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Linux/crypto/ctr.c

  1 /*
  2  * CTR: Counter mode
  3  *
  4  * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
  5  *
  6  * This program is free software; you can redistribute it and/or modify it
  7  * under the terms of the GNU General Public License as published by the Free
  8  * Software Foundation; either version 2 of the License, or (at your option)
  9  * any later version.
 10  *
 11  */
 12 
 13 #include <crypto/algapi.h>
 14 #include <crypto/ctr.h>
 15 #include <crypto/internal/skcipher.h>
 16 #include <linux/err.h>
 17 #include <linux/init.h>
 18 #include <linux/kernel.h>
 19 #include <linux/module.h>
 20 #include <linux/random.h>
 21 #include <linux/scatterlist.h>
 22 #include <linux/slab.h>
 23 
 24 struct crypto_ctr_ctx {
 25         struct crypto_cipher *child;
 26 };
 27 
 28 struct crypto_rfc3686_ctx {
 29         struct crypto_skcipher *child;
 30         u8 nonce[CTR_RFC3686_NONCE_SIZE];
 31 };
 32 
 33 struct crypto_rfc3686_req_ctx {
 34         u8 iv[CTR_RFC3686_BLOCK_SIZE];
 35         struct skcipher_request subreq CRYPTO_MINALIGN_ATTR;
 36 };
 37 
 38 static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
 39                              unsigned int keylen)
 40 {
 41         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
 42         struct crypto_cipher *child = ctx->child;
 43         int err;
 44 
 45         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 46         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
 47                                 CRYPTO_TFM_REQ_MASK);
 48         err = crypto_cipher_setkey(child, key, keylen);
 49         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
 50                              CRYPTO_TFM_RES_MASK);
 51 
 52         return err;
 53 }
 54 
 55 static void crypto_ctr_crypt_final(struct blkcipher_walk *walk,
 56                                    struct crypto_cipher *tfm)
 57 {
 58         unsigned int bsize = crypto_cipher_blocksize(tfm);
 59         unsigned long alignmask = crypto_cipher_alignmask(tfm);
 60         u8 *ctrblk = walk->iv;
 61         u8 tmp[bsize + alignmask];
 62         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
 63         u8 *src = walk->src.virt.addr;
 64         u8 *dst = walk->dst.virt.addr;
 65         unsigned int nbytes = walk->nbytes;
 66 
 67         crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
 68         crypto_xor(keystream, src, nbytes);
 69         memcpy(dst, keystream, nbytes);
 70 
 71         crypto_inc(ctrblk, bsize);
 72 }
 73 
 74 static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
 75                                     struct crypto_cipher *tfm)
 76 {
 77         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
 78                    crypto_cipher_alg(tfm)->cia_encrypt;
 79         unsigned int bsize = crypto_cipher_blocksize(tfm);
 80         u8 *ctrblk = walk->iv;
 81         u8 *src = walk->src.virt.addr;
 82         u8 *dst = walk->dst.virt.addr;
 83         unsigned int nbytes = walk->nbytes;
 84 
 85         do {
 86                 /* create keystream */
 87                 fn(crypto_cipher_tfm(tfm), dst, ctrblk);
 88                 crypto_xor(dst, src, bsize);
 89 
 90                 /* increment counter in counterblock */
 91                 crypto_inc(ctrblk, bsize);
 92 
 93                 src += bsize;
 94                 dst += bsize;
 95         } while ((nbytes -= bsize) >= bsize);
 96 
 97         return nbytes;
 98 }
 99 
100 static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
101                                     struct crypto_cipher *tfm)
102 {
103         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
104                    crypto_cipher_alg(tfm)->cia_encrypt;
105         unsigned int bsize = crypto_cipher_blocksize(tfm);
106         unsigned long alignmask = crypto_cipher_alignmask(tfm);
107         unsigned int nbytes = walk->nbytes;
108         u8 *ctrblk = walk->iv;
109         u8 *src = walk->src.virt.addr;
110         u8 tmp[bsize + alignmask];
111         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
112 
113         do {
114                 /* create keystream */
115                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
116                 crypto_xor(src, keystream, bsize);
117 
118                 /* increment counter in counterblock */
119                 crypto_inc(ctrblk, bsize);
120 
121                 src += bsize;
122         } while ((nbytes -= bsize) >= bsize);
123 
124         return nbytes;
125 }
126 
127 static int crypto_ctr_crypt(struct blkcipher_desc *desc,
128                               struct scatterlist *dst, struct scatterlist *src,
129                               unsigned int nbytes)
130 {
131         struct blkcipher_walk walk;
132         struct crypto_blkcipher *tfm = desc->tfm;
133         struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
134         struct crypto_cipher *child = ctx->child;
135         unsigned int bsize = crypto_cipher_blocksize(child);
136         int err;
137 
138         blkcipher_walk_init(&walk, dst, src, nbytes);
139         err = blkcipher_walk_virt_block(desc, &walk, bsize);
140 
141         while (walk.nbytes >= bsize) {
142                 if (walk.src.virt.addr == walk.dst.virt.addr)
143                         nbytes = crypto_ctr_crypt_inplace(&walk, child);
144                 else
145                         nbytes = crypto_ctr_crypt_segment(&walk, child);
146 
147                 err = blkcipher_walk_done(desc, &walk, nbytes);
148         }
149 
150         if (walk.nbytes) {
151                 crypto_ctr_crypt_final(&walk, child);
