainName] = true
+}
+
+func (r *uTLSHTTPRoundTripperImpl) clearShouldConnectWithH1(domainName string) {
+	r.accessConnectWithH1.Lock()
+	defer r.accessConnectWithH1.Unlock()
+	r.connectWithH1[domainName] = false
+}
+
+func getPendingConnectionID(dest string, alpnIsH2 bool) pendingConnKey {
+	return pendingConnKey{isH2: alpnIsH2, dest: dest}
+}
+
+func (r *uTLSHTTPRoundTripperImpl) putConn(addr string, alpnIsH2 bool, conn net.Conn) {
+	connId := getPendingConnectionID(addr, alpnIsH2)
+	r.pendingConn[connId] = NewUnclaimedConnection(conn, time.Minute)
+}
+func (r *uTLSHTTPRoundTripperImpl) getConn(addr string, alpnIsH2 bool) net.Conn {
+	connId := getPendingConnectionID(addr, alpnIsH2)
+	if conn, ok := r.pendingConn[connId]; ok {
+		delete(r.pendingConn, connId)
+		if claimedConnection, err := conn.claimConnection(); err == nil {
+			return claimedConnection
+		}
+	}
+	return nil
+}
+func (r *uTLSHTTPRoundTripperImpl) dialOrGetTLSWithExpectedALPN(ctx context.Context, addr string, expectedH2 bool) (net.Conn, error) {
+	r.accessDialingConnection.Lock()
+	defer r.accessDialingConnection.Unlock()
+
+	if r.getShouldConnectWithH1(addr) == expectedH2 {
+		return nil, errEAGAIN
+	}
+
+	//Get a cached connection if possible to reduce preflight connection closed without sending data
+	if gconn := r.getConn(addr, expectedH2); gconn != nil {
+		return gconn, nil
+	}
+
+	conn, err := r.dialTLS(ctx, addr)
+	if err != nil {
+		return nil, err
+	}
+
+	protocol := conn.ConnectionState().NegotiatedProtocol
+
+	protocolIsH2 := protocol == http2.NextProtoTLS
+
+	if protocolIsH2 == expectedH2 {
+		return conn, err
+	}
+
+	r.putConn(addr, protocolIsH2, conn)
+
+	if protocolIsH2 {
+		r.clearShouldConnectWithH1(addr)
+	} else {
+		r.setShouldConnectWithH1(addr)
+	}
+
+	return nil, errEAGAIN
+}
+
+// based on https://repo.or.cz/dnstt.git/commitdiff/d92a791b6864901f9263f7d73d97cfd30ac53b09..98bdffa1706dfc041d1e99b86c47f29d72ad3a0c
+// by dcf1
+func (r *uTLSHTTPRoundTripperImpl) dialTLS(ctx context.Context, addr string) (*utls.UConn, error) {
+	config := r.config.Clone()
+
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		return nil, err
+	}
+	config.ServerName = host
+
+	dialer := &net.Dialer{}
+	conn, err := dialer.DialContext(ctx, "tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	uconn := utls.UClient(conn, config, r.clientHelloID)
+	if (net.ParseIP(config.ServerName) != nil) || r.removeSNI {
+		err := uconn.RemoveSNIExtension()
+		if err != nil {
+			uconn.Close()
+			return nil, err
+		}
+	}
+
+	err = uconn.Handshake()
+	if err != nil {
+		return nil, err
+	}
+	return uconn, nil
+}
+
+func (r *uTLSHTTPRoundTripperImpl) init() {
+	r.httpsH2Transport = &http2.Transport{
+		DialTLS: func(network, addr string, cfg *tls.Config) (net.Conn, error) {
+			return r.dialOrGetTLSWithExpectedALPN(context.Background(), addr, true)
+		},
+	}
+	r.httpsH1Transport = &http.Transport{
+		DialTLSContext: func(ctx context.Context, network string, addr string) (net.Conn, error) {
+			return r.dialOrGetTLSWithExpectedALPN(ctx, addr, false)
+		},
+	}
+}
+
+func NewUnclaimedConnection(conn net.Conn, expireTime time.Duration) *unclaimedConnection {
+	c := &unclaimedConnection{
+		Conn: conn,
+	}
+	time.AfterFunc(expireTime, c.tick)
+	return c
+}
+
+type unclaimedConnection struct {
+	net.Conn
+	claimed bool
+	access  sync.Mutex
+}
+
+func (c *unclaimedConnection) claimConnection() (net.Conn, error) {
+	c.access.Lock()
+	defer c.access.Unlock()
+	if !c.claimed {
+		c.claimed = true
+		return c.Conn, nil
+	}
+	return nil, errExpired
+}
+
+func (c *unclaimedConnection) tick() {
+	c.access.Lock()
+	defer c.access.Unlock()
+	if !c.claimed {
+		c.claimed = true
+		c.Conn.Close()
+		c.Conn = nil
+	}
+}

common/utls/roundtripper_test.go

@@ -0,0 +1,164 @@
+package utls
+
+import (
+	"crypto/rsa"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"math/big"
+	"math/rand"
+	"net/http"
+	"testing"
+	"time"
+
+	stdcontext "context"
+
+	utls "github.com/refraction-networking/utls"
+	"golang.org/x/net/http2"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestRoundTripper(t *testing.T) {
+	var selfSignedCert []byte
+	var selfSignedPrivateKey *rsa.PrivateKey
+	httpServerContext, cancel := stdcontext.WithCancel(stdcontext.Background())
+	Convey("[Test]Set up http servers", t, func(c C) {
+		c.Convey("[Test]Generate Self-Signed Cert", func(c C) {
+			// Ported from https://gist.github.com/samuel/8b500ddd3f6118d052b5e6bc16bc4c09
+
+			// note that we use the insecure math/rand here because some platforms
+			// fail the test suite at build time in Debian, due to entropy starvation.
+			// since that's not a problem at test time, we do *not* use a secure
+			// mechanism for key generation.
+			//
+			// DO NOT REUSE THIS CODE IN PRODUCTION, IT IS DANGEROUS
+			insecureRandReader := rand.New(rand.NewSource(1337))
+			priv, err := rsa.GenerateKey(insecureRandReader, 4096)
+			c.So(err, ShouldBeNil)
+			template := x509.Certificate{
+				SerialNumber: big.NewInt(1),
+				Subject: pkix.Name{
+					CommonName: "Testing Certificate",
+				},
+				NotBefore: time.Now(),
+				NotAfter:  time.Now().Add(time.Hour * 24 * 180),
+
+				KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+				ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+				BasicConstraintsValid: true,
+			}
+			derBytes, err := x509.CreateCertificate(insecureRandReader, &template, &template, priv.Public(), priv)
+			c.So(err, ShouldBeNil)
+			selfSignedPrivateKey = priv
+			selfSignedCert = derBytes
+		})
+		c.Convey("[Test]Setup http2 server", func(c C) {
+			listener, err := tls.Listen("tcp", "127.0.0.1:23802", &tls.Config{
+				NextProtos: []string{http2.NextProtoTLS},
+				Certificates: []tls.Certificate{
+					tls.Certificate{Certificate: [][]byte{selfSignedCert}, PrivateKey: selfSignedPrivateKey},
+				},
+			})
+			c.So(err, ShouldBeNil)
+			s := http.Server{}
+			go s.Serve(listener)
+			go func() {
+				<-httpServerContext.Done()
+				s.Close()
+			}()
+		})
+		c.Convey("[Test]Setup http1 server", func(c C) {
+			listener, err := tls.Listen("tcp", "127.0.0.1:23801", &tls.Config{
+				NextProtos: []string{"http/1.1"},
+				Certificates: []tls.Certificate{
+					tls.Certificate{Certificate: [][]byte{selfSignedCert}, PrivateKey: selfSignedPrivateKey},
+				},
+			})
+			c.So(err, ShouldBeNil)
+			s := http.Server{}
+			go s.Serve(listener)
+			go func() {
+				<-httpServerContext.Done()
+				s.Close()
+			}()
+		})
+	})
+	for _, v := range []struct {
+		id   utls.ClientHelloID
+		name string
+	}{
+		{
+			id:   utls.HelloChrome_58,
+			name: "HelloChrome_58",
+		},
+		{
+			id:   utls.HelloChrome_62,
+			name: "HelloChrome_62",
+		},
+		{
+			id:   utls.HelloChrome_70,
+			name: "HelloChrome_70",
+		},
+		{
+			id:   utls.HelloChrome_72,
+			name: "HelloChrome_72",
+		},
+		{
+			id:   utls.HelloChrome_83,
+			name: "HelloChrome_83",
+		},
+		{
+			id:   utls.HelloFirefox_55,
+			name: "HelloFirefox_55",
+		},
+		{
+			id:   utls.HelloFirefox_55,
+			name: "HelloFirefox_55",
+		},
+		{
+			id:   utls.HelloFirefox_63,
+			name: "HelloFirefox_63",
+		},
+		{
+			id:   utls.HelloFirefox_65,
+			name: "HelloFirefox_65",
+		},
+		{
+			id:   utls.HelloIOS_11_1,
+			name: "HelloIOS_11_1",
+		},
+		{
+			id:   utls.HelloIOS_12_1,
+			name: "HelloIOS_12_1",
+		},
+	} {
+		t.Run("Testing fingerprint for "+v.name, func(t *testing.T) {
+			rtter := NewUTLSHTTPRoundTripper(v.id, &utls.Config{
+				InsecureSkipVerify: true,
+			}, http.DefaultTransport, false)
+
+			for count := 0; count <= 10; count++ {
+				Convey("HTTP 1.1 Test", t, func(c C) {
+					{
+						req, err := http.NewRequest("GET", "https://127.0.0.1:23801/", nil)
+						So(err, ShouldBeNil)
+						_, err = rtter.RoundTrip(req)
+						So(err, ShouldBeNil)
+					}
+				})
+
+				Convey("HTTP 2 Test", t, func(c C) {
+					{
+						req, err := http.NewRequest("GET", "https://127.0.0.1:23802/", nil)
+						So(err, ShouldBeNil)
+						_, err = rtter.RoundTrip(req)
+						So(err, ShouldBeNil)
+					}
+				})
+			}
+		})
+	}
+
+	cancel()
+}

