diff options
Diffstat (limited to 'src/script/interpreter.cpp')
| -rw-r--r-- | src/script/interpreter.cpp | 473 |
1 files changed, 426 insertions, 47 deletions
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp index 50a6192476..bb5a7158a5 100644 --- a/src/script/interpreter.cpp +++ b/src/script/interpreter.cpp @@ -342,13 +342,10 @@ public: }; } -/** Helper for OP_CHECKSIG and OP_CHECKSIGVERIFY - * - * A return value of false means the script fails entirely. When true is returned, the - * fSuccess variable indicates whether the signature check itself succeeded. - */ -static bool EvalChecksig(const valtype& vchSig, const valtype& vchPubKey, CScript::const_iterator pbegincodehash, CScript::const_iterator pend, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* serror, bool& fSuccess) +static bool EvalChecksigPreTapscript(const valtype& vchSig, const valtype& vchPubKey, CScript::const_iterator pbegincodehash, CScript::const_iterator pend, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* serror, bool& fSuccess) { + assert(sigversion == SigVersion::BASE || sigversion == SigVersion::WITNESS_V0); + // Subset of script starting at the most recent codeseparator CScript scriptCode(pbegincodehash, pend); @@ -363,7 +360,7 @@ static bool EvalChecksig(const valtype& vchSig, const valtype& vchPubKey, CScrip //serror is set return false; } - fSuccess = checker.CheckSig(vchSig, vchPubKey, scriptCode, sigversion); + fSuccess = checker.CheckECDSASignature(vchSig, vchPubKey, scriptCode, sigversion); if (!fSuccess && (flags & SCRIPT_VERIFY_NULLFAIL) && vchSig.size()) return set_error(serror, SCRIPT_ERR_SIG_NULLFAIL); @@ -371,7 +368,67 @@ static bool EvalChecksig(const valtype& vchSig, const valtype& vchPubKey, CScrip return true; } -bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* serror) +static bool EvalChecksigTapscript(const valtype& sig, const valtype& pubkey, ScriptExecutionData& execdata, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* serror, bool& success) +{ + assert(sigversion == SigVersion::TAPSCRIPT); + + /* + * The following validation sequence is consensus critical. Please note how -- + * upgradable public key versions precede other rules; + * the script execution fails when using empty signature with invalid public key; + * the script execution fails when using non-empty invalid signature. + */ + success = !sig.empty(); + if (success) { + // Implement the sigops/witnesssize ratio test. + // Passing with an upgradable public key version is also counted. + assert(execdata.m_validation_weight_left_init); + execdata.m_validation_weight_left -= VALIDATION_WEIGHT_PER_SIGOP_PASSED; + if (execdata.m_validation_weight_left < 0) { + return set_error(serror, SCRIPT_ERR_TAPSCRIPT_VALIDATION_WEIGHT); + } + } + if (pubkey.size() == 0) { + return set_error(serror, SCRIPT_ERR_PUBKEYTYPE); + } else if (pubkey.size() == 32) { + if (success && !checker.CheckSchnorrSignature(sig, pubkey, sigversion, execdata, serror)) { + return false; // serror is set + } + } else { + /* + * New public key version softforks should be defined before this `else` block. + * Generally, the new code should not do anything but failing the script execution. To avoid + * consensus bugs, it should not modify any existing values (including `success`). + */ + if ((flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_PUBKEYTYPE) != 0) { + return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_PUBKEYTYPE); + } + } + + return true; +} + +/** Helper for OP_CHECKSIG, OP_CHECKSIGVERIFY, and (in Tapscript) OP_CHECKSIGADD. + * + * A return value of false means the script fails entirely. When true is returned, the + * success variable indicates whether the signature check itself succeeded. + */ +static bool