VeraCrypt
aboutsummaryrefslogtreecommitdiff
path: root/src/Volume/EncryptionModeXTS.cpp
blob: e99b977c4da082a8453438fddf8c8fe9daf27e34 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
/*
 Derived from source code of TrueCrypt 7.1a, which is
 Copyright (c) 2008-2012 TrueCrypt Developers Association and which is governed
 by the TrueCrypt License 3.0.

 Modifications and additions to the original source code (contained in this file)
 and all other portions of this file are Copyright (c) 2013-2017 IDRIX
 and are governed by the Apache License 2.0 the full text of which is
 contained in the file License.txt included in VeraCrypt binary and source
 code distribution packages.
*/

#include "EncryptionModeXTS.h"
#include "Common/Crypto.h"

namespace VeraCrypt
{
	void EncryptionModeXTS::Encrypt (byte *data, uint64 length) const
	{
		EncryptBuffer (data, length, 0);
	}

	void EncryptionModeXTS::EncryptBuffer (byte *data, uint64 length, uint64 startDataUnitNo) const
	{
		if_debug (ValidateState());

		CipherList::const_iterator iSecondaryCipher = SecondaryCiphers.begin();

		for (CipherList::const_iterator iCipher = Ciphers.begin(); iCipher != Ciphers.end(); ++iCipher)
		{
			EncryptBufferXTS (**iCipher, **iSecondaryCipher, data, length, startDataUnitNo, 0);
			++iSecondaryCipher;
		}

		assert (iSecondaryCipher == SecondaryCiphers.end());
	}

	void EncryptionModeXTS::EncryptBufferXTS (const Cipher &cipher, const Cipher &secondaryCipher, byte *buffer, uint64 length, uint64 startDataUnitNo, unsigned int startCipherBlockNo) const
	{
		byte finalCarry;
		byte whiteningValues [ENCRYPTION_DATA_UNIT_SIZE];
		byte whiteningValue [BYTES_PER_XTS_BLOCK];
		byte byteBufUnitNo [BYTES_PER_XTS_BLOCK];
		uint64 *whiteningValuesPtr64 = (uint64 *) whiteningValues;
		uint64 *whiteningValuePtr64 = (uint64 *) whiteningValue;
		uint64 *bufPtr = (uint64 *) buffer;
		uint64 *dataUnitBufPtr;
		unsigned int startBlock = startCipherBlockNo, endBlock, block;
		uint64 *const finalInt64WhiteningValuesPtr = whiteningValuesPtr64 + sizeof (whiteningValues) / sizeof (*whiteningValuesPtr64) - 1;
		uint64 blockCount, dataUnitNo;

		startDataUnitNo += SectorOffset;

		/* 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;
		*((uint64 *) byteBufUnitNo) = Endian::Little (dataUnitNo);
		*((uint64 *) 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;

			whiteningValuesPtr64 = finalInt64WhiteningValuesPtr;
			whiteningValuePtr64 = (uint64 *) whiteningValue;

			// Encrypt the data unit number using the secondary key (in order to generate the first
			// whitening value for this data unit)
			*whiteningValuePtr64 = *((uint64 *) byteBufUnitNo);
			*(whiteningValuePtr64 + 1) = 0;
			secondaryCipher.EncryptBlock (whiteningValue);

			// Generate subsequent whitening values for blocks in this data unit. Note that all generated 128-bit
			// whitening values are stored in memory as a sequence of 64-bit integers in reverse order.
			for (block = 0; block < endBlock; block++)
			{
				if (block >= startBlock)
				{
					*whiteningValuesPtr64-- = *whiteningValuePtr64++;
					*whiteningValuesPtr64-- = *whiteningValuePtr64;
				}
				else
					whiteningValuePtr64++;

				// Derive the next whitening value

#if BYTE_ORDER == LITTLE_ENDIAN

				// Little-endian platforms

				finalCarry =
					(*whiteningValuePtr64 & 0x8000000000000000ULL) ?
					135 : 0;

				*whiteningValuePtr64-- <<= 1;

				if (*whiteningValuePtr64 & 0x8000000000000000ULL)
					*(whiteningValuePtr64 + 1) |= 1;

				*whiteningValuePtr64 <<= 1;
#else

				// Big-endian platforms

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

				*whiteningValuePtr64 = Endian::Little (Endian::Little (*whiteningValuePtr64) << 1);

				whiteningValuePtr64--;

				if (*whiteningValuePtr64 & 0x80)
					*(whiteningValuePtr64 + 1) |= 0x0100000000000000ULL;