common/websocketconn/websocketconn.go

@@ -0,0 +1,120 @@
+package websocketconn
+
+import (
+	"io"
+	"time"
+
+	"github.com/gorilla/websocket"
+)
+
+// An abstraction that makes an underlying WebSocket connection look like a
+// net.Conn.
+type Conn struct {
+	*websocket.Conn
+	Reader io.Reader
+	Writer io.Writer
+}
+
+func (conn *Conn) Read(b []byte) (n int, err error) {
+	return conn.Reader.Read(b)
+}
+
+func (conn *Conn) Write(b []byte) (n int, err error) {
+	return conn.Writer.Write(b)
+}
+
+func (conn *Conn) Close() error {
+	conn.Reader.(*io.PipeReader).Close()
+	conn.Writer.(*io.PipeWriter).Close()
+	// Ignore any error in trying to write a Close frame.
+	_ = conn.Conn.WriteControl(websocket.CloseMessage, []byte{}, time.Now().Add(time.Second))
+	return conn.Conn.Close()
+}
+
+func (conn *Conn) SetDeadline(t time.Time) error {
+	errRead := conn.Conn.SetReadDeadline(t)
+	errWrite := conn.Conn.SetWriteDeadline(t)
+	err := errRead
+	if err == nil {
+		err = errWrite
+	}
+	return err
+}
+
+func readLoop(w io.Writer, ws *websocket.Conn) error {
+	for {
+		messageType, r, err := ws.NextReader()
+		if err != nil {
+			return err
+		}
+		if messageType != websocket.BinaryMessage && messageType != websocket.TextMessage {
+			continue
+		}
+		_, err = io.Copy(w, r)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func writeLoop(ws *websocket.Conn, r io.Reader) error {
+	for {
+		var buf [2048]byte
+		n, err := r.Read(buf[:])
+		if err != nil {
+			return err
+		}
+		data := buf[:n]
+		w, err := ws.NextWriter(websocket.BinaryMessage)
+		if err != nil {
+			return err
+		}
+		n, err = w.Write(data)
+		if err != nil {
+			return err
+		}
+		err = w.Close()
+		if err != nil {
+			return err
+		}
+	}
+}
+
+// websocket.Conn methods start returning websocket.CloseError after the
+// connection has been closed. We want to instead interpret that as io.EOF, just
+// as you would find with a normal net.Conn. This only converts
+// websocket.CloseErrors with known codes; other codes like CloseProtocolError
+// and CloseAbnormalClosure will still be reported as anomalous.
+func closeErrorToEOF(err error) error {
+	if websocket.IsCloseError(err, websocket.CloseNormalClosure, websocket.CloseNoStatusReceived) {
+		err = io.EOF
+	}
+	return err
+}
+
+// Create a new Conn.
+func New(ws *websocket.Conn) *Conn {
+	// Set up synchronous pipes to serialize reads and writes to the
+	// underlying websocket.Conn.
+	//
+	// https://godoc.org/github.com/gorilla/websocket#hdr-Concurrency
+	// "Connections support one concurrent reader and one concurrent writer.
+	// Applications are responsible for ensuring that no more than one
+	// goroutine calls the write methods (NextWriter, etc.) concurrently and
+	// that no more than one goroutine calls the read methods (NextReader,
+	// etc.) concurrently. The Close and WriteControl methods can be called
+	// concurrently with all other methods."
+	pr1, pw1 := io.Pipe()
+	go func() {
+		pw1.CloseWithError(closeErrorToEOF(readLoop(pw1, ws)))
+	}()
+	pr2, pw2 := io.Pipe()
+	go func() {
+		pr2.CloseWithError(closeErrorToEOF(writeLoop(ws, pr2)))
+	}()
+	return &Conn{
+		Conn:   ws,
+		Reader: pr1,
+		Writer: pw2,
+	}
+}

common/websocketconn/websocketconn_test.go

@@ -0,0 +1,263 @@
+package websocketconn
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/gorilla/websocket"
+)
+
+// Returns a (server, client) pair of websocketconn.Conns.
+func connPair() (*Conn, *Conn, error) {
+	// Will be assigned inside server.Handler.
+	var serverConn *Conn
+
+	// Start up a web server to receive the request.
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		return nil, nil, err
+	}
+	defer ln.Close()
+	errCh := make(chan error)
+	server := http.Server{
+		Handler: http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+			upgrader := websocket.Upgrader{
+				CheckOrigin: func(*http.Request) bool { return true },
+			}
+			ws, err := upgrader.Upgrade(rw, req, nil)
+			if err != nil {
+				errCh <- err
+				return
+			}
+			serverConn = New(ws)
+			close(errCh)
+		}),
+	}
+	defer server.Close()
+	go func() {
+		err := server.Serve(ln)
+		if err != nil && err != http.ErrServerClosed {
+			errCh <- err
+		}
+	}()
+
+	// Make a request to the web server.
+	urlStr := (&url.URL{Scheme: "ws", Host: ln.Addr().String()}).String()
+	ws, _, err := (&websocket.Dialer{}).Dial(urlStr, nil)
+	if err != nil {
+		return nil, nil, err
+	}
+	clientConn := New(ws)
+
+	// The server is finished when errCh is written to or closed.
+	err = <-errCh
+	if err != nil {
+		return nil, nil, err
+	}
+	return serverConn, clientConn, nil
+}
+
+// Test that you can write in chunks and read the result concatenated.
+func TestWrite(t *testing.T) {
+	tests := [][][]byte{
+		{},
+		{[]byte("foo")},
+		{[]byte("foo"), []byte("bar")},
+		{{}, []byte("foo"), {}, {}, []byte("bar")},
+	}
+
+	for _, test := range tests {
+		s, c, err := connPair()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// This is a little awkward because we need to read to and write
+		// from both ends of the Conn, and we need to do it in separate
+		// goroutines because otherwise a Write may block waiting for
+		// someone to Read it. Here we set up a loop in a separate
+		// goroutine, reading from the Conn s and writing to the dataCh
+		// and errCh channels, whose ultimate effect in the select loop
+		// below is like
+		//   data, err := ioutil.ReadAll(s)
+		dataCh := make(chan []byte)
+		errCh := make(chan error)
+		go func() {
+			for {
+				var buf [1024]byte
+				n, err := s.Read(buf[:])
+				if err != nil {
+					errCh <- err
+					return
+				}
+				p := make([]byte, n)
+				copy(p, buf[:])
+				dataCh <- p
+			}
+		}()
+
+		// Write the data to the client side of the Conn, one chunk at a
+		// time.
+		for i, chunk := range test {
+			n, err := c.Write(chunk)
+			if err != nil || n != len(chunk) {
+				t.Fatalf("%+q Write chunk %d: got (%d, %v), expected (%d, %v)",
+					test, i, n, err, len(chunk), nil)
+			}
+		}
+		// We cannot immediately c.Close here, because that closes the
+		// connection right away, without waiting for buffered data to
+		// be sent.
+
+		// Pull data and err from the server goroutine above.
+		var data []byte
+		err = nil
+	loop:
+		for {
+			select {
+			case p := <-dataCh:
+				data = append(data, p...)
+			case err = <-errCh:
+				break loop
+			case <-time.After(100 * time.Millisecond):
+				break loop
+			}
+		}
+		s.Close()
+		c.Close()
+
+		// Now data and err contain the result of reading everything
+		// from s.
+		expected := bytes.Join(test, []byte{})
+		if err != nil || !bytes.Equal(data, expected) {
+			t.Fatalf("%+q ReadAll: got (%+q, %v), expected (%+q, %v)",
+				test, data, err, expected, nil)
+		}
+	}
+}
+
+// Test that multiple goroutines may call Read on a Conn simultaneously. Run
+// this with
+//   go test -race
+func TestConcurrentRead(t *testing.T) {
+	s, c, err := connPair()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer s.Close()
+
+	// Set up multiple threads reading from the same conn.
+	errCh := make(chan error, 2)
+	var wg sync.WaitGroup
+	wg.Add(2)
+	for i := 0; i < 2; i++ {
+		go func() {
+			defer wg.Done()
+			_, err := io.Copy(ioutil.Discard, s)
+			if err != nil {
+				errCh <- err
+			}
+		}()
+	}
+
+	// Write a bunch of data to the other end.
+	for i := 0; i < 2000; i++ {
+		_, err := fmt.Fprintf(c, "%d", i)
+		if err != nil {
+			c.Close()
+			t.Fatalf("Write: %v", err)
+		}
+	}
+	c.Close()
+
+	wg.Wait()
+	close(errCh)
+
+	err = <-errCh
+	if err != nil {
+		t.Fatalf("Read: %v", err)
+	}
+}
+
+// Test that multiple goroutines may call Write on a Conn simultaneously. Run
+// this with
+//   go test -race
+func TestConcurrentWrite(t *testing.T) {
+	s, c, err := connPair()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Set up multiple threads writing to the same conn.
+	errCh := make(chan error, 3)
+	var wg sync.WaitGroup
+	wg.Add(2)
+	for i := 0; i < 2; i++ {
+		go func() {
+			defer wg.Done()
+			for j := 0; j < 1000; j++ {
+				_, err := fmt.Fprintf(s, "%d", j)
+				if err != nil {
+					errCh <- err
+					break
+				}
+			}
+		}()
+	}
+	go func() {
+		wg.Wait()
+		err := s.Close()
+		if err != nil {
+			errCh <- err
+		}
+		close(errCh)
+	}()
+
+	// Read from the other end.
+	_, err = io.Copy(ioutil.Discard, c)
+	c.Close()
+	if err != nil {
+		t.Fatalf("Read: %v", err)
+	}
+
+	err = <-errCh
+	if err != nil {
+		t.Fatalf("Write: %v", err)
+	}
+}
+
+// Test that Read and Write methods return errors after Close.
+func TestClose(t *testing.T) {
+	s, c, err := connPair()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+
+	err = s.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var buf [10]byte
+	n, err := s.Read(buf[:])
+	if n != 0 || err == nil {
+		t.Fatalf("Read after Close returned (%v, %v), expected (%v, non-nil)", n, err, 0)
+	}
+
+	_, err = s.Write([]byte{1, 2, 3})
+	// Here we break the abstraction a little and look for a specific error,
+	// io.ErrClosedPipe. This is because we know the Conn uses an io.Pipe
+	// internally.
+	if err != io.ErrClosedPipe {
+		t.Fatalf("Write after Close returned %v, expected %v", err, io.ErrClosedPipe)
+	}
+}

distinctcounter/counter.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/ipsetsink/sinkcluster"
+)
+
+func main() {
+	inputFile := flag.String("in", "", "")
+	start := flag.String("from", "", "")
+	end := flag.String("to", "", "")
+	flag.Parse()
+	startTime, err := time.Parse(time.RFC3339, *start)
+	if err != nil {
+		log.Fatal("unable to parse start time:", err)
+	}
+	endTime, err := time.Parse(time.RFC3339, *end)
+	if err != nil {
+		log.Fatal("unable to parse end time:", err)
+	}
+	fd, err := os.Open(*inputFile)
+	if err != nil {
+		log.Fatal("unable to open input file:", err)
+	}
+	counter := sinkcluster.NewClusterCounter(startTime, endTime)
+	result, err := counter.Count(fd)
+	if err != nil {
+		log.Fatal("unable to count:", err)
+	}
+	fmt.Printf("sum = %v\n", result.Sum)
+	fmt.Printf("chunkIncluded = %v\n", result.ChunkIncluded)
+}

doc/broker-spec.txt

@@ -8,7 +8,7 @@ The Snowflake broker is used to hand out Snowflake proxies to clients using the
 
 This document specifies how the Snowflake broker interacts with other parts of the Tor ecosystem, starting with the metrics CollecTor module and to be expanded upon later.
 
