ext-cryptopp/emsa2.cpp
Jeffrey Walton 399a1546de Add CRYPTOPP_ASSERT (Issue 277, CVE-2016-7420)
trap.h and CRYPTOPP_ASSERT has existed for over a year in Master. We deferred on the cut-over waiting for a minor version bump (5.7). We have to use it now due to CVE-2016-7420
2016-09-16 11:27:15 -04:00

36 lines
1.3 KiB
C++

// emsa2.cpp - written and placed in the public domain by Wei Dai
#include "pch.h"
#include "emsa2.h"
#ifndef CRYPTOPP_IMPORTS
NAMESPACE_BEGIN(CryptoPP)
void EMSA2Pad::ComputeMessageRepresentative(RandomNumberGenerator& /*rng*/,
const byte* recoverableMessage, size_t recoverableMessageLength,
HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
byte *representative, size_t representativeBitLength) const
{
CRYPTOPP_UNUSED(recoverableMessage), CRYPTOPP_UNUSED(recoverableMessageLength), CRYPTOPP_UNUSED(representativeBitLength);
CRYPTOPP_ASSERT(representativeBitLength >= MinRepresentativeBitLength(hashIdentifier.second, hash.DigestSize()));
if (representativeBitLength % 8 != 7)
throw PK_SignatureScheme::InvalidKeyLength("EMSA2: EMSA2 requires a key length that is a multiple of 8");
size_t digestSize = hash.DigestSize();
size_t representativeByteLength = BitsToBytes(representativeBitLength);
representative[0] = messageEmpty ? 0x4b : 0x6b;
memset(representative+1, 0xbb, representativeByteLength-digestSize-4); // pad with 0xbb
byte *afterP2 = representative+representativeByteLength-digestSize-3;
afterP2[0] = 0xba;
hash.Final(afterP2+1);
representative[representativeByteLength-2] = *hashIdentifier.first;
representative[representativeByteLength-1] = 0xcc;
}
NAMESPACE_END
#endif