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Change IsDERSignature to BIP66 implementation

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This commit is contained in:
Pieter Wuille 2015-01-13 03:15:39 +01:00
parent 6af674ecdc
commit 80ad135a5e
1 changed files with 63 additions and 63 deletions
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126
src/script/interpreter.cpp
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@ -93,76 +93,76 @@ bool static IsCompressedOrUncompressedPubKey(const valtype &vchPubKey) {
* in which case a single 0 byte is necessary and even required). * in which case a single 0 byte is necessary and even required).
* *
* See https://bitcointalk.org/index.php?topic=8392.msg127623#msg127623 * See https://bitcointalk.org/index.php?topic=8392.msg127623#msg127623
*
* This function is consensus-critical since BIP66.
*/ */
bool static IsDERSignature(const valtype &vchSig) { bool static IsValidSignatureEncoding(const std::vector<unsigned char> &sig) {
// Format: 0x30 [total-length] 0x02 [R-length] [R] 0x02 [S-length] [S] [sighash]
// * total-length: 1-byte length descriptor of everything that follows,
// excluding the sighash byte.
// * R-length: 1-byte length descriptor of the R value that follows.
// * R: arbitrary-length big-endian encoded R value. It must use the shortest
// possible encoding for a positive integers (which means no null bytes at
// the start, except a single one when the next byte has its highest bit set).
// * S-length: 1-byte length descriptor of the S value that follows.
// * S: arbitrary-length big-endian encoded S value. The same rules apply.
// * sighash: 1-byte value indicating what data is hashed (not part of the DER
// signature)
if (vchSig.size() < 9) { // Minimum and maximum size constraints.
// Non-canonical signature: too short if (sig.size() < 9) return false;
return false; if (sig.size() > 73) return false;
}
if (vchSig.size() > 73) {
// Non-canonical signature: too long
return false;
}
if (vchSig[0] != 0x30) {
// Non-canonical signature: wrong type
return false;
}
if (vchSig[1] != vchSig.size()-3) {
// Non-canonical signature: wrong length marker
return false;
}
unsigned int nLenR = vchSig[3];
if (5 + nLenR >= vchSig.size()) {
// Non-canonical signature: S length misplaced
return false;
}
unsigned int nLenS = vchSig[5+nLenR];
if ((unsigned long)(nLenR+nLenS+7) != vchSig.size()) {
// Non-canonical signature: R+S length mismatch
return false;
}
const unsigned char *R = &vchSig[4]; // A signature is of type 0x30 (compound).
if (R[-2] != 0x02) { if (sig[0] != 0x30) return false;
// Non-canonical signature: R value type mismatch
return false; // Make sure the length covers the entire signature.
} if (sig[1] != sig.size() - 3) return false;
if (nLenR == 0) {
// Non-canonical signature: R length is zero // Extract the length of the R element.
return false; unsigned int lenR = sig[3];
}
if (R[0] & 0x80) { // Make sure the length of the S element is still inside the signature.
// Non-canonical signature: R value negative if (5 + lenR >= sig.size()) return false;
return false;
} // Extract the length of the S element.
if (nLenR > 1 && (R[0] == 0x00) && !(R[1] & 0x80)) { unsigned int lenS = sig[5 + lenR];
// Non-canonical signature: R value excessively padded
return false; // Verify that the length of the signature matches the sum of the length
} // of the elements.
if ((size_t)(lenR + lenS + 7) != sig.size()) return false;
// Check whether the R element is an integer.
if (sig[2] != 0x02) return false;
// Zero-length integers are not allowed for R.
if (lenR == 0) return false;
// Negative numbers are not allowed for R.
if (sig[4] & 0x80) return false;
// Null bytes at the start of R are not allowed, unless R would
// otherwise be interpreted as a negative number.
if (lenR > 1 && (sig[4] == 0x00) && !(sig[5] & 0x80)) return false;
// Check whether the S element is an integer.
if (sig[lenR + 4] != 0x02) return false;
// Zero-length integers are not allowed for S.
if (lenS == 0) return false;
// Negative numbers are not allowed for S.
if (sig[lenR + 6] & 0x80) return false;
// Null bytes at the start of S are not allowed, unless S would otherwise be
// interpreted as a negative number.
if (lenS > 1 && (sig[lenR + 6] == 0x00) && !(sig[lenR + 7] & 0x80)) return false;
const unsigned char *S = &vchSig[6+nLenR];
if (S[-2] != 0x02) {
// Non-canonical signature: S value type mismatch
return false;
}
if (nLenS == 0) {
// Non-canonical signature: S length is zero
return false;
}
if (S[0] & 0x80) {
// Non-canonical signature: S value negative
return false;
}
if (nLenS > 1 && (S[0] == 0x00) && !(S[1] & 0x80)) {
// Non-canonical signature: S value excessively padded
return false;
}
return true; return true;
} }
bool static IsLowDERSignature(const valtype &vchSig, ScriptError* serror) { bool static IsLowDERSignature(const valtype &vchSig, ScriptError* serror) {
if (!IsDERSignature(vchSig)) { if (!IsValidSignatureEncoding(vchSig)) {
return set_error(serror, SCRIPT_ERR_SIG_DER); return set_error(serror, SCRIPT_ERR_SIG_DER);
} }
unsigned int nLenR = vchSig[3]; unsigned int nLenR = vchSig[3];
@ -194,7 +194,7 @@ bool static CheckSignatureEncoding(const valtype &vchSig, unsigned int flags, Sc
if (vchSig.size() == 0) { if (vchSig.size() == 0) {
return true; return true;
} }
if ((flags & (SCRIPT_VERIFY_DERSIG | SCRIPT_VERIFY_LOW_S | SCRIPT_VERIFY_STRICTENC)) != 0 && !IsDERSignature(vchSig)) { if ((flags & (SCRIPT_VERIFY_DERSIG | SCRIPT_VERIFY_LOW_S | SCRIPT_VERIFY_STRICTENC)) != 0 && !IsValidSignatureEncoding(vchSig)) {
return set_error(serror, SCRIPT_ERR_SIG_DER); return set_error(serror, SCRIPT_ERR_SIG_DER);
} else if ((flags & SCRIPT_VERIFY_LOW_S) != 0 && !IsLowDERSignature(vchSig, serror)) { } else if ((flags & SCRIPT_VERIFY_LOW_S) != 0 && !IsLowDERSignature(vchSig, serror)) {
// serror is set // serror is set