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BIP141: Witness program

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This commit is contained in:
Pieter Wuille
2015-11-08 01:16:45 +01:00
parent 7030d9eb47
commit 449f9b8deb
16 changed files with 201 additions and 37 deletions
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2
src/script/bitcoinconsensus.cpp
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@@ -85,7 +85,7 @@ int bitcoinconsensus_verify_script(const unsigned char *scriptPubKey, unsigned i
// Regardless of the verification result, the tx did not error.
set_error(err, bitcoinconsensus_ERR_OK);
return VerifyScript(tx.vin[nIn].scriptSig, CScript(scriptPubKey, scriptPubKey + scriptPubKeyLen), flags, TransactionSignatureChecker(&tx, nIn), NULL);
return VerifyScript(tx.vin[nIn].scriptSig, CScript(scriptPubKey, scriptPubKey + scriptPubKeyLen), nIn < tx.wit.vtxinwit.size() ? &tx.wit.vtxinwit[nIn].scriptWitness : NULL, flags, TransactionSignatureChecker(&tx, nIn), NULL);
} catch (const std::exception&) {
return set_error(err, bitcoinconsensus_ERR_TX_DESERIALIZE); // Error deserializing
}

111
src/script/interpreter.cpp
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@@ -1239,8 +1239,67 @@ bool TransactionSignatureChecker::CheckSequence(const CScriptNum& nSequence) con
return true;
}
bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
{
vector<vector<unsigned char> > stack;
CScript scriptPubKey;
if (witversion == 0) {
if (program.size() == 32) {
// Version 0 segregated witness program: SHA256(CScript) inside the program, CScript + inputs in witness
if (witness.stack.size() == 0) {
return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WITNESS_EMPTY);
}
scriptPubKey = CScript(witness.stack.back().begin(), witness.stack.back().end());
stack = std::vector<std::vector<unsigned char> >(witness.stack.begin(), witness.stack.end() - 1);
uint256 hashScriptPubKey;
CSHA256().Write(&scriptPubKey[0], scriptPubKey.size()).Finalize(hashScriptPubKey.begin());
if (memcmp(hashScriptPubKey.begin(), &program[0], 32)) {
return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH);
}
} else if (program.size() == 20) {
// Special case for pay-to-pubkeyhash; signature + pubkey in witness
if (witness.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;
stack = witness.stack;
} else {
return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WRONG_LENGTH);
}
} else if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM) {
return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM);
} else {
// Higher version witness scripts return true for future softfork compatibility
return set_success(serror);
}
// Disallow stack item size > MAX_SCRIPT_ELEMENT_SIZE in witness stack
for (unsigned int i = 0; i < stack.size(); i++) {
if (stack.at(i).size() > MAX_SCRIPT_ELEMENT_SIZE)
return set_error(serror, SCRIPT_ERR_PUSH_SIZE);
}
if (!EvalScript(stack, scriptPubKey, flags, checker, serror)) {
return false;
}
// Scripts inside witness implicitly require cleanstack behaviour
if (stack.size() != 1)
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
if (!CastToBool(stack.back()))
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
return true;
}
bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
{
static const CScriptWitness emptyWitness;
if (witness == NULL) {
witness = &emptyWitness;
}
bool hadWitness = false;
set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);
if ((flags & SCRIPT_VERIFY_SIGPUSHONLY) != 0 && !scriptSig.IsPushOnly()) {
@@ -1261,6 +1320,25 @@ bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigne
if (CastToBool(stack.back()) == false)
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
// Bare witness programs
int witnessversion;
std::vector<unsigned char> witnessprogram;
if (flags & SCRIPT_VERIFY_WITNESS) {
if (scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {
hadWitness = true;
if (scriptSig.size() != 0) {
// 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)) {
return false;
}
// Bypass the cleanstack check at the end. The actual stack is obviously not clean
// for witness programs.
stack.resize(1);
}
}
// Additional validation for spend-to-script-hash transactions:
if ((flags & SCRIPT_VERIFY_P2SH) && scriptPubKey.IsPayToScriptHash())
{
@@ -1287,19 +1365,48 @@ bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigne
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
if (!CastToBool(stack.back()))
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
// P2SH witness program
if (flags & SCRIPT_VERIFY_WITNESS) {
if (pubKey2.IsWitnessProgram(witnessversion, witnessprogram)) {
hadWitness = true;
if (scriptSig != CScript() << std::vector<unsigned char>(pubKey2.begin(), pubKey2.end())) {
// The scriptSig must be _exactly_ a single push of the redeemScript. Otherwise we
// reintroduce malleability.
return set_error(serror, SCRIPT_ERR_WITNESS_MALLEATED_P2SH);
}
if (!VerifyWitnessProgram(*witness, witnessversion, witnessprogram, flags, checker, serror)) {
return false;
}
// Bypass the cleanstack check at the end. The actual stack is obviously not clean
// for witness programs.
stack.resize(1);
}
}
}
// The CLEANSTACK check is only performed after potential P2SH evaluation,
// as the non-P2SH evaluation of a P2SH script will obviously not result in
// a clean stack (the P2SH inputs remain).
// a clean stack (the P2SH inputs remain). The same holds for witness evaluation.
if ((flags & SCRIPT_VERIFY_CLEANSTACK) != 0) {
// Disallow CLEANSTACK without P2SH, as otherwise a switch CLEANSTACK->P2SH+CLEANSTACK
// would be possible, which is not a softfork (and P2SH should be one).
assert((flags & SCRIPT_VERIFY_P2SH) != 0);
assert((flags & SCRIPT_VERIFY_WITNESS) != 0);
if (stack.size() != 1) {
return set_error(serror, SCRIPT_ERR_CLEANSTACK);
}
}
if (flags & SCRIPT_VERIFY_WITNESS) {
// We can't check for correct unexpected witness data if P2SH was off, so require
// that WITNESS implies P2SH. Otherwise, going from WITNESS->P2SH+WITNESS would be
// possible, which is not a softfork.
assert((flags & SCRIPT_VERIFY_P2SH) != 0);
if (!hadWitness && !witness->IsNull()) {
return set_error(serror, SCRIPT_ERR_WITNESS_UNEXPECTED);
}
}
return set_success(serror);
}

