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_attr_type *algt;
 185         struct crypto_alg *alg;
 186         u32 mask;
 187         int err;
 188
 189         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 190         if (err)
 191                 return ERR_PTR(err);
 192
 193         algt = crypto_get_attr_type(tb);
 194         if (IS_ERR(algt))
 195                 return ERR_CAST(algt);
 196
 197         mask = CRYPTO_ALG_TYPE_MASK |
 198                 crypto_requires_off(algt->type, algt->mask,
 199                                     CRYPTO_ALG_NEED_FALLBACK);
 200
 201         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER, mask);
 202         if (IS_ERR(alg))
 203                 return ERR_CAST(alg);
 204
 205         /* Block size must be >= 4 bytes. */
 206         err = -EINVAL;
 207         if (alg->cra_blocksize < 4)
 208                 goto out_put_alg;
 209
 210         /* If this is false we'd fail the alignment of crypto_inc. */
 211         if (alg->cra_blocksize % 4)
 212                 goto out_put_alg;
 213
 214         inst = crypto_alloc_instance("ctr", alg);
 215         if (IS_ERR(inst))
 216                 goto out;
 217
 218         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 219         inst->alg.cra_priority = alg->cra_priority;
 220         inst->alg.cra_blocksize = 1;
 221         inst->alg.cra_alignmask = alg->cra_alignmask;
 222         inst->alg.cra_type = &crypto_blkcipher_type;
 223
 224         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 225         inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
 226         inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
 227
 228         inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
 229
 230         inst->alg.cra_init = crypto_ctr_init_tfm;
 231         inst->alg.cra_exit = crypto_ctr_exit_tfm;
 232
 233         inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
 234         inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
 235         inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
 236
 237         inst->alg.cra_blkcipher.geniv = "chainiv";
 238
 239 out:
 240         crypto_mod_put(alg);
 241         return inst;
 242
 243 out_put_alg:
 244         inst = ERR_PTR(err);
 245         goto out;
 246 }
 247
 248 static void crypto_ctr_free(struct crypto_instance *inst)
 249 {
 250         crypto_drop_spawn(crypto_instance_ctx(inst));
 251         kfree(inst);
 252 }
 253
 254 static struct crypto_template crypto_ctr_tmpl = {
 255         .name = "ctr",
 256         .alloc = crypto_ctr_alloc,
 257         .free = crypto_ctr_free,
 258         .module = THIS_MODULE,
 259 };
 260
 261 static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,
 262                                  const u8 *key, unsigned int keylen)
 263 {
 264         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(parent);
 265         struct crypto_skcipher *child = ctx->child;
 266         int err;
 267
 268         /* the nonce is stored in bytes at end of key */
 269         if (keylen < CTR_RFC3686_NONCE_SIZE)
 270                 return -EINVAL;
 271
 272         memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
 273                CTR_RFC3686_NONCE_SIZE);
 274
 275         keylen -= CTR_RFC3686_NONCE_SIZE;
 276
 277         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 278         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
 279                                          CRYPTO_TFM_REQ_MASK);
 280         err = crypto_skcipher_setkey(child, key, keylen);
 281         crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
 282                                           CRYPTO_TFM_RES_MASK);
 283
 284         return err;
 285 }
 286
 287 static int crypto_rfc3686_crypt(struct skcipher_request *req)
 288 {
 289         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 290         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 291         struct crypto_skcipher *child = ctx->child;
 292         unsigned long align = crypto_skcipher_alignmask(tfm);
 293         struct crypto_rfc3686_req_ctx *rctx =
 294                 (void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);
 295         struct skcipher_request *subreq = &rctx->subreq;
 296         u8 *iv = rctx->iv;
 297
 298         /* set up counter block */
 299         memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
 300         memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
 301
 302         /* initialize counter portion of counter block */
 303         *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
 304                 cpu_to_be32(1);
 305
 306         skcipher_request_set_tfm(subreq, child);
 307         skcipher_request_set_callback(subreq, req->base.flags,
 308                                       req->base.complete, req->base.data);
 309         skcipher_request_set_crypt(subreq, req->src, req->dst,
 310                                    req->cryptlen, iv);
 311
 312         return crypto_skcipher_encrypt(subreq);
 313 }
 314
 315 static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)
 316 {
 317         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 318         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 319         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 320         struct crypto_skcipher *cipher;
 321         unsigned long align;
 322         unsigned int reqsize;
 323
 324         cipher = crypto_spawn_skcipher(spawn);
 325         if (IS_ERR(cipher))
