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 on 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/internal/skcipher.h>
17#include <crypto/scatterwalk.h>
18#include <linux/err.h>
19#include <linux/init.h>
20#include <linux/kernel.h>
21#include <linux/module.h>
22#include <linux/scatterlist.h>
23#include <linux/slab.h>
24
25#include <crypto/xts.h>
26#include <crypto/b128ops.h>
27#include <crypto/gf128mul.h>
28
29struct priv {
30 struct crypto_skcipher *child;
31 struct crypto_cipher *tweak;
32};
33
34struct xts_instance_ctx {
35 struct crypto_skcipher_spawn spawn;
36 char name[CRYPTO_MAX_ALG_NAME];
37};
38
39struct rctx {
40 le128 t;
41 struct skcipher_request subreq;
42};
43
44static int setkey(struct crypto_skcipher *parent, const u8 *key,
45 unsigned int keylen)
46{
47 struct priv *ctx = crypto_skcipher_ctx(parent);
48 struct crypto_skcipher *child;
49 struct crypto_cipher *tweak;
50 int err;
51
52 err = xts_verify_key(parent, key, keylen);
53 if (err)
54 return err;
55
56 keylen /= 2;
57
58 /* we need two cipher instances: one to compute the initial 'tweak'
59 * by encrypting the IV (usually the 'plain' iv) and the other
60 * one to encrypt and decrypt the data */
61
62 /* tweak cipher, uses Key2 i.e. the second half of *key */
63 tweak = ctx->tweak;
64 crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
65 crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
66 CRYPTO_TFM_REQ_MASK);
67 err = crypto_cipher_setkey(tweak, key + keylen, keylen);
68 crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(tweak) &
69 CRYPTO_TFM_RES_MASK);
70 if (err)
71 return err;
72
73 /* data cipher, uses Key1 i.e. the first half of *key */
74 child = ctx->child;
75 crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
76 crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
77 CRYPTO_TFM_REQ_MASK);
78 err = crypto_skcipher_setkey(child, key, keylen);
79 crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
80 CRYPTO_TFM_RES_MASK);
81
82 return err;
83}
84
85/*
86 * We compute the tweak masks twice (both before and after the ECB encryption or
87 * decryption) to avoid having to allocate a temporary buffer and/or make
88 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
89 * just doing the gf128mul_x_ble() calls again.
90 */
91static int xor_tweak(struct skcipher_request *req, bool second_pass)
92{
93 struct rctx *rctx = skcipher_request_ctx(req);
94 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
95 const int bs = XTS_BLOCK_SIZE;
96 struct skcipher_walk w;
97 le128 t = rctx->t;
98 int err;
99
100 if (second_pass) {
101 req = &rctx->subreq;
102 /* set to our TFM to enforce correct alignment: */
103 skcipher_request_set_tfm(req, tfm);
104 }
105 err = skcipher_walk_virt(&w, req, false);
106
107 while (w.nbytes) {
108 unsigned int avail = w.nbytes;
109 le128 *wsrc;
110 le128 *wdst;
111
112 wsrc = w.src.virt.addr;
113 wdst = w.dst.virt.addr;
114
115 do {
116 le128_xor(wdst++, &t, wsrc++);
117 gf128mul_x_ble(&t, &t);
118 } while ((avail -= bs) >= bs);
119
120 err = skcipher_walk_done(&w, avail);
121 }
122
123 return err;
124}
125
126static int xor_tweak_pre(struct skcipher_request *req)
127{
128 return xor_tweak(req, false);
129}
130
131static int xor_tweak_post(struct skcipher_request *req)
132{
133 return xor_tweak(req, true);
134}
135
136static void crypt_done(struct crypto_async_request *areq, int err)
137{
138 struct skcipher_request *req = areq->data;
139
140 if (!err)
141 err = xor_tweak_post(req);
142
143 skcipher_request_complete(req, err);
144}
145
146static void init_crypt(struct skcipher_request *req)
147{
148 struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
149 struct rctx *rctx = skcipher_request_ctx(req);
150 struct skcipher_request *subreq = &rctx->subreq;
151
152 skcipher_request_set_tfm(subreq, ctx->child);
153 skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
154 skcipher_request_set_crypt(subreq, req->dst, req->dst,
155 req->cryptlen, NULL);
156
157 /* calculate first value of T */
158 crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
159}
160
161static int encrypt(struct skcipher_request *req)
162{
163 struct rctx *rctx = skcipher_request_ctx(req);
164 struct skcipher_request *subreq = &rctx->subreq;
165
166 init_crypt(req);
167 return xor_tweak_pre(req) ?:
168 crypto_skcipher_encrypt(subreq) ?:
169 xor_tweak_post(req);
170}
171
172static int decrypt(struct skcipher_request *req)
173{
174 struct rctx *rctx = skcipher_request_ctx(req);
175 struct skcipher_request *subreq = &rctx->subreq;
176
177 init_crypt(req);
178 return xor_tweak_pre(req) ?:
179 crypto_skcipher_decrypt(subreq) ?:
180 xor_tweak_post(req);
181}
182
183static int init_tfm(struct crypto_skcipher *tfm)
184{
