/*
 Copyright (c) 2008 TrueCrypt Foundation. All rights reserved.

 Governed by the TrueCrypt License 2.5 the full text of which is contained
 in the file License.txt included in TrueCrypt binary and source code
 distribution packages.
*/

/* If native 64-bit data types are not available, define TC_NO_COMPILER_INT64. 

For big-endian platforms define BYTE_ORDER as BIG_ENDIAN. */


#ifdef TC_MINIMIZE_CODE_SIZE
//	Preboot/boot version
#	ifndef TC_NO_COMPILER_INT64
#		define TC_NO_COMPILER_INT64
#	endif
#	pragma optimize ("tl", on)
#endif


#include "Xts.h"


#ifndef TC_NO_COMPILER_INT64

// length: number of bytes to encrypt; may be larger than one data unit and must be divisible by the cipher block size
// ks: the primary key schedule
// ks2: the secondary key schedule
// startDataUnitNo: The sequential number of the data unit with which the buffer starts.
// startCipherBlockNo: The sequential number of the first plaintext block to encrypt inside the data unit startDataUnitNo.
//                     When encrypting the data unit from its first block, startCipherBlockNo is 0. 
//                     The startCipherBlockNo value applies only to the first data unit in the buffer; each successive
//                     data unit is encrypted from its first block. The start of the buffer does not have to be
//                     aligned with the start of a data unit. If it is aligned, startCipherBlockNo must be 0; if it
//                     is not aligned, startCipherBlockNo must reflect the misalignment accordingly.
void EncryptBufferXTS (unsigned __int8 *buffer,
					   TC_LARGEST_COMPILER_UINT length,
					   const UINT64_STRUCT *startDataUnitNo,
					   unsigned int startCipherBlockNo,
					   unsigned __int8 *ks,
					   unsigned __int8 *ks2,
					   int cipher)
{
	unsigned __int8 finalCarry;
	unsigned __int8 whiteningValue [BYTES_PER_XTS_BLOCK];
	unsigned __int8 byteBufUnitNo [BYTES_PER_XTS_BLOCK];
	unsigned __int64 *whiteningValuePtr64 = (unsigned __int64 *) whiteningValue;
	unsigned __int64 *bufPtr = (unsigned __int64 *) buffer;
	unsigned int startBlock = startCipherBlockNo, endBlock, block;
	TC_LARGEST_COMPILER_UINT blockCount, dataUnitNo;

	/* The encrypted data unit number (i.e. the resultant ciphertext block) is to be multiplied in the
	finite field GF(2^128) by j-th power of n, where j is the sequential plaintext/ciphertext block
	number and n is 2, a primitive element of GF(2^128). This can be (and is) simplified and implemented
	as a left shift of the preceding whitening value by one bit (with carry propagating). In addition, if
	the shift of the highest byte results in a carry, 135 is XORed into the lowest byte. The value 135 is
	derived from the modulus of the Galois Field (x^128+x^7+x^2+x+1). */

	// Convert the 64-bit data unit number into a little-endian 16-byte array. 
	// Note that as we are converting a 64-bit number into a 16-byte array we can always zero the last 8 bytes.
	dataUnitNo = startDataUnitNo->Value;
	*((unsigned __int64 *) byteBufUnitNo) = LE64 (dataUnitNo);
	*((unsigned __int64 *) byteBufUnitNo + 1) = 0;

	if (length % BYTES_PER_XTS_BLOCK)
		TC_THROW_FATAL_EXCEPTION;

	blockCount = length / BYTES_PER_XTS_BLOCK;

	// Process all blocks in the buffer
	while (blockCount > 0)
	{
		if (blockCount < BLOCKS_PER_XTS_DATA_UNIT)
			endBlock = startBlock + (unsigned int) blockCount;
		else
			endBlock = BLOCKS_PER_XTS_DATA_UNIT;

		whiteningValuePtr64 = (unsigned __int64 *) whiteningValue;

		// Encrypt the data unit number using the secondary key (in order to generate the first 
		// whitening value for this data unit)
		*whiteningValuePtr64 = *((unsigned __int64 *) byteBufUnitNo);
		*(whiteningValuePtr64 + 1) = 0;
		EncipherBlock (cipher, whiteningValue, ks2);

		// Generate (and apply) subsequent whitening values for blocks in this data unit and
		// encrypt all relevant blocks in this data unit
		for (block = 0; block < endBlock; block++)
		{
			if (block >= startBlock)
			{
				// Pre-whitening
				*bufPtr++ ^= *whiteningValuePtr64++;
				*bufPtr-- ^= *whiteningValuePtr64--;

