Differential D1577 Diff 4335 src/script/sigencoding.cpp

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src/script/sigencoding.cpp

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* highest bit not set), and not excessively padded (do not start with a 0 byte,		* highest bit not set), and not excessively padded (do not start with a 0 byte,
* unless an otherwise negative number follows, in which case a single 0 byte is		* unless an otherwise negative number follows, in which case a single 0 byte is
* necessary and even required).		* 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.		* This function is consensus-critical since BIP66.
*/		*/
static bool IsValidSignatureEncoding(const valtype &sig) {		static bool
		IsValidSignatureEncoding(const boost::sliced_range<const valtype> &sig) {
// Format: 0x30 [total-length] 0x02 [R-length] [R] 0x02 [S-length] [S]		// Format: 0x30 [total-length] 0x02 [R-length] [R] 0x02 [S-length] [S]
// [sighash]
// * total-length: 1-byte length descriptor of everything that follows,		// * total-length: 1-byte length descriptor of everything that follows,
// excluding the sighash byte.		// excluding the sighash byte.
// * R-length: 1-byte length descriptor of the R value that follows.		// * R-length: 1-byte length descriptor of the R value that follows.
// * R: arbitrary-length big-endian encoded R value. It must use the		// * R: arbitrary-length big-endian encoded R value. It must use the
// shortest possible encoding for a positive integers (which means no null		// 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		// bytes at the start, except a single one when the next byte has its
// highest bit set).		// highest bit set).
// * S-length: 1-byte length descriptor of the S value that follows.		// * S-length: 1-byte length descriptor of the S value that follows.
// * S: arbitrary-length big-endian encoded S value. The same rules apply.		// * 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)

// Minimum and maximum size constraints.		// Minimum and maximum size constraints.
if (sig.size() < 9 \|\| sig.size() > 73) {		if (sig.size() < 8 \|\| sig.size() > 72) {
return false;		return false;
}		}

/**		/**
* Check that the signature is a coumpound of proper size.		* Check that the signature is a coumpound of proper size.
*/		*/
// A signature is of type 0x30 (compound).		// A signature is of type 0x30 (compound).
if (sig[0] != 0x30) {		if (sig[0] != 0x30) {
return false;		return false;
}		}

// Make sure the length covers the entire signature.		// Make sure the length covers the entire signature.
// Remove:		// Remove:
// * 1 byte for the coupound type.		// * 1 byte for the coupound type.
// * 1 byte for the length of the signature.		// * 1 byte for the length of the signature.
// * 1 byte for the sighash type.		if (sig[1] != sig.size() - 2) {
if (sig[1] != sig.size() - 3) {
return false;		return false;
}		}

/**		/**
* Check that R is an positive integer of sensible size.		* Check that R is an positive integer of sensible size.
*/		*/
// Check whether the R element is an integer.		// Check whether the R element is an integer.
if (sig[2] != 0x02) {		if (sig[2] != 0x02) {
Show All 15 Lines	IsValidSignatureEncoding(const boost::sliced_range<const valtype> &sig) {

// Make sure the length of the S element is still inside the signature.		// Make sure the length of the S element is still inside the signature.
// Remove:		// Remove:
// * 1 byte for the coumpound type.		// * 1 byte for the coumpound type.
// * 1 byte for the length of the signature.		// * 1 byte for the length of the signature.
// * 2 bytes for the integer type of R and S.		// * 2 bytes for the integer type of R and S.
// * 2 bytes for the size of R and S.		// * 2 bytes for the size of R and S.
// * 1 byte for S itself.		// * 1 byte for S itself.
// * 1 byte for the sighash type.		if (lenR > (sig.size() - 7)) {
if (lenR > (sig.size() - 8)) {
return false;		return false;
}		}

// Null bytes at the start of R are not allowed, unless R would otherwise be		// Null bytes at the start of R are not allowed, unless R would otherwise be
// interpreted as a negative number.		// interpreted as a negative number.
//		//
// /!\ This check can only be performed after we checked that lenR is		// /!\ This check can only be performed after we checked that lenR is
// consistent with the size of the signature or we risk to access our of		// consistent with the size of the signature or we risk to access our of
Show All 30 Lines	IsValidSignatureEncoding(const boost::sliced_range<const valtype> &sig) {
if (sig[startS + 2] & 0x80) {		if (sig[startS + 2] & 0x80) {
return false;		return false;
}		}

// Verify that the length of S is consistent with the size of the signature		// Verify that the length of S is consistent with the size of the signature
// including metadatas:		// including metadatas:
// * 1 byte for the integer type of S.		// * 1 byte for the integer type of S.
// * 1 byte for the size of S.		// * 1 byte for the size of S.
// * 1 byte for the sighash type.		if (size_t(startS + lenS + 2) != sig.size()) {
if (size_t(startS + lenS + 3) != sig.size()) {
return false;		return false;
}		}

// Null bytes at the start of S are not allowed, unless S would otherwise be		// Null bytes at the start of S are not allowed, unless S would otherwise be
// interpreted as a negative number.		// interpreted as a negative number.
//		//
// /!\ This check can only be performed after we checked that lenR and lenS		// /!\ This check can only be performed after we checked that lenR and lenS
// are consistent with the size of the signature or we risk to access		// are consistent with the size of the signature or we risk to access
Show All 18 Lines	bool CheckSignatureEncoding(const valtype &vchSig, uint32_t flags,
ScriptError *serror) {		ScriptError *serror) {
// Empty signature. Not strictly DER encoded, but allowed to provide a		// Empty signature. Not strictly DER encoded, but allowed to provide a
// compact way to provide an invalid signature for use with CHECK(MULTI)SIG		// compact way to provide an invalid signature for use with CHECK(MULTI)SIG
if (vchSig.size() == 0) {		if (vchSig.size() == 0) {
return true;		return true;
}		}
if ((flags & (SCRIPT_VERIFY_DERSIG \| SCRIPT_VERIFY_LOW_S \|		if ((flags & (SCRIPT_VERIFY_DERSIG \| SCRIPT_VERIFY_LOW_S \|
SCRIPT_VERIFY_STRICTENC)) != 0 &&		SCRIPT_VERIFY_STRICTENC)) != 0 &&
!IsValidSignatureEncoding(vchSig)) {		!IsValidSignatureEncoding(
		vchSig \| boost::adaptors::sliced(0, vchSig.size() - 1))) {
return set_error(serror, SCRIPT_ERR_SIG_DER);		return set_error(serror, SCRIPT_ERR_SIG_DER);
}		}
if ((flags & SCRIPT_VERIFY_LOW_S) != 0 &&		if ((flags & SCRIPT_VERIFY_LOW_S) != 0 &&
!IsLowDERSignature(vchSig, serror)) {		!IsLowDERSignature(vchSig, serror)) {
// serror is set		// serror is set
return false;		return false;
}		}
if ((flags & SCRIPT_VERIFY_STRICTENC) != 0) {		if ((flags & SCRIPT_VERIFY_STRICTENC) != 0) {
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