-1. Metrics Reporting (version 1.0)
+1. Metrics Reporting (version 1.1)
 
 Metrics data from the Snowflake broker can be retrieved by sending an HTTP GET request to https://[Snowflake broker URL]/metrics and consists of the following items:
 
@@ -31,6 +31,24 @@ Metrics data from the Snowflake broker can be retrieved by sending an HTTP GET r
         A count of the total number of unique IP addresses of Snowflake
         proxies that have polled.
 
+    "snowflake-ips-standalone" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies of type "standalone" that have polled.
+
+    "snowflake-ips-badge" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies of type "badge" that have polled.
+
+    "snowflake-ips-webext" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies of type "webext" that have polled.
+
     "snowflake-idle-count" NUM NL
         [At most once.]
 
@@ -44,8 +62,212 @@ Metrics data from the Snowflake broker can be retrieved by sending an HTTP GET r
         from the broker but no proxies were available, rounded up to
         the nearest multiple of 8.
 
+    "client-restricted-denied-count" NUM NL
+        [At most once.]
+
+        A count of the number of times a client with a restricted or
+        unknown NAT type has requested a proxy from the broker but no
+        proxies were available, rounded up to the nearest multiple of 8.
+
+    "client-unrestricted-denied-count" NUM NL
+        [At most once.]
+
+        A count of the number of times a client with an unrestricted NAT
+        type has requested a proxy from the broker but no proxies were
+        available, rounded up to the nearest multiple of 8.
+
     "client-snowflake-match-count" NUM NL
         [At most once.]
 
         A count of the number of times a client successfully received a
         proxy from the broker, rounded up to the nearest multiple of 8.
+
+    "snowflake-ips-nat-restricted" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies that have a restricted NAT type.
+
+    "snowflake-ips-nat-unrestricted" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies that have an unrestricted NAT type.
+
+    "snowflake-ips-nat-unknown" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies that have an unknown NAT type.
+
+   "snowflake-proxy-poll-with-relay-url-count" NUM NL
+        [At most once.]
+
+        A count of snowflake proxy polls with relay url extension present.
+        This means this proxy understands relay url, and is sending its
+        allowed prefix.
+   "snowflake-proxy-poll-without-relay-url-count" NUM NL
+        [At most once.]
+
+        A count of snowflake proxy polls with relay url extension absent.
+        This means this proxy is not yet updated.
+   "snowflake-proxy-rejected-for-relay-url-count" NUM NL
+        [At most once.]
+
+        A count of snowflake proxy polls with relay url extension rejected
+        based on broker's relay url extension policy.
+        This means an incompatible allowed relay pattern is included in the
+        proxy poll message.
+2. Broker messaging specification and endpoints
+
+The broker facilitates the connection of snowflake clients and snowflake proxies
+through the exchange of WebRTC SDP information with its endpoints.
+
+2.1. Client interactions with the broker
+
+The broker offers multiple ways for clients to exchange registration
+messages.
+
+2.1.1. HTTPS POST
+
+Clients interact with the broker by making a POST request to `/client` with the
+offer SDP in the request body:
+```
+POST /client HTTP
+
+[offer SDP]
+```
+If the broker is behind a domain-fronted connection, this request is accompanied
+with the necessary HOST information.
+
+If the client is matched up with a proxy, they receive a 200 OK response with
+the proxy's answer SDP in the request body:
+```
+HTTP 200 OK
+
+[answer SDP]
+```
+
+If no proxies were available, they receive a 503 status code:
+```
+HTTP 503 Service Unavailable
+```
+
+2.1.2. AMP
+
+The broker's /amp/client endpoint receives client poll messages encoded
+into the URL path, and sends client poll responses encoded as HTML that
+conforms to the requirements of AMP (Accelerated Mobile Pages). This
+endpoint is intended to be accessed through an AMP cache, using the
+-ampcache option of snowflake-client.
+
+The client encodes its poll message into a GET request as follows:
+```
+GET /amp/client/0[0 or more bytes]/[base64 of client poll message]
+```
+The components of the path are as follows:
+* "/amp/client/", the root of the endpoint.
+* "0", a format version number, which controls the interpretation of the
+  rest of the path. Only the first byte matters as a version indicator
+  (not the whole first path component).
+* Any number of slash or non-slash bytes. These may be used as padding
+  or to prevent cache collisions in the AMP cache.
+* A final slash.
+* base64 encoding of the client poll message, using the URL-safe
+  alphabet (which does not include slash).
+
+The broker returns a client poll response message in the HTTP response.
+The message is encoded using AMP armor, an AMP-compatible HTML encoding.
+The data stream is notionally a "0" byte (a format version indicator)
+followed by the base64 encoding of the message (using the standard
+alphabet, with "=" padding). This stream is broken into
+whitespace-separated chunks, which are then bundled into HTML <pre>
+elements. The <pre> elements are then surrounded by AMP boilerplate. To
+decode, search the HTML for <pre> elements, concatenate their contents
+and join on whitespace, discard the "0" prefix, and base64 decode.
+
+2.2 Proxy interactions with the broker
+
+Proxies poll the broker with a proxy poll request to `/proxy`:
+
+```
+POST /proxy HTTP
+
+{
+  Sid: [generated session id of proxy],
+  Version: 1.3,
+  Type: ["badge"|"webext"|"standalone"|"mobile"],
+  NAT: ["unknown"|"restricted"|"unrestricted"],
+  Clients: [number of current clients, rounded down to multiples of 8],
+  AcceptedRelayPattern: [a pattern representing accepted set of relay domains]
+}
+```
+
+If the request is well-formed, they receive a 200 OK response.
+
+If a client is matched:
+```
+HTTP 200 OK
+
+{
+  Status: "client match",
+  {
+    type: offer,
+    sdp: [WebRTC SDP]
+  },
+  RelayURL: [the WebSocket URL proxy should connect to relay Snowflake traffic]
+}
+```
+
+If a client is not matched:
+```
+HTTP 200 OK
+
+{
+    Status: "no match"
+}
+```
+
+If the request is malformed:
+```
+HTTP 400 BadRequest
+```
+
+If they are matched with a client, they provide their SDP answer with a POST
+request to `/answer`:
+```
+POST /answer HTTP
+
+{
+  Sid: [generated session id of proxy],
+  Version: 1.3,
+  Answer:
+  {
+    type: answer,
+    sdp: [WebRTC SDP]
+  }
+}
+```
+
+If the request is well-formed, they receive a 200 OK response.
+
+If the client retrieved the answer:
+```
+HTTP 200 OK
+
+{
+  Status: "success"
+}
+```
+
+If the client left:
+```
+HTTP 200 OK
+
+{
+  Status: "client gone"
+}
+
+3) If the request is malformed:
+HTTP 400 BadRequest
+```

doc/snowflake-client.1

@@ -0,0 +1,50 @@
+.TH SNOWFLAKE-CLIENT "1" "July 2021" "snowflake-client" "User Commands"
+.SH NAME
+snowflake-client \- WebRTC pluggable transport client for Tor
+.SH DESCRIPTION
+Snowflake helps users circumvent censorship by making a WebRTC
+connection to volunteer proxies. These proxies relay Tor traffic to a
+Snowflake bridge and then through the Tor network.
+.SS "Usage of snowflake-client:"
+.HP
+\fB\-ampcache\fR string
+.IP
+URL of AMP cache to use as a proxy for signaling
+.HP
+\fB\-front\fR string
+.IP
+front domain
+.HP
+\fB\-ice\fR string
+.IP
+comma\-separated list of ICE servers
+.HP
+\fB\-keep\-local\-addresses\fR
+.IP
+keep local LAN address ICE candidates
+.HP
+\fB\-log\fR string
+.IP
+name of log file
+.HP
+\fB\-log\-to\-state\-dir\fR
+.IP
+resolve the log file relative to tor's pt state dir
+.HP
+\fB\-logToStateDir\fR
+.IP
+use \fB\-log\-to\-state\-dir\fR instead
+.HP
+\fB\-max\fR int
+.IP
+capacity for number of multiplexed WebRTC peers (default 1)
+.HP
+\fB\-unsafe\-logging\fR
+.IP
+prevent logs from being scrubbed
+.HP
+\fB\-url\fR string
+.IP
+URL of signaling broker
+.SH "SEE ALSO"
+https://snowflake.torproject.org

doc/snowflake-proxy.1

@@ -0,0 +1,38 @@
+.TH SNOWFLAKE-PROXY "1" "June 2021" "swnoflake-proxy" "User Commands"
+.SH NAME
+snowflake-proxy \- WebRTC pluggable transport proxy for Tor
+.SH DESCRIPTION
+Snowflake helps users circumvent censorship by making a WebRTC
+connection to volunteer proxies. These proxies relay Tor traffic to a
+Snowflake bridge and then through the Tor network.
+.SS "Usage of snowflake-proxy:"
+.HP
+\fB\-broker\fR string
+.IP
+broker URL (default "https://snowflake\-broker.torproject.net/")
+.HP
+\fB\-capacity\fR uint
+.IP
+maximum concurrent clients (default 10)
+.HP
+\fB\-keep\-local\-addresses\fR
+.IP
+keep local LAN address ICE candidates
+.HP
+\fB\-log\fR string
+.IP
+log filename
+.HP
+\fB\-relay\fR string
+.IP
+websocket relay URL (default "wss://snowflake.torproject.net/")
+.HP
+\fB\-stun\fR string
+.IP
+stun URL (default "stun:stun.stunprotocol.org:3478")
+.HP
+\fB\-unsafe\-logging\fR
+.IP
+prevent logs from being scrubbed
+.SH "SEE ALSO"
+https://snowflake.torproject.org