				// Actual encryption
				EncipherBlock (cipher, bufPtr, ks);

				// Post-whitening
				*bufPtr++ ^= *whiteningValuePtr64++;
				*bufPtr++ ^= *whiteningValuePtr64;
			}
			else
				whiteningValuePtr64++;

			// Derive the next whitening value

#if BYTE_ORDER == LITTLE_ENDIAN

			// Little-endian platforms

			finalCarry = 
				(*whiteningValuePtr64 & 0x8000000000000000) ?
				135 : 0;

			*whiteningValuePtr64-- <<= 1;

			if (*whiteningValuePtr64 & 0x8000000000000000)
				*(whiteningValuePtr64 + 1) |= 1;	

			*whiteningValuePtr64 <<= 1;
#else

			// Big-endian platforms

			finalCarry = 
				(*whiteningValuePtr64 & 0x80) ?
				135 : 0;

			*whiteningValuePtr64 = LE64 (LE64 (*whiteningValuePtr64) << 1);

			whiteningValuePtr64--;

			if (*whiteningValuePtr64 & 0x80)
				*(whiteningValuePtr64 + 1) |= 0x0100000000000000;	

			*whiteningValuePtr64 = LE64 (LE64 (*whiteningValuePtr64) << 1);
#endif

			whiteningValue[0] ^= finalCarry;
		}

		blockCount -= endBlock - startBlock;
		startBlock = 0;
		dataUnitNo++;
		*((unsigned __int64 *) byteBufUnitNo) = LE64 (dataUnitNo);
	}

	FAST_ERASE64 (whiteningValue, sizeof (whiteningValue));
}


// For descriptions of the input parameters, see EncryptBufferXTS().
void DecryptBufferXTS (unsigned __int8 *buffer,
					   TC_LARGEST_COMPILER_UINT length,
					   const UINT64_STRUCT *startDataUnitNo,
					   unsigned int startCipherBlockNo,
					   unsigned __int8 *ks,
					   unsigned __int8 *ks2,
					   int cipher)
{
	unsigned __int8 finalCarry;
	unsigned __int8 whiteningValue [BYTES_PER_XTS_BLOCK];
	unsigned __int8 byteBufUnitNo [BYTES_PER_XTS_BLOCK];
	unsigned __int64 *whiteningValuePtr64 = (unsigned __int64 *) whiteningValue;
	unsigned __int64 *bufPtr = (unsigned __int64 *) buffer;
	unsigned int startBlock = startCipherBlockNo, endBlock, block;
	TC_LARGEST_COMPILER_UINT blockCount, dataUnitNo;

	// Convert the 64-bit data unit number into a little-endian 16-byte array. 
	// Note that as we are converting a 64-bit number into a 16-byte array we can always zero the last 8 bytes.
	dataUnitNo = startDataUnitNo->Value;
	*((unsigned __int64 *) byteBufUnitNo) = LE64 (dataUnitNo);
	*((unsigned __int64 *) byteBufUnitNo + 1) = 0;

	if (length % BYTES_PER_XTS_BLOCK)
		TC_THROW_FATAL_EXCEPTION;

	blockCount = length / BYTES_PER_XTS_BLOCK;

	// Process all blocks in the buffer
	while (blockCount > 0)
	{
		if (blockCount < BLOCKS_PER_XTS_DATA_UNIT)
			endBlock = startBlock + (unsigned int) blockCount;
		else
			endBlock = BLOCKS_PER_XTS_DATA_UNIT;

		whiteningValuePtr64 = (unsigned __int64 *) whiteningValue;

		// Encrypt the data unit number using the secondary key (in order to generate the first 
		// whitening value for this data unit)
		*whiteningValuePtr64 = *((unsigned __int64 *) byteBufUnitNo);
		*(whiteningValuePtr64 + 1) = 0;
		EncipherBlock (cipher, whiteningValue, ks2);

		// Generate (and apply) subsequent whitening values for blocks in this data unit and
		// decrypt all relevant blocks in this data unit
		for (block = 0; block < endBlock; block++)
		{
			if (block >= startBlock)
			{
				// Post-whitening
				*bufPtr++ ^= *whiteningValuePtr64++;
				*bufPtr-- ^= *whiteningValuePtr64--;

