File: strciphr.cpp

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// strciphr.cpp - originally written and placed in the public domain by Wei Dai

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "strciphr.h"

// Squash MS LNK4221 and libtool warnings
#ifndef CRYPTOPP_MANUALLY_INSTANTIATE_TEMPLATES
extern const char STRCIPHER_FNAME[] = __FILE__;
#endif

NAMESPACE_BEGIN(CryptoPP)

template <class S>
void AdditiveCipherTemplate<S>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
{
	PolicyInterface &policy = this->AccessPolicy();
	policy.CipherSetKey(params, key, length);
	m_leftOver = 0;
	unsigned int bufferByteSize = policy.CanOperateKeystream() ? GetBufferByteSize(policy) : RoundUpToMultipleOf(1024U, GetBufferByteSize(policy));
	m_buffer.New(bufferByteSize);

	if (this->IsResynchronizable())
	{
		size_t ivLength;
		const byte *iv = this->GetIVAndThrowIfInvalid(params, ivLength);
		policy.CipherResynchronize(m_buffer, iv, ivLength);
	}
}

template <class S>
void AdditiveCipherTemplate<S>::GenerateBlock(byte *outString, size_t length)
{
	if (m_leftOver > 0)
	{
		const size_t len = STDMIN(m_leftOver, length);
		memcpy(outString, PtrSub(KeystreamBufferEnd(), m_leftOver), len);

		length -= len; m_leftOver -= len;
		outString = PtrAdd(outString, len);
		if (!length) {return;}
	}

	PolicyInterface &policy = this->AccessPolicy();
	unsigned int bytesPerIteration = policy.GetBytesPerIteration();

	if (length >= bytesPerIteration)
	{
		const size_t iterations = length / bytesPerIteration;
		policy.WriteKeystream(outString, iterations);
		length -= iterations * bytesPerIteration;
		outString = PtrAdd(outString, iterations * bytesPerIteration);
	}

	if (length > 0)
	{
		size_t bufferByteSize = RoundUpToMultipleOf(length, bytesPerIteration);
		size_t bufferIterations = bufferByteSize / bytesPerIteration;

		policy.WriteKeystream(PtrSub(KeystreamBufferEnd(), bufferByteSize), bufferIterations);
		memcpy(outString, PtrSub(KeystreamBufferEnd(), bufferByteSize), length);
		m_leftOver = bufferByteSize - length;
	}
}

template <class S>
void AdditiveCipherTemplate<S>::ProcessData(byte *outString, const byte *inString, size_t length)
{
	if (m_leftOver > 0)
	{
		const size_t len = STDMIN(m_leftOver, length);
		xorbuf(outString, inString, KeystreamBufferEnd()-m_leftOver, len);

		length -= len; m_leftOver -= len;
		inString = PtrAdd(inString, len);
		outString = PtrAdd(outString, len);
	}

	PolicyInterface &policy = this->AccessPolicy();
	unsigned int bytesPerIteration = policy.GetBytesPerIteration();

	if (policy.CanOperateKeystream() && length >= bytesPerIteration)
	{
		const size_t iterations = length / bytesPerIteration;
		unsigned int alignment = policy.GetAlignment();
		KeystreamOperation operation = KeystreamOperation((IsAlignedOn(inString, alignment) * 2) | (int)IsAlignedOn(outString, alignment));
		policy.OperateKeystream(operation, outString, inString, iterations);

		inString = PtrAdd(inString, iterations * bytesPerIteration);
		outString = PtrAdd(outString, iterations * bytesPerIteration);
		length -= iterations * bytesPerIteration;
	}

	size_t bufferByteSize = m_buffer.size();
	size_t bufferIterations = bufferByteSize / bytesPerIteration;

	while (length >= bufferByteSize)
	{
		policy.WriteKeystream(m_buffer, bufferIterations);
		xorbuf(outString, inString, KeystreamBufferBegin(), bufferByteSize);

		length -= bufferByteSize;
		inString = PtrAdd(inString, bufferByteSize);
		outString = PtrAdd(outString, bufferByteSize);
	}

	if (length > 0)
	{
		bufferByteSize = RoundUpToMultipleOf(length, bytesPerIteration);
		bufferIterations = bufferByteSize / bytesPerIteration;

		policy.WriteKeystream(PtrSub(KeystreamBufferEnd(), bufferByteSize), bufferIterations);
		xorbuf(outString, inString, PtrSub(KeystreamBufferEnd(), bufferByteSize), length);
		m_leftOver = bufferByteSize - length;
	}
}

template <class S>
void AdditiveCipherTemplate<S>::Resynchronize(const byte *iv, int length)
{
	PolicyInterface &policy = this->AccessPolicy();
	m_leftOver = 0;
	m_buffer.New(GetBufferByteSize(policy));
	policy.CipherResynchronize(m_buffer, iv, this->ThrowIfInvalidIVLength(length));
}

template <class BASE>
void AdditiveCipherTemplate<BASE>::Seek(lword position)
{
	PolicyInterface &policy = this->AccessPolicy();
	word32 bytesPerIteration = policy.GetBytesPerIteration();

	policy.SeekToIteration(position / bytesPerIteration);
	position %= bytesPerIteration;

	if (position > 0)
	{
		policy.WriteKeystream(PtrSub(KeystreamBufferEnd(), bytesPerIteration), 1);
		m_leftOver = bytesPerIteration - static_cast<word32>(position);
	}
	else
		m_leftOver = 0;
}