doc/using-the-snowflake-library.md

@@ -0,0 +1,164 @@
+Snowflake is available as a general-purpose pluggable transports library and adheres to the [pluggable transports v2.1 Go API](https://github.com/Pluggable-Transports/Pluggable-Transports-spec/blob/master/releases/PTSpecV2.1/Pluggable%20Transport%20Specification%20v2.1%20-%20Go%20Transport%20API.pdf).
+
+### Client library
+
+The Snowflake client library contains functions for running a Snowflake client.
+
+Example usage:
+
+```Golang
+package main
+
+import (
+    "log"
+
+    sf "git.torproject.org/pluggable-transports/snowflake.git/v2/client/lib"
+)
+
+func main() {
+
+    config := sf.ClientConfig{
+        BrokerURL:   "https://snowflake-broker.example.com",
+        FrontDomain: "https://friendlyfrontdomain.net",
+        ICEAddresses: []string{
+            "stun:stun.voip.blackberry.com:3478",
+            "stun:stun.stunprotocol.org:3478"},
+        Max: 1,
+    }
+    transport, err := sf.NewSnowflakeClient(config)
+    if err != nil {
+        log.Fatal("Failed to start snowflake transport: ", err)
+    }
+
+    // transport implements the ClientFactory interface and returns a net.Conn
+    conn, err := transport.Dial()
+    if err != nil {
+        log.Printf("dial error: %s", err)
+        return
+    }
+    defer conn.Close()
+
+    // ...
+
+}
+```
+
+#### Using your own rendezvous method
+
+You can define and use your own rendezvous method to communicate with a Snowflake broker by implementing the `RendezvousMethod` interface.
+
+```Golang
+
+package main
+
+import (
+    "log"
+
+    sf "git.torproject.org/pluggable-transports/snowflake.git/v2/client/lib"
+)
+
+type StubMethod struct {
+}
+
+func (m *StubMethod) Exchange(pollReq []byte) ([]byte, error) {
+    var brokerResponse []byte
+    var err error
+
+    //Implement the logic you need to communicate with the Snowflake broker here
+
+    return brokerResponse, err
+}
+
+func main() {
+    config := sf.ClientConfig{
+        ICEAddresses:       []string{
+            "stun:stun.voip.blackberry.com:3478",
+            "stun:stun.stunprotocol.org:3478"},
+    }
+    transport, err := sf.NewSnowflakeClient(config)
+    if err != nil {
+        log.Fatal("Failed to start snowflake transport: ", err)
+    }
+
+    // custom rendezvous methods can be set with `SetRendezvousMethod`
+    rendezvous := &StubMethod{}
+    transport.SetRendezvousMethod(rendezvous)
+
+    // transport implements the ClientFactory interface and returns a net.Conn
+    conn, err := transport.Dial()
+    if err != nil {
+        log.Printf("dial error: %s", err)
+        return
+    }
+    defer conn.Close()
+
+    // ...
+
+}
+```
+
+### Server library
+
+The Snowflake server library contains functions for running a Snowflake server.
+
+Example usage:
+```Golang
+
+package main
+
+import (
+    "log"
+    "net"
+
+    sf "git.torproject.org/pluggable-transports/snowflake.git/v2/server/lib"
+    "golang.org/x/crypto/acme/autocert"
+)
+
+func main() {
+
+    // The snowflake server runs a websocket server. To run this securely, you will
+    // need a valid certificate.
+    certManager := &autocert.Manager{
+        Prompt:     autocert.AcceptTOS,
+        HostPolicy: autocert.HostWhitelist("snowflake.yourdomain.com"),
+        Email:      "you@yourdomain.com",
+    }
+
+    transport := sf.NewSnowflakeServer(certManager.GetCertificate)
+
+    addr, err := net.ResolveTCPAddr("tcp", "127.0.0.1:443")
+    if err != nil {
+        log.Printf("error resolving bind address: %s", err.Error())
+    }
+    ln, err := transport.Listen(addr)
+    if err != nil {
+        log.Printf("error opening listener: %s", err.Error())
+    }
+    for {
+        conn, err := ln.Accept()
+        if err != nil {
+            if err, ok := err.(net.Error); ok && err.Temporary() {
+                continue
+            }
+            log.Printf("Snowflake accept error: %s", err)
+            break
+        }
+        go func() {
+            // ...
+
+            defer conn.Close()
+        }()
+    }
+
+    // ...
+
+}
+
+```
+### Running your own Snowflake infrastructure
+
+At the moment we do not have the ability to share Snowfake infrastructure between different types of applications. If you are planning on using Snowflake as a transport for your application, you will need to:
+
+- Run a Snowflake broker. See our [broker documentation](../broker/) and [installation guide](https://gitlab.torproject.org/tpo/anti-censorship/team/-/wikis/Survival-Guides/Snowflake-Broker-Installation-Guide) for more information
+
+- Run Snowflake proxies. These can be run as [standalone Go proxies](../proxy/) or [browser-based proxies](https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake-webext).

go.mod

@@ -0,0 +1,24 @@
+module git.torproject.org/pluggable-transports/snowflake.git/v2
+
+go 1.13
+
+require (
+	git.torproject.org/pluggable-transports/goptlib.git v1.1.0
+	github.com/clarkduvall/hyperloglog v0.0.0-20171127014514-a0107a5d8004 // indirect
+	github.com/gorilla/websocket v1.4.1
+	github.com/pion/ice/v2 v2.2.6
+	github.com/pion/sdp/v3 v3.0.5
+	github.com/pion/stun v0.3.5
+	github.com/pion/webrtc/v3 v3.1.41
+	github.com/prometheus/client_golang v1.10.0
+	github.com/prometheus/client_model v0.2.0
+	github.com/refraction-networking/utls v1.0.0
+	github.com/smartystreets/goconvey v1.6.4
+	github.com/stretchr/testify v1.7.1
+	github.com/xtaci/kcp-go/v5 v5.6.1
+	github.com/xtaci/smux v1.5.15
+	gitlab.torproject.org/tpo/anti-censorship/geoip v0.0.0-20210928150955-7ce4b3d98d01
+	golang.org/x/crypto v0.0.0-20220516162934-403b01795ae8
+	golang.org/x/net v0.0.0-20220425223048-2871e0cb64e4
+	google.golang.org/protobuf v1.26.0
+)

go.sum

@@ -0,0 +1,558 @@
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probetest/Dockerfile

@@ -0,0 +1,3 @@
+FROM golang:1.13
+
+COPY probetest /go/bin

probetest/README.md

@@ -0,0 +1,53 @@
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of Contents**
+
+- [Overview](#overview)
+- [Running your own](#running-your-own)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+This is code for a remote probe test component of Snowflake.
+
+### Overview
+
+This is a probe test server to allow proxies to test their compatability
+with Snowflake. Right now the only type of test implemented is a
+compatability check for clients with symmetric NATs.
+
+### Running your own
+
+The server uses TLS by default.
+There is a `--disable-tls` option for testing purposes,
+but you should use TLS in production.
+
+To build the probe server, run
+```go build```
+
+To deploy the probe server, first set the necessary env variables with
+```
+export HOSTNAMES=${YOUR HOSTNAMES}
+export EMAIL=${YOUR EMAIL}
+```
+then run ```docker-compose up```
+
+Setting up a symmetric NAT configuration requires a few extra steps. After
+upping the docker container, run
+```docker inspect snowflake-probetest```
+to find the subnet used by the probetest container. Then run
+```sudo iptables -L -t nat``` to find the POSTROUTING rules for the subnet.
+It should look something like this:
+```
+Chain POSTROUTING (policy ACCEPT)
+target     prot opt source               destination
+MASQUERADE  all  --  172.19.0.0/16        anywhere
+```
+to modify this rule, execute the command
+```sudo iptables -t nat -R POSTROUTING $RULE_NUM -s 172.19.0.0/16 -j MASQUERADE --random```
+where RULE_NUM is the numbered rule corresponding to your docker container's subnet masquerade rule.
+Afterwards, you should see the rule changed to be:
+```
+Chain POSTROUTING (policy ACCEPT)
+target     prot opt source               destination
+MASQUERADE  all  --  172.19.0.0/16        anywhere      random
+```

probetest/docker-compose.yml

@@ -0,0 +1,11 @@
+ version: "3.8"
+
+ services:
+    snowflake-probetest:
+        build: .
+        container_name: snowflake-probetest
+        ports:
+         - "8443:8443"
+        volumes:
+        - /home/snowflake-broker/acme-cert-cache:/go/bin/acme-cert-cache
+        entrypoint: [ "probetest" , "-addr", ":8443" , "-acme-hostnames", $HOSTNAMES, "-acme-email", $EMAIL, "-acme-cert-cache", "/go/bin/acme-cert-cache"]

