Add SCRIPT_VERIFY_SIGPUSHONLY (BIP62 rule 2)

src/script/interpreter.cpp

@@ -980,6 +980,10 @@ bool SignatureChecker::CheckSig(const vector<unsigned char>& vchSigIn, const vec
 
 bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const BaseSignatureChecker& checker)
 {
+    if ((flags & SCRIPT_VERIFY_SIGPUSHONLY) != 0 && !scriptSig.IsPushOnly()) {
+        return false;
+    }
+
     vector<vector<unsigned char> > stack, stackCopy;
     if (!EvalScript(stack, scriptSig, flags, checker))
         return false;

src/script/interpreter.h

@@ -46,6 +46,9 @@ enum
 
     // verify dummy stack item consumed by CHECKMULTISIG is of zero-length (softfork safe, BIP62 rule 7).
     SCRIPT_VERIFY_NULLDUMMY = (1U << 4),
+
+    // Using a non-push operator in the scriptSig causes script failure (softfork safe, BIP62 rule 2).
+    SCRIPT_VERIFY_SIGPUSHONLY = (1U << 5),
 };
 
 uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);

src/script/script.cpp

@@ -230,7 +230,7 @@ bool CScript::IsPushOnly() const
             return false;
         // Note that IsPushOnly() *does* consider OP_RESERVED to be a
         // push-type opcode, however execution of OP_RESERVED fails, so
-        // it's not relevant to P2SH as the scriptSig would fail prior to
+        // it's not relevant to P2SH/BIP62 as the scriptSig would fail prior to
         // the P2SH special validation code being executed.
         if (opcode > OP_16)
             return false;

src/script/script.h

@@ -551,7 +551,7 @@ public:
 
     bool IsPayToScriptHash() const;
 
-    // Called by IsStandardTx and P2SH VerifyScript (which makes it consensus-critical).
+    // Called by IsStandardTx and P2SH/BIP62 VerifyScript (which makes it consensus-critical).
     bool IsPushOnly() const;
 
     // Called by IsStandardTx.