blob: 51976187b2bf81516f2c64b388387484714037d2
1 | /* |
2 | * CTS: Cipher Text Stealing mode |
3 | * |
4 | * COPYRIGHT (c) 2008 |
5 | * The Regents of the University of Michigan |
6 | * ALL RIGHTS RESERVED |
7 | * |
8 | * Permission is granted to use, copy, create derivative works |
9 | * and redistribute this software and such derivative works |
10 | * for any purpose, so long as the name of The University of |
11 | * Michigan is not used in any advertising or publicity |
12 | * pertaining to the use of distribution of this software |
13 | * without specific, written prior authorization. If the |
14 | * above copyright notice or any other identification of the |
15 | * University of Michigan is included in any copy of any |
16 | * portion of this software, then the disclaimer below must |
17 | * also be included. |
18 | * |
19 | * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION |
20 | * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY |
21 | * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF |
22 | * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING |
23 | * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF |
24 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE |
25 | * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE |
26 | * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR |
27 | * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING |
28 | * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN |
29 | * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF |
30 | * SUCH DAMAGES. |
31 | */ |
32 | |
33 | /* Derived from various: |
34 | * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au> |
35 | */ |
36 | |
37 | /* |
38 | * This is the Cipher Text Stealing mode as described by |
39 | * Section 8 of rfc2040 and referenced by rfc3962. |
40 | * rfc3962 includes errata information in its Appendix A. |
41 | */ |
42 | |
43 | #include <crypto/internal/skcipher.h> |
44 | #include <linux/err.h> |
45 | #include <linux/init.h> |
46 | #include <linux/kernel.h> |
47 | #include <linux/log2.h> |
48 | #include <linux/module.h> |
49 | #include <linux/scatterlist.h> |
50 | #include <crypto/scatterwalk.h> |
51 | #include <linux/slab.h> |
52 | |
53 | struct crypto_cts_ctx { |
54 | struct crypto_skcipher *child; |
55 | }; |
56 | |
57 | struct crypto_cts_reqctx { |
58 | struct scatterlist sg[2]; |
59 | unsigned offset; |
60 | struct skcipher_request subreq; |
61 | }; |
62 | |
63 | static inline u8 *crypto_cts_reqctx_space(struct skcipher_request *req) |
64 | { |
65 | struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
66 | struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
67 | struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
68 | struct crypto_skcipher *child = ctx->child; |
69 | |
70 | return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child), |
71 | crypto_skcipher_alignmask(tfm) + 1); |
72 | } |
73 | |
74 | static int crypto_cts_setkey(struct crypto_skcipher *parent, const u8 *key, |
75 | unsigned int keylen) |
76 | { |
77 | struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent); |
78 | struct crypto_skcipher *child = ctx->child; |
79 | int err; |
80 | |
81 | crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); |
82 | crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) & |
83 | CRYPTO_TFM_REQ_MASK); |
84 | err = crypto_skcipher_setkey(child, key, keylen); |
85 | crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) & |
86 | CRYPTO_TFM_RES_MASK); |
87 | return err; |
88 | } |
89 | |
90 | static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err) |
91 | { |
92 | struct skcipher_request *req = areq->data; |
93 | |
94 | if (err == -EINPROGRESS) |
95 | return; |
96 | |
97 | skcipher_request_complete(req, err); |
98 | } |
99 | |