probetest/probetest.go

@@ -0,0 +1,238 @@
+/*
+Probe test server to check the reachability of Snowflake proxies from
+clients with symmetric NATs.
+
+The probe server receives an offer from a proxy, returns an answer, and then
+attempts to establish a datachannel connection to that proxy. The proxy will
+self-determine whether the connection opened successfully.
+*/
+package main
+
+import (
+	"crypto/tls"
+	"flag"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/messages"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/safelog"
+	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/util"
+
+	"github.com/pion/webrtc/v3"
+	"golang.org/x/crypto/acme/autocert"
+)
+
+const (
+	readLimit          = 100000                         //Maximum number of bytes to be read from an HTTP request
+	dataChannelTimeout = 20 * time.Second               //time after which we assume proxy data channel will not open
+	stunUrl            = "stun:stun.l.google.com:19302" //default STUN URL
+)
+
+// Create a PeerConnection from an SDP offer. Blocks until the gathering of ICE
+// candidates is complete and the answer is available in LocalDescription.
+func makePeerConnectionFromOffer(sdp *webrtc.SessionDescription,
+	dataChan chan struct{}) (*webrtc.PeerConnection, error) {
+
+	config := webrtc.Configuration{
+		ICEServers: []webrtc.ICEServer{
+			{
+				URLs: []string{stunUrl},
+			},
+		},
+	}
+	pc, err := webrtc.NewPeerConnection(config)
+	if err != nil {
+		return nil, fmt.Errorf("accept: NewPeerConnection: %s", err)
+	}
+	pc.OnDataChannel(func(dc *webrtc.DataChannel) {
+		dc.OnOpen(func() {
+			close(dataChan)
+		})
+		dc.OnClose(func() {
+			dc.Close()
+		})
+	})
+	// As of v3.0.0, pion-webrtc uses trickle ICE by default.
+	// We have to wait for candidate gathering to complete
+	// before we send the offer
+	done := webrtc.GatheringCompletePromise(pc)
+	err = pc.SetRemoteDescription(*sdp)
+	if err != nil {
+		if inerr := pc.Close(); inerr != nil {
+			log.Printf("unable to call pc.Close after pc.SetRemoteDescription with error: %v", inerr)
+		}
+		return nil, fmt.Errorf("accept: SetRemoteDescription: %s", err)
+	}
+
+	answer, err := pc.CreateAnswer(nil)
+	if err != nil {
+		if inerr := pc.Close(); inerr != nil {
+			log.Printf("ICE gathering has generated an error when calling pc.Close: %v", inerr)
+		}
+		return nil, err
+	}
+
+	err = pc.SetLocalDescription(answer)
+	if err != nil {
+		if err = pc.Close(); err != nil {
+			log.Printf("pc.Close after setting local description returned : %v", err)
+		}
+		return nil, err
+	}
+	// Wait for ICE candidate gathering to complete
+	<-done
+	return pc, nil
+}
+
+func probeHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	resp, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
+	if nil != err {
+		log.Println("Invalid data.")
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	offer, _, err := messages.DecodePollResponse(resp)
+	if err != nil {
+		log.Printf("Error reading offer: %s", err.Error())
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	if offer == "" {
+		log.Printf("Error processing session description: %s", err.Error())
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	sdp, err := util.DeserializeSessionDescription(offer)
+	if err != nil {
+		log.Printf("Error processing session description: %s", err.Error())
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	dataChan := make(chan struct{})
+	pc, err := makePeerConnectionFromOffer(sdp, dataChan)
+	if err != nil {
+		log.Printf("Error making WebRTC connection: %s", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	sdp = &webrtc.SessionDescription{
+		Type: pc.LocalDescription().Type,
+		SDP:  util.StripLocalAddresses(pc.LocalDescription().SDP),
+	}
+	answer, err := util.SerializeSessionDescription(sdp)
+	if err != nil {
+		log.Printf("Error making WebRTC connection: %s", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	body, err := messages.EncodeAnswerRequest(answer, "stub-sid")
+	if err != nil {
+		log.Printf("Error making WebRTC connection: %s", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	w.Write(body)
+	// Set a timeout on peerconnection. If the connection state has not
+	// advanced to PeerConnectionStateConnected in this time,
+	// destroy the peer connection and return the token.
+	go func() {
+		timer := time.NewTimer(dataChannelTimeout)
+		defer timer.Stop()
+
+		select {
+		case <-dataChan:
+		case <-timer.C:
+		}
+
+		if err := pc.Close(); err != nil {
+			log.Printf("Error calling pc.Close: %v", err)
+		}
+	}()
+	return
+
+}
+
+func main() {
+	var acmeEmail string
+	var acmeHostnamesCommas string
+	var acmeCertCacheDir string
+	var addr string
+	var disableTLS bool
+	var certFilename, keyFilename string
+	var unsafeLogging bool
+
+	flag.StringVar(&acmeEmail, "acme-email", "", "optional contact email for Let's Encrypt notifications")
+	flag.StringVar(&acmeHostnamesCommas, "acme-hostnames", "", "comma-separated hostnames for TLS certificate")
+	flag.StringVar(&acmeCertCacheDir, "acme-cert-cache", "acme-cert-cache", "directory in which certificates should be cached")
+	flag.StringVar(&certFilename, "cert", "", "TLS certificate file")
+	flag.StringVar(&keyFilename, "key", "", "TLS private key file")
+	flag.StringVar(&addr, "addr", ":8443", "address to listen on")
+	flag.BoolVar(&disableTLS, "disable-tls", false, "don't use HTTPS")
+	flag.BoolVar(&unsafeLogging, "unsafe-logging", false, "prevent logs from being scrubbed")
+	flag.Parse()
+
+	var logOutput io.Writer = os.Stderr
+	if unsafeLogging {
+		log.SetOutput(logOutput)
+	} else {
+		// Scrub log output just in case an address ends up there
+		log.SetOutput(&safelog.LogScrubber{Output: logOutput})
+	}
+
+	log.SetFlags(log.LstdFlags | log.LUTC)
+
+	http.HandleFunc("/probe", probeHandler)
+
+	server := http.Server{
+		Addr: addr,
+	}
+
+	var err error
+	if acmeHostnamesCommas != "" {
+		acmeHostnames := strings.Split(acmeHostnamesCommas, ",")
+		log.Printf("ACME hostnames: %q", acmeHostnames)
+
+		var cache autocert.Cache
+		if err = os.MkdirAll(acmeCertCacheDir, 0700); err != nil {
+			log.Printf("Warning: Couldn't create cache directory %q (reason: %s) so we're *not* using our certificate cache.", acmeCertCacheDir, err)
+		} else {
+			cache = autocert.DirCache(acmeCertCacheDir)
+		}
+
+		certManager := autocert.Manager{
+			Cache:      cache,
+			Prompt:     autocert.AcceptTOS,
+			HostPolicy: autocert.HostWhitelist(acmeHostnames...),
+			Email:      acmeEmail,
+		}
+		// start certificate manager handler
+		go func() {
+			log.Printf("Starting HTTP-01 listener")
+			log.Fatal(http.ListenAndServe(":80", certManager.HTTPHandler(nil)))
+		}()
+
+		server.TLSConfig = &tls.Config{GetCertificate: certManager.GetCertificate}
+		err = server.ListenAndServeTLS("", "")
+	} else if certFilename != "" && keyFilename != "" {
+		err = server.ListenAndServeTLS(certFilename, keyFilename)
+	} else if disableTLS {
+		err = server.ListenAndServe()
+	} else {
+		log.Fatal("the --cert and --key, --acme-hostnames, or --disable-tls option is required")
+	}
+
+	if err != nil {
+		log.Println(err)
+	}
+}

proxy-go/README.md

@@ -1,3 +0,0 @@
-This is a standalone (not browser-based) version of the Snowflake proxy.
-
-Usage: ./proxy-go