 326                 return PTR_ERR(cipher);
 327
 328         ctx->child = cipher;
 329
 330         align = crypto_skcipher_alignmask(tfm);
 331         align &= ~(crypto_tfm_ctx_alignment() - 1);
 332         reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
 333                   crypto_skcipher_reqsize(cipher);
 334         crypto_skcipher_set_reqsize(tfm, reqsize);
 335
 336         return 0;
 337 }
 338
 339 static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)
 340 {
 341         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 342
 343         crypto_free_skcipher(ctx->child);
 344 }
 345
 346 static void crypto_rfc3686_free(struct skcipher_instance *inst)
 347 {
 348         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 349
 350         crypto_drop_skcipher(spawn);
 351         kfree(inst);
 352 }
 353
 354 static int crypto_rfc3686_create(struct crypto_template *tmpl,
 355                                  struct rtattr **tb)
 356 {
 357         struct crypto_attr_type *algt;
 358         struct skcipher_instance *inst;
 359         struct skcipher_alg *alg;
 360         struct crypto_skcipher_spawn *spawn;
 361         const char *cipher_name;
 362         u32 mask;
 363
 364         int err;
 365
 366         algt = crypto_get_attr_type(tb);
 367         if (IS_ERR(algt))
 368                 return PTR_ERR(algt);
 369
 370         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 371                 return -EINVAL;
 372
 373         cipher_name = crypto_attr_alg_name(tb[1]);
 374         if (IS_ERR(cipher_name))
 375                 return PTR_ERR(cipher_name);
 376
 377         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 378         if (!inst)
 379                 return -ENOMEM;
 380
 381         mask = crypto_requires_sync(algt->type, algt->mask) |
 382                 crypto_requires_off(algt->type, algt->mask,
 383                                     CRYPTO_ALG_NEED_FALLBACK);
 384
 385         spawn = skcipher_instance_ctx(inst);
 386
 387         crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
 388         err = crypto_grab_skcipher(spawn, cipher_name, 0, mask);
 389         if (err)
 390                 goto err_free_inst;
 391
 392         alg = crypto_spawn_skcipher_alg(spawn);
 393
 394         /* We only support 16-byte blocks. */
 395         err = -EINVAL;
 396         if (crypto_skcipher_alg_ivsize(alg) != CTR_RFC3686_BLOCK_SIZE)
 397                 goto err_drop_spawn;
 398
 399         /* Not a stream cipher? */
 400         if (alg->base.cra_blocksize != 1)
 401                 goto err_drop_spawn;
 402
 403         err = -ENAMETOOLONG;
 404         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 405                      "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
 406                 goto err_drop_spawn;
 407         if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 408                      "rfc3686(%s)", alg->base.cra_driver_name) >=
 409             CRYPTO_MAX_ALG_NAME)
 410                 goto err_drop_spawn;
 411
 412         inst->alg.base.cra_priority = alg->base.cra_priority;
 413         inst->alg.base.cra_blocksize = 1;
 414         inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
 415
 416         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 417
 418         inst->alg.ivsize = CTR_RFC3686_IV_SIZE;
 419         inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
 420         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 421                                 CTR_RFC3686_NONCE_SIZE;
 422         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 423                                 CTR_RFC3686_NONCE_SIZE;
 424
 425         inst->alg.setkey = crypto_rfc3686_setkey;
 426         inst->alg.encrypt = crypto_rfc3686_crypt;
 427         inst->alg.decrypt = crypto_rfc3686_crypt;
 428
 429         inst->alg.base.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
 430
 431         inst->alg.init = crypto_rfc3686_init_tfm;
 432         inst->alg.exit = crypto_rfc3686_exit_tfm;
 433
 434         inst->free = crypto_rfc3686_free;
 435
 436         err = skcipher_register_instance(tmpl, inst);
 437         if (err)
 438                 goto err_drop_spawn;
 439
 440 out:
 441         return err;
 442
 443 err_drop_spawn:
 444         crypto_drop_skcipher(spawn);
 445 err_free_inst:
 446         kfree(inst);
 447         goto out;
 448 }
 449
 450 static struct crypto_template crypto_rfc3686_tmpl = {
 451         .name = "rfc3686",
 452         .create = crypto_rfc3686_create,
 453         .module = THIS_MODULE,
 454 };
 455
 456 static int __init crypto_ctr_module_init(void)
 457 {
 458         int err;
 459
 460         err = crypto_register_template(&crypto_ctr_tmpl);
 461         if (err)
 462                 goto out;
 463
 464         err = crypto_register_template(&crypto_rfc3686_tmpl);
 465         if (err)
 466                 goto out_drop_ctr;
 467
 468 out:
 469         return err;
 470
 471 out_drop_ctr:
 472         crypto_unregister_template(&crypto_ctr_tmpl);
 473         goto out;
 474 }
 475
 476 static void __exit crypto_ctr_module_exit(void)
 477 {
 478         crypto_unregister_template(&crypto_rfc3686_tmpl);
 479         crypto_unregister_template(&crypto_ctr_tmpl);
 480 }
 481
 482 module_init(crypto_ctr_module_init);
 483 module_exit(crypto_ctr_module_exit);
 484
 485 MODULE_LICENSE("GPL");
 486 MODULE_DESCRIPTION("CTR Counter block mode");
 487 MODULE_ALIAS_CRYPTO("rfc3686");
 488 MODULE_ALIAS_CRYPTO("ctr");