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Merge #18388: Make VerifyWitnessProgram use a Span stack

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2b0fcff7f2 Make VerifyWitnessProgram use a Span stack (Pieter Wuille)

Pull request description:

  Here is a follow-up to #18002, again with the goal of simplifying (potential) BIP341 code.

  Instead of passing a begin and end iterator of the initial stack to `ExecuteWitnessScript`, they are turned into a `Span<const valtype>`, representing a span of `valtype`s in memory. This allows `VerifyWitnessProgram` to operate on that span directly, instead of juggling iterators around (which would be exacerbated by #17977 if trying to avoid copying the stack).

ACKs for top commit:
  ajtowns:
    ACK 2b0fcff7f2
  elichai:
    ReACK on the diff 2b0fcff7f2
  instagibbs:
    re-ACK 2b0fcff7f2
  theStack:
    re-ACK 2b0fcff7f2
  Empact:
    ACK 2b0fcff7f2
  jnewbery:
    utACK 2b0fcff7f2

Tree-SHA512: 38eb4ce17f1947674c1c274caa40feb6ea8266bd96134d9cf1bc41e6fbf1114d4dde6c7a9e26e1ca8f3d0155429ef0911cc8ec0c1037d8fe7d6ec7f9e7184e93
This commit is contained in:
fanquake
2020-03-27 13:07:35 +08:00
parent e3154aacf4 2b0fcff7f2
commit 54646167db
2 changed files with 23 additions and 7 deletions
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16
src/script/interpreter.cpp
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@@ -1478,9 +1478,9 @@ bool GenericTransactionSignatureChecker<T>::CheckSequence(const CScriptNum& nSeq
template class GenericTransactionSignatureChecker<CTransaction>;
template class GenericTransactionSignatureChecker<CMutableTransaction>;
static bool ExecuteWitnessScript(std::vector<valtype>::const_iterator begin, std::vector<valtype>::const_iterator end, 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, ScriptError* serror)
{
std::vector<valtype> stack{begin, end};
std::vector<valtype> stack{stack_span.begin(), stack_span.end()};
// Disallow stack item size > MAX_SCRIPT_ELEMENT_SIZE in witness stack
for (const valtype& elem : stack) {
@@ -1499,27 +1499,29 @@ static bool ExecuteWitnessScript(std::vector<valtype>::const_iterator begin, std
static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
{
CScript scriptPubKey;
Span<const valtype> stack = MakeSpan(witness.stack);
if (witversion == 0) {
if (program.size() == WITNESS_V0_SCRIPTHASH_SIZE) {
// Version 0 segregated witness program: SHA256(CScript) inside the program, CScript + inputs in witness
if (witness.stack.size() == 0) {
if (stack.size() == 0) {
return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WITNESS_EMPTY);
}
scriptPubKey = CScript(witness.stack.back().begin(), witness.stack.back().end());
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)) {
return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH);
}
return ExecuteWitnessScript(witness.stack.begin(), witness.stack.end() - 1, scriptPubKey, flags, SigVersion::WITNESS_V0, checker, serror);
return ExecuteWitnessScript(stack, scriptPubKey, flags, SigVersion::WITNESS_V0, checker, serror);
} else if (program.size() == WITNESS_V0_KEYHASH_SIZE) {
// Special case for pay-to-pubkeyhash; signature + pubkey in witness
if (witness.stack.size() != 2) {
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(witness.stack.begin(), witness.stack.end(), scriptPubKey, flags, SigVersion::WITNESS_V0, checker, serror);
return ExecuteWitnessScript(stack, scriptPubKey, flags, SigVersion::WITNESS_V0, checker, serror);
} else {
return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WRONG_LENGTH);
}