policy: make bare OP_CHECKTEMPLATEVERIFY standard

Co-authored-by: James O'Beirne <github@au92.org>

src/addresstype.cpp

@@ -98,6 +98,7 @@ bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
     case TxoutType::MULTISIG:
     case TxoutType::NULL_DATA:
     case TxoutType::NONSTANDARD:
+    case TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY:
         addressRet = CNoDestination(scriptPubKey);
         return false;
     } // no default case, so the compiler can warn about missing cases

src/policy/policy.cpp

@@ -212,6 +212,11 @@ bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
             if (subscript.GetSigOpCount(true) > MAX_P2SH_SIGOPS) {
                 return false;
             }
+        } else if (whichType == TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY) {
+            // after activation, only allow bare with no scriptsig.
+            // pre-activation disallowing enforced via discouraged logic in the
+            // interpreter.
+            if (tx.vin[i].scriptSig.size() != 0) return false;
         }
     }
 

src/policy/policy.h

@@ -124,7 +124,10 @@ static constexpr unsigned int STANDARD_SCRIPT_VERIFY_FLAGS{MANDATORY_SCRIPT_VERI
                                                              SCRIPT_VERIFY_CONST_SCRIPTCODE |
                                                              SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_TAPROOT_VERSION |
                                                              SCRIPT_VERIFY_DISCOURAGE_OP_SUCCESS |
-                                                             SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_PUBKEYTYPE};
+                                                             SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_PUBKEYTYPE |
+                                                             SCRIPT_VERIFY_DISCOURAGE_CHECKTEMPLATEVERIFY |
+                                                             SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_CHECKTEMPLATEVERIFY |
+                                                             SCRIPT_VERIFY_CHECKTEMPLATEVERIFY};
 
 /** For convenience, standard but not mandatory verify flags. */
 static constexpr unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS{STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS};

src/rpc/rawtransaction.cpp

@@ -544,6 +544,8 @@ static RPCHelpMan decodescript()
         case TxoutType::WITNESS_UNKNOWN:
         case TxoutType::WITNESS_V1_TAPROOT:
         case TxoutType::ANCHOR:
+        // don't wrap CTV because P2SH CTV is a hash cycle
+        case TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY:
             // Should not be wrapped
             return false;
         } // no default case, so the compiler can warn about missing cases
@@ -587,6 +589,8 @@ static RPCHelpMan decodescript()
             case TxoutType::WITNESS_V0_SCRIPTHASH:
             case TxoutType::WITNESS_V1_TAPROOT:
             case TxoutType::ANCHOR:
+            // don't wrap CTV because P2SH CTV is a hash cycle
+            case TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY:
                 // Should not be wrapped
                 return false;
             } // no default case, so the compiler can warn about missing cases

src/script/script.cpp

@@ -221,6 +221,14 @@ bool CScript::IsPayToAnchor(int version, const std::vector<unsigned char>& progr
         program[1] == 0x73;
 }
 
+bool CScript::IsPayToBareDefaultCheckTemplateVerifyHash() const
+{
+    // Extra-fast test for pay-to-bare-default-check-template-verify-hash CScripts:
+    return (this->size() == 34 &&
+            (*this)[0] == 0x20 &&
+            (*this)[33] == OP_CHECKTEMPLATEVERIFY);
+}
+
 bool CScript::IsPayToScriptHash() const
 {
     // Extra-fast test for pay-to-script-hash CScripts:

src/script/script.h

@@ -553,6 +553,8 @@ public:
      */
     static bool IsPayToAnchor(int version, const std::vector<unsigned char>& program);
 