100 | static int cts_cbc_encrypt(struct skcipher_request *req) |
101 | { |
102 | struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
103 | struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
104 | struct skcipher_request *subreq = &rctx->subreq; |
105 | int bsize = crypto_skcipher_blocksize(tfm); |
106 | u8 d[bsize * 2] __attribute__ ((aligned(__alignof__(u32)))); |
107 | struct scatterlist *sg; |
108 | unsigned int offset; |
109 | int lastn; |
110 | |
111 | offset = rctx->offset; |
112 | lastn = req->cryptlen - offset; |
113 | |
114 | sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize); |
115 | scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0); |
116 | |
117 | memset(d, 0, bsize); |
118 | scatterwalk_map_and_copy(d, req->src, offset, lastn, 0); |
119 | |
120 | scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1); |
121 | memzero_explicit(d, sizeof(d)); |
122 | |
123 | skcipher_request_set_callback(subreq, req->base.flags & |
124 | CRYPTO_TFM_REQ_MAY_BACKLOG, |
125 | cts_cbc_crypt_done, req); |
126 | skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv); |
127 | return crypto_skcipher_encrypt(subreq); |
128 | } |
129 | |
130 | static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err) |
131 | { |
132 | struct skcipher_request *req = areq->data; |
133 | |
134 | if (err) |
135 | goto out; |
136 | |
137 | err = cts_cbc_encrypt(req); |
138 | if (err == -EINPROGRESS || |
139 | (err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG)) |
140 | return; |
141 | |
142 | out: |
143 | skcipher_request_complete(req, err); |
144 | } |
145 | |
146 | static int crypto_cts_encrypt(struct skcipher_request *req) |
147 | { |
148 | struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
149 | struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
150 | struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
151 | struct skcipher_request *subreq = &rctx->subreq; |
152 | int bsize = crypto_skcipher_blocksize(tfm); |
153 | unsigned int nbytes = req->cryptlen; |
154 | int cbc_blocks = (nbytes + bsize - 1) / bsize - 1; |
155 | unsigned int offset; |
156 | |
157 | skcipher_request_set_tfm(subreq, ctx->child); |
158 | |
159 | if (cbc_blocks <= 0) { |
160 | skcipher_request_set_callback(subreq, req->base.flags, |
161 | req->base.complete, |
162 | req->base.data); |
163 | skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes, |
164 | req->iv); |
165 | return crypto_skcipher_encrypt(subreq); |
166 | } |
167 | |
168 | offset = cbc_blocks * bsize; |
169 | rctx->offset = offset; |
170 | |
171 | skcipher_request_set_callback(subreq, req->base.flags, |
172 | crypto_cts_encrypt_done, req); |
173 | skcipher_request_set_crypt(subreq, req->src, req->dst, |
174 | offset, req->iv); |
175 | |
176 | return crypto_skcipher_encrypt(subreq) ?: |
177 | cts_cbc_encrypt(req); |
178 | } |
179 | |
180 | static int cts_cbc_decrypt(struct skcipher_request *req) |
181 | { |
182 | struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
183 | struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
184 | struct skcipher_request *subreq = &rctx->subreq; |
185 | int bsize = crypto_skcipher_blocksize(tfm); |
186 | u8 d[bsize * 2] __attribute__ ((aligned(__alignof__(u32)))); |
187 | struct scatterlist *sg; |
188 | unsigned int offset; |
189 | u8 *space; |
190 | int lastn; |
191 | |
192 | offset = rctx->offset; |
193 | lastn = req->cryptlen - offset; |
194 | |
195 | sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize); |
196 | |
197 | /* 1. Decrypt Cn-1 (s) to create Dn */ |
198 | scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0); |
199 | space = crypto_cts_reqctx_space(req); |
200 | crypto_xor(d + bsize, space, bsize); |
201 | /* 2. Pad Cn with zeros at the end to create C of length BB */ |
202 | memset(d, 0, bsize); |