EvalChecksig(const valtype& sig, const valtype& pubkey, CScript::const_iterator pbegincodehash, CScript::const_iterator pend, ScriptExecutionData& execdata, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* serror, bool& success) +{ + switch (sigversion) { + case SigVersion::BASE: + case SigVersion::WITNESS_V0: + return EvalChecksigPreTapscript(sig, pubkey, pbegincodehash, pend, flags, checker, sigversion, serror, success); + case SigVersion::TAPSCRIPT: + return EvalChecksigTapscript(sig, pubkey, execdata, flags, checker, sigversion, serror, success); + case SigVersion::TAPROOT: + // Key path spending in Taproot has no script, so this is unreachable. + break; + } + assert(false); +} + +bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror) { static const CScriptNum bnZero(0); static const CScriptNum bnOne(1); @@ -381,6 +438,9 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& // static const valtype vchZero(0); static const valtype vchTrue(1, 1); + // sigversion cannot be TAPROOT here, as it admits no script execution. + assert(sigversion == SigVersion::BASE || sigversion == SigVersion::WITNESS_V0 || sigversion == SigVersion::TAPSCRIPT); + CScript::const_iterator pc = script.begin(); CScript::const_iterator pend = script.end(); CScript::const_iterator pbegincodehash = script.begin(); @@ -389,15 +449,18 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& ConditionStack vfExec; std::vector<valtype> altstack; set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR); - if (script.size() > MAX_SCRIPT_SIZE) + if ((sigversion == SigVersion::BASE || sigversion == SigVersion::WITNESS_V0) && script.size() > MAX_SCRIPT_SIZE) { return set_error(serror, SCRIPT_ERR_SCRIPT_SIZE); + } int nOpCount = 0; bool fRequireMinimal = (flags & SCRIPT_VERIFY_MINIMALDATA) != 0; + uint32_t opcode_pos = 0; + execdata.m_codeseparator_pos = 0xFFFFFFFFUL; + execdata.m_codeseparator_pos_init = true; try { - while (pc < pend) - { + for (; pc < pend; ++opcode_pos) { bool fExec = vfExec.all_true(); // @@ -408,9 +471,12 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& if (vchPushValue.size() > MAX_SCRIPT_ELEMENT_SIZE) return set_error(serror, SCRIPT_ERR_PUSH_SIZE); - // Note how OP_RESERVED does not count towards the opcode limit. - if (opcode > OP_16 && ++nOpCount > MAX_OPS_PER_SCRIPT) - return set_error(serror, SCRIPT_ERR_OP_COUNT); + if (sigversion == SigVersion::BASE || sigversion == SigVersion::WITNESS_V0) { + // Note how OP_RESERVED does not count towards the opcode limit. + if (opcode > OP_16 && ++nOpCount > MAX_OPS_PER_SCRIPT) { + return set_error(serror, SCRIPT_ERR_OP_COUNT); + } + } if (opcode == OP_CAT || opcode == OP_SUBSTR || @@ -568,6 +634,15 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& if (stack.size() < 1) return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL); valtype& vch = stacktop(-1); + // Tapscript requires minimal IF/NOTIF inputs as a consensus rule. + if (sigversion == SigVersion::TAPSCRIPT) { + // The input argument to the OP_IF and OP_NOTIF opcodes must be either + // exactly 0 (the empty vector) or exactly 1 (the one-byte vector with value 1). + if (vch.size() > 1 || (vch.size() == 1 && vch[0] != 1)) { + return set_error(serror, SCRIPT_ERR_TAPSCRIPT_MINIMALIF); + } + } + // Under witness v0 rules it is only a policy rule, enabled through SCRIPT_VERIFY_MINIMALIF. if (sigversion == SigVersion::WITNESS_V0 && (flags & SCRIPT_VERIFY_MINIMALIF)) { if (vch.size() > 1) return set_error(serror, SCRIPT_ERR_MINIMALIF); @@ -1001,6 +1076,7 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& // Hash starts after the code separator pbegincodehash = pc; + execdata.m_codeseparator_pos = opcode_pos; } break; @@ -1015,7 +1091,7 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& valtype& vchPubKey = stacktop(-1); bool fSuccess = true; - if (!EvalChecksig(vchSig, vchPubKey, pbegincodehash, pend, flags, checker, sigversion, serror, fSuccess)) return false; + if (!EvalChecksig(vchSig, vchPubKey, pbegincodehash, pend, execdata, flags, checker, sigversion, serror, fSuccess)) return false; popstack(stack); popstack(stack); stack.push_back(fSuccess ? vchTrue : vchFalse); @@ -1029,9 +1105,32 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& } break; + case OP_CHECKSIGADD: + { + // OP_CHECKSIGADD is only available in Tapscript + if (sigversion == SigVersion::BASE || sigversion == SigVersion::WITNESS_V0) return set_error(serror, SCRIPT_ERR_BAD_OPCODE); + + // (sig num pubkey -- num) + if (stack.size() < 3) return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION); + + const valtype& sig = stacktop(-3); + const CScriptNum num(stacktop(-2), fRequireMinimal); + const valtype& pubkey = stacktop(-1); + + bool success = true; + if (!EvalChecksig(sig, pubkey, pbegincodehash, pend, execdata, flags, checker, sigversion, serror, success)) return false; + popstack(stack); + popstack(stack); + popstack(stack); + stack.push_back((num + (success ? 1 : 0)).getvch()); + } + break; + case OP_CHECKMULTISIG: case OP_CHECKMULTISIGVERIFY: { + if (sigversion == SigVersion::TAPSCRIPT) return set_error(serror, SCRIPT_ERR_TAPSCRIPT_CHECKMULTISIG); + // ([sig ...] num_of_signatures [pubkey ...] num_of_pubkeys -- bool) int i = 1; @@ -1089,7 +1188,7 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& } // Check signature - bool fOk = checker.CheckSig(vchSig, vchPubKey, scriptCode, sigversion); + bool fOk = checker.CheckECDSASignature(vchSig, vchPubKey, scriptCode, sigversion); if (fOk) { isig++; @@ -1159,6 +1258,12 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& return set_success(serror); } +bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* serror) +{ + ScriptExecutionData execdata; + return EvalScript(stack, script, flags, checker, sigversion, execdata, serror); +} + namespace { /** @@ -1291,35 +1396,183 @@ uint256 GetOutputsSHA256(const T& txTo) return ss.GetSHA256(); } +/** Compute the (single) SHA256 of the concatenation of all amounts spent by a tx. */ +uint256 GetSpentAmountsSHA256(const std::vector<CTxOut>& outputs_spent) +{ + CHashWriter ss(SER_GETHASH, 0); + for (const auto& txout : outputs_spent) { + ss << txout.nValue; + } + return ss.GetSHA256(); +} + +/** Compute the (single) SHA256 of the concatenation of all scriptPubKeys spent by a tx. */ +uint256 GetSpentScriptsSHA256(const std::vector<CTxOut>& outputs_spent) +{ + CHashWriter ss(SER_GETHASH, 0); + for (const auto& txout : outputs_spent) { + ss << txout.scriptPubKey; + } + return ss.GetSHA256(); +} + + } // namespace template <class T> -void PrecomputedTransactionData::Init(const T& txTo) +void PrecomputedTransactionData::Init(const T& txTo, std::vector<CTxOut>&& spent_outputs) { - assert(!m_ready); + assert(!m_spent_outputs_ready); - // Cache is calculated only for transactions with witness - if (txTo.HasWitness()) { - hashPrevouts = SHA256Uint256(GetPrevoutsSHA256(txTo)); - hashSequence = SHA256Uint256(GetSequencesSHA256(txTo)); - hashOutputs = SHA256Uint256(GetOutputsSHA256(txTo)); + m_spent_outputs = std::move(spent_outputs); + if (!m_spent_outputs.empty()) { + assert(m_spent_outputs.size() == txTo.vin.size()); + m_spent_outputs_ready = true; } - m_ready = true; + // Determine which precomputation-impacting features this transaction uses. + bool uses_bip143_segwit = false; + bool uses_bip341_taproot = false; + for (size_t inpos = 0; inpos < txTo.vin.size(); ++inpos) { + if (!txTo.vin[inpos].scriptWitness.IsNull()) { + if (m_spent_outputs_ready && m_spent_outputs[inpos].scriptPubKey.size() == 