proxy-go/snowflake.go

@@ -1,482 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"crypto/rand"
-	"encoding/base64"
-	"encoding/json"
-	"flag"
-	"fmt"
-	"io"
-	"io/ioutil"
-	"log"
-	"net"
-	"net/http"
-	"net/url"
-	"os"
-	"regexp"
-	"strings"
-	"sync"
-	"time"
-
-	"git.torproject.org/pluggable-transports/snowflake.git/common/safelog"
-	"github.com/pion/webrtc"
-	"golang.org/x/net/websocket"
-)
-
-const defaultBrokerURL = "https://snowflake-broker.bamsoftware.com/"
-const defaultRelayURL = "wss://snowflake.bamsoftware.com/"
-const defaultSTUNURL = "stun:stun.l.google.com:19302"
-const pollInterval = 5 * time.Second
-
-//amount of time after sending an SDP answer before the proxy assumes the
-//client is not going to connect
-const dataChannelTimeout = 20 * time.Second
-
-const readLimit = 100000 //Maximum number of bytes to be read from an HTTP request
-
-var brokerURL *url.URL
-var relayURL string
-
-const (
-	sessionIDLength = 16
-)
-
-var (
-	tokens chan bool
-	config webrtc.Configuration
-	client http.Client
-)
-
-var remoteIPPatterns = []*regexp.Regexp{
-	/* IPv4 */
-	regexp.MustCompile(`(?m)^c=IN IP4 ([\d.]+)(?:(?:\/\d+)?\/\d+)?(:? |\r?\n)`),
-	/* IPv6 */
-	regexp.MustCompile(`(?m)^c=IN IP6 ([0-9A-Fa-f:.]+)(?:\/\d+)?(:? |\r?\n)`),
-}
-
-// https://tools.ietf.org/html/rfc4566#section-5.7
-func remoteIPFromSDP(sdp string) net.IP {
-	for _, pattern := range remoteIPPatterns {
-		m := pattern.FindStringSubmatch(sdp)
-		if m != nil {
-			// Ignore parsing errors, ParseIP returns nil.
-			return net.ParseIP(m[1])
-		}
-	}
-	return nil
-}
-
-type webRTCConn struct {
-	dc *webrtc.DataChannel
-	pc *webrtc.PeerConnection
-	pr *io.PipeReader
-
-	lock sync.Mutex // Synchronization for DataChannel destruction
-	once sync.Once  // Synchronization for PeerConnection destruction
-}
-
-func (c *webRTCConn) Read(b []byte) (int, error) {
-	return c.pr.Read(b)
-}
-
-func (c *webRTCConn) Write(b []byte) (int, error) {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-	// log.Printf("webrtc Write %d %+q", len(b), string(b))
-	log.Printf("Write %d bytes --> WebRTC", len(b))
-	if c.dc != nil {
-		c.dc.Send(b)
-	}
-	return len(b), nil
-}
-
-func (c *webRTCConn) Close() (err error) {
-	c.once.Do(func() {
-		err = c.pc.Close()
-	})
-	return
-}
-
-func (c *webRTCConn) LocalAddr() net.Addr {
-	return nil
-}
-
-func (c *webRTCConn) RemoteAddr() net.Addr {
-	//Parse Remote SDP offer and extract client IP
-	clientIP := remoteIPFromSDP(c.pc.RemoteDescription().SDP)
-	if clientIP == nil {
-		return nil
-	}
-	return &net.IPAddr{IP: clientIP, Zone: ""}
-}
-
-func (c *webRTCConn) SetDeadline(t time.Time) error {
-	// nolint: golint
-	return fmt.Errorf("SetDeadline not implemented")
-}
-
-func (c *webRTCConn) SetReadDeadline(t time.Time) error {
-	// nolint: golint
-	return fmt.Errorf("SetReadDeadline not implemented")
-}
-
-func (c *webRTCConn) SetWriteDeadline(t time.Time) error {
-	// nolint: golint
-	return fmt.Errorf("SetWriteDeadline not implemented")
-}
-
-func getToken() {
-	<-tokens
-}
-
-func retToken() {
-	tokens <- true
-}
-
-func genSessionID() string {
-	buf := make([]byte, sessionIDLength)
-	_, err := rand.Read(buf)
-	if err != nil {
-		panic(err.Error())
-	}
-	return strings.TrimRight(base64.StdEncoding.EncodeToString(buf), "=")
-}
-
-func limitedRead(r io.Reader, limit int64) ([]byte, error) {
-	p, err := ioutil.ReadAll(&io.LimitedReader{R: r, N: limit + 1})
-	if err != nil {
-		return p, err
-	} else if int64(len(p)) == limit+1 {
-		return p[0:limit], io.ErrUnexpectedEOF
-	}
-	return p, err
-}
-
-func pollOffer(sid string) *webrtc.SessionDescription {
-	broker := brokerURL.ResolveReference(&url.URL{Path: "proxy"})
-	timeOfNextPoll := time.Now()
-	for {
-		// Sleep until we're scheduled to poll again.
-		now := time.Now()
-		time.Sleep(timeOfNextPoll.Sub(now))
-		// Compute the next time to poll -- if it's in the past, that
-		// means that the POST took longer than pollInterval, so we're
-		// allowed to do another one immediately.
-		timeOfNextPoll = timeOfNextPoll.Add(pollInterval)
-		if timeOfNextPoll.Before(now) {
-			timeOfNextPoll = now
-		}
-
-		req, _ := http.NewRequest("POST", broker.String(), bytes.NewBuffer([]byte(sid)))
-		req.Header.Set("X-Session-ID", sid)
-		resp, err := client.Do(req)
-		if err != nil {
-			log.Printf("error polling broker: %s", err)
-		} else {
-			defer resp.Body.Close()
-			if resp.StatusCode != http.StatusOK {
-				log.Printf("broker returns: %d", resp.StatusCode)
-			} else {
-				body, err := limitedRead(resp.Body, readLimit)
-				if err != nil {
-					log.Printf("error reading broker response: %s", err)
-				} else {
-					return deserializeSessionDescription(string(body))
-				}
-			}
-		}
-	}
-}
-
-func sendAnswer(sid string, pc *webrtc.PeerConnection) error {
-	broker := brokerURL.ResolveReference(&url.URL{Path: "answer"})
-	body := bytes.NewBuffer([]byte(serializeSessionDescription(pc.LocalDescription())))
-	req, _ := http.NewRequest("POST", broker.String(), body)
-	req.Header.Set("X-Session-ID", sid)
-	resp, err := client.Do(req)
-	if err != nil {
-		return err
-	}
-	if resp.StatusCode != http.StatusOK {
-		return fmt.Errorf("broker returned %d", resp.StatusCode)
-	}
-	return nil
-}
-
-func CopyLoop(c1 net.Conn, c2 net.Conn) {
-	var wg sync.WaitGroup
-	copyer := func(dst io.ReadWriteCloser, src io.ReadWriteCloser) {
-		defer wg.Done()
-		if _, err := io.Copy(dst, src); err != nil {
-			log.Printf("io.Copy inside CopyLoop generated an error: %v", err)
-		}
-		dst.Close()
-		src.Close()
-	}
-	wg.Add(2)
-	go copyer(c1, c2)
-	go copyer(c2, c1)
-	wg.Wait()
-}
-
-// We pass conn.RemoteAddr() as an additional parameter, rather than calling
-// conn.RemoteAddr() inside this function, as a workaround for a hang that
-// otherwise occurs inside of conn.pc.RemoteDescription() (called by
-// RemoteAddr). https://bugs.torproject.org/18628#comment:8
-func datachannelHandler(conn *webRTCConn, remoteAddr net.Addr) {
-	defer conn.Close()
-	defer retToken()
-
-	u, err := url.Parse(relayURL)
-	if err != nil {
-		log.Fatalf("invalid relay url: %s", err)
-	}
-
-	// Retrieve client IP address
-	if remoteAddr != nil {
-		// Encode client IP address in relay URL
-		q := u.Query()
-		clientIP := remoteAddr.String()
-		q.Set("client_ip", clientIP)
-		u.RawQuery = q.Encode()
-	} else {
-		log.Printf("no remote address given in websocket")
-	}
-
-	wsConn, err := websocket.Dial(u.String(), "", relayURL)
-	if err != nil {
-		log.Printf("error dialing relay: %s", err)
-		return
-	}
-	log.Printf("connected to relay")
-	defer wsConn.Close()
-	wsConn.PayloadType = websocket.BinaryFrame
-	CopyLoop(conn, wsConn)
-	log.Printf("datachannelHandler ends")
-}
-
-// Create a PeerConnection from an SDP offer. Blocks until the gathering of ICE
-// candidates is complete and the answer is available in LocalDescription.
-// Installs an OnDataChannel callback that creates a webRTCConn and passes it to
-// datachannelHandler.
-func makePeerConnectionFromOffer(sdp *webrtc.SessionDescription, config webrtc.Configuration, dataChan chan struct{}) (*webrtc.PeerConnection, error) {
-	pc, err := webrtc.NewPeerConnection(config)
-	if err != nil {
-		return nil, fmt.Errorf("accept: NewPeerConnection: %s", err)
-	}
-	pc.OnDataChannel(func(dc *webrtc.DataChannel) {
-		log.Println("OnDataChannel")
-		close(dataChan)
-
-		pr, pw := io.Pipe()
-		conn := &webRTCConn{pc: pc, dc: dc, pr: pr}
-
-		dc.OnOpen(func() {
-			log.Println("OnOpen channel")
-		})
-		dc.OnClose(func() {
-			conn.lock.Lock()
-			defer conn.lock.Unlock()
-			log.Println("OnClose channel")
-			conn.dc = nil
-			dc.Close()
-			pw.Close()
-		})
-		dc.OnMessage(func(msg webrtc.DataChannelMessage) {
-			log.Printf("OnMessage <--- %d bytes", len(msg.Data))
-			var n int
-			n, err = pw.Write(msg.Data)
-			if err != nil {
-				if inerr := pw.CloseWithError(err); inerr != nil {
-					log.Printf("close with error generated an error: %v", inerr)
-				}
-			}
-			if n != len(msg.Data) {
-				panic("short write")
-			}
-		})
-
-		go datachannelHandler(conn, conn.RemoteAddr())
-	})
-
-	err = pc.SetRemoteDescription(*sdp)
-	if err != nil {
-		if inerr := pc.Close(); inerr != nil {
-			log.Printf("unable to call pc.Close after pc.SetRemoteDescription with error: %v", inerr)
-		}
-		return nil, fmt.Errorf("accept: SetRemoteDescription: %s", err)
-	}
-	log.Println("sdp offer successfully received.")
-
-	log.Println("Generating answer...")
-	answer, err := pc.CreateAnswer(nil)
-	// blocks on ICE gathering. we need to add a timeout if needed
-	// not putting this in a separate go routine, because we need
-	// SetLocalDescription(answer) to be called before sendAnswer
-	if err != nil {
-		if inerr := pc.Close(); inerr != nil {
-			log.Printf("ICE gathering has generated an error when calling pc.Close: %v", inerr)
-		}
-		return nil, err
-	}
-
-	err = pc.SetLocalDescription(answer)
-	if err != nil {
-		if err = pc.Close(); err != nil {
-			log.Printf("pc.Close after setting local description returned : %v", err)
-		}
-		return nil, err
-	}
-
-	return pc, nil
-}
-
-func runSession(sid string) {
-	offer := pollOffer(sid)
-	if offer == nil {
-		log.Printf("bad offer from broker")
-		retToken()
-		return
-	}
-	dataChan := make(chan struct{})
-	pc, err := makePeerConnectionFromOffer(offer, config, dataChan)
-	if err != nil {
-		log.Printf("error making WebRTC connection: %s", err)
-		retToken()
-		return
-	}
-	err = sendAnswer(sid, pc)
-	if err != nil {
-		log.Printf("error sending answer to client through broker: %s", err)
-		if inerr := pc.Close(); inerr != nil {
-			log.Printf("error calling pc.Close: %v", inerr)
-		}
-		retToken()
-		return
-	}
-	// Set a timeout on peerconnection. If the connection state has not
-	// advanced to PeerConnectionStateConnected in this time,
-	// destroy the peer connection and return the token.
-	select {
-	case <-dataChan:
-		log.Println("Connection successful.")
-	case <-time.After(dataChannelTimeout):
-		log.Println("Timed out waiting for client to open data channel.")
-		if err := pc.Close(); err != nil {
-			log.Printf("error calling pc.Close: %v", err)
-		}
-		retToken()
-	}
-}
-
-func main() {
-	var capacity uint
-	var stunURL string
-	var logFilename string
-	var rawBrokerURL string
-
-	flag.UintVar(&capacity, "capacity", 10, "maximum concurrent clients")
-	flag.StringVar(&rawBrokerURL, "broker", defaultBrokerURL, "broker URL")
-	flag.StringVar(&relayURL, "relay", defaultRelayURL, "websocket relay URL")
-	flag.StringVar(&stunURL, "stun", defaultSTUNURL, "stun URL")
-	flag.StringVar(&logFilename, "log", "", "log filename")
-	flag.Parse()
-
-	var logOutput io.Writer = os.Stderr
-	log.SetFlags(log.LstdFlags | log.LUTC)
-	if logFilename != "" {
-		f, err := os.OpenFile(logFilename, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0600)
-		if err != nil {
-			log.Fatal(err)
-		}
-		defer f.Close()
-		logOutput = io.MultiWriter(os.Stderr, f)
-	}
-	//We want to send the log output through our scrubber first
-	log.SetOutput(&safelog.LogScrubber{Output: logOutput})
-
-	log.Println("starting")
-
-	var err error
-	brokerURL, err = url.Parse(rawBrokerURL)
-	if err != nil {
-		log.Fatalf("invalid broker url: %s", err)
-	}
-	_, err = url.Parse(stunURL)
-	if err != nil {
-		log.Fatalf("invalid stun url: %s", err)
-	}
-	_, err = url.Parse(relayURL)
-	if err != nil {
-		log.Fatalf("invalid relay url: %s", err)
-	}
-
-	config = webrtc.Configuration{
-		ICEServers: []webrtc.ICEServer{
-			{
-				URLs: []string{stunURL},
-			},
-		},
-	}
-	tokens = make(chan bool, capacity)
-	for i := uint(0); i < capacity; i++ {
-		tokens <- true
-	}
-
-	for {
-		getToken()
-		sessionID := genSessionID()
-		runSession(sessionID)
-	}
-}
-
-func deserializeSessionDescription(msg string) *webrtc.SessionDescription {
-	var parsed map[string]interface{}
-	err := json.Unmarshal([]byte(msg), &parsed)
-	if nil != err {
-		log.Println(err)
-		return nil
-	}
-	if _, ok := parsed["type"]; !ok {
-		log.Println("Cannot deserialize SessionDescription without type field.")
-		return nil
-	}
-	if _, ok := parsed["sdp"]; !ok {
-		log.Println("Cannot deserialize SessionDescription without sdp field.")
-		return nil
-	}
-
-	var stype webrtc.SDPType
-	switch parsed["type"].(string) {
-	default:
-		log.Println("Unknown SDP type")
-		return nil
-	case "offer":
-		stype = webrtc.SDPTypeOffer
-	case "pranswer":
-		stype = webrtc.SDPTypePranswer
-	case "answer":
-		stype = webrtc.SDPTypeAnswer
-	case "rollback":
-		stype = webrtc.SDPTypeRollback
-	}
-
-	if err != nil {
-		log.Println(err)
-		return nil
-	}
-	return &webrtc.SessionDescription{
-		Type: stype,
-		SDP:  parsed["sdp"].(string),
-	}
-}
-
-func serializeSessionDescription(desc *webrtc.SessionDescription) string {
-	bytes, err := json.Marshal(*desc)
-	if nil != err {
-		log.Println(err)
-		return ""
-	}
-	return string(bytes)
-}

