xref: /freebsd/sys/opencrypto/xform_aes_xts.c (revision e17f5b1d)
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(void *, const uint8_t *, int);
56 static	void aes_xts_encrypt(void *, const uint8_t *, uint8_t *);
57 static	void aes_xts_decrypt(void *, const uint8_t *, uint8_t *);
58 static	void aes_xts_reinit(void *, const uint8_t *);
59 
60 /* Encryption instances */
61 struct enc_xform enc_xform_aes_xts = {
62 	.type = CRYPTO_AES_XTS,
63 	.name = "AES-XTS",
64 	.ctxsize = sizeof(struct aes_xts_ctx),
65 	.blocksize = AES_BLOCK_LEN,
66 	.ivsize = AES_XTS_IV_LEN,
67 	.minkey = AES_XTS_MIN_KEY,
68 	.maxkey = AES_XTS_MAX_KEY,
69 	.encrypt = aes_xts_encrypt,
70 	.decrypt = aes_xts_decrypt,
71 	.setkey = aes_xts_setkey,
72 	.reinit = aes_xts_reinit
73 };
74 
75 /*
76  * Encryption wrapper routines.
77  */
78 static void
79 aes_xts_reinit(void *key, const uint8_t *iv)
80 {
81 	struct aes_xts_ctx *ctx = key;
82 	uint64_t blocknum;
83 	u_int i;
84 
85 	/*
86 	 * Prepare tweak as E_k2(IV). IV is specified as LE representation
87 	 * of a 64-bit block number which we allow to be passed in directly.
88 	 */
89 	bcopy(iv, &blocknum, AES_XTS_IVSIZE);
90 	for (i = 0; i < AES_XTS_IVSIZE; i++) {
91 		ctx->tweak[i] = blocknum & 0xff;
92 		blocknum >>= 8;
93 	}
94 	/* Last 64 bits of IV are always zero */
95 	bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE);
96 
97 	rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak);
98 }
99 
100 static void
101 aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out,
102     u_int do_encrypt)
103 {
104 	uint8_t block[AES_XTS_BLOCKSIZE];
105 	u_int i, carry_in, carry_out;
106 
107 	for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
108 		block[i] = in[i] ^ ctx->tweak[i];
109 
110 	if (do_encrypt)
111 		rijndael_encrypt(&ctx->key1, block, out);
112 	else
113 		rijndael_decrypt(&ctx->key1, block, out);
114 
115 	for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
116 		out[i] ^= ctx->tweak[i];
117 
118 	/* Exponentiate tweak */
119 	carry_in = 0;
120 	for (i = 0; i < AES_XTS_BLOCKSIZE; i++) {
121 		carry_out = ctx->tweak[i] & 0x80;
122 		ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0);
123 		carry_in = carry_out;
124 	}
125 	if (carry_in)
126 		ctx->tweak[0] ^= AES_XTS_ALPHA;
127 	explicit_bzero(block, sizeof(block));
128 }
129 
130 static void
131 aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out)
132 {
133 	aes_xts_crypt(key, in, out, 1);
134 }
135 
136 static void
137 aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out)
138 {
139 	aes_xts_crypt(key, in, out, 0);
140 }
141 
142 static int
143 aes_xts_setkey(void *sched, const uint8_t *key, int len)
144 {
145 	struct aes_xts_ctx *ctx;
146 
147 	if (len != 32 && len != 64)
148 		return (EINVAL);
149 
150 	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