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_cpy(dst, keystream, src, nbytes);
  69
  70         crypto_inc(ctrblk, bsize);
  71 }
  72
  73 static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
  74                                     struct crypto_cipher *tfm)
  75 {
  76         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  77                    crypto_cipher_alg(tfm)->cia_encrypt;
  78         unsigned int bsize = crypto_cipher_blocksize(tfm);
  79         u8 *ctrblk = walk->iv;
  80         u8 *src = walk->src.virt.addr;
  81         u8 *dst = walk->dst.virt.addr;
  82         unsigned int nbytes = walk->nbytes;
  83
  84         do {
  85                 /* create keystream */
  86                 fn(crypto_cipher_tfm(tfm), dst, ctrblk);
  87                 crypto_xor(dst, src, bsize);
  88
  89                 /* increment counter in counterblock */
  90                 crypto_inc(ctrblk, bsize);
  91
  92                 src += bsize;
  93                 dst += bsize;
  94         } while ((nbytes -= bsize) >= bsize);
  95
  96         return nbytes;
  97 }
  98
  99 static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
 100                                     struct crypto_cipher *tfm)
 101 {
 102         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
 103                    crypto_cipher_alg(tfm)->cia_encrypt;
 104         unsigned int bsize = crypto_cipher_blocksize(tfm);
 105         unsigned long alignmask = crypto_cipher_alignmask(tfm);
 106         unsigned int nbytes = walk->nbytes;
 107         u8 *ctrblk = walk->iv;
 108         u8 *src = walk->src.virt.addr;
 109         u8 tmp[bsize + alignmask];
 110         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
 111
 112         do {
 113                 /* create keystream */
 114                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
 115                 crypto_xor(src, keystream, bsize);
 116
 117                 /* increment counter in counterblock */
 118                 crypto_inc(ctrblk, bsize);
 119
 120                 src += bsize;
 121         } while ((nbytes -= bsize) >= bsize);
 122
 123         return nbytes;
 124 }
 125
 126 static int crypto_ctr_crypt(struct blkcipher_desc *desc,
 127                               struct scatterlist *dst, struct scatterlist *src,
 128                               unsigned int nbytes)
 129 {
 130         struct blkcipher_walk walk;
 131         struct crypto_blkcipher *tfm = desc->tfm;
 132         struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
 133         struct crypto_cipher *child = ctx->child;
 134         unsigned int bsize = crypto_cipher_blocksize(child);
 135         int err;
 136
 137         blkcipher_walk_init(&walk, dst, src, nbytes);
 138         err = blkcipher_walk_virt_block(desc, &walk, bsize);
 139
 140         while (walk.nbytes >= bsize) {
 141                 if (walk.src.virt.addr == walk.dst.virt.addr)
 142                         nbytes = crypto_ctr_crypt_inplace(&walk, child);
 143                 else
 144                         nbytes = crypto_ctr_crypt_segment(&walk, child);
 145
 146                 err = blkcipher_walk_done(desc, &walk, nbytes);
 147         }
 148
 149         if (walk.nbytes) {
 150                 crypto_ctr_crypt_final(&walk, child);
 151                 err = blkcipher_walk_done(desc, &walk, 0);
 152         }
 153
 154         return err;
 155 }
 156
 157 static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
 158 {
 159         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 160         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 161         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
 162         struct crypto_cipher *cipher;
 163
 164         cipher = crypto_spawn_cipher(spawn);
 165         if (IS_ERR(cipher))
 166                 return PTR_ERR(cipher);
 167
 168         ctx->child = cipher;
 169
 170         return 0;
 171 }
 172
 173 static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
 174 {
 175         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
 176
 177         crypto_free_cipher(ctx->child);
 178 }
 179
 180 static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
 181 {
 182         struct crypto_instance *inst;
 183         struct crypto_attr_type *algt;
 184         struct crypto_alg *alg;
 185         u32 mask;
 186         int err;
 187
 188         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 189         if (err)
 190                 return ERR_PTR(err);
 191
 192         algt = crypto_get_attr_type(tb);
 193         if (IS_ERR(algt))
 194                 return ERR_CAST(algt);
 195
 196         mask = CRYPTO_ALG_TYPE_MASK |
 197                 crypto_requires_off(algt->type, algt->mask,
 198                                     CRYPTO_ALG_NEED_FALLBACK);
 199
 200         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER, mask);
 201         if (IS_ERR(alg))
 202                 return ERR_CAST(alg);
 203
 204         /* Block size must be >= 4 bytes. */
 205         err = -EINVAL;
 206         if (alg->cra_blocksize < 4)
