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
54static	int aes_xts_setkey(void *, const uint8_t *, int);
55static	void aes_xts_encrypt(void *, const uint8_t *, uint8_t *);
56static	void aes_xts_decrypt(void *, const uint8_t *, uint8_t *);
57static	void aes_xts_encrypt_multi(void *, const uint8_t *, uint8_t *, size_t);
58static	void aes_xts_decrypt_multi(void *, const uint8_t *, uint8_t *, size_t);
59static	void aes_xts_reinit(void *, const uint8_t *, size_t);
60
61/* Encryption instances */
62const 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 */
81static void
82aes_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
106static void
107aes_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
143static void
144aes_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
149static void
150aes_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
155static void
156aes_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
161static void
162aes_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
167static int
168aes_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