blob: 4773c188e6d9281fe7cc2dc7c1ba569e2d500f8b [file] [log] [blame]
Kevin Coffman76cb9522008-03-24 21:26:16 +08001/*
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
Herbert Xu0605c412016-07-12 13:17:48 +080043#include <crypto/internal/skcipher.h>
Kevin Coffman76cb9522008-03-24 21:26:16 +080044#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>
Gideon Israel Dsouzad8c34b92016-12-31 21:26:23 +053052#include <linux/compiler.h>
Kevin Coffman76cb9522008-03-24 21:26:16 +080053
54struct crypto_cts_ctx {
Herbert Xu0605c412016-07-12 13:17:48 +080055 struct crypto_skcipher *child;
Kevin Coffman76cb9522008-03-24 21:26:16 +080056};
57
Herbert Xu0605c412016-07-12 13:17:48 +080058struct crypto_cts_reqctx {
59 struct scatterlist sg[2];
60 unsigned offset;
61 struct skcipher_request subreq;
62};
63
64static inline u8 *crypto_cts_reqctx_space(struct skcipher_request *req)
65{
66 struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
67 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
68 struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
69 struct crypto_skcipher *child = ctx->child;
70
71 return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),
72 crypto_skcipher_alignmask(tfm) + 1);
73}
74
75static int crypto_cts_setkey(struct crypto_skcipher *parent, const u8 *key,
Kevin Coffman76cb9522008-03-24 21:26:16 +080076 unsigned int keylen)
77{
Herbert Xu0605c412016-07-12 13:17:48 +080078 struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent);
79 struct crypto_skcipher *child = ctx->child;
Kevin Coffman76cb9522008-03-24 21:26:16 +080080 int err;
81
Herbert Xu0605c412016-07-12 13:17:48 +080082 crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
83 crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
84 CRYPTO_TFM_REQ_MASK);
85 err = crypto_skcipher_setkey(child, key, keylen);
86 crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
87 CRYPTO_TFM_RES_MASK);
Kevin Coffman76cb9522008-03-24 21:26:16 +080088 return err;
89}
90
Herbert Xu0605c412016-07-12 13:17:48 +080091static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
Kevin Coffman76cb9522008-03-24 21:26:16 +080092{
Herbert Xu0605c412016-07-12 13:17:48 +080093 struct skcipher_request *req = areq->data;
Kevin Coffman76cb9522008-03-24 21:26:16 +080094
Herbert Xu0605c412016-07-12 13:17:48 +080095 if (err == -EINPROGRESS)
96 return;
Kevin Coffman76cb9522008-03-24 21:26:16 +080097
Herbert Xu0605c412016-07-12 13:17:48 +080098 skcipher_request_complete(req, err);
Kevin Coffman76cb9522008-03-24 21:26:16 +080099}
100
Herbert Xu0605c412016-07-12 13:17:48 +0800101static int cts_cbc_encrypt(struct skcipher_request *req)
Kevin Coffman76cb9522008-03-24 21:26:16 +0800102{
Herbert Xu0605c412016-07-12 13:17:48 +0800103 struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
104 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
105 struct skcipher_request *subreq = &rctx->subreq;
106 int bsize = crypto_skcipher_blocksize(tfm);
Gideon Israel Dsouzad8c34b92016-12-31 21:26:23 +0530107 u8 d[bsize * 2] __aligned(__alignof__(u32));
Herbert Xu0605c412016-07-12 13:17:48 +0800108 struct scatterlist *sg;
109 unsigned int offset;
110 int lastn;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800111
Herbert Xu0605c412016-07-12 13:17:48 +0800112 offset = rctx->offset;
113 lastn = req->cryptlen - offset;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800114
Herbert Xu0605c412016-07-12 13:17:48 +0800115 sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
116 scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800117
Herbert Xu0605c412016-07-12 13:17:48 +0800118 memset(d, 0, bsize);
119 scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
120
121 scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
122 memzero_explicit(d, sizeof(d));
123
124 skcipher_request_set_callback(subreq, req->base.flags &
125 CRYPTO_TFM_REQ_MAY_BACKLOG,
126 cts_cbc_crypt_done, req);
127 skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
128 return crypto_skcipher_encrypt(subreq);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800129}
130
Herbert Xu0605c412016-07-12 13:17:48 +0800131static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
Kevin Coffman76cb9522008-03-24 21:26:16 +0800132{
Herbert Xu0605c412016-07-12 13:17:48 +0800133 struct skcipher_request *req = areq->data;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800134
Kevin Coffman76cb9522008-03-24 21:26:16 +0800135 if (err)
Herbert Xu0605c412016-07-12 13:17:48 +0800136 goto out;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800137
Herbert Xu0605c412016-07-12 13:17:48 +0800138 err = cts_cbc_encrypt(req);
Gilad Ben-Yossef4e5b0ad2017-10-18 08:00:36 +0100139 if (err == -EINPROGRESS || err == -EBUSY)
