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
|
/*
* Copyright (C) 2018 Red Hat, Inc.
*
* Author: Simo Sorce
*
* This file is part of GnuTLS.
*
* The GnuTLS is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
*/
/* #############################################
* THIS IS A BACKPORT FROM NETTLE, DO NOT MODIFY
* #############################################
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#ifndef HAVE_NETTLE_XTS_ENCRYPT_MESSAGE
#include "xts.h"
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <nettle/macros.h>
#include <nettle/memxor.h>
/* An aligned 16-byte block. */
union _backport_nettle_block16
{
uint8_t b[16];
unsigned long w[16 / sizeof(unsigned long)];
uint64_t u64[2];
};
/* shift left one and XOR with 0x87 if there is carry. */
/* the algorithm reads this as a 128bit Little Endian number */
/* src and dest can point to the same buffer for in-place operations */
#if WORDS_BIGENDIAN
#define BE_SHIFT(x) ((((x) & 0x7f7f7f7f7f7f7f7f) << 1) | \
(((x) & 0x8080808080808080) >> 15))
static void
xts_shift(union _backport_nettle_block16 *dst,
const union _backport_nettle_block16 *src)
{
uint64_t carry = (src->u64[1] & 0x80) >> 7;
dst->u64[1] = BE_SHIFT(src->u64[1]) | ((src->u64[0] & 0x80) << 49);
dst->u64[0] = BE_SHIFT(src->u64[0]);
dst->u64[0] ^= 0x8700000000000000 & -carry;
}
#else /* !WORDS_BIGENDIAN */
static void
xts_shift(union _backport_nettle_block16 *dst,
const union _backport_nettle_block16 *src)
{
uint64_t carry = src->u64[1] >> 63;
dst->u64[1] = (src->u64[1] << 1) | (src->u64[0] >> 63);
dst->u64[0] = src->u64[0] << 1;
dst->u64[0] ^= 0x87 & -carry;
}
#endif /* !WORDS_BIGNDIAN */
static void
check_length(size_t length, uint8_t *dst)
{
assert(length >= XTS_BLOCK_SIZE);
/* asserts may be compiled out, try to save the user by zeroing the dst in
* case the buffer contains sensitive data (like the clear text for inplace
* encryption) */
if (length < XTS_BLOCK_SIZE)
memset(dst, '\0', length);
}
/* works also for inplace encryption/decryption */
void
xts_encrypt_message(const void *enc_ctx, const void *twk_ctx,
nettle_cipher_func *encf,
const uint8_t *tweak, size_t length,
uint8_t *dst, const uint8_t *src)
{
union _backport_nettle_block16 T;
union _backport_nettle_block16 P;
check_length(length, dst);
encf(twk_ctx, XTS_BLOCK_SIZE, T.b, tweak);
/* the zeroth power of alpha is the initial ciphertext value itself, so we
* skip shifting and do it at the end of each block operation instead */
for (;length >= 2 * XTS_BLOCK_SIZE || length == XTS_BLOCK_SIZE;
length -= XTS_BLOCK_SIZE, src += XTS_BLOCK_SIZE, dst += XTS_BLOCK_SIZE)
{
memxor3(P.b, src, T.b, XTS_BLOCK_SIZE); /* P -> PP */
encf(enc_ctx, XTS_BLOCK_SIZE, dst, P.b); /* CC */
memxor(dst, T.b, XTS_BLOCK_SIZE); /* CC -> C */
/* shift T for next block if any */
if (length > XTS_BLOCK_SIZE)
xts_shift(&T, &T);
}
/* if the last block is partial, handle via stealing */
if (length)
{
/* S Holds the real C(n-1) (Whole last block to steal from) */
union _backport_nettle_block16 S;
memxor3(P.b, src, T.b, XTS_BLOCK_SIZE); /* P -> PP */
encf(enc_ctx, XTS_BLOCK_SIZE, S.b, P.b); /* CC */
memxor(S.b, T.b, XTS_BLOCK_SIZE); /* CC -> S */
/* shift T for next block */
xts_shift(&T, &T);
length -= XTS_BLOCK_SIZE;
src += XTS_BLOCK_SIZE;
memxor3(P.b, src, T.b, length); /* P |.. */
/* steal ciphertext to complete block */
memxor3(P.b + length, S.b + length, T.b + length,
XTS_BLOCK_SIZE - length); /* ..| S_2 -> PP */
encf(enc_ctx, XTS_BLOCK_SIZE, dst, P.b); /* CC */
memxor(dst, T.b, XTS_BLOCK_SIZE); /* CC -> C(n-1) */
/* Do this after we read src so inplace operations do not break */
dst += XTS_BLOCK_SIZE;
memcpy(dst, S.b, length); /* S_1 -> C(n) */
