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/types.h>
51 #include <sys/systm.h>
52 #include <opencrypto/xform_enc.h>
53
54 static int aes_xts_setkey(void *, const uint8_t *, int);
55 static void aes_xts_encrypt(void *, const uint8_t *, uint8_t *);
56 static void aes_xts_decrypt(void *, const uint8_t *, uint8_t *);
57 static void aes_xts_encrypt_multi(void *, const uint8_t *, uint8_t *, size_t);
58 static void aes_xts_decrypt_multi(void *, const uint8_t *, uint8_t *, size_t);
59 static void aes_xts_reinit(void *, const uint8_t *, size_t);
60
61 /* Encryption instances */
62 const 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 .setkey = aes_xts_setkey,
71 .reinit = aes_xts_reinit,
72 .encrypt = aes_xts_encrypt,
73 .decrypt = aes_xts_decrypt,
74 .encrypt_multi = aes_xts_encrypt_multi,
75 .decrypt_multi = aes_xts_decrypt_multi,
76 };
77
78 /*
79 * Encryption wrapper routines.
80 */
81 static void
aes_xts_reinit(void * key,const uint8_t * iv,size_t ivlen)82 aes_xts_reinit(void *key, const uint8_t *iv, size_t ivlen)
83 {
84 struct aes_xts_ctx *ctx = key;
85 uint64_t blocknum;
86 u_int i;
87
88 KASSERT(ivlen == sizeof(blocknum),
89 ("%s: invalid IV length", __func__));
90
91 /*
92 * Prepare tweak as E_k2(IV). IV is specified as LE representation
93 * of a 64-bit block number which we allow to be passed in directly.
94 */
95 bcopy(iv, &blocknum, AES_XTS_IVSIZE);
96 for (i = 0; i < AES_XTS_IVSIZE; i++) {
97 ctx->tweak[i] = blocknum & 0xff;
98 blocknum >>= 8;
99 }
100 /* Last 64 bits of IV are always zero */
101 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE);
102
103 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak);
104 }
105
106 static void
aes_xts_crypt(struct aes_xts_ctx * ctx,const uint8_t * in,uint8_t * out,size_t len,bool do_encrypt)107 aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out,
108 size_t len, bool do_encrypt)
109 {
110 uint8_t block[AES_XTS_BLOCKSIZE];
111 u_int i, carry_in, carry_out;
112
113 KASSERT(len % AES_XTS_BLOCKSIZE == 0, ("%s: invalid length", __func__));
114 while (len > 0) {
115 for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
116 block[i] = in[i] ^ ctx->tweak[i];
117
118 if (do_encrypt)
119 rijndael_encrypt(&ctx->key1, block, out);
120 else
121 rijndael_decrypt(&ctx->key1, block, out);
122
123 for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
124 out[i] ^= ctx->tweak[i];
125
126 /* Exponentiate tweak */
127 carry_in = 0;
128 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) {
129 carry_out = ctx->tweak[i] & 0x80;
130 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0);
131 carry_in = carry_out;
132 }
133 if (carry_in)
134 ctx->tweak[0] ^= AES_XTS_ALPHA;
135
136 in += AES_XTS_BLOCKSIZE;
137 out += AES_XTS_BLOCKSIZE;
138 len -= AES_XTS_BLOCKSIZE;
139 }
140 explicit_bzero(block, sizeof(block));
141 }
142
143 static void
aes_xts_encrypt(void * key,const uint8_t * in,uint8_t * out)144 aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out)
145 {
146 aes_xts_crypt(key, in, out, AES_XTS_BLOCKSIZE, true);
147 }
148
149 static void
aes_xts_decrypt(void * key,const uint8_t * in,uint8_t * out)150 aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out)
151 {
152 aes_xts_crypt(key, in, out, AES_XTS_BLOCKSIZE, false);
153 }
154
155 static void
aes_xts_encrypt_multi(void * vctx,const uint8_t * in,uint8_t * out,size_t len)156 aes_xts_encrypt_multi(void *vctx, const uint8_t *in, uint8_t *out, size_t len)
157 {
158 aes_xts_crypt(vctx, in, out, len, true);
159 }
160
161 static void
aes_xts_decrypt_multi(void * vctx,const uint8_t * in,uint8_t * out,size_t len)162 aes_xts_decrypt_multi(void *vctx, const uint8_t *in, uint8_t *out, size_t len)
163 {
164 aes_xts_crypt(vctx, in, out, len, false);
165 }
166
167 static int
aes_xts_setkey(void * sched,const uint8_t * key,int len)168 aes_xts_setkey(void *sched, const uint8_t *key, int len)
169 {
170 struct aes_xts_ctx *ctx;
171
172 if (len != 32 && len != 64)
173 return (EINVAL);
174
175 ctx = sched;
176
177 rijndael_set_key(&ctx->key1, key, len * 4);
178 rijndael_set_key(&ctx->key2, key + (len / 2), len * 4);
179
180 return (0);
181 }
182