12
src/script/interpreter.h
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@@ -74,7 +74,7 @@ enum
// "At least one stack element must remain, and when interpreted as a boolean, it must be true" to
// "Exactly one stack element must remain, and when interpreted as a boolean, it must be true".
// (softfork safe, BIP62 rule 6)
// Note: CLEANSTACK should never be used without P2SH.
// Note: CLEANSTACK should never be used without P2SH or WITNESS.
SCRIPT_VERIFY_CLEANSTACK = (1U << 8),
// Verify CHECKLOCKTIMEVERIFY
@@ -86,6 +86,14 @@ enum
//
// See BIP112 for details
SCRIPT_VERIFY_CHECKSEQUENCEVERIFY = (1U << 10),
// Support segregated witness
//
SCRIPT_VERIFY_WITNESS = (1U << 11),
// Making v1-v16 witness program non-standard
//
SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM = (1U << 12),
};
bool CheckSignatureEncoding(const std::vector<unsigned char> &vchSig, unsigned int flags, ScriptError* serror);
@@ -139,6 +147,6 @@ public:
};
bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* error = NULL);
bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* error = NULL);
bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror = NULL);
#endif // BITCOIN_SCRIPT_INTERPRETER_H

18
src/script/script.cpp
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@@ -210,6 +210,24 @@ bool CScript::IsPayToScriptHash() const
(*this)[22] == OP_EQUAL);
}
// A witness program is any valid CScript that consists of a 1-byte push opcode
// followed by a data push between 2 and 40 bytes.
bool CScript::IsWitnessProgram(int& version, std::vector<unsigned char>& program) const
{
if (this->size() < 4 || this->size() > 42) {
return false;
}
if ((*this)[0] != OP_0 && ((*this)[0] < OP_1 || (*this)[0] > OP_16)) {
return false;
}
if ((size_t)((*this)[1] + 2) == this->size()) {
version = DecodeOP_N((opcodetype)(*this)[0]);
program = std::vector<unsigned char>(this->begin() + 2, this->end());
return true;
}
return false;
}
bool CScript::IsPushOnly(const_iterator pc) const
{
while (pc < end())

1
src/script/script.h
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@@ -621,6 +621,7 @@ public:
unsigned int GetSigOpCount(const CScript& scriptSig) const;
bool IsPayToScriptHash() const;
bool IsWitnessProgram(int& version, std::vector<unsigned char>& program) const;
/** Called by IsStandardTx and P2SH/BIP62 VerifyScript (which makes it consensus-critical). */
bool IsPushOnly(const_iterator pc) const;

14
src/script/script_error.cpp
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@@ -65,8 +65,22 @@ const char* ScriptErrorString(const ScriptError serror)
return "Dummy CHECKMULTISIG argument must be zero";
case SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS:
return "NOPx reserved for soft-fork upgrades";
case SCRIPT_ERR_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM:
return "Witness version reserved for soft-fork upgrades";
case SCRIPT_ERR_PUBKEYTYPE:
return "Public key is neither compressed or uncompressed";
case SCRIPT_ERR_WITNESS_PROGRAM_WRONG_LENGTH:
return "Witness program has incorrect length";
case SCRIPT_ERR_WITNESS_PROGRAM_WITNESS_EMPTY:
return "Witness program was passed an empty witness";
case SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH:
return "Witness program hash mismatch";
case SCRIPT_ERR_WITNESS_MALLEATED:
return "Witness requires empty scriptSig";
case SCRIPT_ERR_WITNESS_MALLEATED_P2SH:
return "Witness requires only-redeemscript scriptSig";
case SCRIPT_ERR_WITNESS_UNEXPECTED:
return "Witness provided for non-witness script";
case SCRIPT_ERR_UNKNOWN_ERROR:
case SCRIPT_ERR_ERROR_COUNT:
default: break;

9
src/script/script_error.h
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@@ -51,6 +51,15 @@ typedef enum ScriptError_t
/* softfork safeness */
SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS,
SCRIPT_ERR_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM,
/* segregated witness */
SCRIPT_ERR_WITNESS_PROGRAM_WRONG_LENGTH,
SCRIPT_ERR_WITNESS_PROGRAM_WITNESS_EMPTY,
SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH,
SCRIPT_ERR_WITNESS_MALLEATED,
SCRIPT_ERR_WITNESS_MALLEATED_P2SH,
SCRIPT_ERR_WITNESS_UNEXPECTED,
SCRIPT_ERR_ERROR_COUNT
} ScriptError;

2
src/script/sign.cpp
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@@ -123,7 +123,7 @@ bool ProduceSignature(const BaseSignatureCreator& creator, const CScript& fromPu
}
// Test solution
return VerifyScript(scriptSig, fromPubKey, STANDARD_SCRIPT_VERIFY_FLAGS, creator.Checker());
return VerifyScript(scriptSig, fromPubKey, NULL, STANDARD_SCRIPT_VERIFY_FLAGS, creator.Checker());
}
bool SignSignature(const CKeyStore &keystore, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, int nHashType)