xref: /freebsd/sys/opencrypto/xform_aes_xts.c (revision af6a5351a1fdb1130f18be6c782c4d48916eb971)
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 }
165