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Add some signature length validation to DL_VerifierBase

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Based on testing during GH #981 we found an undersized buffer caused an out-of-bounds read.
This commit is contained in:
Jeffrey Walton 2020-12-02 16:40:25 -05:00
parent aa4cf301b4
commit 301c169f9a
No known key found for this signature in database
GPG Key ID: B36AB348921B1838
1 changed files with 9 additions and 2 deletions
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11
pubkey.h
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@ -1714,14 +1714,21 @@ public:
void InputSignature(PK_MessageAccumulator &messageAccumulator, const byte *signature, size_t signatureLength) const
{
CRYPTOPP_UNUSED(signature); CRYPTOPP_UNUSED(signatureLength);
PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
const DL_ElgamalLikeSignatureAlgorithm<T> &alg = this->GetSignatureAlgorithm();
const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
// Validation due to https://github.com/weidai11/cryptopp/issues/981
// We allow a caller to provide R and S in oversized buffer. R and S are
// read based on the field element size, and not the buffer size.
const size_t rLen = alg.RLen(params);
const size_t sLen = alg.SLen(params);
CRYPTOPP_ASSERT(signatureLength >= rLen + sLen);
if (signatureLength < rLen + sLen)
throw InvalidDataFormat("DL_VerifierBase: signature length is not valid.");
ma.m_semisignature.Assign(signature, rLen);
ma.m_s.Decode(signature+rLen, alg.SLen(params));
ma.m_s.Decode(signature+rLen, sLen);
this->GetMessageEncodingInterface().ProcessSemisignature(ma.AccessHash(), ma.m_semisignature, ma.m_semisignature.size());
}