}
}
void
xts_decrypt_message(const void *dec_ctx, const void *twk_ctx,
nettle_cipher_func *decf, nettle_cipher_func *encf,
const uint8_t *tweak, size_t length,
uint8_t *dst, const uint8_t *src)
{
union _backport_nettle_block16 T;
union _backport_nettle_block16 C;
check_length(length, dst);
encf(twk_ctx, XTS_BLOCK_SIZE, T.b, tweak);
for (;length >= 2 * XTS_BLOCK_SIZE || length == XTS_BLOCK_SIZE;
length -= XTS_BLOCK_SIZE, src += XTS_BLOCK_SIZE, dst += XTS_BLOCK_SIZE)
{
memxor3(C.b, src, T.b, XTS_BLOCK_SIZE); /* c -> CC */
decf(dec_ctx, XTS_BLOCK_SIZE, dst, C.b); /* PP */
memxor(dst, T.b, XTS_BLOCK_SIZE); /* PP -> P */
/* shift T for next block if any */
if (length > XTS_BLOCK_SIZE)
xts_shift(&T, &T);
}
/* if the last block is partial, handle via stealing */
if (length)
{
union _backport_nettle_block16 T1;
/* S Holds the real P(n) (with part of stolen ciphertext) */
union _backport_nettle_block16 S;
/* we need the last T(n) and save the T(n-1) for later */
xts_shift(&T1, &T);
memxor3(C.b, src, T1.b, XTS_BLOCK_SIZE); /* C -> CC */
decf(dec_ctx, XTS_BLOCK_SIZE, S.b, C.b); /* PP */
memxor(S.b, T1.b, XTS_BLOCK_SIZE); /* PP -> S */
/* process next block (Pn-1) */
length -= XTS_BLOCK_SIZE;
src += XTS_BLOCK_SIZE;
/* Prepare C, P holds the real P(n) */
memxor3(C.b, src, T.b, length); /* C_1 |.. */
memxor3(C.b + length, S.b + length, T.b + length,
XTS_BLOCK_SIZE - length); /* ..| S_2 -> CC */
decf(dec_ctx, XTS_BLOCK_SIZE, dst, C.b); /* PP */
memxor(dst, T.b, XTS_BLOCK_SIZE); /* PP -> P(n-1) */
/* Do this after we read src so inplace operations do not break */
dst += XTS_BLOCK_SIZE;
memcpy(dst, S.b, length); /* S_1 -> P(n) */
}
}
void
xts_aes128_set_encrypt_key(struct xts_aes128_key *xts_key, const uint8_t *key)
{
aes128_set_encrypt_key(&xts_key->cipher, key);
aes128_set_encrypt_key(&xts_key->tweak_cipher, &key[AES128_KEY_SIZE]);
}
void
xts_aes128_set_decrypt_key(struct xts_aes128_key *xts_key, const uint8_t *key)
{
aes128_set_decrypt_key(&xts_key->cipher, key);
aes128_set_encrypt_key(&xts_key->tweak_cipher, &key[AES128_KEY_SIZE]);
}
void
xts_aes128_encrypt_message(struct xts_aes128_key *xts_key,
const uint8_t *tweak, size_t length,
uint8_t *dst, const uint8_t *src)
{
xts_encrypt_message(&xts_key->cipher, &xts_key->tweak_cipher,
(nettle_cipher_func *) aes128_encrypt,
tweak, length, dst, src);
}
void
xts_aes128_decrypt_message(struct xts_aes128_key *xts_key,
const uint8_t *tweak, size_t length,
uint8_t *dst, const uint8_t *src)
{
xts_decrypt_message(&xts_key->cipher, &xts_key->tweak_cipher,
(nettle_cipher_func *) aes128_decrypt,
(nettle_cipher_func *) aes128_encrypt,
tweak, length, dst, src);
}
void
xts_aes256_set_encrypt_key(struct xts_aes256_key *xts_key, const uint8_t *key)
{
aes256_set_encrypt_key(&xts_key->cipher, key);
aes256_set_encrypt_key(&xts_key->tweak_cipher, &key[AES256_KEY_SIZE]);
}
void
xts_aes256_set_decrypt_key(struct xts_aes256_key *xts_key, const uint8_t *key)
{
aes256_set_decrypt_key(&xts_key->cipher, key);
aes256_set_encrypt_key(&xts_key->tweak_cipher, &key[AES256_KEY_SIZE]);
}
void
xts_aes256_encrypt_message(struct xts_aes256_key *xts_key,
const uint8_t *tweak, size_t length,
uint8_t *dst, const uint8_t *src)
{
xts_encrypt_message(&xts_key->cipher, &xts_key->tweak_cipher,
(nettle_cipher_func *) aes256_encrypt,
tweak, length, dst, src);
}
void
xts_aes256_decrypt_message(struct xts_aes256_key *xts_key,
const uint8_t *tweak, size_t length,
uint8_t *dst, const uint8_t *src)
{
xts_decrypt_message(&xts_key->cipher, &xts_key->tweak_cipher,
(nettle_cipher_func *) aes256_decrypt,
(nettle_cipher_func *) aes256_encrypt,
tweak, length, dst, src);
}
#endif /* HAVE_NETTLE_XTS_ENCRYPT_MESSAGE */
|
