From 0c80f9494715c7dacd6c74a6a56092b416a4d60d Mon Sep 17 00:00:00 2001
From: MASM fan <masmfan@gmail.com>
Date: Wed, 12 Feb 2014 08:58:27 +0400
Subject: [PATCH] Add -enforcecanonical option

Allows user enforce transaction scripts to use canonical PUSH operators, enabled by default.
---
 src/init.cpp   |    3 +++
 src/main.cpp   |    6 ++++++
 src/main.h     |    2 ++
 src/script.cpp |   27 +++++++++++++++++++++++++++
 src/script.h   |    4 +++-
 5 files changed, 41 insertions(+), 1 deletions(-)

diff --git a/src/init.cpp b/src/init.cpp
index 66ffda6..36c4a3a 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -30,6 +30,7 @@ CWallet* pwalletMain;
 CClientUIInterface uiInterface;
 std::string strWalletFileName;
 bool fConfChange;
+bool fEnforceCanonical;
 unsigned int nNodeLifespan;
 unsigned int nDerivationMethodIndex;
 unsigned int nMinerSleep;
@@ -291,6 +292,7 @@ std::string HelpMessage()
         "  -blocknotify=<cmd>     " + _("Execute command when the best block changes (%s in cmd is replaced by block hash)") + "\n" +
         "  -walletnotify=<cmd>    " + _("Execute command when a wallet transaction changes (%s in cmd is replaced by TxID)") + "\n" +
         "  -confchange            " + _("Require a confirmations for change (default: 0)") + "\n" +
+        "  -enforcecanonical      " + _("Enforce transaction scripts to use canonical PUSH operators (default: 1)") + "\n" +
         "  -upgradewallet         " + _("Upgrade wallet to latest format") + "\n" +
         "  -keypool=<n>           " + _("Set key pool size to <n> (default: 100)") + "\n" +
         "  -rescan                " + _("Rescan the block chain for missing wallet transactions") + "\n" +
@@ -472,6 +474,7 @@ bool AppInit2()
     }
 
     fConfChange = GetBoolArg("-confchange", false);
+    fEnforceCanonical = GetBoolArg("-enforcecanonical", true);
 
     if (mapArgs.count("-mininput"))
     {
diff --git a/src/main.cpp b/src/main.cpp
index 6e7d2a4..c4f3d17 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -309,12 +309,18 @@ bool CTransaction::IsStandard() const
             return false;
         if (!txin.scriptSig.IsPushOnly())
             return false;
+        if (fEnforceCanonical && !txin.scriptSig.HasCanonicalPushes()) {
+            return false;
+        }
     }
     BOOST_FOREACH(const CTxOut& txout, vout) {
         if (!::IsStandard(txout.scriptPubKey))
             return false;
         if (txout.nValue == 0)
             return false;
+        if (fEnforceCanonical && !txout.scriptPubKey.HasCanonicalPushes()) {
+            return false;
+        }
     }
     return true;
 }
diff --git a/src/main.h b/src/main.h
index 58ec9fa..fe64412 100644
--- a/src/main.h
+++ b/src/main.h
@@ -93,6 +93,8 @@ extern int64 nMinimumInputValue;
 extern bool fUseFastIndex;
 extern unsigned int nDerivationMethodIndex;
 
+extern bool fEnforceCanonical;
+
 // Minimum disk space required - used in CheckDiskSpace()
 static const uint64 nMinDiskSpace = 52428800;
 
diff --git a/src/script.cpp b/src/script.cpp
index 34c02cf..2bf2cbf 100644
--- a/src/script.cpp
+++ b/src/script.cpp
@@ -1881,6 +1881,33 @@ bool CScript::IsPayToScriptHash() const
             this->at(22) == OP_EQUAL);
 }
 
+bool CScript::HasCanonicalPushes() const
+{
+    const_iterator pc = begin();
+    while (pc < end())
+    {
+        opcodetype opcode;
+        std::vector<unsigned char> data;
+        if (!GetOp(pc, opcode, data))
+            return false;
+        if (opcode > OP_16)
+            continue;
+        if (opcode < OP_PUSHDATA1 && opcode > OP_0 && (data.size() == 1 && data[0] <= 16))
+            // Could have used an OP_n code, rather than a 1-byte push.
+            return false;
+        if (opcode == OP_PUSHDATA1 && data.size() < OP_PUSHDATA1)
+            // Could have used a normal n-byte push, rather than OP_PUSHDATA1.
+            return false;
+        if (opcode == OP_PUSHDATA2 && data.size() <= 0xFF)
+            // Could have used an OP_PUSHDATA1.
+            return false;
+        if (opcode == OP_PUSHDATA4 && data.size() <= 0xFFFF)
+            // Could have used an OP_PUSHDATA2.
+            return false;
+    }
+    return true;
+}
+
 class CScriptVisitor : public boost::static_visitor<bool>
 {
 private:
diff --git a/src/script.h b/src/script.h
index 711b03c..577e80c 100644
--- a/src/script.h
+++ b/src/script.h
@@ -522,7 +522,7 @@ public:
 
     bool IsPayToScriptHash() const;
 
-    // Called by CTransaction::IsStandard
+    // Called by CTransaction::IsStandard and P2SH VerifyScript (which makes it consensus-critical).
     bool IsPushOnly() const
     {
         const_iterator pc = begin();
@@ -537,6 +537,8 @@ public:
         return true;
     }
 
+    // Called by CTransaction::IsStandard.
+    bool HasCanonicalPushes() const;
 
     void SetDestination(const CTxDestination& address);
     void SetMultisig(int nRequired, const std::vector<CKey>& keys);
-- 
1.7.1