203 | scatterwalk_map_and_copy(d, req->src, offset, lastn, 0); |
204 | /* 3. Exclusive-or Dn with C to create Xn */ |
205 | /* 4. Select the first Ln bytes of Xn to create Pn */ |
206 | crypto_xor(d + bsize, d, lastn); |
207 | |
208 | /* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */ |
209 | memcpy(d + lastn, d + bsize + lastn, bsize - lastn); |
210 | /* 6. Decrypt En to create Pn-1 */ |
211 | |
212 | scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1); |
213 | memzero_explicit(d, sizeof(d)); |
214 | |
215 | skcipher_request_set_callback(subreq, req->base.flags & |
216 | CRYPTO_TFM_REQ_MAY_BACKLOG, |
217 | cts_cbc_crypt_done, req); |
218 | |
219 | skcipher_request_set_crypt(subreq, sg, sg, bsize, space); |
220 | return crypto_skcipher_decrypt(subreq); |
221 | } |
222 | |
223 | static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err) |
224 | { |
225 | struct skcipher_request *req = areq->data; |
226 | |
227 | if (err) |
228 | goto out; |
229 | |
230 | err = cts_cbc_decrypt(req); |
231 | if (err == -EINPROGRESS || |
232 | (err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG)) |
233 | return; |
234 | |
235 | out: |
236 | skcipher_request_complete(req, err); |
237 | } |
238 | |
239 | static int crypto_cts_decrypt(struct skcipher_request *req) |
240 | { |
241 | struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
242 | struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
243 | struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
244 | struct skcipher_request *subreq = &rctx->subreq; |
245 | int bsize = crypto_skcipher_blocksize(tfm); |
246 | unsigned int nbytes = req->cryptlen; |
247 | int cbc_blocks = (nbytes + bsize - 1) / bsize - 1; |
248 | unsigned int offset; |
249 | u8 *space; |
250 | |
251 | skcipher_request_set_tfm(subreq, ctx->child); |
252 | |
253 | if (cbc_blocks <= 0) { |
254 | skcipher_request_set_callback(subreq, req->base.flags, |
255 | req->base.complete, |
256 | req->base.data); |
257 | skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes, |
258 | req->iv); |
259 | return crypto_skcipher_decrypt(subreq); |
260 | } |
261 | |
262 | skcipher_request_set_callback(subreq, req->base.flags, |
263 | crypto_cts_decrypt_done, req); |
264 | |
265 | space = crypto_cts_reqctx_space(req); |
266 | |
267 | offset = cbc_blocks * bsize; |
268 | rctx->offset = offset; |
269 | |
270 | if (cbc_blocks <= 1) |
271 | memcpy(space, req->iv, bsize); |
272 | else |
273 | scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize, |
274 | bsize, 0); |
275 | |
276 | skcipher_request_set_crypt(subreq, req->src, req->dst, |
277 | offset, req->iv); |
278 | |
279 | return crypto_skcipher_decrypt(subreq) ?: |
280 | cts_cbc_decrypt(req); |
281 | } |
282 | |
283 | static int crypto_cts_init_tfm(struct crypto_skcipher *tfm) |
284 | { |
285 | struct skcipher_instance *inst = skcipher_alg_instance(tfm); |
286 | struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst); |
287 | struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
288 | struct crypto_skcipher *cipher; |
289 | unsigned reqsize; |
290 | unsigned bsize; |
291 | unsigned align; |
292 | |
293 | cipher = crypto_spawn_skcipher2(spawn); |
294 | if (IS_ERR(cipher)) |
295 | return PTR_ERR(cipher); |
296 | |
297 | ctx->child = cipher; |
298 | |
299 | align = crypto_skcipher_alignmask(tfm); |
300 | bsize = crypto_skcipher_blocksize(cipher); |
301 | reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) + |
302 | crypto_skcipher_reqsize(cipher), |
303 | crypto_tfm_ctx_alignment()) + |
304 | (align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize; |
305 | |
306 | crypto_skcipher_set_reqsize(tfm, reqsize); |
307 | |
308 | return 0; |
309 | } |
310 | |
311 | static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm) |
312 | { |
