1 /* 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
9 * and redistribute this software and such der
10 * for any purpose, so long as the name of The
11 * Michigan is not used in any advertising or
12 * pertaining to the use of distribution of th
13 * without specific, written prior authorizati
14 * above copyright notice or any other identif
15 * University of Michigan is included in any c
16 * portion of this software, then the disclaim
17 * also be included.
18 *
19 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT RE
20 * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS F
21 * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVER
22 * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMP
23 * WITHOUT LIMITATION THE IMPLIED WARRANTIES O
24 * MERCHANTABILITY AND FITNESS FOR A PARTICULA
25 * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL
26 * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIREC
27 * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY
28 * OUT OF OR IN CONNECTION WITH THE USE OF THE
29 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF T
30 * SUCH DAMAGES.
31 */
32
33 /* Derived from various:
34 * Copyright (c) 2006 Herbert Xu <herbert
35 */
36
37 /*
38 * This is the Cipher Text Stealing mode as de
39 * Section 8 of rfc2040 and referenced by rfc3
40 * rfc3962 includes errata information in its
41 */
42
43 #include <crypto/algapi.h>
44 #include <crypto/internal/skcipher.h>
45 #include <linux/err.h>
46 #include <linux/init.h>
47 #include <linux/kernel.h>
48 #include <linux/log2.h>
49 #include <linux/module.h>
50 #include <linux/scatterlist.h>
51 #include <crypto/scatterwalk.h>
52 #include <linux/slab.h>
53 #include <linux/compiler.h>
54
55 struct crypto_cts_ctx {
56 struct crypto_skcipher *child;
57 };
58
59 struct crypto_cts_reqctx {
60 struct scatterlist sg[2];
61 unsigned offset;
62 struct skcipher_request subreq;
63 };
64
65 static inline u8 *crypto_cts_reqctx_space(stru
66 {
67 struct crypto_cts_reqctx *rctx = skcip
68 struct crypto_skcipher *tfm = crypto_s
69 struct crypto_cts_ctx *ctx = crypto_sk
70 struct crypto_skcipher *child = ctx->c
71
72 return PTR_ALIGN((u8 *)(rctx + 1) + cr
73 crypto_skcipher_align
74 }
75
76 static int crypto_cts_setkey(struct crypto_skc
77 unsigned int keyl
78 {
79 struct crypto_cts_ctx *ctx = crypto_sk
80 struct crypto_skcipher *child = ctx->c
81
82 crypto_skcipher_clear_flags(child, CRY
83 crypto_skcipher_set_flags(child, crypt
84 CRYPT
85 return crypto_skcipher_setkey(child, k
86 }
87
88 static void cts_cbc_crypt_done(void *data, int
89 {
90 struct skcipher_request *req = data;
91
92 if (err == -EINPROGRESS)
93 return;
94
95 skcipher_request_complete(req, err);
96 }
97
98 static int cts_cbc_encrypt(struct skcipher_req
99 {
100 struct crypto_cts_reqctx *rctx = skcip
101 struct crypto_skcipher *tfm = crypto_s
102 struct skcipher_request *subreq = &rct
103 int bsize = crypto_skcipher_blocksize(
104 u8 d[MAX_CIPHER_BLOCKSIZE * 2] __align
105 struct scatterlist *sg;
106 unsigned int offset;
107 int lastn;
108
109 offset = rctx->offset;
110 lastn = req->cryptlen - offset;
111
112 sg = scatterwalk_ffwd(rctx->sg, req->d
113 scatterwalk_map_and_copy(d + bsize, sg
114
115 memset(d, 0, bsize);
116 scatterwalk_map_and_copy(d, req->src,
117
118 scatterwalk_map_and_copy(d, sg, 0, bsi
119 memzero_explicit(d, sizeof(d));
120
121 skcipher_request_set_callback(subreq,
122
123 cts_cbc_
