Merge #11423: [Policy] Several transaction standardness rules

364bae5 qa: Pad scriptPubKeys to get minimum sized txs (MarcoFalke)
7485488 Policy to reject extremely small transactions (Johnson Lau)
0f8719b Add transaction tests for constant scriptCode (Johnson Lau)
9dabfe4 Add constant scriptCode policy in non-segwit scripts (Johnson Lau)

Pull request description:

  This disables `OP_CODESEPARATOR` in non-segwit scripts (even in an unexecuted branch), and makes a positive `FindAndDelete` result invalid. This ensures that the `scriptCode` serialized in `SignatureHash` is always the same as the script passing to the `EvalScript`.

Tree-SHA512: a0552cb920294d130251c48053fa2ff1fbdd26332e62b52147d918837852750f0ce35ce2cd1cbdb86588943312f8154ccb4925e850dbb7c2254bc353070cd5f8

1 files changed, 13 insertions, 2 deletions

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index e0d193fa38..13f41a7cbf 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -336,6 +336,10 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
                 opcode == OP_RSHIFT)
                 return set_error(serror, SCRIPT_ERR_DISABLED_OPCODE); // Disabled opcodes.
 
+            // With SCRIPT_VERIFY_CONST_SCRIPTCODE, OP_CODESEPARATOR in non-segwit script is rejected even in an unexecuted branch
+            if (opcode == OP_CODESEPARATOR && sigversion == SigVersion::BASE && (flags & SCRIPT_VERIFY_CONST_SCRIPTCODE))
+                return set_error(serror, SCRIPT_ERR_OP_CODESEPARATOR);
+
             if (fExec && 0 <= opcode && opcode <= OP_PUSHDATA4) {
                 if (fRequireMinimal && !CheckMinimalPush(vchPushValue, opcode)) {
                     return set_error(serror, SCRIPT_ERR_MINIMALDATA);
@@ -899,6 +903,9 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
 
                 case OP_CODESEPARATOR:
                 {
+                    // If SCRIPT_VERIFY_CONST_SCRIPTCODE flag is set, use of OP_CODESEPARATOR is rejected in pre-segwit
+                    // script, even in an unexecuted branch (this is checked above the opcode case statement).
+
                     // Hash starts after the code separator
                     pbegincodehash = pc;
                 }
@@ -919,7 +926,9 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
 
                     // Drop the signature in pre-segwit scripts but not segwit scripts
                     if (sigversion == SigVersion::BASE) {
-                        FindAndDelete(scriptCode, CScript(vchSig));
+                        int found = FindAndDelete(scriptCode, CScript(vchSig));
+                        if (found > 0 && (flags & SCRIPT_VERIFY_CONST_SCRIPTCODE))
+                            return set_error(serror, SCRIPT_ERR_SIG_FINDANDDELETE);
                     }
 
                     if (!CheckSignatureEncoding(vchSig, flags, serror) || !CheckPubKeyEncoding(vchPubKey, flags, sigversion, serror)) {
@@ -983,7 +992,9 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
                     {
                         valtype& vchSig = stacktop(-isig-k);
                         if (sigversion == SigVersion::BASE) {
-                            FindAndDelete(scriptCode, CScript(vchSig));
+                            int found = FindAndDelete(scriptCode, CScript(vchSig));
+                            if (found > 0 && (flags & SCRIPT_VERIFY_CONST_SCRIPTCODE))
+                                return set_error(serror, SCRIPT_ERR_SIG_FINDANDDELETE);
                         }
                     }