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 <linux/err.h>
  16 #include <linux/init.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19 #include <linux/random.h>
  20 #include <linux/scatterlist.h>
  21 #include <linux/slab.h>
  22
  23 struct crypto_ctr_ctx {
  24         struct crypto_cipher *child;
  25 };
  26
  27 struct crypto_rfc3686_ctx {
  28         struct crypto_blkcipher *child;
  29         u8 nonce[CTR_RFC3686_NONCE_SIZE];
  30 };
  31
  32 static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
  33                              unsigned int keylen)
  34 {
  35         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
  36         struct crypto_cipher *child = ctx->child;
  37         int err;
  38
  39         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  40         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  41                                 CRYPTO_TFM_REQ_MASK);
  42         err = crypto_cipher_setkey(child, key, keylen);
  43         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  44                              CRYPTO_TFM_RES_MASK);
  45
  46         return err;
  47 }
  48
  49 static void crypto_ctr_crypt_final(struct blkcipher_walk *walk,
  50                                    struct crypto_cipher *tfm)
  51 {
  52         unsigned int bsize = crypto_cipher_blocksize(tfm);
  53         unsigned long alignmask = crypto_cipher_alignmask(tfm);
  54         u8 *ctrblk = walk->iv;
  55         u8 tmp[bsize + alignmask];
  56         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
  57         u8 *src = walk->src.virt.addr;
  58         u8 *dst = walk->dst.virt.addr;
  59         unsigned int nbytes = walk->nbytes;
  60
  61         crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
  62         crypto_xor(keystream, src, nbytes);
  63         memcpy(dst, keystream, nbytes);
  64
  65         crypto_inc(ctrblk, bsize);
  66 }
  67
  68 static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
  69                                     struct crypto_cipher *tfm)
  70 {
  71         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  72                    crypto_cipher_alg(tfm)->cia_encrypt;
  73         unsigned int bsize = crypto_cipher_blocksize(tfm);
  74         u8 *ctrblk = walk->iv;
  75         u8 *src = walk->src.virt.addr;
  76         u8 *dst = walk->dst.virt.addr;
  77         unsigned int nbytes = walk->nbytes;
  78
  79         do {
  80                 /* create keystream */
  81                 fn(crypto_cipher_tfm(tfm), dst, ctrblk);
  82                 crypto_xor(dst, src, bsize);
  83
  84                 /* increment counter in counterblock */
  85                 crypto_inc(ctrblk, bsize);
  86
  87                 src += bsize;
  88                 dst += bsize;
  89         } while ((nbytes -= bsize) >= bsize);
  90
  91         return nbytes;
  92 }
  93
  94 static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
  95                                     struct crypto_cipher *tfm)
  96 {
  97         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  98                    crypto_cipher_alg(tfm)->cia_encrypt;
  99         unsigned int bsize = crypto_cipher_blocksize(tfm);
 100         unsigned long alignmask = crypto_cipher_alignmask(tfm);
 101         unsigned int nbytes = walk->nbytes;
 102         u8 *ctrblk = walk->iv;
 103         u8 *src = walk->src.virt.addr;
 104         u8 tmp[bsize + alignmask];
 105         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
 106
 107         do {
 108                 /* create keystream */
 109                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
 110                 crypto_xor(src, keystream, bsize);
 111
 112                 /* increment counter in counterblock */
 113                 crypto_inc(ctrblk, bsize);
 114
 115                 src += bsize;
 116         } while ((nbytes -= bsize) >= bsize);
 117
 118         return nbytes;
 119 }
 120
 121 static int crypto_ctr_crypt(struct blkcipher_desc *desc,
 122                               struct scatterlist *dst, struct scatterlist *src,
 123                               unsigned int nbytes)
 124 {
 125         struct blkcipher_walk walk;
 126         struct crypto_blkcipher *tfm = desc->tfm;
 127         struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
 128         struct crypto_cipher *child = ctx->child;
 129         unsigned int bsize = crypto_cipher_blocksize(child);
 130         int err;
 131