				*whiteningValuePtr64 = Endian::Little (Endian::Little (*whiteningValuePtr64) << 1);
#endif

				whiteningValue[0] ^= finalCarry;
			}

			dataUnitBufPtr = bufPtr;
			whiteningValuesPtr64 = finalInt64WhiteningValuesPtr;

			// Encrypt all blocks in this data unit

			for (block = startBlock; block < endBlock; block++)
			{
				// Pre-whitening
				*bufPtr++ ^= *whiteningValuesPtr64--;
				*bufPtr++ ^= *whiteningValuesPtr64--;
			}

			// Actual encryption
			cipher.EncryptBlocks ((byte *) dataUnitBufPtr, endBlock - startBlock);

			bufPtr = dataUnitBufPtr;
			whiteningValuesPtr64 = finalInt64WhiteningValuesPtr;

			for (block = startBlock; block < endBlock; block++)
			{
				// Post-whitening
				*bufPtr++ ^= *whiteningValuesPtr64--;
				*bufPtr++ ^= *whiteningValuesPtr64--;
			}

			blockCount -= endBlock - startBlock;
			startBlock = 0;
			dataUnitNo++;
			*((uint64 *) byteBufUnitNo) = Endian::Little (dataUnitNo);
		}

		FAST_ERASE64 (whiteningValue, sizeof (whiteningValue));
		FAST_ERASE64 (whiteningValues, sizeof (whiteningValues));
	}

	void EncryptionModeXTS::EncryptSectorsCurrentThread (byte *data, uint64 sectorIndex, uint64 sectorCount, size_t sectorSize) const
	{
		EncryptBuffer (data, sectorCount * sectorSize, sectorIndex * sectorSize / ENCRYPTION_DATA_UNIT_SIZE);
	}

	size_t EncryptionModeXTS::GetKeySize () const
	{
		if (Ciphers.empty())
			throw NotInitialized (SRC_POS);

		size_t keySize = 0;
		foreach_ref (const Cipher &cipher, SecondaryCiphers)
		{
			keySize += cipher.GetKeySize();
		}

		return keySize;
	}

	void EncryptionModeXTS::Decrypt (byte *data, uint64 length) const
	{
		DecryptBuffer (data, length, 0);
	}

	void EncryptionModeXTS::DecryptBuffer (byte *data, uint64 length, uint64 startDataUnitNo) const
	{
		if_debug (ValidateState());

		CipherList::const_iterator iSecondaryCipher = SecondaryCiphers.end();

		for (CipherList::const_reverse_iterator iCipher = Ciphers.rbegin(); iCipher != Ciphers.rend(); ++iCipher)
		{
			--iSecondaryCipher;
			DecryptBufferXTS (**iCipher, **iSecondaryCipher, data, length, startDataUnitNo, 0);
		}

		assert (iSecondaryCipher == SecondaryCiphers.begin());
	}

	void EncryptionModeXTS::DecryptBufferXTS (const Cipher &cipher, const Cipher &secondaryCipher, byte *buffer, uint64 length, uint64 startDataUnitNo, unsigned int startCipherBlockNo) const
	{
		byte finalCarry;
		byte whiteningValues [ENCRYPTION_DATA_UNIT_SIZE];
		byte whiteningValue [BYTES_PER_XTS_BLOCK];
		byte byteBufUnitNo [BYTES_PER_XTS_BLOCK];
		uint64 *whiteningValuesPtr64 = (uint64 *) whiteningValues;
		uint64 *whiteningValuePtr64 = (uint64 *) whiteningValue;
		uint64 *bufPtr = (uint64 *) buffer;
		uint64 *dataUnitBufPtr;
		unsigned int startBlock = startCipherBlockNo, endBlock, block;
		uint64 *const finalInt64WhiteningValuesPtr = whiteningValuesPtr64 + sizeof (whiteningValues) / sizeof (*whiteningValuesPtr64) - 1;
		uint64 blockCount, dataUnitNo;

		startDataUnitNo += SectorOffset;

		// 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;
		*((uint64 *) byteBufUnitNo) = Endian::Little (dataUnitNo);
		*((uint64 *) 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;

			whiteningValuesPtr64 = finalInt64WhiteningValuesPtr;
			whiteningValuePtr64 = (uint64 *) whiteningValue;

