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 <sys/types.h>
54 #include <opencrypto/xform_enc.h>
55
56 static int aes_xts_setkey(void *, const uint8_t *, int);
57 static void aes_xts_encrypt(void *, const uint8_t *, uint8_t *);
58 static void aes_xts_decrypt(void *, const uint8_t *, uint8_t *);
59 static void aes_xts_reinit(void *, const uint8_t *);
60
61 /* Encryption instances */
62 struct enc_xform enc_xform_aes_xts = {
63 .type = CRYPTO_AES_XTS,
64 .name = "AES-XTS",
65 .ctxsize = sizeof(struct aes_xts_ctx),
66 .blocksize = AES_BLOCK_LEN,
67 .ivsize = AES_XTS_IV_LEN,
68 .minkey = AES_XTS_MIN_KEY,
69 .maxkey = AES_XTS_MAX_KEY,
70 .encrypt = aes_xts_encrypt,
71 .decrypt = aes_xts_decrypt,
72 .setkey = aes_xts_setkey,
73 .reinit = aes_xts_reinit
74 };
75
76 /*
77 * Encryption wrapper routines.
78 */
79 static void
80 aes_xts_reinit(void *key, const uint8_t *iv)
81 {
82 struct aes_xts_ctx *ctx = key;
83 uint64_t blocknum;
84 u_int i;
85
86 /*
87 * Prepare tweak as E_k2(IV). IV is specified as LE representation
88 * of a 64-bit block number which we allow to be passed in directly.
89 */
90 bcopy(iv, &blocknum, AES_XTS_IVSIZE);
91 for (i = 0; i < AES_XTS_IVSIZE; i++) {
92 ctx->tweak[i] = blocknum & 0xff;
93 blocknum >>= 8;
94 }
95 /* Last 64 bits of IV are always zero */
96 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE);
97
98 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak);
99 }
100
101 static void
102 aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out,
103 u_int do_encrypt)
104 {
105 uint8_t block[AES_XTS_BLOCKSIZE];
106 u_int i, carry_in, carry_out;
107
108 for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
109 block[i] = in[i] ^ ctx->tweak[i];
110
111 if (do_encrypt)
112 rijndael_encrypt(&ctx->key1, block, out);
113 else
114 rijndael_decrypt(&ctx->key1, block, out);
115
116 for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
117 out[i] ^= ctx->tweak[i];
118
119 /* Exponentiate tweak */
120 carry_in = 0;
121 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) {
122 carry_out = ctx->tweak[i] & 0x80;
123 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0);
124 carry_in = carry_out;
125 }
126 if (carry_in)
127 ctx->tweak[0] ^= AES_XTS_ALPHA;
128 explicit_bzero(block, sizeof(block));
129 }
130
131 static void
132 aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out)
133 {
134 aes_xts_crypt(key, in, out, 1);
135 }
136
137 static void
138 aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out)
139 {
140 aes_xts_crypt(key, in, out, 0);
141 }
142
143 static int
144 aes_xts_setkey(void *sched, const uint8_t *key, int len)
145 {
146 struct aes_xts_ctx *ctx;
147
148 if (len != 32 && len != 64)
149 return (EINVAL);
150
151 ctx = sched;
152
153 rijndael_set_key(&ctx->key1, key, len * 4);
154 rijndael_set_key(&ctx->key2, key + (len / 2), len * 4);
155
156 return (0);
157 }
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