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TOMOYO Linux Cross Reference
Linux/crypto/cts.c

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  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/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(struct skcipher_request *req)
 66 {
 67         struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
 68         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 69         struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
 70         struct crypto_skcipher *child = ctx->child;
 71 
 72         return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),
 73                          crypto_skcipher_alignmask(tfm) + 1);
 74 }
 75 
 76 static int crypto_cts_setkey(struct crypto_skcipher *parent, const u8 *key,
 77                              unsigned int keylen)
 78 {
 79         struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent);
 80         struct crypto_skcipher *child = ctx->child;
 81         int err;
 82 
 83         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 84         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
 85                                          CRYPTO_TFM_REQ_MASK);
 86         err = crypto_skcipher_setkey(child, key, keylen);
 87         crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
 88                                           CRYPTO_TFM_RES_MASK);
 89         return err;
 90 }
 91 
 92 static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
 93 {
 94         struct skcipher_request *req = areq->data;
 95 
 96         if (err == -EINPROGRESS)
 97                 return;
 98 
 99         skcipher_request_complete(req, err);
100 }
101 
102 static int cts_cbc_encrypt(struct skcipher_request *req)
103 {
104         struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
105         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
106         struct skcipher_request *subreq = &rctx->subreq;
107         int bsize = crypto_skcipher_blocksize(tfm);
108         u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32));
109         struct scatterlist *sg;
110         unsigned int offset;
111         int lastn;
112 
113         offset = rctx->offset;
114         lastn = req->cryptlen - offset;
115 
116         sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
117         scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
118 
119         memset(d, 0, bsize);
120         scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
121 
122         scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
123         memzero_explicit(d, sizeof(d));
124 
125         skcipher_request_set_callback(subreq, req->base.flags &
126                                               CRYPTO_TFM_REQ_MAY_BACKLOG,
127                                       cts_cbc_crypt_done, req);
128         skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
129         return crypto_skcipher_encrypt(subreq);
130 }
131 
132 static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
133 {
134         struct skcipher_request *req = areq->data;
135 
136         if (err)
137                 goto out;
138 
139         err = cts_cbc_encrypt(req);
140         if (err == -EINPROGRESS || err == -EBUSY)
141                 return;
142 
143 out:
144         skcipher_request_complete(req, err);
145 }
146 
147 static int crypto_cts_encrypt(struct skcipher_request *req)
148 {
149         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
150         struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
151         struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
152         struct skcipher_request *subreq = &rctx->subreq;
153         int bsize = crypto_skcipher_blocksize(tfm);
154         unsigned int nbytes = req->cryptlen;
155         unsigned int offset;
156 
157         skcipher_request_set_tfm(subreq, ctx->child);
158 
159         if (nbytes < bsize)
160                 return -EINVAL;
161 
162         if (nbytes == bsize) {
163                 skcipher_request_set_callback(subreq, req->base.flags,
164                                               req->base.complete,
165                                               req->base.data);
166                 skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
167                                            req->iv);
168                 return crypto_skcipher_encrypt(subreq);
169         }
170 
171         offset = rounddown(nbytes - 1, bsize);
172         rctx->offset = offset;
173 
174         skcipher_request_set_callback(subreq, req->base.flags,
175                                       crypto_cts_encrypt_done, req);
176         skcipher_request_set_crypt(subreq, req->src, req->dst,
177                                    offset, req->iv);
178 
179         return crypto_skcipher_encrypt(subreq) ?:
180                cts_cbc_encrypt(req);
181 }
182 
183 static int cts_cbc_decrypt(struct skcipher_request *req)
184 {
185         struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
186         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
187         struct skcipher_request *subreq = &rctx->subreq;
188         int bsize = crypto_skcipher_blocksize(tfm);
189         u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32));
190         struct scatterlist *sg;
191         unsigned int offset;
192         u8 *space;
193         int lastn;
194 
195         offset = rctx->offset;
196         lastn = req->cryptlen - offset;
197 
198         sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
199 
200         /* 1. Decrypt Cn-1 (s) to create Dn */
201         scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
202         space = crypto_cts_reqctx_space(req);
203         crypto_xor(d + bsize, space, bsize);
204         /* 2. Pad Cn with zeros at the end to create C of length BB */
205         memset(d, 0, bsize);
206         scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
207         /* 3. Exclusive-or Dn with C to create Xn */
208         /* 4. Select the first Ln bytes of Xn to create Pn */
209         crypto_xor(d + bsize, d, lastn);
210 
211         /* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */
212         memcpy(d + lastn, d + bsize + lastn, bsize - lastn);
213         /* 6. Decrypt En to create Pn-1 */
214 
215         scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
216         memzero_explicit(d, sizeof(d));
217 
218         skcipher_request_set_callback(subreq, req->base.flags &
219                                               CRYPTO_TFM_REQ_MAY_BACKLOG,
220                                       cts_cbc_crypt_done, req);
221 
222         skcipher_request_set_crypt(subreq, sg, sg, bsize, space);
223         return crypto_skcipher_decrypt(subreq);
224 }
225 
226 static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err)
227 {
228         struct skcipher_request *req = areq->data;
229 
230         if (err)
231                 goto out;
232 
233         err = cts_cbc_decrypt(req);
234         if (err == -EINPROGRESS || err == -EBUSY)
