subservers: add WhiteListedURLs to the SubServer interface

Add a new `WhiteListedURLs` method to the `SubServer` interface
so that Lit can easily collect the set of permissions from each
sub-server that does not require a macaroon.

subservers/faraday.go

@@ -118,3 +118,11 @@ func (f *faradaySubServer) MacPath() string {
 func (f *faradaySubServer) Permissions() map[string][]bakery.Op {
 	return perms.RequiredPermissions
 }
+
+// WhiteListedURLs returns a map of all the sub-server's URLs that can be
+// accessed without a macaroon.
+//
+// NOTE: this is part of the SubServer interface.
+func (f *faradaySubServer) WhiteListedURLs() map[string]struct{} {
+	return nil
+}

subservers/interface.go

@@ -58,4 +58,8 @@ type SubServer interface {
 	// Permissions returns a map of all RPC methods and their required
 	// macaroon permissions to access the sub-server.
 	Permissions() map[string][]bakery.Op
+
+	// WhiteListedURLs returns a map of all the sub-server's URLs that can
+	// be accessed without a macaroon.
+	WhiteListedURLs() map[string]struct{}
 }

subservers/loop.go

@@ -128,3 +128,11 @@ func (l *loopSubServer) MacPath() string {
 func (l *loopSubServer) Permissions() map[string][]bakery.Op {
 	return perms.RequiredPermissions
 }
+
+// WhiteListedURLs returns a map of all the sub-server's URLs that can be
+// accessed without a macaroon.
+//
+// NOTE: this is part of the SubServer interface.
+func (l *loopSubServer) WhiteListedURLs() map[string]struct{} {
+	return nil
+}

subservers/pool.go

@@ -118,3 +118,11 @@ func (p *poolSubServer) MacPath() string {
 func (p *poolSubServer) Permissions() map[string][]bakery.Op {
 	return perms.RequiredPermissions
 }
+
+// WhiteListedURLs returns a map of all the sub-server's URLs that can be
+// accessed without a macaroon.
+//
+// NOTE: this is part of the SubServer interface.
+func (p *poolSubServer) WhiteListedURLs() map[string]struct{} {
+	return nil
+}

subservers/taproot-assets.go

@@ -174,3 +174,19 @@ func (t *taprootAssetsSubServer) MacPath() string {
 func (t *taprootAssetsSubServer) Permissions() map[string][]bakery.Op {
 	return perms.RequiredPermissions
 }
+
+// WhiteListedURLs returns a map of all the sub-server's URLs that can be
+// accessed without a macaroon.
+//
+// NOTE: this is part of the SubServer interface.
+func (t *taprootAssetsSubServer) WhiteListedURLs() map[string]struct{} {
+	// If the taproot-asset daemon is running in integrated mode, then we
+	// use cfg.RpcConf.AllowPublicStats to determine if the public stats
+	// endpoints should be included in the whitelist. If it is running in
+	// remote mode, however, then we don't know if the public stats are
+	// allowed, and so we just allow the request through since the remote
+	// daemon will handle blocking the call if it is not whitelisted there.
+	return perms.MacaroonWhitelist(
+		t.cfg.RpcConf.AllowPublicStats || t.remote,
+	)
+}