 207                 goto out_put_alg;
 208
 209         /* If this is false we'd fail the alignment of crypto_inc. */
 210         if (alg->cra_blocksize % 4)
 211                 goto out_put_alg;
 212
 213         inst = crypto_alloc_instance("ctr", alg);
 214         if (IS_ERR(inst))
 215                 goto out;
 216
 217         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 218         inst->alg.cra_priority = alg->cra_priority;
 219         inst->alg.cra_blocksize = 1;
 220         inst->alg.cra_alignmask = alg->cra_alignmask;
 221         inst->alg.cra_type = &crypto_blkcipher_type;
 222
 223         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 224         inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
 225         inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
 226
 227         inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
 228
 229         inst->alg.cra_init = crypto_ctr_init_tfm;
 230         inst->alg.cra_exit = crypto_ctr_exit_tfm;
 231
 232         inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
 233         inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
 234         inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
 235
 236         inst->alg.cra_blkcipher.geniv = "chainiv";
 237
 238 out:
 239         crypto_mod_put(alg);
 240         return inst;
 241
 242 out_put_alg:
 243         inst = ERR_PTR(err);
 244         goto out;
 245 }
 246
 247 static void crypto_ctr_free(struct crypto_instance *inst)
 248 {
 249         crypto_drop_spawn(crypto_instance_ctx(inst));
 250         kfree(inst);
 251 }
 252
 253 static struct crypto_template crypto_ctr_tmpl = {
 254         .name = "ctr",
 255         .alloc = crypto_ctr_alloc,
 256         .free = crypto_ctr_free,
 257         .module = THIS_MODULE,
 258 };
 259
 260 static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,
 261                                  const u8 *key, unsigned int keylen)
 262 {
 263         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(parent);
 264         struct crypto_skcipher *child = ctx->child;
 265         int err;
 266
 267         /* the nonce is stored in bytes at end of key */
 268         if (keylen < CTR_RFC3686_NONCE_SIZE)
 269                 return -EINVAL;
 270
 271         memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
 272                CTR_RFC3686_NONCE_SIZE);
 273
 274         keylen -= CTR_RFC3686_NONCE_SIZE;
 275
 276         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 277         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
 278                                          CRYPTO_TFM_REQ_MASK);
 279         err = crypto_skcipher_setkey(child, key, keylen);
 280         crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
 281                                           CRYPTO_TFM_RES_MASK);
 282
 283         return err;
 284 }
 285
 286 static int crypto_rfc3686_crypt(struct skcipher_request *req)
 287 {
 288         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 289         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 290         struct crypto_skcipher *child = ctx->child;
 291         unsigned long align = crypto_skcipher_alignmask(tfm);
 292         struct crypto_rfc3686_req_ctx *rctx =
 293                 (void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);
 294         struct skcipher_request *subreq = &rctx->subreq;
 295         u8 *iv = rctx->iv;
 296
 297         /* set up counter block */
 298         memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
 299         memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
 300
 301         /* initialize counter portion of counter block */
 302         *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
 303                 cpu_to_be32(1);
 304
 305         skcipher_request_set_tfm(subreq, child);
 306         skcipher_request_set_callback(subreq, req->base.flags,
 307                                       req->base.complete, req->base.data);
 308         skcipher_request_set_crypt(subreq, req->src, req->dst,
 309                                    req->cryptlen, iv);
 310
 311         return crypto_skcipher_encrypt(subreq);
 312 }
 313
 314 static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)
 315 {
 316         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 317         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 318         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 319         struct crypto_skcipher *cipher;
 320         unsigned long align;
 321         unsigned int reqsize;
 322
 323         cipher = crypto_spawn_skcipher(spawn);
 324         if (IS_ERR(cipher))
 325                 return PTR_ERR(cipher);
 326
 327         ctx->child = cipher;
 328
 329         align = crypto_skcipher_alignmask(tfm);
 330         align &= ~(crypto_tfm_ctx_alignment() - 1);
 331         reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
 332                   crypto_skcipher_reqsize(cipher);
 333         crypto_skcipher_set_reqsize(tfm, reqsize);
 334
 335         return 0;
 336 }
 337