proxy-go/webrtc_test.go

@@ -1,109 +0,0 @@
-package main
-
-import (
-	"net"
-	"strings"
-	"testing"
-)
-
-func TestRemoteIPFromSDP(t *testing.T) {
-	tests := []struct {
-		sdp      string
-		expected net.IP
-	}{
-		// https://tools.ietf.org/html/rfc4566#section-5
-		{`v=0
-o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5
-s=SDP Seminar
-i=A Seminar on the session description protocol
-u=http://www.example.com/seminars/sdp.pdf
-e=j.doe@example.com (Jane Doe)
-c=IN IP4 224.2.17.12/127
-t=2873397496 2873404696
-a=recvonly
-m=audio 49170 RTP/AVP 0
-m=video 51372 RTP/AVP 99
-a=rtpmap:99 h263-1998/90000
-`, net.ParseIP("224.2.17.12")},
-		// Missing c= line
-		{`v=0
-o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5
-s=SDP Seminar
-i=A Seminar on the session description protocol
-u=http://www.example.com/seminars/sdp.pdf
-e=j.doe@example.com (Jane Doe)
-t=2873397496 2873404696
-a=recvonly
-m=audio 49170 RTP/AVP 0
-m=video 51372 RTP/AVP 99
-a=rtpmap:99 h263-1998/90000
-`, nil},
-		// Single line, IP address only
-		{`c=IN IP4 224.2.1.1
-`, net.ParseIP("224.2.1.1")},
-		// Same, with TTL
-		{`c=IN IP4 224.2.1.1/127
-`, net.ParseIP("224.2.1.1")},
-		// Same, with TTL and multicast addresses
-		{`c=IN IP4 224.2.1.1/127/3
-`, net.ParseIP("224.2.1.1")},
-		// IPv6, address only
-		{`c=IN IP6 FF15::101
-`, net.ParseIP("ff15::101")},
-		// Same, with multicast addresses
-		{`c=IN IP6 FF15::101/3
-`, net.ParseIP("ff15::101")},
-		// Multiple c= lines
-		{`c=IN IP4 1.2.3.4
-c=IN IP4 5.6.7.8
-`, net.ParseIP("1.2.3.4")},
-		// Modified from SDP sent by snowflake-client.
-		{`v=0
-o=- 7860378660295630295 2 IN IP4 127.0.0.1
-s=-
-t=0 0
-a=group:BUNDLE data
-a=msid-semantic: WMS
-m=application 54653 DTLS/SCTP 5000
-c=IN IP4 1.2.3.4
-a=candidate:3581707038 1 udp 2122260223 192.168.0.1 54653 typ host generation 0 network-id 1 network-cost 50
-a=candidate:2617212910 1 tcp 1518280447 192.168.0.1 59673 typ host tcptype passive generation 0 network-id 1 network-cost 50
-a=candidate:2082671819 1 udp 1686052607 1.2.3.4 54653 typ srflx raddr 192.168.0.1 rport 54653 generation 0 network-id 1 network-cost 50
-a=ice-ufrag:IBdf
-a=ice-pwd:G3lTrrC9gmhQx481AowtkhYz
-a=fingerprint:sha-256 53:F8:84:D9:3C:1F:A0:44:AA:D6:3C:65:80:D3:CB:6F:23:90:17:41:06:F9:9C:10:D8:48:4A:A8:B6:FA:14:A1
-a=setup:actpass
-a=mid:data
-a=sctpmap:5000 webrtc-datachannel 1024
-`, net.ParseIP("1.2.3.4")},
-		// Improper character within IPv4
-		{`c=IN IP4 224.2z.1.1
-`, nil},
-		// Improper character within IPv6
-		{`c=IN IP6 ff15:g::101
-`, nil},
-		// Bogus "IP7" addrtype
-		{`c=IN IP7 1.2.3.4
-`, nil},
-	}
-
-	for _, test := range tests {
-		// https://tools.ietf.org/html/rfc4566#section-5: "The sequence
-		// CRLF (0x0d0a) is used to end a record, although parsers
-		// SHOULD be tolerant and also accept records terminated with a
-		// single newline character." We represent the test cases with
-		// LF line endings for convenience, and test them both that way
-		// and with CRLF line endings.
-		lfSDP := test.sdp
-		crlfSDP := strings.Replace(lfSDP, "\n", "\r\n", -1)
-
-		ip := remoteIPFromSDP(lfSDP)
-		if !ip.Equal(test.expected) {
-			t.Errorf("expected %q, got %q from %q", test.expected, ip, lfSDP)
-		}
-		ip = remoteIPFromSDP(crlfSDP)
-		if !ip.Equal(test.expected) {
-			t.Errorf("expected %q, got %q from %q", test.expected, ip, crlfSDP)
-		}
-	}
-}

proxy/.eslintignore

@@ -1,7 +0,0 @@
-build/
-test/
-webext/snowflake.js
-
-# FIXME: Whittle these away
-spec/
-shims.js

proxy/.eslintrc.json

@@ -1,13 +0,0 @@
-{
-    "env": {
-        "browser": true,
-        "es6": true
-    },
-    "extends": "eslint:recommended",
-    "rules": {
-        "indent": ["error", 2, {
-          "SwitchCase": 1,
-          "MemberExpression": 0
-        }]
-    }
-}

proxy/README.md

@@ -1,75 +1,48 @@
-This is the browser proxy component of Snowflake.
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of Contents**
 
-### Embedding
+- [Dependencies](#dependencies)
+- [Building the standalone Snowflake proxy](#building-the-standalone-snowflake-proxy)
+- [Running a standalone Snowflake proxy](#running-a-standalone-snowflake-proxy)
 
-See https://snowflake.torproject.org/ for more info:
-```
-<iframe src="https://snowflake.torproject.org/embed.html" width="88" height="16" frameborder="0" scrolling="no"></iframe>
-```
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
-### Building
+This is a standalone (not browser-based) version of the Snowflake proxy. For browser-based versions of the Snowflake proxy, see https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake-webext.
+
+### Dependencies
+
+- Go 1.13+
+- We use the [pion/webrtc](https://github.com/pion/webrtc) library for WebRTC communication with Snowflake proxies. Note: running `go get` will fetch this dependency automatically during the build process.
+
+### Building the standalone Snowflake proxy
+
+To build the Snowflake proxy, make sure you are in the `proxy/` directory, and then run:
 
 ```
-npm run build
+go get
+go build
 ```
 
-### Testing
+### Running a standalone Snowflake proxy
 
-Unit testing with Jasmine are available with:
+The Snowflake proxy can be run with the following options:
 ```
-npm install
-npm test
+Usage of ./proxy:
+  -broker string
+        broker URL (default "https://snowflake-broker.torproject.net/")
+  -capacity uint
+        maximum concurrent clients
+  -keep-local-addresses
+        keep local LAN address ICE candidates
+  -log string
+        log filename
+  -relay string
+        websocket relay URL (default "wss://snowflake.torproject.net/")
+  -stun string
+        stun URL (default "stun:stun.stunprotocol.org:3478")
+  -unsafe-logging
+        prevent logs from being scrubbed
 ```
 
-To run locally, start an http server in `build/` and navigate to `/embed.html`.
-
-### Preparing to deploy
-
-Background information:
- * https://bugs.torproject.org/23947#comment:8
- * https://help.torproject.org/tsa/doc/static-sites/
- * https://help.torproject.org/tsa/doc/ssh-jump-host/
-
-You need to be in LDAP group "snowflake" and have set up an SSH key with your LDAP account.
-In your ~/.ssh/config file, you should have something like:
-
-```
-Host staticiforme
-HostName staticiforme.torproject.org
-User <your user name>
-ProxyJump people.torproject.org
-IdentityFile ~/.ssh/tor
-```
-
-### Deploying
-
-```
-npm run build
-```
-
-Do a "dry run" rsync with `-n` to check that only expected files are being changed. If you don't understand why a file would be updated, you can add the `-i` option to see the reason.
-
-```
-rsync -n --chown=:snowflake --chmod ug=rw,D+x --perms --delete -crv build/ staticiforme:/srv/snowflake.torproject.org/htdocs/
-```
-
-If it looks good, then repeat the rsync without `-n`.
-
-```
-rsync --chown=:snowflake --chmod ug=rw,D+x --perms --delete -crv build/ staticiforme:/srv/snowflake.torproject.org/htdocs/
-```
-
-You can ignore errors of the form `rsync: failed to set permissions on "<dirname>/": Operation not permitted (1)`.
-
-Then run the command to copy the new files to the live web servers:
-
-```
-ssh staticiforme 'static-update-component snowflake.torproject.org'
-```
-
-### Parameters
-
-With no parameters,
-snowflake uses the default relay `snowflake.freehaven.net:443` and
-uses automatic signaling with the default broker at
-`https://snowflake-broker.freehaven.net/`.
+For more information on how to run a Snowflake proxy in deployment, see our [community documentation](https://community.torproject.org/relay/setup/snowflake/standalone/).