2 + WITNESS_V1_TAPROOT_SIZE && + m_spent_outputs[inpos].scriptPubKey[0] == OP_1) { + // Treat every witness-bearing spend with 34-byte scriptPubKey that starts with OP_1 as a Taproot + // spend. This only works if spent_outputs was provided as well, but if it wasn't, actual validation + // will fail anyway. Note that this branch may trigger for scriptPubKeys that aren't actually segwit + // but in that case validation will fail as SCRIPT_ERR_WITNESS_UNEXPECTED anyway. + uses_bip341_taproot = true; + } else { + // Treat every spend that's not known to native witness v1 as a Witness v0 spend. This branch may + // also be taken for unknown witness versions, but it is harmless, and being precise would require + // P2SH evaluation to find the redeemScript. + uses_bip143_segwit = true; + } + } + if (uses_bip341_taproot && uses_bip143_segwit) break; // No need to scan further if we already need all. + } + + if (uses_bip143_segwit || uses_bip341_taproot) { + // Computations shared between both sighash schemes. + m_prevouts_single_hash = GetPrevoutsSHA256(txTo); + m_sequences_single_hash = GetSequencesSHA256(txTo); + m_outputs_single_hash = GetOutputsSHA256(txTo); + } + if (uses_bip143_segwit) { + hashPrevouts = SHA256Uint256(m_prevouts_single_hash); + hashSequence = SHA256Uint256(m_sequences_single_hash); + hashOutputs = SHA256Uint256(m_outputs_single_hash); + m_bip143_segwit_ready = true; + } + if (uses_bip341_taproot) { + m_spent_amounts_single_hash = GetSpentAmountsSHA256(m_spent_outputs); + m_spent_scripts_single_hash = GetSpentScriptsSHA256(m_spent_outputs); + m_bip341_taproot_ready = true; + } } template <class T> PrecomputedTransactionData::PrecomputedTransactionData(const T& txTo) { - Init(txTo); + Init(txTo, {}); } // explicit instantiation -template void PrecomputedTransactionData::Init(const CTransaction& txTo); -template void PrecomputedTransactionData::Init(const CMutableTransaction& txTo); +template void PrecomputedTransactionData::Init(const CTransaction& txTo, std::vector<CTxOut>&& spent_outputs); +template void PrecomputedTransactionData::Init(const CMutableTransaction& txTo, std::vector<CTxOut>&& spent_outputs); template PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo); template PrecomputedTransactionData::PrecomputedTransactionData(const CMutableTransaction& txTo); +static const CHashWriter HASHER_TAPSIGHASH = TaggedHash("TapSighash"); +static const CHashWriter HASHER_TAPLEAF = TaggedHash("TapLeaf"); +static const CHashWriter HASHER_TAPBRANCH = TaggedHash("TapBranch"); +static const CHashWriter HASHER_TAPTWEAK = TaggedHash("TapTweak"); + +template<typename T> +bool SignatureHashSchnorr(uint256& hash_out, const ScriptExecutionData& execdata, const T& tx_to, uint32_t in_pos, uint8_t hash_type, SigVersion sigversion, const PrecomputedTransactionData& cache) +{ + uint8_t ext_flag, key_version; + switch (sigversion) { + case SigVersion::TAPROOT: + ext_flag = 0; + // key_version is not used and left uninitialized. + break; + case SigVersion::TAPSCRIPT: + ext_flag = 1; + // key_version must be 0 for now, representing the current version of + // 32-byte public keys in the tapscript signature opcode execution. + // An upgradable public key version (with a size not 32-byte) may + // request a different key_version with a new sigversion. + key_version = 0; + break; + default: + assert(false); + } + assert(in_pos < tx_to.vin.size()); + assert(cache.m_bip341_taproot_ready && cache.m_spent_outputs_ready); + + CHashWriter ss = HASHER_TAPSIGHASH; + + // Epoch + static constexpr uint8_t EPOCH = 0; + ss << EPOCH; + + // Hash type + const uint8_t output_type = (hash_type == SIGHASH_DEFAULT) ? SIGHASH_ALL : (hash_type & SIGHASH_OUTPUT_MASK); // Default (no sighash byte) is equivalent to SIGHASH_ALL + const uint8_t input_type = hash_type & SIGHASH_INPUT_MASK; + if (!