				// Actual decryption
				DecipherBlock (cipher, bufPtr, ks);

				// Pre-whitening
				*bufPtr++ ^= *whiteningValuePtr64++;
				*bufPtr++ ^= *whiteningValuePtr64;
			}
			else
				whiteningValuePtr64++;

			// Derive the next whitening value

#if BYTE_ORDER == LITTLE_ENDIAN

			// Little-endian platforms

			finalCarry = 
				(*whiteningValuePtr64 & 0x8000000000000000) ?
				135 : 0;

			*whiteningValuePtr64-- <<= 1;

			if (*whiteningValuePtr64 & 0x8000000000000000)
				*(whiteningValuePtr64 + 1) |= 1;	

			*whiteningValuePtr64 <<= 1;

#else
			// Big-endian platforms

			finalCarry = 
				(*whiteningValuePtr64 & 0x80) ?
				135 : 0;

			*whiteningValuePtr64 = LE64 (LE64 (*whiteningValuePtr64) << 1);

			whiteningValuePtr64--;

			if (*whiteningValuePtr64 & 0x80)
				*(whiteningValuePtr64 + 1) |= 0x0100000000000000;	

			*whiteningValuePtr64 = LE64 (LE64 (*whiteningValuePtr64) << 1);
#endif

			whiteningValue[0] ^= finalCarry;
		}

		blockCount -= endBlock - startBlock;
		startBlock = 0;
		dataUnitNo++;
		*((unsigned __int64 *) byteBufUnitNo) = LE64 (dataUnitNo);
	}

	FAST_ERASE64 (whiteningValue, sizeof (whiteningValue));
}



#else	// TC_NO_COMPILER_INT64

/* ---- The following code is to be used only when native 64-bit data types are not available. ---- */

#if BYTE_ORDER == BIG_ENDIAN
#error The TC_NO_COMPILER_INT64 version of the XTS code is not compatible with big-endian platforms
#endif 


// Converts a 64-bit unsigned integer (passed as two 32-bit integers for compatibility with non-64-bit
// environments/platforms) into a little-endian 16-byte array.
static void Uint64ToLE16ByteArray (unsigned __int8 *byteBuf, unsigned __int32 highInt32, unsigned __int32 lowInt32)
{
	unsigned __int32 *bufPtr32 = (unsigned __int32 *) byteBuf;

	*bufPtr32++ = lowInt32;
	*bufPtr32++ = highInt32;

	// We're converting a 64-bit number into a little-endian 16-byte array so we can zero the last 8 bytes
	*bufPtr32++ = 0;
	*bufPtr32 = 0;
}


// Encrypts or decrypts all blocks in the buffer in XTS mode. For descriptions of the input parameters,
// see the 64-bit version of EncryptBufferXTS().
static void EncryptDecryptBufferXTS32 (const unsigned __int8 *buffer,
							TC_LARGEST_COMPILER_UINT length,
							const UINT64_STRUCT *startDataUnitNo,
							unsigned int startBlock,
							unsigned __int8 *ks,
							unsigned __int8 *ks2,
							int cipher,
							BOOL decryption)
{
	TC_LARGEST_COMPILER_UINT blockCount;
	UINT64_STRUCT dataUnitNo;
	unsigned int block;
	unsigned int endBlock;
	unsigned __int8 byteBufUnitNo [BYTES_PER_XTS_BLOCK];
	unsigned __int8 whiteningValue [BYTES_PER_XTS_BLOCK];
	unsigned __int32 *bufPtr32 = (unsigned __int32 *) buffer;
	unsigned __int32 *whiteningValuePtr32 = (unsigned __int32 *) whiteningValue;
	unsigned __int8 finalCarry;
	unsigned __int32 *const finalDwordWhiteningValuePtr = whiteningValuePtr32 + sizeof (whiteningValue) / sizeof (*whiteningValuePtr32) - 1;

	// Store the 64-bit data unit number in a way compatible with non-64-bit environments/platforms
	dataUnitNo.HighPart = startDataUnitNo->HighPart;
	dataUnitNo.LowPart = startDataUnitNo->LowPart;

	blockCount = length / BYTES_PER_XTS_BLOCK;

	// Convert the 64-bit data unit number into a little-endian 16-byte array. 
	// (Passed as two 32-bit integers for compatibility with non-64-bit environments/platforms.)
	Uint64ToLE16ByteArray (byteBufUnitNo, dataUnitNo.HighPart, dataUnitNo.LowPart);