124 skcipher_request_set_crypt(subreq, sg,
125 return crypto_skcipher_encrypt(subreq)
126 }
127
128 static void crypto_cts_encrypt_done(void *data
129 {
130 struct skcipher_request *req = data;
131
132 if (err)
133 goto out;
134
135 err = cts_cbc_encrypt(req);
136 if (err == -EINPROGRESS || err == -EBU
137 return;
138
139 out:
140 skcipher_request_complete(req, err);
141 }
142
143 static int crypto_cts_encrypt(struct skcipher_
144 {
145 struct crypto_skcipher *tfm = crypto_s
146 struct crypto_cts_reqctx *rctx = skcip
147 struct crypto_cts_ctx *ctx = crypto_sk
148 struct skcipher_request *subreq = &rct
149 int bsize = crypto_skcipher_blocksize(
150 unsigned int nbytes = req->cryptlen;
151 unsigned int offset;
152
153 skcipher_request_set_tfm(subreq, ctx->
154
155 if (nbytes < bsize)
156 return -EINVAL;
157
158 if (nbytes == bsize) {
159 skcipher_request_set_callback(
160
161
162 skcipher_request_set_crypt(sub
163 req
164 return crypto_skcipher_encrypt
165 }
166
167 offset = rounddown(nbytes - 1, bsize);
168 rctx->offset = offset;
169
170 skcipher_request_set_callback(subreq,
171 crypto_c
172 skcipher_request_set_crypt(subreq, req
173 offset, req
174
175 return crypto_skcipher_encrypt(subreq)
176 cts_cbc_encrypt(req);
177 }
178
179 static int cts_cbc_decrypt(struct skcipher_req
180 {
181 struct crypto_cts_reqctx *rctx = skcip
182 struct crypto_skcipher *tfm = crypto_s
183 struct skcipher_request *subreq = &rct
184 int bsize = crypto_skcipher_blocksize(
185 u8 d[MAX_CIPHER_BLOCKSIZE * 2] __align
186 struct scatterlist *sg;
187 unsigned int offset;
188 u8 *space;
189 int lastn;
190
191 offset = rctx->offset;
192 lastn = req->cryptlen - offset;
193
194 sg = scatterwalk_ffwd(rctx->sg, req->d
195
196 /* 1. Decrypt Cn-1 (s) to create Dn */
197 scatterwalk_map_and_copy(d + bsize, sg
198 space = crypto_cts_reqctx_space(req);
199 crypto_xor(d + bsize, space, bsize);
200 /* 2. Pad Cn with zeros at the end to
201 memset(d, 0, bsize);
202 scatterwalk_map_and_copy(d, req->src,
203 /* 3. Exclusive-or Dn with C to create
204 /* 4. Select the first Ln bytes of Xn
205 crypto_xor(d + bsize, d, lastn);
206
207 /* 5. Append the tail (BB - Ln) bytes
208 memcpy(d + lastn, d + bsize + lastn, b
209 /* 6. Decrypt En to create Pn-1 */
210
211 scatterwalk_map_and_copy(d, sg, 0, bsi
212 memzero_explicit(d, sizeof(d));
213
214 skcipher_request_set_callback(subreq,
215
216 cts_cbc_
217
218 skcipher_request_set_crypt(subreq, sg,
219 return crypto_skcipher_decrypt(subreq)
220 }
221
222 static void crypto_cts_decrypt_done(void *data
223 {
224 struct skcipher_request *req = data;
225
226 if (err)
227 goto out;
228
229 err = cts_cbc_decrypt(req);
230 if (err == -EINPROGRESS || err == -EBU
231 return;
232
233 out:
234 skcipher_request_complete(req, err);
235 }
236
237 static int crypto_cts_decrypt(struct skcipher_
238 {
239 struct crypto_skcipher *tfm = crypto_s
240 struct crypto_cts_reqctx *rctx = skcip
241 struct crypto_cts_ctx *ctx = crypto_sk
242 struct skcipher_request *subreq = &rct
243 int bsize = crypto_skcipher_blocksize(
244 unsigned int nbytes = req->cryptlen;
245 unsigned int offset;
246 u8 *space;
247
248 skcipher_request_set_tfm(subreq, ctx->
249
250 if (nbytes < bsize)
251 return -EINVAL;
252
253 if (nbytes == bsize) {
254 skcipher_request_set_callback(
255
256
257 skcipher_request_set_crypt(sub
258 req
259 return crypto_skcipher_decrypt
260 }
261
262 skcipher_request_set_callback(subreq,
263 crypto_c
264