+    bool IsPayToBareDefaultCheckTemplateVerifyHash() const;
+
     bool IsPayToScriptHash() const;
     bool IsPayToWitnessScriptHash() const;
     bool IsWitnessProgram(int& version, std::vector<unsigned char>& program) const;

src/script/sign.cpp

@@ -412,6 +412,7 @@ static bool SignStep(const SigningProvider& provider, const BaseSignatureCreator
     case TxoutType::NONSTANDARD:
     case TxoutType::NULL_DATA:
     case TxoutType::WITNESS_UNKNOWN:
+    case TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY:
         return false;
     case TxoutType::PUBKEY:
         if (!CreateSig(creator, sigdata, provider, sig, CPubKey(vSolutions[0]), scriptPubKey, sigversion)) return false;

src/script/solver.cpp

@@ -29,6 +29,7 @@ std::string GetTxnOutputType(TxoutType t)
     case TxoutType::WITNESS_V0_SCRIPTHASH: return "witness_v0_scripthash";
     case TxoutType::WITNESS_V1_TAPROOT: return "witness_v1_taproot";
     case TxoutType::WITNESS_UNKNOWN: return "witness_unknown";
+    case TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY: return "bare_default_ctv_hash";
     } // no default case, so the compiler can warn about missing cases
     assert(false);
 }
@@ -151,6 +152,10 @@ TxoutType Solver(const CScript& scriptPubKey, std::vector<std::vector<unsigned c
         return TxoutType::SCRIPTHASH;
     }
 
+    if (scriptPubKey.IsPayToBareDefaultCheckTemplateVerifyHash()) {
+        return TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY;
+    }
+
     int witnessversion;
     std::vector<unsigned char> witnessprogram;
     if (scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {

src/script/solver.h

@@ -31,6 +31,7 @@ enum class TxoutType {
     WITNESS_V0_SCRIPTHASH,
     WITNESS_V0_KEYHASH,
     WITNESS_V1_TAPROOT,
+    TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY,
     WITNESS_UNKNOWN, //!< Only for Witness versions not already defined above
 };
 

src/test/fuzz/script.cpp

@@ -76,6 +76,7 @@ FUZZ_TARGET(script, .init = initialize_script)
         assert(which_type == TxoutType::PUBKEY ||
                which_type == TxoutType::NONSTANDARD ||
                which_type == TxoutType::NULL_DATA ||
+               which_type == TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY ||
                which_type == TxoutType::MULTISIG);
     }
     if (which_type == TxoutType::NONSTANDARD ||

src/test/transaction_tests.cpp

@@ -70,6 +70,9 @@ static std::map<std::string, unsigned int> mapFlagNames = {
     {std::string("DISCOURAGE_UPGRADABLE_PUBKEYTYPE"), (unsigned int)SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_PUBKEYTYPE},
     {std::string("DISCOURAGE_OP_SUCCESS"), (unsigned int)SCRIPT_VERIFY_DISCOURAGE_OP_SUCCESS},
     {std::string("DISCOURAGE_UPGRADABLE_TAPROOT_VERSION"), (unsigned int)SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_TAPROOT_VERSION},
+    {std::string("DISCOURAGE_UPGRADABLE_CHECKTEMPLATEVERIFY"), (unsigned int)SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_CHECKTEMPLATEVERIFY},
+    {std::string("DISCOURAGE_CHECKTEMPLATEVERIFY"), (unsigned int)SCRIPT_VERIFY_DISCOURAGE_CHECKTEMPLATEVERIFY},
+    {std::string("CHECKTEMPLATEVERIFY"), (unsigned int)SCRIPT_VERIFY_CHECKTEMPLATEVERIFY},
 };
 
 unsigned int ParseScriptFlags(std::string strFlags)

src/wallet/rpc/backup.cpp

@@ -912,6 +912,8 @@ static std::string RecurseImportData(const CScript& script, ImportData& import_d
     case TxoutType::WITNESS_V1_TAPROOT:
     case TxoutType::ANCHOR:
         return "unrecognized script";
+    case TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY:
+        return "bare default CheckTemplateVerify hash";
     } // no default case, so the compiler can warn about missing cases
     NONFATAL_UNREACHABLE();
 }

src/wallet/scriptpubkeyman.cpp

@@ -208,6 +208,11 @@ IsMineResult IsMineInner(const LegacyDataSPKM& keystore, const CScript& scriptPu
         }
         break;
     }
+    case TxoutType::TX_BARE_DEFAULT_CHECKTEMPLATEVERIFY:
+    {
+        ret = IsMineResult::NO;
+        break;
+    }
     } // no default case, so the compiler can warn about missing cases
 
     if (ret == IsMineResult::NO && keystore.HaveWatchOnly(scriptPubKey)) {