152                 err = blkcipher_walk_done(desc, &walk, 0);
153         }
154 
155         return err;
156 }
157 
158 static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
159 {
160         struct crypto_instance *inst = (void *)tfm->__crt_alg;
161         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
162         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
163         struct crypto_cipher *cipher;
164 
165         cipher = crypto_spawn_cipher(spawn);
166         if (IS_ERR(cipher))
167                 return PTR_ERR(cipher);
168 
169         ctx->child = cipher;
170 
171         return 0;
172 }
173 
174 static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
175 {
176         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
177 
178         crypto_free_cipher(ctx->child);
179 }
180 
181 static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
182 {
183         struct crypto_instance *inst;
184         struct crypto_alg *alg;
185         int err;
186 
187         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
188         if (err)
189                 return ERR_PTR(err);
190 
191         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
192                                   CRYPTO_ALG_TYPE_MASK);
193         if (IS_ERR(alg))
194                 return ERR_CAST(alg);
195 
196         /* Block size must be >= 4 bytes. */
197         err = -EINVAL;
198         if (alg->cra_blocksize < 4)
199                 goto out_put_alg;
200 
201         /* If this is false we'd fail the alignment of crypto_inc. */
202         if (alg->cra_blocksize % 4)
203                 goto out_put_alg;
204 
205         inst = crypto_alloc_instance("ctr", alg);
206         if (IS_ERR(inst))
207                 goto out;
208 
209         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
210         inst->alg.cra_priority = alg->cra_priority;
211         inst->alg.cra_blocksize = 1;
212         inst->alg.cra_alignmask = alg->cra_alignmask | (__alignof__(u32) - 1);
213         inst->alg.cra_type = &crypto_blkcipher_type;
214 
215         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
216         inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
217         inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
218 
219         inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
220 
221         inst->alg.cra_init = crypto_ctr_init_tfm;
222         inst->alg.cra_exit = crypto_ctr_exit_tfm;
223 
224         inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
225         inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
226         inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
227 
228         inst->alg.cra_blkcipher.geniv = "chainiv";
229 
230 out:
231         crypto_mod_put(alg);
232         return inst;
233 
234 out_put_alg:
235         inst = ERR_PTR(err);
236         goto out;
237 }
238 
239 static void crypto_ctr_free(struct crypto_instance *inst)
240 {
241         crypto_drop_spawn(crypto_instance_ctx(inst));
242         kfree(inst);
243 }
244 
245 static struct crypto_template crypto_ctr_tmpl = {
246         .name = "ctr",
247         .alloc = crypto_ctr_alloc,
248         .free = crypto_ctr_free,
249         .module = THIS_MODULE,
250 };
251 
252 static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,
253                                  const u8 *key, unsigned int keylen)
254 {
255         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(parent);
256         struct crypto_skcipher *child = ctx->child;
257         int err;
258 
259         /* the nonce is stored in bytes at end of key */
260         if (keylen < CTR_RFC3686_NONCE_SIZE)
261                 return -EINVAL;
262 
263         memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
264                CTR_RFC3686_NONCE_SIZE);
265 
266         keylen -= CTR_RFC3686_NONCE_SIZE;
267 
268         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
269         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
270                                          CRYPTO_TFM_REQ_MASK);
271         err = crypto_skcipher_setkey(child, key, keylen);
272         crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
273                                           CRYPTO_TFM_RES_MASK);
274 
275         return err;
276 }
277 
278 static int crypto_rfc3686_crypt(struct skcipher_request *req)
279 {
280         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
281         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
282         struct crypto_skcipher *child = ctx->child;
283         unsigned long align = crypto_skcipher_alignmask(tfm);
284         struct crypto_rfc3686_req_ctx *rctx =
285                 (void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);
286         struct skcipher_request *subreq = &rctx->subreq;
287         u8 *iv = rctx->iv;
288 
289         /* set up counter block */
290         memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
291         memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
292 
293         /* initialize counter portion of counter block */
294         *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
295                 cpu_to_be32(1);
296 
297         skcipher_request_set_tfm(subreq, child);
298         skcipher_request_set_callback(subreq, req->base.flags,
299                                       req->base.complete, req->base.data);
300         skcipher_request_set_crypt(subreq, req->src, req->dst,
301                                    req->cryptlen, iv);
302 
303         return crypto_skcipher_encrypt(subreq);
304 }
305 
306 static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)
307 {
308         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