Herbert Xu0605c412016-07-12 13:17:48 +0800140 return;
Daniel Borkmann7185ad22014-09-07 23:23:38 +0200141
Herbert Xu0605c412016-07-12 13:17:48 +0800142out:
143 skcipher_request_complete(req, err);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800144}
145
Herbert Xu0605c412016-07-12 13:17:48 +0800146static int crypto_cts_encrypt(struct skcipher_request *req)
Kevin Coffman76cb9522008-03-24 21:26:16 +0800147{
Herbert Xu0605c412016-07-12 13:17:48 +0800148 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;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800156
Herbert Xu0605c412016-07-12 13:17:48 +0800157 skcipher_request_set_tfm(subreq, ctx->child);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800158
Herbert Xu0605c412016-07-12 13:17:48 +0800159 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);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800166 }
Herbert Xu0605c412016-07-12 13:17:48 +0800167
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);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800178}
179
Herbert Xu0605c412016-07-12 13:17:48 +0800180static int cts_cbc_decrypt(struct skcipher_request *req)
Kevin Coffman76cb9522008-03-24 21:26:16 +0800181{
Herbert Xu0605c412016-07-12 13:17:48 +0800182 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);
Gideon Israel Dsouzad8c34b92016-12-31 21:26:23 +0530186 u8 d[bsize * 2] __aligned(__alignof__(u32));
Herbert Xu0605c412016-07-12 13:17:48 +0800187 struct scatterlist *sg;
188 unsigned int offset;
189 u8 *space;
190 int lastn;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800191
Herbert Xu0605c412016-07-12 13:17:48 +0800192 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
223static 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);
Gilad Ben-Yossef4e5b0ad2017-10-18 08:00:36 +0100231 if (err == -EINPROGRESS || err == -EBUSY)
Herbert Xu0605c412016-07-12 13:17:48 +0800232 return;
233
234out:
235 skcipher_request_complete(req, err);
236}
237
238static int crypto_cts_decrypt(struct skcipher_request *req)
239{
240 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
241 struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
242 struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
243 struct skcipher_request *subreq = &rctx->subreq;
244 int bsize = crypto_skcipher_blocksize(tfm);
245 unsigned int nbytes = req->cryptlen;
246 int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
247 unsigned int offset;
248 u8 *space;
249
250 skcipher_request_set_tfm(subreq, ctx->child);
251
252 if (cbc_blocks <= 0) {
253 skcipher_request_set_callback(subreq, req->base.flags,
254 req->base.complete,
255 req->base.data);
256 skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
257 req->iv);
258 return crypto_skcipher_decrypt(subreq);
259 }
260
261 skcipher_request_set_callback(subreq, req->base.flags,
262 crypto_cts_decrypt_done, req);
263
264 space = crypto_cts_reqctx_space(req);
265
266 offset = cbc_blocks * bsize;
267 rctx->offset = offset;
268
269 if (cbc_blocks <= 1)
270 memcpy(space, req->iv, bsize);
271 else
272 scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
273 bsize, 0);
274
275 skcipher_request_set_crypt(subreq, req->src, req->dst,
276 offset, req->iv);
277
278 return crypto_skcipher_decrypt(subreq) ?:
279 cts_cbc_decrypt(req);
280}
281
282static int crypto_cts_init_tfm(struct crypto_skcipher *tfm)
283{
284 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
285 struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
286 struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
287 struct crypto_skcipher *cipher;
288 unsigned reqsize;
289 unsigned bsize;
290 unsigned align;
291
Eric Biggers60425a82016-10-28 09:52:19 -0700292 cipher = crypto_spawn_skcipher(spawn);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800293 if (IS_ERR(cipher))
294 return PTR_ERR(cipher);
295
296 ctx->child = cipher;
Herbert Xu0605c412016-07-12 13:17:48 +0800297
298 align = crypto_skcipher_alignmask(tfm);
299 bsize = crypto_skcipher_blocksize(cipher);
300 reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +
301 crypto_skcipher_reqsize(cipher),
302 crypto_tfm_ctx_alignment()) +
303 (align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize;
304
305 crypto_skcipher_set_reqsize(tfm, reqsize);
306
Kevin Coffman76cb9522008-03-24 21:26:16 +0800307 return 0;
308}
309
Herbert Xu0605c412016-07-12 13:17:48 +0800310static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm)
Kevin Coffman76cb9522008-03-24 21:26:16 +0800311{
Herbert Xu0605c412016-07-12 13:17:48 +0800312 struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
313