(hash_type <= 0x03 || (hash_type >= 0x81 && hash_type <= 0x83))) return false; + ss << hash_type; + + // Transaction level data + ss << tx_to.nVersion; + ss << tx_to.nLockTime; + if (input_type != SIGHASH_ANYONECANPAY) { + ss << cache.m_prevouts_single_hash; + ss << cache.m_spent_amounts_single_hash; + ss << cache.m_spent_scripts_single_hash; + ss << cache.m_sequences_single_hash; + } + if (output_type == SIGHASH_ALL) { + ss << cache.m_outputs_single_hash; + } + + // Data about the input/prevout being spent + assert(execdata.m_annex_init); + const bool have_annex = execdata.m_annex_present; + const uint8_t spend_type = (ext_flag << 1) + (have_annex ? 1 : 0); // The low bit indicates whether an annex is present. + ss << spend_type; + if (input_type == SIGHASH_ANYONECANPAY) { + ss << tx_to.vin[in_pos].prevout; + ss << cache.m_spent_outputs[in_pos]; + ss << tx_to.vin[in_pos].nSequence; + } else { + ss << in_pos; + } + if (have_annex) { + ss << execdata.m_annex_hash; + } + + // Data about the output (if only one). + if (output_type == SIGHASH_SINGLE) { + if (in_pos >= tx_to.vout.size()) return false; + CHashWriter sha_single_output(SER_GETHASH, 0); + sha_single_output << tx_to.vout[in_pos]; + ss << sha_single_output.GetSHA256(); + } + + // Additional data for BIP 342 signatures + if (sigversion == SigVersion::TAPSCRIPT) { + assert(execdata.m_tapleaf_hash_init); + ss << execdata.m_tapleaf_hash; + ss << key_version; + assert(execdata.m_codeseparator_pos_init); + ss << execdata.m_codeseparator_pos; + } + + hash_out = ss.GetSHA256(); + return true; +} + template <class T> uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache) { @@ -1329,7 +1582,7 @@ uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn uint256 hashPrevouts; uint256 hashSequence; uint256 hashOutputs; - const bool cacheready = cache && cache->m_ready; + const bool cacheready = cache && cache->m_bip143_segwit_ready; if (!(nHashType & SIGHASH_ANYONECANPAY)) { hashPrevouts = cacheready ? cache->hashPrevouts : SHA256Uint256(GetPrevoutsSHA256(txTo)); @@ -1389,13 +1642,19 @@ uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn } template <class T> -bool GenericTransactionSignatureChecker<T>::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const +bool GenericTransactionSignatureChecker<T>::VerifyECDSASignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const { return pubkey.Verify(sighash, vchSig); } template <class T> -bool GenericTransactionSignatureChecker<T>::CheckSig(const std::vector<unsigned char>& vchSigIn, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const +bool GenericTransactionSignatureChecker<T>::VerifySchnorrSignature(Span<const unsigned char> sig, const XOnlyPubKey& pubkey, const uint256& sighash) const +{ + return pubkey.VerifySchnorr(sighash, sig); +} + +template <class T> +bool GenericTransactionSignatureChecker<T>::CheckECDSASignature(const std::vector<unsigned char>& vchSigIn, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const { CPubKey pubkey(vchPubKey); if (!pubkey.IsValid()) @@ -1410,13 +1669,41 @@ bool GenericTransactionSignatureChecker<T>::CheckSig(const std::vector<unsigned uint256 sighash = SignatureHash(scriptCode, *txTo, nIn, nHashType, amount, sigversion, this->txdata); - if (!VerifySignature(vchSig, pubkey, sighash)) + if (!VerifyECDSASignature(vchSig, pubkey, sighash)) return false; return true; } template <class T> +bool GenericTransactionSignatureChecker<T>::CheckSchnorrSignature(Span<const unsigned char> sig, Span<const unsigned char> pubkey_in, SigVersion sigversion, const ScriptExecutionData& execdata, ScriptError* serror) const +{ + assert(sigversion == SigVersion::TAPROOT || sigversion == SigVersion::TAPSCRIPT); + // Schnorr signatures have 32-byte public keys. The caller is responsible for enforcing this. + assert(pubkey_in.size() == 32); + // Note that in Tapscript evaluation, empty signatures are treated specially (invalid signature that does not + // abort script execution). This is implemented in EvalChecksigTapscript, which won't invoke + // CheckSchnorrSignature in that case. In other contexts, they are invalid like every other signature with + // size different from 64 or 65. + if (sig.size() != 64 && sig.size() != 65) return set_error(serror, SCRIPT_ERR_SCHNORR_SIG_SIZE); + + XOnlyPubKey pubkey{pubkey_in}; + + uint8_t hashtype = SIGHASH_DEFAULT; + if (sig.size() == 65) { + hashtype = SpanPopBack(sig); + if (hashtype == SIGHASH_DEFAULT) return set_error(serror, SCRIPT_ERR_SCHNORR_SIG_HASHTYPE); + } + uint256 sighash; + assert(this->txdata); + if (!SignatureHashSchnorr(sighash, execdata, *txTo, nIn, hashtype, sigversion, *this->txdata)) { + return set_error(serror, SCRIPT_ERR_SCHNORR_SIG_HASHTYPE); + } + if (!VerifySchnorrSignature(sig, pubkey, sighash)) return set_error(serror, SCRIPT_ERR_SCHNORR_SIG); + return true; +} + +template <class T> bool GenericTransactionSignatureChecker<T>::CheckLockTime(const CScriptNum& nLockTime) const { // There are two kinds of nLockTime: lock-by-blockheight @@ -1504,17 +1791,39 @@ bool GenericTransactionSignatureChecker<T>::CheckSequence(const CScriptNum& nSeq template class GenericTransactionSignatureChecker<CTransaction>; template class GenericTransactionSignatureChecker<CMutableTransaction>; -static bool ExecuteWitnessScript(const Span<const valtype>& stack_span, const CScript& scriptPubKey, unsigned int flags, SigVersion sigversion, const BaseSignatureChecker& checker, ScriptError* serror) +static bool ExecuteWitnessScript(const Span<const valtype>& stack_span, const CScript& scriptPubKey, unsigned int flags, SigVersion sigversion, const BaseSignatureChecker& checker, ScriptExecutionData& execdata, ScriptError* serror) { std::vector<valtype> stack{stack_span.begin(), stack_span.end()}; + if (sigversion == SigVersion::TAPSCRIPT) { + // OP_SUCCESSx processing overrides everything, including stack element size limits + CScript::const_iterator pc = scriptPubKey.begin(); + while (pc < scriptPubKey.end()) { + opcodetype opcode; + if (!scriptPubKey.GetOp(pc, opcode)) { + // Note how this condition would not be reached if an unknown OP_SUCCESSx was found + return set_error(serror, SCRIPT_ERR_BAD_OPCODE); + } + // New opcodes will be listed here. May use a different sigversion to modify existing opcodes. + if (IsOpSuccess(opcode)) { + if (flags & SCRIPT_VERIFY_DISCOURAGE_OP_SUCCESS) { + return set_error(serror, SCRIPT_ERR_DISCOURAGE_OP_SUCCESS); + } + return set_success(serror); + } + } + + // Tapscript enforces initial stack size limits (altstack is empty here) + if (stack.size() > MAX_STACK_SIZE) return set_error(serror, SCRIPT_ERR_STACK_SIZE); + } + // Disallow stack item size > MAX_SCRIPT_ELEMENT_SIZE in witness stack for (const valtype& elem : stack) { if (elem.size() > MAX_SCRIPT_ELEMENT_SIZE) return set_error(serror, SCRIPT_ERR_PUSH_SIZE); } // Run the script interpreter. - if (!EvalScript(stack, scriptPubKey, flags, checker, sigversion, serror)) return false; + if (!EvalScript(stack, scriptPubKey, flags, checker, sigversion, execdata, serror)) return false; // Scripts inside witness implicitly require cleanstack behaviour if (stack.size() != 1) return set_error(serror, SCRIPT_ERR_CLEANSTACK); @@ -1522,40 +1831,110 @@ static bool ExecuteWitnessScript(const Span<const valtype>& stack_span, const CS return true; } -static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror) +static bool VerifyTaprootCommitment(const