185 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
186 struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
187 struct priv *ctx = crypto_skcipher_ctx(tfm);
188 struct crypto_skcipher *child;
189 struct crypto_cipher *tweak;
190
191 child = crypto_spawn_skcipher(&ictx->spawn);
192 if (IS_ERR(child))
193 return PTR_ERR(child);
194
195 ctx->child = child;
196
197 tweak = crypto_alloc_cipher(ictx->name, 0, 0);
198 if (IS_ERR(tweak)) {
199 crypto_free_skcipher(ctx->child);
200 return PTR_ERR(tweak);
201 }
202
203 ctx->tweak = tweak;
204
205 crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
206 sizeof(struct rctx));
207
208 return 0;
209}
210
211static void exit_tfm(struct crypto_skcipher *tfm)
212{
213 struct priv *ctx = crypto_skcipher_ctx(tfm);
214
215 crypto_free_skcipher(ctx->child);
216 crypto_free_cipher(ctx->tweak);
217}
218
219static void free(struct skcipher_instance *inst)
220{
221 crypto_drop_skcipher(skcipher_instance_ctx(inst));
222 kfree(inst);
223}
224
225static int create(struct crypto_template *tmpl, struct rtattr **tb)
226{
227 struct skcipher_instance *inst;
228 struct crypto_attr_type *algt;
229 struct xts_instance_ctx *ctx;
230 struct skcipher_alg *alg;
231 const char *cipher_name;
232 u32 mask;
233 int err;
234
235 algt = crypto_get_attr_type(tb);
236 if (IS_ERR(algt))
237 return PTR_ERR(algt);
238
239 if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
240 return -EINVAL;
241
242 cipher_name = crypto_attr_alg_name(tb[1]);
243 if (IS_ERR(cipher_name))
244 return PTR_ERR(cipher_name);
245
246 inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
247 if (!inst)
248 return -ENOMEM;
249
250 ctx = skcipher_instance_ctx(inst);
251
252 crypto_set_skcipher_spawn(&ctx->spawn, skcipher_crypto_instance(inst));
253
254 mask = crypto_requires_off(algt->type, algt->mask,
255 CRYPTO_ALG_NEED_FALLBACK |
256 CRYPTO_ALG_ASYNC);
257
258 err = crypto_grab_skcipher(&ctx->spawn, cipher_name, 0, mask);
259 if (err == -ENOENT) {
260 err = -ENAMETOOLONG;
261 if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
262 cipher_name) >= CRYPTO_MAX_ALG_NAME)
263 goto err_free_inst;
264
265 err = crypto_grab_skcipher(&ctx->spawn, ctx->name, 0, mask);
266 }
267
268 if (err)
269 goto err_free_inst;
270
271 alg = crypto_skcipher_spawn_alg(&ctx->spawn);
272
273 err = -EINVAL;
274 if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
275 goto err_drop_spawn;
276
277 if (crypto_skcipher_alg_ivsize(alg))
278 goto err_drop_spawn;
279
280 err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
281 &alg->base);
282 if (err)
283 goto err_drop_spawn;
284
285 err = -EINVAL;
286 cipher_name = alg->base.cra_name;
287
288 /* Alas we screwed up the naming so we have to mangle the
289 * cipher name.
290 */
291 if (!strncmp(cipher_name, "ecb(", 4)) {
292 unsigned len;
293
294 len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
295 if (len < 2 || len >= sizeof(ctx->name))
296 goto err_drop_spawn;
297
298 if (ctx->name[len - 1] != ')')
299 goto err_drop_spawn;
300
301 ctx->name[len - 1] = 0;
302
303 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
304 "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) {
305 err = -ENAMETOOLONG;
306 goto err_drop_spawn;
307 }
308 } else
309 goto err_drop_spawn;
310
311 inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
312 inst->alg.base.cra_priority = alg->base.cra_priority;
313 inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
314 inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
315 (__alignof__(u64) - 1);
316
317 inst->alg.ivsize = XTS_BLOCK_SIZE;
318 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
319 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
320
321 inst->alg.base.cra_ctxsize = sizeof(struct priv);
322
323 inst->alg.init = init_tfm;
324 inst->alg.exit = exit_tfm;
325
326 inst->alg.setkey = setkey;
327 inst->alg.encrypt = encrypt;
328 inst->alg.decrypt = decrypt;
329
330 inst->free = free;
331
332 err = skcipher_register_instance(tmpl, inst);
333 if (err)
334 goto err_drop_spawn;
335
336out:
337 return err;
338
339err_drop_spawn:
340 crypto_drop_skcipher(&ctx->spawn);
341err_free_inst:
342 kfree(inst);
343 goto out;
344}
345
346static struct crypto_template crypto_tmpl = {
347 .name = "xts",
348 .create = create,
349 .module = THIS_MODULE,
350};
351
352static int __init crypto_module_init(void)
353{
354 return crypto_register_template(&crypto_tmpl);
355}
356
357static void __exit crypto_module_exit(void)
358{
359 crypto_unregister_template(&crypto_tmpl);
360}
361
362module_init(crypto_module_init);
363module_exit(crypto_module_exit);
364
365MODULE_LICENSE("GPL");
366MODULE_DESCRIPTION("XTS block cipher mode");
367MODULE_ALIAS_CRYPTO("xts");
368