Result
BitStringWithNoUnusedBits(Reader& input, /*out*/ Input& value)
{
Reader valueWithUnusedBits;
Result rv = ExpectTagAndGetValue(input, BIT_STRING, valueWithUnusedBits);
if (rv != Success) {
return rv;
}
uint8_t unusedBitsAtEnd;
if (valueWithUnusedBits.Read(unusedBitsAtEnd) != Success) {
return Result::ERROR_BAD_DER;
}
// XXX: Really the constraint should be that unusedBitsAtEnd must be less
// than 7. But, we suspect there are no real-world values in OCSP responses
// or certificates with non-zero unused bits. It seems like NSS assumes this
// in various places, so we enforce it too in order to simplify this code. If
// we find compatibility issues, we'll know we're wrong and we'll have to
// figure out how to shift the bits around.
if (unusedBitsAtEnd != 0) {
return Result::ERROR_BAD_DER;
}
Reader::Mark mark(valueWithUnusedBits.GetMark());
valueWithUnusedBits.SkipToEnd();
return valueWithUnusedBits.GetInput(mark, value);
}
Result
SignedData(Reader& input, /*out*/ Reader& tbs,
/*out*/ SignedDataWithSignature& signedData)
{
Reader::Mark mark(input.GetMark());
Result rv;
rv = ExpectTagAndGetValue(input, SEQUENCE, tbs);
if (rv != Success) {
return rv;
}
rv = input.GetInput(mark, signedData.data);
if (rv != Success) {
return rv;
}
rv = SignatureAlgorithmIdentifier(input, signedData.algorithm);
if (rv != Success) {
return rv;
}
rv = BitStringWithNoUnusedBits(input, signedData.signature);
if (rv == Result::ERROR_BAD_DER) {
rv = Result::ERROR_BAD_SIGNATURE;
}
return rv;
}
