1 files changed, 97 insertions, 0 deletions
diff --git a/src-cryptopp/oaep.cpp b/src-cryptopp/oaep.cpp
new file mode 100644
index 0000000..1d474be
--- /dev/null
+++ b/src-cryptopp/oaep.cpp
@@ -0,0 +1,97 @@
+// oaep.cpp - written and placed in the public domain by Wei Dai
+
+#include "pch.h"
+
+#ifndef CRYPTOPP_IMPORTS
+
+#include "oaep.h"
+#include <functional>
+
+NAMESPACE_BEGIN(CryptoPP)
+
+// ********************************************************
+
+size_t OAEP_Base::MaxUnpaddedLength(size_t paddedLength) const
+{
+	return SaturatingSubtract(paddedLength/8, 1+2*DigestSize());
+}
+
+void OAEP_Base::Pad(RandomNumberGenerator &rng, const byte *input, size_t inputLength, byte *oaepBlock, size_t oaepBlockLen, const NameValuePairs &parameters) const
+{
+	assert (inputLength <= MaxUnpaddedLength(oaepBlockLen));
+
+	// convert from bit length to byte length
+	if (oaepBlockLen % 8 != 0)
+	{
+		oaepBlock[0] = 0;
+		oaepBlock++;
+	}
+	oaepBlockLen /= 8;
+
+	std::auto_ptr<HashTransformation> pHash(NewHash());
+	const size_t hLen = pHash->DigestSize();
+	const size_t seedLen = hLen, dbLen = oaepBlockLen-seedLen;
+	byte *const maskedSeed = oaepBlock;
+	byte *const maskedDB = oaepBlock+seedLen;
+
+	ConstByteArrayParameter encodingParameters;
+	parameters.GetValue(Name::EncodingParameters(), encodingParameters);
+
+	// DB = pHash || 00 ... || 01 || M
+	pHash->CalculateDigest(maskedDB, encodingParameters.begin(), encodingParameters.size());
+	memset(maskedDB+hLen, 0, dbLen-hLen-inputLength-1);
+	maskedDB[dbLen-inputLength-1] = 0x01;
+	memcpy(maskedDB+dbLen-inputLength, input, inputLength);
+
+	rng.GenerateBlock(maskedSeed, seedLen);
+	std::auto_ptr<MaskGeneratingFunction> pMGF(NewMGF());
+	pMGF->GenerateAndMask(*pHash, maskedDB, dbLen, maskedSeed, seedLen);
+	pMGF->GenerateAndMask(*pHash, maskedSeed, seedLen, maskedDB, dbLen);
+}
+
+DecodingResult OAEP_Base::Unpad(const byte *oaepBlock, size_t oaepBlockLen, byte *output, const NameValuePairs &parameters) const
+{
+	bool invalid = false;
+
+	// convert from bit length to byte length
+	if (oaepBlockLen % 8 != 0)
+	{
+		invalid = (oaepBlock[0] != 0) || invalid;
+		oaepBlock++;
+	}
+	oaepBlockLen /= 8;
+
+	std::auto_ptr<HashTransformation> pHash(NewHash());
+	const size_t hLen = pHash->DigestSize();
+	const size_t seedLen = hLen, dbLen = oaepBlockLen-seedLen;
+
+	invalid = (oaepBlockLen < 2*hLen+1) || invalid;
+
+	SecByteBlock t(oaepBlock, oaepBlockLen);
+	byte *const maskedSeed = t;
+	byte *const maskedDB = t+seedLen;
+
+	std::auto_ptr<MaskGeneratingFunction> pMGF(NewMGF());
+	pMGF->GenerateAndMask(*pHash, maskedSeed, seedLen, maskedDB, dbLen);
+	pMGF->GenerateAndMask(*pHash, maskedDB, dbLen, maskedSeed, seedLen);
+
+	ConstByteArrayParameter encodingParameters;
+	parameters.GetValue(Name::EncodingParameters(), encodingParameters);
+
+	// DB = pHash' || 00 ... || 01 || M
+	byte *M = std::find(maskedDB+hLen, maskedDB+dbLen, 0x01);
+	invalid = (M == maskedDB+dbLen) || invalid;
+	invalid = (std::find_if(maskedDB+hLen, M, std::bind2nd(std::not_equal_to<byte>(), 0)) != M) || invalid;
+	invalid = !pHash->VerifyDigest(maskedDB, encodingParameters.begin(), encodingParameters.size()) || invalid;
+
+	if (invalid)
+		return DecodingResult();
+
+	M++;
+	memcpy(output, M, maskedDB+dbLen-M);
+	return DecodingResult(maskedDB+dbLen-M);
+}
+
+NAMESPACE_END
+
+#endif