309         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
310         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
311         struct crypto_skcipher *cipher;
312         unsigned long align;
313         unsigned int reqsize;
314 
315         cipher = crypto_spawn_skcipher(spawn);
316         if (IS_ERR(cipher))
317                 return PTR_ERR(cipher);
318 
319         ctx->child = cipher;
320 
321         align = crypto_skcipher_alignmask(tfm);
322         align &= ~(crypto_tfm_ctx_alignment() - 1);
323         reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
324                   crypto_skcipher_reqsize(cipher);
325         crypto_skcipher_set_reqsize(tfm, reqsize);
326 
327         return 0;
328 }
329 
330 static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)
331 {
332         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
333 
334         crypto_free_skcipher(ctx->child);
335 }
336 
337 static void crypto_rfc3686_free(struct skcipher_instance *inst)
338 {
339         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
340 
341         crypto_drop_skcipher(spawn);
342         kfree(inst);
343 }
344 
345 static int crypto_rfc3686_create(struct crypto_template *tmpl,
346                                  struct rtattr **tb)
347 {
348         struct crypto_attr_type *algt;
349         struct skcipher_instance *inst;
350         struct skcipher_alg *alg;
351         struct crypto_skcipher_spawn *spawn;
352         const char *cipher_name;
353         int err;
354 
355         algt = crypto_get_attr_type(tb);
356         if (IS_ERR(algt))
357                 return PTR_ERR(algt);
358 
359         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
360                 return -EINVAL;
361 
362         cipher_name = crypto_attr_alg_name(tb[1]);
363         if (IS_ERR(cipher_name))
364                 return PTR_ERR(cipher_name);
365 
366         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
367         if (!inst)
368                 return -ENOMEM;
369 
370         spawn = skcipher_instance_ctx(inst);
371 
372         crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
373         err = crypto_grab_skcipher(spawn, cipher_name, 0,
374                                    crypto_requires_sync(algt->type,
375                                                         algt->mask));
376         if (err)
377                 goto err_free_inst;
378 
379         alg = crypto_spawn_skcipher_alg(spawn);
380 
381         /* We only support 16-byte blocks. */
382         err = -EINVAL;
383         if (crypto_skcipher_alg_ivsize(alg) != CTR_RFC3686_BLOCK_SIZE)
384                 goto err_drop_spawn;
385 
386         /* Not a stream cipher? */
387         if (alg->base.cra_blocksize != 1)
388                 goto err_drop_spawn;
389 
390         err = -ENAMETOOLONG;
391         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
392                      "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
393                 goto err_drop_spawn;
394         if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
395                      "rfc3686(%s)", alg->base.cra_driver_name) >=
396             CRYPTO_MAX_ALG_NAME)
397                 goto err_drop_spawn;
398 
399         inst->alg.base.cra_priority = alg->base.cra_priority;
400         inst->alg.base.cra_blocksize = 1;
401         inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
402 
403         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
404 
405         inst->alg.ivsize = CTR_RFC3686_IV_SIZE;
406         inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
407         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
408                                 CTR_RFC3686_NONCE_SIZE;
409         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
410                                 CTR_RFC3686_NONCE_SIZE;
411 
412         inst->alg.setkey = crypto_rfc3686_setkey;
413         inst->alg.encrypt = crypto_rfc3686_crypt;
414         inst->alg.decrypt = crypto_rfc3686_crypt;
415 
416         inst->alg.base.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
417 
418         inst->alg.init = crypto_rfc3686_init_tfm;
419         inst->alg.exit = crypto_rfc3686_exit_tfm;
420 
421         inst->free = crypto_rfc3686_free;
422 
423         err = skcipher_register_instance(tmpl, inst);
424         if (err)
425                 goto err_drop_spawn;
426 
427 out:
428         return err;
429 
430 err_drop_spawn:
431         crypto_drop_skcipher(spawn);
432 err_free_inst:
433         kfree(inst);
434         goto out;
435 }
436 
437 static struct crypto_template crypto_rfc3686_tmpl = {
438         .name = "rfc3686",
439         .create = crypto_rfc3686_create,
440         .module = THIS_MODULE,
441 };
442 
443 static int __init crypto_ctr_module_init(void)
444 {
445         int err;
446 
447         err = crypto_register_template(&crypto_ctr_tmpl);
448         if (err)
449                 goto out;
450 
451         err = crypto_register_template(&crypto_rfc3686_tmpl);
452         if (err)
453                 goto out_drop_ctr;
454 
455 out:
456         return err;
457 
458 out_drop_ctr:
459         crypto_unregister_template(&crypto_ctr_tmpl);
460         goto out;
461 }
462 
463 static void __exit crypto_ctr_module_exit(void)
464 {
465         crypto_unregister_template(&crypto_rfc3686_tmpl);
466         crypto_unregister_template(&crypto_ctr_tmpl);
467 }
468 
469 module_init(crypto_ctr_module_init);
470 module_exit(crypto_ctr_module_exit);
471 
472 MODULE_LICENSE("GPL");
473 MODULE_DESCRIPTION("CTR Counter block mode");
474 MODULE_ALIAS_CRYPTO("rfc3686");
475 MODULE_ALIAS_CRYPTO("ctr");
476 

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