From 80dbffe3ec72da60b7b9d5397a23b85bad1baef7 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Mon, 8 Jun 2015 18:55:07 -0700
Subject: [PATCH] Switch Alerts to use a scriptPubKey instead of a static key

---
 src/alert.cpp       | 37 ++++++++++++++++++++++++++++---------
 src/alert.h         |  5 +++--
 src/chainparams.cpp |  3 +--
 src/chainparams.h   |  5 ++---
 4 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/src/alert.cpp b/src/alert.cpp
index 64399a4260..68c304973e 100644
--- a/src/alert.cpp
+++ b/src/alert.cpp
@@ -7,6 +7,7 @@
 
 #include "chainparams.h"
 #include "clientversion.h"
+#include "hash.h"
 #include "net.h"
 #include "pubkey.h"
 #include "timedata.h"
@@ -86,7 +87,7 @@ void CAlert::SetNull()
 {
     CUnsignedAlert::SetNull();
     vchMsg.clear();
-    vchSig.clear();
+    scriptSig.clear();
 }
 
 bool CAlert::IsNull() const
@@ -145,16 +146,34 @@ bool CAlert::RelayTo(CNode* pnode) const
     return false;
 }
 
+namespace {
+class NaiveSignatureChecker : public BaseSignatureChecker
+{
+protected:
+    uint256 hash;
+
+public:
+    NaiveSignatureChecker(const std::vector<unsigned char>& vchMsg)
+    {
+        CSHA256().Write(&vchMsg[0], vchMsg.size()).Finalize(hash.begin());
+    }
+
+    bool CheckSig(const std::vector<unsigned char>& vchSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode) const
+    {
+        CPubKey pubkey(vchPubKey);
+        if (!pubkey.IsValid())
+            return false;
+        return pubkey.Verify(hash, vchSig);
+    }
+};
+}
+
 bool CAlert::CheckSignature() const
 {
-    CPubKey key(Params().AlertKey());
-    if (!key.Verify(Hash(vchMsg.begin(), vchMsg.end()), vchSig))
-        return error("CAlert::CheckSignature() : verify signature failed");
-
-    // Now unserialize the data
-    CDataStream sMsg(vchMsg, SER_NETWORK, PROTOCOL_VERSION);
-    sMsg >> *(CUnsignedAlert*)this;
-    return true;
+    const CScript& scriptPubKey = Params().AlertKey();
+    NaiveSignatureChecker checker(vchMsg);
+    unsigned int flags = SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_STRICTENC | SCRIPT_VERIFY_NULLDUMMY | SCRIPT_VERIFY_SIGPUSHONLY | SCRIPT_VERIFY_MINIMALDATA | SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS;
+    return VerifyScript(scriptSig, scriptPubKey, flags, checker, NULL);
 }
 
 CAlert CAlert::getAlertByHash(const uint256 &hash)
diff --git a/src/alert.h b/src/alert.h
index 96c203b557..82238772d7 100644
--- a/src/alert.h
+++ b/src/alert.h
@@ -6,6 +6,7 @@
 #ifndef BITCOIN_ALERT_H
 #define BITCOIN_ALERT_H
 
+#include "script/interpreter.h"
 #include "serialize.h"
 #include "sync.h"
 
@@ -77,7 +78,7 @@ class CAlert : public CUnsignedAlert
 {
 public:
     std::vector<unsigned char> vchMsg;
-    std::vector<unsigned char> vchSig;
+    CScript scriptSig;
 
     CAlert()
     {
@@ -89,7 +90,7 @@ public:
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action, int nType, int nVersion) {
         READWRITE(vchMsg);
-        READWRITE(vchSig);
+        READWRITE(scriptSig);
     }
 
     void SetNull();
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 4fb9b6cc67..66871958d6 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -92,7 +92,7 @@ public:
         pchMessageStart[1] = 0xbe;
         pchMessageStart[2] = 0xb4;
         pchMessageStart[3] = 0xd9;
-        vAlertPubKey = ParseHex("04fc9702847840aaf195de8442ebecedf5b095cdbb9bc716bda9110971b28a49e0ead8564ff0db22209e0374782c093bb899692d524e9d6a6956e7c5ecbcd68284");
+        scriptAlert = CScript() << OP_TRUE;
         nDefaultPort = 8333;
         bnProofOfWorkLimit = ~uint256(0) >> 32;
         nSubsidyHalvingInterval = 210000;
@@ -176,7 +176,6 @@ public:
         pchMessageStart[1] = 0x11;
         pchMessageStart[2] = 0x09;
         pchMessageStart[3] = 0x07;
-        vAlertPubKey = ParseHex("04302390343f91cc401d56d68b123028bf52e5fca1939df127f63c6467cdf9c8e2c14b61104cf817d0b780da337893ecc4aaff1309e536162dabbdb45200ca2b0a");
         nDefaultPort = 18333;
         nEnforceBlockUpgradeMajority = 51;
         nRejectBlockOutdatedMajority = 75;
diff --git a/src/chainparams.h b/src/chainparams.h
index 34206100a2..6a79edaa8d 100644
--- a/src/chainparams.h
+++ b/src/chainparams.h
@@ -44,7 +44,7 @@ public:
 
     const uint256& HashGenesisBlock() const { return hashGenesisBlock; }
     const MessageStartChars& MessageStart() const { return pchMessageStart; }
-    const std::vector<unsigned char>& AlertKey() const { return vAlertPubKey; }
+    const CScript& AlertKey() const { return scriptAlert; }
     int GetDefaultPort() const { return nDefaultPort; }
     const uint256& ProofOfWorkLimit() const { return bnProofOfWorkLimit; }
     int SubsidyHalvingInterval() const { return nSubsidyHalvingInterval; }
@@ -85,8 +85,7 @@ protected:
 
     uint256 hashGenesisBlock;
     MessageStartChars pchMessageStart;
-    //! Raw pub key bytes for the broadcast alert signing key.
-    std::vector<unsigned char> vAlertPubKey;
+    CScript scriptAlert;
     int nDefaultPort;
     uint256 bnProofOfWorkLimit;
     int nSubsidyHalvingInterval;