 338 static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)
 339 {
 340         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 341
 342         crypto_free_skcipher(ctx->child);
 343 }
 344
 345 static void crypto_rfc3686_free(struct skcipher_instance *inst)
 346 {
 347         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 348
 349         crypto_drop_skcipher(spawn);
 350         kfree(inst);
 351 }
 352
 353 static int crypto_rfc3686_create(struct crypto_template *tmpl,
 354                                  struct rtattr **tb)
 355 {
 356         struct crypto_attr_type *algt;
 357         struct skcipher_instance *inst;
 358         struct skcipher_alg *alg;
 359         struct crypto_skcipher_spawn *spawn;
 360         const char *cipher_name;
 361         u32 mask;
 362
 363         int err;
 364
 365         algt = crypto_get_attr_type(tb);
 366         if (IS_ERR(algt))
 367                 return PTR_ERR(algt);
 368
 369         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 370                 return -EINVAL;
 371
 372         cipher_name = crypto_attr_alg_name(tb[1]);
 373         if (IS_ERR(cipher_name))
 374                 return PTR_ERR(cipher_name);
 375
 376         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 377         if (!inst)
 378                 return -ENOMEM;
 379
 380         mask = crypto_requires_sync(algt->type, algt->mask) |
 381                 crypto_requires_off(algt->type, algt->mask,
 382                                     CRYPTO_ALG_NEED_FALLBACK);
 383
 384         spawn = skcipher_instance_ctx(inst);
 385
 386         crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
 387         err = crypto_grab_skcipher(spawn, cipher_name, 0, mask);
 388         if (err)
 389                 goto err_free_inst;
 390
 391         alg = crypto_spawn_skcipher_alg(spawn);
 392
 393         /* We only support 16-byte blocks. */
 394         err = -EINVAL;
 395         if (crypto_skcipher_alg_ivsize(alg) != CTR_RFC3686_BLOCK_SIZE)
 396                 goto err_drop_spawn;
 397
 398         /* Not a stream cipher? */
 399         if (alg->base.cra_blocksize != 1)
 400                 goto err_drop_spawn;
 401
 402         err = -ENAMETOOLONG;
 403         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 404                      "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
 405                 goto err_drop_spawn;
 406         if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 407                      "rfc3686(%s)", alg->base.cra_driver_name) >=
 408             CRYPTO_MAX_ALG_NAME)
 409                 goto err_drop_spawn;
 410
 411         inst->alg.base.cra_priority = alg->base.cra_priority;
 412         inst->alg.base.cra_blocksize = 1;
 413         inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
 414
 415         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 416
 417         inst->alg.ivsize = CTR_RFC3686_IV_SIZE;
 418         inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
 419         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 420                                 CTR_RFC3686_NONCE_SIZE;
 421         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 422                                 CTR_RFC3686_NONCE_SIZE;
 423
 424         inst->alg.setkey = crypto_rfc3686_setkey;
 425         inst->alg.encrypt = crypto_rfc3686_crypt;
 426         inst->alg.decrypt = crypto_rfc3686_crypt;
 427
 428         inst->alg.base.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
 429
 430         inst->alg.init = crypto_rfc3686_init_tfm;
 431         inst->alg.exit = crypto_rfc3686_exit_tfm;
 432
 433         inst->free = crypto_rfc3686_free;
 434
 435         err = skcipher_register_instance(tmpl, inst);
 436         if (err)
 437                 goto err_drop_spawn;
 438
 439 out:
 440         return err;
 441
 442 err_drop_spawn:
 443         crypto_drop_skcipher(spawn);
 444 err_free_inst:
 445         kfree(inst);
 446         goto out;
 447 }
 448
 449 static struct crypto_template crypto_rfc3686_tmpl = {
 450         .name = "rfc3686",
 451         .create = crypto_rfc3686_create,
 452         .module = THIS_MODULE,
 453 };
 454
 455 static int __init crypto_ctr_module_init(void)
 456 {
 457         int err;
 458
 459         err = crypto_register_template(&crypto_ctr_tmpl);
 460         if (err)
 461                 goto out;
 462
 463         err = crypto_register_template(&crypto_rfc3686_tmpl);
 464         if (err)
 465                 goto out_drop_ctr;
 466
 467 out:
 468         return err;
 469
 470 out_drop_ctr:
 471         crypto_unregister_template(&crypto_ctr_tmpl);
 472         goto out;
 473 }
 474
 475 static void __exit crypto_ctr_module_exit(void)
 476 {
 477         crypto_unregister_template(&crypto_rfc3686_tmpl);
 478         crypto_unregister_template(&crypto_ctr_tmpl);
 479 }
 480
 481 module_init(crypto_ctr_module_init);
 482 module_exit(crypto_ctr_module_exit);
 483
 484 MODULE_LICENSE("GPL");
 485 MODULE_DESCRIPTION("CTR Counter block mode");
 486 MODULE_ALIAS_CRYPTO("rfc3686");
 487 MODULE_ALIAS_CRYPTO("ctr");