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
56static	int aes_xts_setkey(void *, const uint8_t *, int);
57static	void aes_xts_encrypt(void *, const uint8_t *, uint8_t *);
58static	void aes_xts_decrypt(void *, const uint8_t *, uint8_t *);
59static	void aes_xts_reinit(void *, const uint8_t *);
60
61/* Encryption instances */
62struct 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 */
79static void
80aes_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
101static void
102aes_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
131static void
132aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out)
133{
134	aes_xts_crypt(key, in, out, 1);
135}
136
137static void
138aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out)
139{
140	aes_xts_crypt(key, in, out, 0);
141}
142
143static int
144aes_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}
158