			// Encrypt the data unit number using the secondary key (in order to generate the first
			// whitening value for this data unit)
			*whiteningValuePtr64 = *((uint64 *) byteBufUnitNo);
			*(whiteningValuePtr64 + 1) = 0;
			secondaryCipher.EncryptBlock (whiteningValue);

			// Generate subsequent whitening values for blocks in this data unit. Note that all generated 128-bit
			// whitening values are stored in memory as a sequence of 64-bit integers in reverse order.
			for (block = 0; block < endBlock; block++)
			{
				if (block >= startBlock)
				{
					*whiteningValuesPtr64-- = *whiteningValuePtr64++;
					*whiteningValuesPtr64-- = *whiteningValuePtr64;
				}
				else
					whiteningValuePtr64++;

				// Derive the next whitening value

#if BYTE_ORDER == LITTLE_ENDIAN

				// Little-endian platforms

				finalCarry =
					(*whiteningValuePtr64 & 0x8000000000000000ULL) ?
					135 : 0;

				*whiteningValuePtr64-- <<= 1;

				if (*whiteningValuePtr64 & 0x8000000000000000ULL)
					*(whiteningValuePtr64 + 1) |= 1;

				*whiteningValuePtr64 <<= 1;

#else
				// Big-endian platforms

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

				*whiteningValuePtr64 = Endian::Little (Endian::Little (*whiteningValuePtr64) << 1);

				whiteningValuePtr64--;

				if (*whiteningValuePtr64 & 0x80)
					*(whiteningValuePtr64 + 1) |= 0x0100000000000000ULL;

				*whiteningValuePtr64 = Endian::Little (Endian::Little (*whiteningValuePtr64) << 1);
#endif

				whiteningValue[0] ^= finalCarry;
			}

			dataUnitBufPtr = bufPtr;
			whiteningValuesPtr64 = finalInt64WhiteningValuesPtr;

			// Decrypt blocks in this data unit

			for (block = startBlock; block < endBlock; block++)
			{
				*bufPtr++ ^= *whiteningValuesPtr64--;
				*bufPtr++ ^= *whiteningValuesPtr64--;
			}

			cipher.DecryptBlocks ((byte *) dataUnitBufPtr, endBlock - startBlock);

			bufPtr = dataUnitBufPtr;
			whiteningValuesPtr64 = finalInt64WhiteningValuesPtr;

			for (block = startBlock; block < endBlock; block++)
			{
				*bufPtr++ ^= *whiteningValuesPtr64--;
				*bufPtr++ ^= *whiteningValuesPtr64--;
			}

			blockCount -= endBlock - startBlock;
			startBlock = 0;
			dataUnitNo++;

			*((uint64 *) byteBufUnitNo) = Endian::Little (dataUnitNo);
		}

		FAST_ERASE64 (whiteningValue, sizeof (whiteningValue));
		FAST_ERASE64 (whiteningValues, sizeof (whiteningValues));
	}

	void EncryptionModeXTS::DecryptSectorsCurrentThread (byte *data, uint64 sectorIndex, uint64 sectorCount, size_t sectorSize) const
	{
		DecryptBuffer (data, sectorCount * sectorSize, sectorIndex * sectorSize / ENCRYPTION_DATA_UNIT_SIZE);
	}

	void EncryptionModeXTS::SetCiphers (const CipherList &ciphers)
	{
		EncryptionMode::SetCiphers (ciphers);

		SecondaryCiphers.clear();

		foreach_ref (const Cipher &cipher, ciphers)
		{
			SecondaryCiphers.push_back (cipher.GetNew());
		}

		if (SecondaryKey.Size() > 0)
			SetSecondaryCipherKeys();
	}

	void EncryptionModeXTS::SetKey (const ConstBufferPtr &key)
	{
		SecondaryKey.Allocate (key.Size());
		SecondaryKey.CopyFrom (key);

		if (!SecondaryCiphers.empty())
			SetSecondaryCipherKeys();
	}

	void EncryptionModeXTS::SetSecondaryCipherKeys ()
	{
		size_t keyOffset = 0;
		foreach_ref (Cipher &cipher, SecondaryCiphers)
		{
			cipher.SetKey (SecondaryKey.GetRange (keyOffset, cipher.GetKeySize()));
			keyOffset += cipher.GetKeySize();
		}

		KeySet = true;
	}
}