mirror of
https://github.com/shadps4-emu/ext-cryptopp.git
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104 lines
2.9 KiB
C++
104 lines
2.9 KiB
C++
// oaep.cpp - written and placed in the public domain by Wei Dai
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#include "pch.h"
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#include "oaep.h"
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#include <functional>
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NAMESPACE_BEGIN(CryptoPP)
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// ********************************************************
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ANONYMOUS_NAMESPACE_BEGIN
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template <class H, byte *P, unsigned int PLen>
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struct PHashComputation
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{
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PHashComputation() {H().CalculateDigest(pHash, P, PLen);}
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byte pHash[H::DIGESTSIZE];
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};
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template <class H, byte *P, unsigned int PLen>
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const byte *PHash()
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{
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static PHashComputation<H,P,PLen> pHash;
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return pHash.pHash;
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}
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NAMESPACE_END
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template <class H, class MGF, byte *P, unsigned int PLen>
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unsigned int OAEP<H,MGF,P,PLen>::MaxUnpaddedLength(unsigned int paddedLength) const
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{
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return paddedLength/8 > 1+2*H::DIGESTSIZE ? paddedLength/8-1-2*H::DIGESTSIZE : 0;
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}
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template <class H, class MGF, byte *P, unsigned int PLen>
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void OAEP<H,MGF,P,PLen>::Pad(RandomNumberGenerator &rng, const byte *input, unsigned int inputLength, byte *oaepBlock, unsigned int oaepBlockLen) const
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{
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assert (inputLength <= MaxUnpaddedLength(oaepBlockLen));
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// convert from bit length to byte length
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if (oaepBlockLen % 8 != 0)
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{
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oaepBlock[0] = 0;
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oaepBlock++;
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}
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oaepBlockLen /= 8;
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const unsigned int hLen = H::DIGESTSIZE;
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const unsigned int seedLen = hLen, dbLen = oaepBlockLen-seedLen;
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byte *const maskedSeed = oaepBlock;
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byte *const maskedDB = oaepBlock+seedLen;
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// DB = pHash || 00 ... || 01 || M
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memcpy(maskedDB, PHash<H,P,PLen>(), hLen);
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memset(maskedDB+hLen, 0, dbLen-hLen-inputLength-1);
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maskedDB[dbLen-inputLength-1] = 0x01;
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memcpy(maskedDB+dbLen-inputLength, input, inputLength);
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rng.GenerateBlock(maskedSeed, seedLen);
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MGF::GenerateAndMask(maskedDB, dbLen, maskedSeed, seedLen);
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MGF::GenerateAndMask(maskedSeed, seedLen, maskedDB, dbLen);
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}
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template <class H, class MGF, byte *P, unsigned int PLen>
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DecodingResult OAEP<H,MGF,P,PLen>::Unpad(const byte *oaepBlock, unsigned int oaepBlockLen, byte *output) const
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{
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bool invalid = false;
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// convert from bit length to byte length
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if (oaepBlockLen % 8 != 0)
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{
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invalid = (oaepBlock[0] != 0) || invalid;
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oaepBlock++;
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}
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oaepBlockLen /= 8;
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const unsigned int hLen = H::DIGESTSIZE;
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const unsigned int seedLen = hLen, dbLen = oaepBlockLen-seedLen;
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invalid = (oaepBlockLen < 2*hLen+1) || invalid;
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SecByteBlock t(oaepBlock, oaepBlockLen);
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byte *const maskedSeed = t;
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byte *const maskedDB = t+seedLen;
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MGF::GenerateAndMask(maskedSeed, seedLen, maskedDB, dbLen);
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MGF::GenerateAndMask(maskedDB, dbLen, maskedSeed, seedLen);
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// DB = pHash' || 00 ... || 01 || M
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byte *M = std::find(maskedDB+hLen, maskedDB+dbLen, 0x01);
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invalid = (M == maskedDB+dbLen) || invalid;
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invalid = (std::find_if(maskedDB+hLen, M, std::bind2nd(std::not_equal_to<byte>(), 0)) != M) || invalid;
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invalid = (memcmp(maskedDB, PHash<H,P,PLen>(), hLen) != 0) || invalid;
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if (invalid)
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return DecodingResult();
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M++;
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memcpy(output, M, maskedDB+dbLen-M);
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return DecodingResult(maskedDB+dbLen-M);
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}
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NAMESPACE_END
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