235                 return;
236 
237 out:
238         skcipher_request_complete(req, err);
239 }
240 
241 static int crypto_cts_decrypt(struct skcipher_request *req)
242 {
243         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
244         struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
245         struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
246         struct skcipher_request *subreq = &rctx->subreq;
247         int bsize = crypto_skcipher_blocksize(tfm);
248         unsigned int nbytes = req->cryptlen;
249         unsigned int offset;
250         u8 *space;
251 
252         skcipher_request_set_tfm(subreq, ctx->child);
253 
254         if (nbytes < bsize)
255                 return -EINVAL;
256 
257         if (nbytes == bsize) {
258                 skcipher_request_set_callback(subreq, req->base.flags,
259                                               req->base.complete,
260                                               req->base.data);
261                 skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
262                                            req->iv);
263                 return crypto_skcipher_decrypt(subreq);
264         }
265 
266         skcipher_request_set_callback(subreq, req->base.flags,
267                                       crypto_cts_decrypt_done, req);
268 
269         space = crypto_cts_reqctx_space(req);
270 
271         offset = rounddown(nbytes - 1, bsize);
272         rctx->offset = offset;
273 
274         if (offset <= bsize)
275                 memcpy(space, req->iv, bsize);
276         else
277                 scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
278                                          bsize, 0);
279 
280         skcipher_request_set_crypt(subreq, req->src, req->dst,
281                                    offset, req->iv);
282 
283         return crypto_skcipher_decrypt(subreq) ?:
284                cts_cbc_decrypt(req);
285 }
286 
287 static int crypto_cts_init_tfm(struct crypto_skcipher *tfm)
288 {
289         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
290         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
291         struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
292         struct crypto_skcipher *cipher;
293         unsigned reqsize;
294         unsigned bsize;
295         unsigned align;
296 
297         cipher = crypto_spawn_skcipher(spawn);
298         if (IS_ERR(cipher))
299                 return PTR_ERR(cipher);
300 
301         ctx->child = cipher;
302 
303         align = crypto_skcipher_alignmask(tfm);
304         bsize = crypto_skcipher_blocksize(cipher);
305         reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +
306                         crypto_skcipher_reqsize(cipher),
307                         crypto_tfm_ctx_alignment()) +
308                   (align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize;
309 
310         crypto_skcipher_set_reqsize(tfm, reqsize);
311 
312         return 0;
313 }
314 
315 static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm)
316 {
317         struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
318 
319         crypto_free_skcipher(ctx->child);
320 }
321 
322 static void crypto_cts_free(struct skcipher_instance *inst)
323 {
324         crypto_drop_skcipher(skcipher_instance_ctx(inst));
325         kfree(inst);
326 }
327 
328 static int crypto_cts_create(struct crypto_template *tmpl, struct rtattr **tb)
329 {
330         struct crypto_skcipher_spawn *spawn;
331         struct skcipher_instance *inst;
332         struct crypto_attr_type *algt;
333         struct skcipher_alg *alg;
334         const char *cipher_name;
335         int err;
336 
337         algt = crypto_get_attr_type(tb);
338         if (IS_ERR(algt))
339                 return PTR_ERR(algt);
340 
341         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
342                 return -EINVAL;
343 
344         cipher_name = crypto_attr_alg_name(tb[1]);
345         if (IS_ERR(cipher_name))
346                 return PTR_ERR(cipher_name);
347 
348         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
349         if (!inst)
350                 return -ENOMEM;
351 
352         spawn = skcipher_instance_ctx(inst);
353 
354         crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
355         err = crypto_grab_skcipher(spawn, cipher_name, 0,
356                                    crypto_requires_sync(algt->type,
357                                                         algt->mask));
358         if (err)
359                 goto err_free_inst;
360 
361         alg = crypto_spawn_skcipher_alg(spawn);
362 
363         err = -EINVAL;
364         if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
365                 goto err_drop_spawn;
366 
367         if (strncmp(alg->base.cra_name, "cbc(", 4))
368                 goto err_drop_spawn;
369 
370         err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
371                                   &alg->base);
372         if (err)
373                 goto err_drop_spawn;
374 
375         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
376         inst->alg.base.cra_priority = alg->base.cra_priority;
377         inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
378         inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
379 
380         inst->alg.ivsize = alg->base.cra_blocksize;
381         inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
382         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
383         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);
384 
385         inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx);
386 
387         inst->alg.init = crypto_cts_init_tfm;
388         inst->alg.exit = crypto_cts_exit_tfm;
389 
390         inst->alg.setkey = crypto_cts_setkey;
391         inst->alg.encrypt = crypto_cts_encrypt;
392         inst->alg.decrypt = crypto_cts_decrypt;
393 
394         inst->free = crypto_cts_free;
395 
396         err = skcipher_register_instance(tmpl, inst);
397         if (err)
398                 goto err_drop_spawn;
399 
400 out:
401         return err;
402 
403 err_drop_spawn:
404         crypto_drop_skcipher(spawn);
405 err_free_inst:
406         kfree(inst);
407         goto out;
408 }
409 
410 static struct crypto_template crypto_cts_tmpl = {
411         .name = "cts",
412         .create = crypto_cts_create,
413         .module = THIS_MODULE,
414 };
415 
416 static int __init crypto_cts_module_init(void)
417 {
418         return crypto_register_template(&crypto_cts_tmpl);
419 }
420 
421 static void __exit crypto_cts_module_exit(void)
422 {
423         crypto_unregister_template(&crypto_cts_tmpl);
424 }
425 
426 subsys_initcall(crypto_cts_module_init);
427 module_exit(crypto_cts_module_exit);
428 
429 MODULE_LICENSE("Dual BSD/GPL");
430 MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
431 MODULE_ALIAS_CRYPTO("cts");
432 

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