1 /* XTS: as defined in IEEE1619/D16
2 * http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
3 * (sector sizes which are not a multiple of 16 bytes are,
4 * however currently unsupported)
5 *
6 * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
7 *
8 * Based om ecb.c
9 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
10 *
11 * This program is free software; you can redistribute it and/or modify it
12 * under the terms of the GNU General Public License as published by the Free
13 * Software Foundation; either version 2 of the License, or (at your option)
14 * any later version.
15 */
16 #include <crypto/algapi.h>
17 #include <linux/err.h>
18 #include <linux/init.h>
19 #include <linux/kernel.h>
20 #include <linux/module.h>
21 #include <linux/scatterlist.h>
22 #include <linux/slab.h>
23
24 #include <crypto/b128ops.h>
25 #include <crypto/gf128mul.h>
26
27 struct priv {
28 struct crypto_cipher *child;
29 struct crypto_cipher *tweak;
30 };
31
32 static int setkey(struct crypto_tfm *parent, const u8 *key,
33 unsigned int keylen)
34 {
35 struct priv *ctx = crypto_tfm_ctx(parent);
36 struct crypto_cipher *child = ctx->tweak;
37 u32 *flags = &parent->crt_flags;
38 int err;
39
40 /* key consists of keys of equal size concatenated, therefore
41 * the length must be even */
42 if (keylen % 2) {
43 /* tell the user why there was an error */
44 *flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
45 return -EINVAL;
46 }
47
48 /* we need two cipher instances: one to compute the inital 'tweak'
49 * by encrypting the IV (usually the 'plain' iv) and the other
50 * one to encrypt and decrypt the data */
51
52 /* tweak cipher, uses Key2 i.e. the second half of *key */
53 crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
54 crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
55 CRYPTO_TFM_REQ_MASK);
56 err = crypto_cipher_setkey(child, key + keylen/2, keylen/2);
57 if (err)
58 return err;
59
60 crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
61 CRYPTO_TFM_RES_MASK);
62
63 child = ctx->child;
64
65 /* data cipher, uses Key1 i.e. the first half of *key */
66 crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
67 crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
68 CRYPTO_TFM_REQ_MASK);
69 err = crypto_cipher_setkey(child, key, keylen/2);
70 if (err)
71 return err;
72
73 crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
74 CRYPTO_TFM_RES_MASK);
75
76 return 0;
77 }
78
79 struct sinfo {
80 be128 *t;
81 struct crypto_tfm *tfm;
82 void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
83 };
84
85 static inline void xts_round(struct sinfo *s, void *dst, const void *src)
86 {
87 be128_xor(dst, s->t, src); /* PP <- T xor P */
88 s->fn(s->tfm, dst, dst); /* CC <- E(Key1,PP) */
89 be128_xor(dst, dst, s->t); /* C <- T xor CC */
90 }
91
92 static int crypt(struct blkcipher_desc *d,
93 struct blkcipher_walk *w, struct priv *ctx,
94 void (*tw)(struct crypto_tfm *, u8 *, const u8 *),
95 void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
96 {
97 int err;
98 unsigned int avail;
99 const int bs = crypto_cipher_blocksize(ctx->child);
100 struct sinfo s = {
101 .tfm = crypto_cipher_tfm(ctx->child),
102 .fn = fn
103 };
104 u8 *wsrc;
105 u8 *wdst;
106
107 err = blkcipher_walk_virt(d, w);
108 if (!w->nbytes)
109 return err;
110
111 s.t = (be128 *)w->iv;
112 avail = w->nbytes;
113
114 wsrc = w->src.virt.addr;
115 wdst = w->dst.virt.addr;
116
117 /* calculate first value of T */
118 tw(crypto_cipher_tfm(ctx->tweak), w->iv, w->iv);
119
120 goto first;
121
122 for (;;) {
123 do {
124 gf128mul_x_ble(s.t, s.t);
125
126 first:
127 xts_round(&s, wdst, wsrc);
128
129 wsrc += bs;
130 wdst += bs;
131 } while ((avail -= bs) >= bs);
132
133 err = blkcipher_walk_done(d, w, avail);
134 if (!w->nbytes)
135 break;
136
137 avail = w->nbytes;
138
139 wsrc = w->src.virt.addr;
140 wdst = w->dst.virt.addr;
141 }
142
143 return err;
144 }
145
146 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
147 struct scatterlist *src, unsigned int nbytes)