std::vector<unsigned char>& control, const std::vector<unsigned char>& program, const CScript& script, uint256& tapleaf_hash) { - CScript scriptPubKey; + const int path_len = (control.size() - TAPROOT_CONTROL_BASE_SIZE) / TAPROOT_CONTROL_NODE_SIZE; + //! The inner pubkey (x-only, so no Y coordinate parity). + const XOnlyPubKey p{uint256(std::vector<unsigned char>(control.begin() + 1, control.begin() + TAPROOT_CONTROL_BASE_SIZE))}; + //! The output pubkey (taken from the scriptPubKey). + const XOnlyPubKey q{uint256(program)}; + // Compute the tapleaf hash. + tapleaf_hash = (CHashWriter(HASHER_TAPLEAF) << uint8_t(control[0] & TAPROOT_LEAF_MASK) << script).GetSHA256(); + // Compute the Merkle root from the leaf and the provided path. + uint256 k = tapleaf_hash; + for (int i = 0; i < path_len; ++i) { + CHashWriter ss_branch{HASHER_TAPBRANCH}; + Span<const unsigned char> node(control.data() + TAPROOT_CONTROL_BASE_SIZE + TAPROOT_CONTROL_NODE_SIZE * i, TAPROOT_CONTROL_NODE_SIZE); + if (std::lexicographical_compare(k.begin(), k.end(), node.begin(), node.end())) { + ss_branch << k << node; + } else { + ss_branch << node << k; + } + k = ss_branch.GetSHA256(); + } + // Compute the tweak from the Merkle root and the inner pubkey. + k = (CHashWriter(HASHER_TAPTWEAK) << MakeSpan(p) << k).GetSHA256(); + // Verify that the output pubkey matches the tweaked inner pubkey, after correcting for parity. + return q.CheckPayToContract(p, k, control[0] & 1); +} + +static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror, bool is_p2sh) +{ + CScript exec_script; //!< Actually executed script (last stack item in P2WSH; implied P2PKH script in P2WPKH; leaf script in P2TR) Span<const valtype> stack{witness.stack}; + ScriptExecutionData execdata; if (witversion == 0) { if (program.size() == WITNESS_V0_SCRIPTHASH_SIZE) { - // Version 0 segregated witness program: SHA256(CScript) inside the program, CScript + inputs in witness + // BIP141 P2WSH: 32-byte witness v0 program (which encodes SHA256(script)) if (stack.size() == 0) { return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WITNESS_EMPTY); } const valtype& script_bytes = SpanPopBack(stack); - scriptPubKey = CScript(script_bytes.begin(), script_bytes.end()); - uint256 hashScriptPubKey; - CSHA256().Write(&scriptPubKey[0], scriptPubKey.size()).Finalize(hashScriptPubKey.begin()); - if (memcmp(hashScriptPubKey.begin(), program.data(), 32)) { + exec_script = CScript(script_bytes.begin(), script_bytes.end()); + uint256 hash_exec_script; + CSHA256().Write(&exec_script[0], exec_script.size()).Finalize(hash_exec_script.begin()); + if (memcmp(hash_exec_script.begin(), program.data(), 32)) { return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH); } - return ExecuteWitnessScript(stack, scriptPubKey, flags, SigVersion::WITNESS_V0, checker, serror); + return ExecuteWitnessScript(stack, exec_script, flags, SigVersion::WITNESS_V0, checker, execdata, serror); } else if (program.size() == WITNESS_V0_KEYHASH_SIZE) { - // Special case for pay-to-pubkeyhash; signature + pubkey in witness + // BIP141 P2WPKH: 20-byte witness v0 program (which encodes Hash160(pubkey)) if (stack.size() != 2) { return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH); // 2 items in witness } - scriptPubKey << OP_DUP << OP_HASH160 << program << OP_EQUALVERIFY << OP_CHECKSIG; - return ExecuteWitnessScript(stack, scriptPubKey, flags, SigVersion::WITNESS_V0, checker, serror); + exec_script << OP_DUP << OP_HASH160 << program << OP_EQUALVERIFY << OP_CHECKSIG; + return ExecuteWitnessScript(stack, exec_script, flags, SigVersion::WITNESS_V0, checker, execdata, serror); } else { return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WRONG_LENGTH); } + } else if (witversion == 1 && program.size() == WITNESS_V1_TAPROOT_SIZE && !is_p2sh) { + // BIP341 Taproot: 32-byte non-P2SH witness v1 program (which encodes a P2C-tweaked pubkey) + if (!