template <class BASE>
void CFB_CipherTemplate<BASE>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
{
	PolicyInterface &policy = this->AccessPolicy();
	policy.CipherSetKey(params, key, length);

	if (this->IsResynchronizable())
	{
		size_t ivLength;
		const byte *iv = this->GetIVAndThrowIfInvalid(params, ivLength);
		policy.CipherResynchronize(iv, ivLength);
	}

	m_leftOver = policy.GetBytesPerIteration();
}

template <class BASE>
void CFB_CipherTemplate<BASE>::Resynchronize(const byte *iv, int length)
{
	PolicyInterface &policy = this->AccessPolicy();
	policy.CipherResynchronize(iv, this->ThrowIfInvalidIVLength(length));
	m_leftOver = policy.GetBytesPerIteration();
}

template <class BASE>
void CFB_CipherTemplate<BASE>::ProcessData(byte *outString, const byte *inString, size_t length)
{
	CRYPTOPP_ASSERT(outString); CRYPTOPP_ASSERT(inString);
	CRYPTOPP_ASSERT(length % this->MandatoryBlockSize() == 0);

	PolicyInterface &policy = this->AccessPolicy();
	word32 bytesPerIteration = policy.GetBytesPerIteration();
	byte *reg = policy.GetRegisterBegin();

	if (m_leftOver)
	{
		const size_t len = STDMIN(m_leftOver, length);
		CombineMessageAndShiftRegister(outString, PtrAdd(reg, bytesPerIteration - m_leftOver), inString, len);

		m_leftOver -= len; length -= len;
		inString = PtrAdd(inString, len);
		outString = PtrAdd(outString, len);
	}

	// TODO: Figure out what is happening on ARM A-32. x86, Aarch64 and PowerPC are OK.
	//       The issue surfaced for CFB mode when we cut-in Cryptogams AES ARMv7 asm.
	//       Using 'outString' for both input and output leads to incorrect results.
	//
	//       Benchmarking on Cortex-A7 and Cortex-A9 indicates removing the block
	//       below costs about 9 cpb for CFB mode on ARM.
	//
	//       Also see https://github.com/weidai11/cryptopp/issues/683.
	//
	// UPDATE: It appears the issue is related to alignment checks. When we made
	//       the alignment check result volatile GCC and Clang stopped short-
	//       circuiting the transform, which is what we wanted. I suspect
	//       there's a little more to the issue, but we can enable the block again.

	const unsigned int alignment = policy.GetAlignment();
	volatile bool isAligned = IsAlignedOn(outString, alignment);
	if (policy.CanIterate() && length >= bytesPerIteration && isAligned)
	{
		isAligned &= IsAlignedOn(inString, alignment);
		const CipherDir cipherDir = GetCipherDir(*this);
		if (isAligned)
			policy.Iterate(outString, inString, cipherDir, length / bytesPerIteration);
		else
		{
			// GCC and Clang does not like this on ARM. The incorrect result is a string
			// of 0's instead of ciphertext (or plaintext if decrypting). The 0's trace
			// back to the allocation for the std::string in datatest.cpp. Elements in the
			// string are initialized to their default value, which is 0.
			//
			// It almost feels as if the compiler does not see the string is transformed
			// in-place so it short-circuits the transform. However, if we use a stand-alone
			// reproducer with the same data then the issue is _not_ present.
			//
			// When working on this issue we introduced PtrAdd and PtrSub to ensure we were
			// not running afoul of pointer arithmetic rules of the language. Namely we need
			// to use ptrdiff_t when subtracting pointers. We believe the relevant code paths
			// are clean.
			//
			// One workaround is a distinct and aligned temporary buffer. It [mostly] works
			// as expected but requires an extra allocation (casts not shown):
			//
			//   std::string temp(inString, length);
			//   policy.Iterate(outString, &temp[0], cipherDir, length / bytesPerIteration);
			//
			memcpy(outString, inString, length);
			policy.Iterate(outString, outString, cipherDir, length / bytesPerIteration);
		}
		const size_t remainder = length % bytesPerIteration;
		inString = PtrAdd(inString, length - remainder);
		outString = PtrAdd(outString, length - remainder);
		length = remainder;
	}

	while (length >= bytesPerIteration)
	{
		policy.TransformRegister();
		CombineMessageAndShiftRegister(outString, reg, inString, bytesPerIteration);
		length -= bytesPerIteration;
		inString = PtrAdd(inString, bytesPerIteration);
		outString = PtrAdd(outString, bytesPerIteration);
	}

	if (length > 0)
	{
		policy.TransformRegister();
		CombineMessageAndShiftRegister(outString, reg, inString, length);
		m_leftOver = bytesPerIteration - length;
	}
}

template <class BASE>
void CFB_EncryptionTemplate<BASE>::CombineMessageAndShiftRegister(byte *output, byte *reg, const byte *message, size_t length)
{
	xorbuf(reg, message, length);
	memcpy(output, reg, length);
}

template <class BASE>
void CFB_DecryptionTemplate<BASE>::CombineMessageAndShiftRegister(byte *output, byte *reg, const byte *message, size_t length)
{
	for (size_t i=0; i<length; i++)
	{
		byte b = message[i];
		output[i] = reg[i] ^ b;
		reg[i] = b;
	}
}

NAMESPACE_END

#endif