	// Generate whitening values for all blocks in the buffer
	while (blockCount > 0)
	{
		if (blockCount < BLOCKS_PER_XTS_DATA_UNIT)
			endBlock = startBlock + (unsigned int) blockCount;
		else
			endBlock = BLOCKS_PER_XTS_DATA_UNIT;

		// Encrypt the data unit number using the secondary key (in order to generate the first 
		// whitening value for this data unit)
		memcpy (whiteningValue, byteBufUnitNo, BYTES_PER_XTS_BLOCK);
		EncipherBlock (cipher, whiteningValue, ks2);

		// Generate (and apply) subsequent whitening values for blocks in this data unit and
		// encrypt/decrypt all relevant blocks in this data unit
		for (block = 0; block < endBlock; block++)
		{
			if (block >= startBlock)
			{
				whiteningValuePtr32 = (unsigned __int32 *) whiteningValue;

				// Whitening
				*bufPtr32++ ^= *whiteningValuePtr32++;
				*bufPtr32++ ^= *whiteningValuePtr32++;
				*bufPtr32++ ^= *whiteningValuePtr32++;
				*bufPtr32 ^= *whiteningValuePtr32;

				bufPtr32 -= BYTES_PER_XTS_BLOCK / sizeof (*bufPtr32) - 1;

				// Actual encryption/decryption
				if (decryption)
					DecipherBlock (cipher, bufPtr32, ks);
				else
					EncipherBlock (cipher, bufPtr32, ks);

				whiteningValuePtr32 = (unsigned __int32 *) whiteningValue;

				// Whitening
				*bufPtr32++ ^= *whiteningValuePtr32++;
				*bufPtr32++ ^= *whiteningValuePtr32++;
				*bufPtr32++ ^= *whiteningValuePtr32++;
				*bufPtr32++ ^= *whiteningValuePtr32;
			}

			// Derive the next whitening value

			finalCarry = 0;

			for (whiteningValuePtr32 = finalDwordWhiteningValuePtr;
				whiteningValuePtr32 >= (unsigned __int32 *) whiteningValue;
				whiteningValuePtr32--)
			{
				if (*whiteningValuePtr32 & 0x80000000)	// If the following shift results in a carry
				{
					if (whiteningValuePtr32 != finalDwordWhiteningValuePtr)	// If not processing the highest double word
					{
						// A regular carry
						*(whiteningValuePtr32 + 1) |= 1;
					}
					else 
					{
						// The highest byte shift will result in a carry
						finalCarry = 135;
					}
				}

				*whiteningValuePtr32 <<= 1;
			}

			whiteningValue[0] ^= finalCarry;
		}

		blockCount -= endBlock - startBlock;
		startBlock = 0;

		// Increase the data unit number by one
		if (!++dataUnitNo.LowPart)
		{
			dataUnitNo.HighPart++;
		}

		// Convert the 64-bit data unit number into a little-endian 16-byte array. 
		Uint64ToLE16ByteArray (byteBufUnitNo, dataUnitNo.HighPart, dataUnitNo.LowPart);
	}

	FAST_ERASE64 (whiteningValue, sizeof (whiteningValue));
}


// For descriptions of the input parameters, see the 64-bit version of EncryptBufferXTS() above.
void EncryptBufferXTS (unsigned __int8 *buffer,
					   TC_LARGEST_COMPILER_UINT length,
					   const UINT64_STRUCT *startDataUnitNo,
					   unsigned int startCipherBlockNo,
					   unsigned __int8 *ks,
					   unsigned __int8 *ks2,
					   int cipher)
{
	// Encrypt all plaintext blocks in the buffer
	EncryptDecryptBufferXTS32 (buffer, length, startDataUnitNo, startCipherBlockNo, ks, ks2, cipher, FALSE);
}


// For descriptions of the input parameters, see the 64-bit version of EncryptBufferXTS().
void DecryptBufferXTS (unsigned __int8 *buffer,
					   TC_LARGEST_COMPILER_UINT length,
					   const UINT64_STRUCT *startDataUnitNo,
					   unsigned int startCipherBlockNo,
					   unsigned __int8 *ks,
					   unsigned __int8 *ks2,
					   int cipher)
{
	// Decrypt all ciphertext blocks in the buffer
	EncryptDecryptBufferXTS32 (buffer, length, startDataUnitNo, startCipherBlockNo, ks, ks2, cipher, TRUE);
}

#endif	// TC_NO_COMPILER_INT64