(flags & SCRIPT_VERIFY_TAPROOT)) return set_success(serror); + if (stack.size() == 0) return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WITNESS_EMPTY); + if (stack.size() >= 2 && !stack.back().empty() && stack.back()[0] == ANNEX_TAG) { + // Drop annex (this is non-standard; see IsWitnessStandard) + const valtype& annex = SpanPopBack(stack); + execdata.m_annex_hash = (CHashWriter(SER_GETHASH, 0) << annex).GetSHA256(); + execdata.m_annex_present = true; + } else { + execdata.m_annex_present = false; + } + execdata.m_annex_init = true; + if (stack.size() == 1) { + // Key path spending (stack size is 1 after removing optional annex) + if (!checker.CheckSchnorrSignature(stack.front(), program, SigVersion::TAPROOT, execdata, serror)) { + return false; // serror is set + } + return set_success(serror); + } else { + // Script path spending (stack size is >1 after removing optional annex) + const valtype& control = SpanPopBack(stack); + const valtype& script_bytes = SpanPopBack(stack); + exec_script = CScript(script_bytes.begin(), script_bytes.end()); + if (control.size() < TAPROOT_CONTROL_BASE_SIZE || control.size() > TAPROOT_CONTROL_MAX_SIZE || ((control.size() - TAPROOT_CONTROL_BASE_SIZE) % TAPROOT_CONTROL_NODE_SIZE) != 0) { + return set_error(serror, SCRIPT_ERR_TAPROOT_WRONG_CONTROL_SIZE); + } + if (!VerifyTaprootCommitment(control, program, exec_script, execdata.m_tapleaf_hash)) { + return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH); + } + execdata.m_tapleaf_hash_init = true; + if ((control[0] & TAPROOT_LEAF_MASK) == TAPROOT_LEAF_TAPSCRIPT) { + // Tapscript (leaf version 0xc0) + execdata.m_validation_weight_left = ::GetSerializeSize(witness.stack, PROTOCOL_VERSION) + VALIDATION_WEIGHT_OFFSET; + execdata.m_validation_weight_left_init = true; + return ExecuteWitnessScript(stack, exec_script, flags, SigVersion::TAPSCRIPT, checker, execdata, serror); + } + if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_TAPROOT_VERSION) { + return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_TAPROOT_VERSION); + } + return set_success(serror); + } } else { if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM) { return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM); } - // Higher version witness scripts return true for future softfork compatibility + // Other version/size/p2sh combinations return true for future softfork compatibility return true; } // There is intentionally no return statement here, to be able to use "control reaches end of non-void function" warnings to detect gaps in the logic above. @@ -1601,7 +1980,7 @@ bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const C // The scriptSig must be _exactly_ CScript(), otherwise we reintroduce malleability. return set_error(serror, SCRIPT_ERR_WITNESS_MALLEATED); } - if (!VerifyWitnessProgram(*witness, witnessversion, witnessprogram, flags, checker, serror)) { + if (!VerifyWitnessProgram(*witness, witnessversion, witnessprogram, flags, checker, serror, /* is_p2sh */ false)) { return false; } // Bypass the cleanstack check at the end. The actual stack is obviously not clean @@ -1646,7 +2025,7 @@ bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const C // reintroduce malleability. return set_error(serror, SCRIPT_ERR_WITNESS_MALLEATED_P2SH); } - if (!VerifyWitnessProgram(*witness, witnessversion, witnessprogram, flags, checker, serror)) { + if (!VerifyWitnessProgram(*witness, witnessversion, witnessprogram, flags, checker, serror, /* is_p2sh */ true)) { return false; } // Bypass the cleanstack check at the end. The actual stack is obviously not clean |