proxy/broker.js

@@ -1,122 +0,0 @@
-/* global log, dbg, snowflake */
-
-/*
-Communication with the snowflake broker.
-
-Browser snowflakes must register with the broker in order
-to get assigned to clients.
-*/
-
-// Represents a broker running remotely.
-class Broker {
-
-  // When interacting with the Broker, snowflake must generate a unique session
-  // ID so the Broker can keep track of each proxy's signalling channels.
-  // On construction, this Broker object does not do anything until
-  // |getClientOffer| is called.
-  constructor(url) {
-    // Promises some client SDP Offer.
-    // Registers this Snowflake with the broker using an HTTP POST request, and
-    // waits for a response containing some client offer that the Broker chooses
-    // for this proxy..
-    // TODO: Actually support multiple clients.
-    this.getClientOffer = this.getClientOffer.bind(this);
-    // urlSuffix for the broker is different depending on what action
-    // is desired.
-    this._postRequest = this._postRequest.bind(this);
-    this.url = url;
-    this.clients = 0;
-    if (0 === this.url.indexOf('localhost', 0)) {
-      // Ensure url has the right protocol + trailing slash.
-      this.url = 'http://' + this.url;
-    }
-    if (0 !== this.url.indexOf('http', 0)) {
-      this.url = 'https://' + this.url;
-    }
-    if ('/' !== this.url.substr(-1)) {
-      this.url += '/';
-    }
-  }
-
-  getClientOffer(id) {
-    return new Promise((fulfill, reject) => {
-      var xhr;
-      xhr = new XMLHttpRequest();
-      xhr.onreadystatechange = function() {
-        if (xhr.DONE !== xhr.readyState) {
-          return;
-        }
-        switch (xhr.status) {
-          case Broker.STATUS.OK:
-            return fulfill(xhr.responseText); // Should contain offer.
-          case Broker.STATUS.GATEWAY_TIMEOUT:
-            return reject(Broker.MESSAGE.TIMEOUT);
-          default:
-            log('Broker ERROR: Unexpected ' + xhr.status + ' - ' + xhr.statusText);
-            snowflake.ui.setStatus(' failure. Please refresh.');
-            return reject(Broker.MESSAGE.UNEXPECTED);
-        }
-      };
-      this._xhr = xhr; // Used by spec to fake async Broker interaction
-      return this._postRequest(id, xhr, 'proxy', id);
-    });
-  }
-
-  // Assumes getClientOffer happened, and a WebRTC SDP answer has been generated.
-  // Sends it back to the broker, which passes it to back to the original client.
-  sendAnswer(id, answer) {
-    var xhr;
-    dbg(id + ' - Sending answer back to broker...\n');
-    dbg(answer.sdp);
-    xhr = new XMLHttpRequest();
-    xhr.onreadystatechange = function() {
-      if (xhr.DONE !== xhr.readyState) {
-        return;
-      }
-      switch (xhr.status) {
-        case Broker.STATUS.OK:
-          dbg('Broker: Successfully replied with answer.');
-          return dbg(xhr.responseText);
-        case Broker.STATUS.GONE:
-          return dbg('Broker: No longer valid to reply with answer.');
-        default:
-          dbg('Broker ERROR: Unexpected ' + xhr.status + ' - ' + xhr.statusText);
-          return snowflake.ui.setStatus(' failure. Please refresh.');
-      }
-    };
-    return this._postRequest(id, xhr, 'answer', JSON.stringify(answer));
-  }
-
-  _postRequest(id, xhr, urlSuffix, payload) {
-    var err;
-    try {
-      xhr.open('POST', this.url + urlSuffix);
-      xhr.setRequestHeader('X-Session-ID', id);
-    } catch (error) {
-      err = error;
-      /*
-      An exception happens here when, for example, NoScript allows the domain
-      on which the proxy badge runs, but not the domain to which it's trying
-      to make the HTTP xhr. The exception message is like "Component
-      returned failure code: 0x805e0006 [nsIXMLHttpRequest.open]" on Firefox.
-      */
-      log('Broker: exception while connecting: ' + err.message);
-      return;
-    }
-    return xhr.send(payload);
-  }
-
-}
-
-Broker.STATUS = {
-  OK: 200,
-  GONE: 410,
-  GATEWAY_TIMEOUT: 504
-};
-
-Broker.MESSAGE = {
-  TIMEOUT: 'Timed out waiting for a client offer.',
-  UNEXPECTED: 'Unexpected status.'
-};
-
-Broker.prototype.clients = 0;

proxy/config.js

@@ -1,36 +0,0 @@
-
-class Config {}
-
-Config.prototype.brokerUrl = 'snowflake-broker.freehaven.net';
-
-Config.prototype.relayAddr = {
-  host: 'snowflake.freehaven.net',
-  port: '443'
-};
-
-// Original non-wss relay:
-// host: '192.81.135.242'
-// port: 9902
-Config.prototype.cookieName = "snowflake-allow";
-
-// Bytes per second. Set to undefined to disable limit.
-Config.prototype.rateLimitBytes = void 0;
-
-Config.prototype.minRateLimit = 10 * 1024;
-
-Config.prototype.rateLimitHistory = 5.0;
-
-Config.prototype.defaultBrokerPollInterval = 300.0 * 1000;
-
-Config.prototype.maxNumClients = 1;
-
-Config.prototype.connectionsPerClient = 1;
-
-// TODO: Different ICE servers.
-Config.prototype.pcConfig = {
-  iceServers: [
-    {
-      urls: ['stun:stun.l.google.com:19302']
-    }
-  ]
-};

proxy/init-badge.js

@@ -1,223 +0,0 @@
-/* global Util, Params, Config, UI, Broker, Snowflake, Popup, Parse, availableLangs, WS */
-
-/*
-UI
-*/
-
-class Messages {
-  constructor(json) {
-    this.json = json;
-  }
-  getMessage(m, ...rest) {
-    let message = this.json[m].message;
-    return message.replace(/\$(\d+)/g, (...args) => {
-      return rest[Number(args[1]) - 1];
-    });
-  }
-}
-
-let messages = null;
-
-class BadgeUI extends UI {
-
-  constructor() {
-    super();
-    this.popup = new Popup();
-  }
-
-  setStatus() {}
-
-  missingFeature(missing) {
-    this.popup.setEnabled(false);
-    this.popup.setActive(false);
-    this.popup.setStatusText(messages.getMessage('popupStatusOff'));
-    this.setIcon('off');
-    this.popup.setStatusDesc(missing, true);
-    this.popup.hideButton();
-  }
-
-  turnOn() {
-    const clients = this.active ? 1 : 0;
-    this.popup.setChecked(true);
-    if (clients > 0) {
-      this.popup.setStatusText(messages.getMessage('popupStatusOn', String(clients)));
-      this.setIcon('running');
-    } else {
-      this.popup.setStatusText(messages.getMessage('popupStatusReady'));
-      this.setIcon('on');
-    }
-    // FIXME: Share stats from webext
-    this.popup.setStatusDesc('');
-    this.popup.setEnabled(true);
-    this.popup.setActive(this.active);
-  }
-
-  turnOff() {
-    this.popup.setChecked(false);
-    this.popup.setStatusText(messages.getMessage('popupStatusOff'));
-    this.setIcon('off');
-    this.popup.setStatusDesc('');
-    this.popup.setEnabled(false);
-    this.popup.setActive(false);
-  }
-
-  setActive(connected) {
-    super.setActive(connected);
-    this.turnOn();
-  }
-
-  setIcon(status) {
-    document.getElementById('icon').href = `assets/toolbar-${status}.ico`;
-  }
-
-}
-
-BadgeUI.prototype.popup = null;
-
-
-/*
-Entry point.
-*/
-
-// Defaults to opt-in.
-var COOKIE_NAME = "snowflake-allow";
-var COOKIE_LIFETIME = "Thu, 01 Jan 2038 00:00:00 GMT";
-var COOKIE_EXPIRE = "Thu, 01 Jan 1970 00:00:01 GMT";
-
-function setSnowflakeCookie(val, expires) {
-  document.cookie = `${COOKIE_NAME}=${val}; path=/; expires=${expires};`;
-}
-
-const defaultLang = 'en_US';
-
-// Resolve as in,
-// https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Internationalization#Localized_string_selection
-function getLang() {
-  let lang = navigator.language || defaultLang;
-  lang = lang.replace(/-/g, '_');
-  if (availableLangs.has(lang)) {
-    return lang;
-  }
-  lang = lang.split('_')[0];
-  if (availableLangs.has(lang)) {
-    return lang;
-  }
-  return defaultLang;
-}
-
-var debug, snowflake, config, broker, ui, log, dbg, init, update, silenceNotifications, query;
-
-(function() {
-
-  snowflake = null;
-
-  query = new URLSearchParams(location.search);
-
-  debug = Params.getBool(query, 'debug', false);
-
-  silenceNotifications = Params.getBool(query, 'silent', false);
-
-  // Log to both console and UI if applicable.
-  // Requires that the snowflake and UI objects are hooked up in order to
-  // log to console.
-  log = function(msg) {
-    console.log('Snowflake: ' + msg);
-    return snowflake != null ? snowflake.ui.log(msg) : void 0;
-  };
-
-  dbg = function(msg) {
-    if (debug) { log(msg); }
-  };
-
-  update = function() {
-    const cookies = Parse.cookie(document.cookie);
-    if (cookies[COOKIE_NAME] !== '1') {
-      ui.turnOff();
-      snowflake.disable();
-      log('Currently not active.');
-      return;
-    }
-
-    if (!Util.hasWebRTC()) {
-      ui.missingFeature(messages.getMessage('popupWebRTCOff'));
-      snowflake.disable();
-      return;
-    }
-
-    WS.probeWebsocket(config.relayAddr)
-    .then(
-      () => {
-        ui.turnOn();
-        dbg('Contacting Broker at ' + broker.url);
-        log('Starting snowflake');
-        snowflake.setRelayAddr(config.relayAddr);
-        snowflake.beginWebRTC();
-      },
-      () => {
-        ui.missingFeature(messages.getMessage('popupBridgeUnreachable'));
-        snowflake.disable();
-        log('Could not connect to bridge.');
-      }
-    );
-  };
-
-  init = function() {
-    ui = new BadgeUI();
-
-    if (!Util.hasCookies()) {
-      ui.missingFeature(messages.getMessage('badgeCookiesOff'));
-      return;
-    }
-
-    config = new Config;
-    if ('off' !== query.get('ratelimit')) {
-      config.rateLimitBytes = Params.getByteCount(query, 'ratelimit', config.rateLimitBytes);
-    }
-    broker = new Broker(config.brokerUrl);
-    snowflake = new Snowflake(config, ui, broker);
-    log('== snowflake proxy ==');
-    update();
-
-    document.getElementById('enabled').addEventListener('change', (event) => {
-      if (event.target.checked) {
-        setSnowflakeCookie('1', COOKIE_LIFETIME);
-      } else {
-        setSnowflakeCookie('', COOKIE_EXPIRE);
-      }
-      update();
-    })
-  };
-
-  // Notification of closing tab with active proxy.
-  window.onbeforeunload = function() {
-    if (
-      !silenceNotifications &&
-      snowflake !== null &&
-      Snowflake.MODE.WEBRTC_READY === snowflake.state
-    ) {
-      return Snowflake.MESSAGE.CONFIRMATION;
-    }
-    return null;
-  };
-
-  window.onunload = function() {
-    if (snowflake !== null) { snowflake.disable(); }
-    return null;
-  };
-
-  window.onload = function() {
-    fetch(`./_locales/${getLang()}/messages.json`)
-    .then((res) => {
-      if (!res.ok) { return; }
-      return res.json();
-    })
-    .then((json) => {
-      messages = new Messages(json);
-      Popup.fill(document.body, (m) => {
-        return messages.getMessage(m);
-      });
-      init();
-    });
-  }
-
-}());