314 crypto_free_skcipher(ctx->child);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800315}
316
Herbert Xu0605c412016-07-12 13:17:48 +0800317static void crypto_cts_free(struct skcipher_instance *inst)
Kevin Coffman76cb9522008-03-24 21:26:16 +0800318{
Herbert Xu0605c412016-07-12 13:17:48 +0800319 crypto_drop_skcipher(skcipher_instance_ctx(inst));
320 kfree(inst);
321}
322
323static int crypto_cts_create(struct crypto_template *tmpl, struct rtattr **tb)
324{
325 struct crypto_skcipher_spawn *spawn;
326 struct skcipher_instance *inst;
327 struct crypto_attr_type *algt;
328 struct skcipher_alg *alg;
329 const char *cipher_name;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800330 int err;
331
Herbert Xu0605c412016-07-12 13:17:48 +0800332 algt = crypto_get_attr_type(tb);
333 if (IS_ERR(algt))
334 return PTR_ERR(algt);
335
336 if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
337 return -EINVAL;
338
339 cipher_name = crypto_attr_alg_name(tb[1]);
340 if (IS_ERR(cipher_name))
341 return PTR_ERR(cipher_name);
342
343 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
344 if (!inst)
345 return -ENOMEM;
346
347 spawn = skcipher_instance_ctx(inst);
348
349 crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
Eric Biggersa35528e2016-10-28 09:51:13 -0700350 err = crypto_grab_skcipher(spawn, cipher_name, 0,
351 crypto_requires_sync(algt->type,
352 algt->mask));
Kevin Coffman76cb9522008-03-24 21:26:16 +0800353 if (err)
Herbert Xu0605c412016-07-12 13:17:48 +0800354 goto err_free_inst;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800355
Herbert Xu0605c412016-07-12 13:17:48 +0800356 alg = crypto_spawn_skcipher_alg(spawn);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800357
Herbert Xu0605c412016-07-12 13:17:48 +0800358 err = -EINVAL;
359 if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
360 goto err_drop_spawn;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800361
Herbert Xu0605c412016-07-12 13:17:48 +0800362 if (strncmp(alg->base.cra_name, "cbc(", 4))
363 goto err_drop_spawn;
Herbert Xu988dc012015-01-16 19:38:17 +1100364
Herbert Xu0605c412016-07-12 13:17:48 +0800365 err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
366 &alg->base);
367 if (err)
368 goto err_drop_spawn;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800369
Herbert Xu0605c412016-07-12 13:17:48 +0800370 inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
371 inst->alg.base.cra_priority = alg->base.cra_priority;
372 inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
373 inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800374
Herbert Xu0605c412016-07-12 13:17:48 +0800375 inst->alg.ivsize = alg->base.cra_blocksize;
376 inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
377 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
378 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800379
Herbert Xu0605c412016-07-12 13:17:48 +0800380 inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx);
Kevin Coffman76cb9522008-03-24 21:26:16 +0800381
Herbert Xu0605c412016-07-12 13:17:48 +0800382 inst->alg.init = crypto_cts_init_tfm;
383 inst->alg.exit = crypto_cts_exit_tfm;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800384
Herbert Xu0605c412016-07-12 13:17:48 +0800385 inst->alg.setkey = crypto_cts_setkey;
386 inst->alg.encrypt = crypto_cts_encrypt;
387 inst->alg.decrypt = crypto_cts_decrypt;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800388
Herbert Xu0605c412016-07-12 13:17:48 +0800389 inst->free = crypto_cts_free;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800390
Herbert Xu0605c412016-07-12 13:17:48 +0800391 err = skcipher_register_instance(tmpl, inst);
392 if (err)
393 goto err_drop_spawn;
394
395out:
396 return err;
397
398err_drop_spawn:
399 crypto_drop_skcipher(spawn);
400err_free_inst:
Kevin Coffman76cb9522008-03-24 21:26:16 +0800401 kfree(inst);
Herbert Xu0605c412016-07-12 13:17:48 +0800402 goto out;
Kevin Coffman76cb9522008-03-24 21:26:16 +0800403}
404
405static struct crypto_template crypto_cts_tmpl = {
406 .name = "cts",
Herbert Xu0605c412016-07-12 13:17:48 +0800407 .create = crypto_cts_create,
Kevin Coffman76cb9522008-03-24 21:26:16 +0800408 .module = THIS_MODULE,
409};
410
411static int __init crypto_cts_module_init(void)
412{
413 return crypto_register_template(&crypto_cts_tmpl);
414}
415
416static void __exit crypto_cts_module_exit(void)
417{
418 crypto_unregister_template(&crypto_cts_tmpl);
419}
420
421module_init(crypto_cts_module_init);
422module_exit(crypto_cts_module_exit);
423
424MODULE_LICENSE("Dual BSD/GPL");
425MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
Kees Cook4943ba12014-11-24 16:32:38 -0800426MODULE_ALIAS_CRYPTO("cts");