148 {
149 struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
150 struct blkcipher_walk w;
151
152 blkcipher_walk_init(&w, dst, src, nbytes);
153 return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
154 crypto_cipher_alg(ctx->child)->cia_encrypt);
155 }
156
157 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
158 struct scatterlist *src, unsigned int nbytes)
159 {
160 struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
161 struct blkcipher_walk w;
162
163 blkcipher_walk_init(&w, dst, src, nbytes);
164 return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
165 crypto_cipher_alg(ctx->child)->cia_decrypt);
166 }
167
168 static int init_tfm(struct crypto_tfm *tfm)
169 {
170 struct crypto_cipher *cipher;
171 struct crypto_instance *inst = (void *)tfm->__crt_alg;
172 struct crypto_spawn *spawn = crypto_instance_ctx(inst);
173 struct priv *ctx = crypto_tfm_ctx(tfm);
174 u32 *flags = &tfm->crt_flags;
175
176 cipher = crypto_spawn_cipher(spawn);
177 if (IS_ERR(cipher))
178 return PTR_ERR(cipher);
179
180 if (crypto_cipher_blocksize(cipher) != 16) {
181 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
182 crypto_free_cipher(cipher);
183 return -EINVAL;
184 }
185
186 ctx->child = cipher;
187
188 cipher = crypto_spawn_cipher(spawn);
189 if (IS_ERR(cipher)) {
190 crypto_free_cipher(ctx->child);
191 return PTR_ERR(cipher);
192 }
193
194 /* this check isn't really needed, leave it here just in case */
195 if (crypto_cipher_blocksize(cipher) != 16) {
196 crypto_free_cipher(cipher);
197 crypto_free_cipher(ctx->child);
198 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
199 return -EINVAL;
200 }
201
202 ctx->tweak = cipher;
203
204 return 0;
205 }
206
207 static void exit_tfm(struct crypto_tfm *tfm)
208 {
209 struct priv *ctx = crypto_tfm_ctx(tfm);
210 crypto_free_cipher(ctx->child);
211 crypto_free_cipher(ctx->tweak);
212 }
213
214 static struct crypto_instance *alloc(struct rtattr **tb)
215 {
216 struct crypto_instance *inst;
217 struct crypto_alg *alg;
218 int err;
219
220 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
221 if (err)
222 return ERR_PTR(err);
223
224 alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
225 CRYPTO_ALG_TYPE_MASK);
226 if (IS_ERR(alg))
227 return ERR_PTR(PTR_ERR(alg));
228
229 inst = crypto_alloc_instance("xts", alg);
230 if (IS_ERR(inst))
231 goto out_put_alg;
232
233 inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
234 inst->alg.cra_priority = alg->cra_priority;
235 inst->alg.cra_blocksize = alg->cra_blocksize;
236
237 if (alg->cra_alignmask < 7)
238 inst->alg.cra_alignmask = 7;
239 else
240 inst->alg.cra_alignmask = alg->cra_alignmask;
241
242 inst->alg.cra_type = &crypto_blkcipher_type;
243
244 inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
245 inst->alg.cra_blkcipher.min_keysize =
246 2 * alg->cra_cipher.cia_min_keysize;
247 inst->alg.cra_blkcipher.max_keysize =
248 2 * alg->cra_cipher.cia_max_keysize;
249
250 inst->alg.cra_ctxsize = sizeof(struct priv);
251
252 inst->alg.cra_init = init_tfm;
253 inst->alg.cra_exit = exit_tfm;
254
255 inst->alg.cra_blkcipher.setkey = setkey;
256 inst->alg.cra_blkcipher.encrypt = encrypt;
257 inst->alg.cra_blkcipher.decrypt = decrypt;
258
259 out_put_alg:
260 crypto_mod_put(alg);
261 return inst;
262 }
263
264 static void free(struct crypto_instance *inst)
265 {
266 crypto_drop_spawn(crypto_instance_ctx(inst));
267 kfree(inst);
268 }
269
270 static struct crypto_template crypto_tmpl = {
271 .name = "xts",
272 .alloc = alloc,
273 .free = free,
274 .module = THIS_MODULE,
275 };
276
277 static int __init crypto_module_init(void)
278 {
279 return crypto_register_template(&crypto_tmpl);
280 }
281
282 static void __exit crypto_module_exit(void)
283 {
284 crypto_unregister_template(&crypto_tmpl);
285 }
286
287 module_init(crypto_module_init);
288 module_exit(crypto_module_exit);
289
290 MODULE_LICENSE("GPL");
291 MODULE_DESCRIPTION("XTS block cipher mode");
292
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