1 /* $OpenBSD: xform.c,v 1.16 2001/08/28 12:20:43 ben Exp $ */
2 /*-
3 * The authors of this code are John Ioannidis (ji@tla.org),
4 * Angelos D. Keromytis (kermit@csd.uch.gr),
5 * Niels Provos (provos@physnet.uni-hamburg.de) and
6 * Damien Miller (djm@mindrot.org).
7 *
8 * This code was written by John Ioannidis for BSD/OS in Athens, Greece,
9 * in November 1995.
10 *
11 * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
12 * by Angelos D. Keromytis.
13 *
14 * Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis
15 * and Niels Provos.
16 *
17 * Additional features in 1999 by Angelos D. Keromytis.
18 *
19 * AES XTS implementation in 2008 by Damien Miller
20 *
21 * Copyright (C) 1995, 1996, 1997, 1998, 1999 by John Ioannidis,
22 * Angelos D. Keromytis and Niels Provos.
23 *
24 * Copyright (C) 2001, Angelos D. Keromytis.
25 *
26 * Copyright (C) 2008, Damien Miller
27 * Copyright (c) 2014 The FreeBSD Foundation
28 * All rights reserved.
29 *
30 * Portions of this software were developed by John-Mark Gurney
31 * under sponsorship of the FreeBSD Foundation and
32 * Rubicon Communications, LLC (Netgate).
33 *
34 * Permission to use, copy, and modify this software with or without fee
35 * is hereby granted, provided that this entire notice is included in
36 * all copies of any software which is or includes a copy or
37 * modification of this software.
38 * You may use this code under the GNU public license if you so wish. Please
39 * contribute changes back to the authors under this freer than GPL license
40 * so that we may further the use of strong encryption without limitations to
41 * all.
42 *
43 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
44 * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
45 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
46 * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
47 * PURPOSE.
48 */
49
50 #include <sys/cdefs.h>
51 __FBSDID("$FreeBSD$");
52
53 #include <opencrypto/xform_enc.h>
54
55 static int aes_xts_setkey(u_int8_t **, u_int8_t *, int);
56 static void aes_xts_encrypt(caddr_t, u_int8_t *);
57 static void aes_xts_decrypt(caddr_t, u_int8_t *);
58 static void aes_xts_zerokey(u_int8_t **);
59 static void aes_xts_reinit(caddr_t, u_int8_t *);
60
61 /* Encryption instances */
62 struct enc_xform enc_xform_aes_xts = {
63 CRYPTO_AES_XTS, "AES-XTS",
64 AES_BLOCK_LEN, AES_XTS_IV_LEN, AES_XTS_MIN_KEY, AES_XTS_MAX_KEY,
65 aes_xts_encrypt,
66 aes_xts_decrypt,
67 aes_xts_setkey,
68 aes_xts_zerokey,
69 aes_xts_reinit
70 };
71
72 /*
73 * Encryption wrapper routines.
74 */
75 static void
76 aes_xts_reinit(caddr_t key, u_int8_t *iv)
77 {
78 struct aes_xts_ctx *ctx = (struct aes_xts_ctx *)key;
79 u_int64_t blocknum;
80 u_int i;
81
82 /*
83 * Prepare tweak as E_k2(IV). IV is specified as LE representation
84 * of a 64-bit block number which we allow to be passed in directly.
85 */
86 bcopy(iv, &blocknum, AES_XTS_IVSIZE);
87 for (i = 0; i < AES_XTS_IVSIZE; i++) {
88 ctx->tweak[i] = blocknum & 0xff;
89 blocknum >>= 8;
90 }
91 /* Last 64 bits of IV are always zero */
92 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE);
93
94 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak);
95 }
96
97 static void
98 aes_xts_crypt(struct aes_xts_ctx *ctx, u_int8_t *data, u_int do_encrypt)
99 {
100 u_int8_t block[AES_XTS_BLOCKSIZE];
101 u_int i, carry_in, carry_out;
102
103 for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
104 block[i] = data[i] ^ ctx->tweak[i];
105
106 if (do_encrypt)
107 rijndael_encrypt(&ctx->key1, block, data);
108 else
109 rijndael_decrypt(&ctx->key1, block, data);
110
111 for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
112 data[i] ^= ctx->tweak[i];
113
114 /* Exponentiate tweak */
115 carry_in = 0;
116 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) {
117 carry_out = ctx->tweak[i] & 0x80;
118 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0);
119 carry_in = carry_out;
120 }
121 if (carry_in)
122 ctx->tweak[0] ^= AES_XTS_ALPHA;
123 bzero(block, sizeof(block));
124 }
125
126 static void
127 aes_xts_encrypt(caddr_t key, u_int8_t *data)
128 {
129 aes_xts_crypt((struct aes_xts_ctx *)key, data, 1);
130 }
131
132 static void
133 aes_xts_decrypt(caddr_t key, u_int8_t *data)
134 {
135 aes_xts_crypt((struct aes_xts_ctx *)key, data, 0);
136 }
137
138 static int
139 aes_xts_setkey(u_int8_t **sched, u_int8_t *key, int len)
140 {
141 struct aes_xts_ctx *ctx;
142
143 if (len != 32 && len != 64)
144 return EINVAL;
145
146 *sched = KMALLOC(sizeof(struct aes_xts_ctx), M_CRYPTO_DATA,
147 M_NOWAIT | M_ZERO);
148 if (*sched == NULL)
149 return ENOMEM;
150 ctx = (struct aes_xts_ctx *)*sched;
151
152 rijndael_set_key(&ctx->key1, key, len * 4);
153 rijndael_set_key(&ctx->key2, key + (len / 2), len * 4);
154
155 return 0;
156 }
157
158 static void
159 aes_xts_zerokey(u_int8_t **sched)
160 {
161 bzero(*sched, sizeof(struct aes_xts_ctx));
162 KFREE(*sched, M_CRYPTO_DATA);
163 *sched = NULL;
164 }
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