265 space = crypto_cts_reqctx_space(req);
266
267 offset = rounddown(nbytes - 1, bsize);
268 rctx->offset = offset;
269
270 if (offset <= bsize)
271 memcpy(space, req->iv, bsize);
272 else
273 scatterwalk_map_and_copy(space
274 bsize
275
276 skcipher_request_set_crypt(subreq, req
277 offset, req
278
279 return crypto_skcipher_decrypt(subreq)
280 cts_cbc_decrypt(req);
281 }
282
283 static int crypto_cts_init_tfm(struct crypto_s
284 {
285 struct skcipher_instance *inst = skcip
286 struct crypto_skcipher_spawn *spawn =
287 struct crypto_cts_ctx *ctx = crypto_sk
288 struct crypto_skcipher *cipher;
289 unsigned reqsize;
290 unsigned bsize;
291 unsigned align;
292
293 cipher = crypto_spawn_skcipher(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(ciph
301 reqsize = ALIGN(sizeof(struct crypto_c
302 crypto_skcipher_reqsiz
303 crypto_tfm_ctx_alignme
304 (align & ~(crypto_tfm_ctx_al
305
306 crypto_skcipher_set_reqsize(tfm, reqsi
307
308 return 0;
309 }
310
311 static void crypto_cts_exit_tfm(struct crypto_
312 {
313 struct crypto_cts_ctx *ctx = crypto_sk
314
315 crypto_free_skcipher(ctx->child);
316 }
317
318 static void crypto_cts_free(struct skcipher_in
319 {
320 crypto_drop_skcipher(skcipher_instance
321 kfree(inst);
322 }
323
324 static int crypto_cts_create(struct crypto_tem
325 {
326 struct crypto_skcipher_spawn *spawn;
327 struct skcipher_alg_common *alg;
328 struct skcipher_instance *inst;
329 u32 mask;
330 int err;
331
332 err = crypto_check_attr_type(tb, CRYPT
333 if (err)
334 return err;
335
336 inst = kzalloc(sizeof(*inst) + sizeof(
337 if (!inst)
338 return -ENOMEM;
339
340 spawn = skcipher_instance_ctx(inst);
341
342 err = crypto_grab_skcipher(spawn, skci
343 crypto_attr
344 if (err)
345 goto err_free_inst;
346
347 alg = crypto_spawn_skcipher_alg_common
348
349 err = -EINVAL;
350 if (alg->ivsize != alg->base.cra_block
351 goto err_free_inst;
352
353 if (strncmp(alg->base.cra_name, "cbc("
354 goto err_free_inst;
355
356 err = crypto_inst_setname(skcipher_cry
357 &alg->base);
358 if (err)
359 goto err_free_inst;
360
361 inst->alg.base.cra_priority = alg->bas
362 inst->alg.base.cra_blocksize = alg->ba
363 inst->alg.base.cra_alignmask = alg->ba
364
365 inst->alg.ivsize = alg->base.cra_block
366 inst->alg.chunksize = alg->chunksize;
367 inst->alg.min_keysize = alg->min_keysi
368 inst->alg.max_keysize = alg->max_keysi
369
370 inst->alg.base.cra_ctxsize = sizeof(st
371
372 inst->alg.init = crypto_cts_init_tfm;
373 inst->alg.exit = crypto_cts_exit_tfm;
374
375 inst->alg.setkey = crypto_cts_setkey;
376 inst->alg.encrypt = crypto_cts_encrypt
377 inst->alg.decrypt = crypto_cts_decrypt
378
379 inst->free = crypto_cts_free;
380
381 err = skcipher_register_instance(tmpl,
382 if (err) {
383 err_free_inst:
384 crypto_cts_free(inst);
385 }
386 return err;
387 }
388
389 static struct crypto_template crypto_cts_tmpl
390 .name = "cts",
391 .create = crypto_cts_create,
392 .module = THIS_MODULE,
393 };
394
395 static int __init crypto_cts_module_init(void)
396 {
397 return crypto_register_template(&crypt
398 }
399
400 static void __exit crypto_cts_module_exit(void
401 {
402 crypto_unregister_template(&crypto_cts
403 }
404
405 subsys_initcall(crypto_cts_module_init);
406 module_exit(crypto_cts_module_exit);
407
408 MODULE_LICENSE("Dual BSD/GPL");
409 MODULE_DESCRIPTION("CTS-CBC CipherText Stealin
410 MODULE_ALIAS_CRYPTO("cts");
411
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