313 | struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
314 | |
315 | crypto_free_skcipher(ctx->child); |
316 | } |
317 | |
318 | static void crypto_cts_free(struct skcipher_instance *inst) |
319 | { |
320 | crypto_drop_skcipher(skcipher_instance_ctx(inst)); |
321 | kfree(inst); |
322 | } |
323 | |
324 | static int crypto_cts_create(struct crypto_template *tmpl, struct rtattr **tb) |
325 | { |
326 | struct crypto_skcipher_spawn *spawn; |
327 | struct skcipher_instance *inst; |
328 | struct crypto_attr_type *algt; |
329 | struct skcipher_alg *alg; |
330 | const char *cipher_name; |
331 | int err; |
332 | |
333 | algt = crypto_get_attr_type(tb); |
334 | if (IS_ERR(algt)) |
335 | return PTR_ERR(algt); |
336 | |
337 | if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask) |
338 | return -EINVAL; |
339 | |
340 | cipher_name = crypto_attr_alg_name(tb[1]); |
341 | if (IS_ERR(cipher_name)) |
342 | return PTR_ERR(cipher_name); |
343 | |
344 | inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL); |
345 | if (!inst) |
346 | return -ENOMEM; |
347 | |
348 | spawn = skcipher_instance_ctx(inst); |
349 | |
350 | crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst)); |
351 | err = crypto_grab_skcipher2(spawn, cipher_name, 0, |
352 | crypto_requires_sync(algt->type, |
353 | algt->mask)); |
354 | if (err) |
355 | goto err_free_inst; |
356 | |
357 | alg = crypto_spawn_skcipher_alg(spawn); |
358 | |
359 | err = -EINVAL; |
360 | if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize) |
361 | goto err_drop_spawn; |
362 | |
363 | if (strncmp(alg->base.cra_name, "cbc(", 4)) |
364 | goto err_drop_spawn; |
365 | |
366 | err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts", |
367 | &alg->base); |
368 | if (err) |
369 | goto err_drop_spawn; |
370 | |
371 | inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC; |
372 | inst->alg.base.cra_priority = alg->base.cra_priority; |
373 | inst->alg.base.cra_blocksize = alg->base.cra_blocksize; |
374 | inst->alg.base.cra_alignmask = alg->base.cra_alignmask; |
375 | |
376 | /* We access the data as u32s when xoring. */ |
377 | inst->alg.base.cra_alignmask |= __alignof__(u32) - 1; |
378 | |
379 | inst->alg.ivsize = alg->base.cra_blocksize; |
380 | inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg); |
381 | inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg); |
382 | inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg); |
383 | |
384 | inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx); |
385 | |
386 | inst->alg.init = crypto_cts_init_tfm; |
387 | inst->alg.exit = crypto_cts_exit_tfm; |
388 | |
389 | inst->alg.setkey = crypto_cts_setkey; |
390 | inst->alg.encrypt = crypto_cts_encrypt; |
391 | inst->alg.decrypt = crypto_cts_decrypt; |
392 | |
393 | inst->free = crypto_cts_free; |
394 | |
395 | err = skcipher_register_instance(tmpl, inst); |
396 | if (err) |
397 | goto err_drop_spawn; |
398 | |
399 | out: |
400 | return err; |
401 | |
402 | err_drop_spawn: |
403 | crypto_drop_skcipher(spawn); |
404 | err_free_inst: |
405 | kfree(inst); |
406 | goto out; |
407 | } |
408 | |
409 | static struct crypto_template crypto_cts_tmpl = { |
410 | .name = "cts", |
411 | .create = crypto_cts_create, |
412 | .module = THIS_MODULE, |
413 | }; |
414 | |
415 | static int __init crypto_cts_module_init(void) |
416 | { |
417 | return crypto_register_template(&crypto_cts_tmpl); |
418 | } |
419 | |
420 | static void __exit crypto_cts_module_exit(void) |
421 | { |
422 | crypto_unregister_template(&crypto_cts_tmpl); |
423 | } |
424 | |
425 | module_init(crypto_cts_module_init); |
426 | module_exit(crypto_cts_module_exit); |
427 | |
428 | MODULE_LICENSE("Dual BSD/GPL"); |
429 | MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC"); |
430 | MODULE_ALIAS_CRYPTO("cts"); |
431 |