 132         blkcipher_walk_init(&walk, dst, src, nbytes);
 133         err = blkcipher_walk_virt_block(desc, &walk, bsize);
 134
 135         while (walk.nbytes >= bsize) {
 136                 if (walk.src.virt.addr == walk.dst.virt.addr)
 137                         nbytes = crypto_ctr_crypt_inplace(&walk, child);
 138                 else
 139                         nbytes = crypto_ctr_crypt_segment(&walk, child);
 140
 141                 err = blkcipher_walk_done(desc, &walk, nbytes);
 142         }
 143
 144         if (walk.nbytes) {
 145                 crypto_ctr_crypt_final(&walk, child);
 146                 err = blkcipher_walk_done(desc, &walk, 0);
 147         }
 148
 149         return err;
 150 }
 151
 152 static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
 153 {
 154         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 155         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 156         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
 157         struct crypto_cipher *cipher;
 158
 159         cipher = crypto_spawn_cipher(spawn);
 160         if (IS_ERR(cipher))
 161                 return PTR_ERR(cipher);
 162
 163         ctx->child = cipher;
 164
 165         return 0;
 166 }
 167
 168 static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
 169 {
 170         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
 171
 172         crypto_free_cipher(ctx->child);
 173 }
 174
 175 static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
 176 {
 177         struct crypto_instance *inst;
 178         struct crypto_alg *alg;
 179         int err;
 180
 181         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 182         if (err)
 183                 return ERR_PTR(err);
 184
 185         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
 186                                   CRYPTO_ALG_TYPE_MASK);
 187         if (IS_ERR(alg))
 188                 return ERR_CAST(alg);
 189
 190         /* Block size must be >= 4 bytes. */
 191         err = -EINVAL;
 192         if (alg->cra_blocksize < 4)
 193                 goto out_put_alg;
 194
 195         /* If this is false we'd fail the alignment of crypto_inc. */
 196         if (alg->cra_blocksize % 4)
 197                 goto out_put_alg;
 198
 199         inst = crypto_alloc_instance("ctr", alg);
 200         if (IS_ERR(inst))
 201                 goto out;
 202
 203         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 204         inst->alg.cra_priority = alg->cra_priority;
 205         inst->alg.cra_blocksize = 1;
 206         inst->alg.cra_alignmask = alg->cra_alignmask | (__alignof__(u32) - 1);
 207         inst->alg.cra_type = &crypto_blkcipher_type;
 208
 209         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 210         inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
 211         inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
 212
 213         inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
 214
 215         inst->alg.cra_init = crypto_ctr_init_tfm;
 216         inst->alg.cra_exit = crypto_ctr_exit_tfm;
 217
 218         inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
 219         inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
 220         inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
 221
 222         inst->alg.cra_blkcipher.geniv = "chainiv";
 223
 224 out:
 225         crypto_mod_put(alg);
 226         return inst;
 227
 228 out_put_alg:
 229         inst = ERR_PTR(err);
 230         goto out;
 231 }
 232
 233 static void crypto_ctr_free(struct crypto_instance *inst)
 234 {
 235         crypto_drop_spawn(crypto_instance_ctx(inst));
 236         kfree(inst);
 237 }
 238
 239 static struct crypto_template crypto_ctr_tmpl = {
 240         .name = "ctr",
 241         .alloc = crypto_ctr_alloc,
 242         .free = crypto_ctr_free,
 243         .module = THIS_MODULE,
 244 };
 245
 246 static int crypto_rfc3686_setkey(struct crypto_tfm *parent, const u8 *key,
 247                                  unsigned int keylen)
 248 {
 249         struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(parent);
 250         struct crypto_blkcipher *child = ctx->child;
 251         int err;
 252
 253         /* the nonce is stored in bytes at end of key */
 254         if (keylen < CTR_RFC3686_NONCE_SIZE)
 255                 return -EINVAL;
 256
 257         memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
 258                CTR_RFC3686_NONCE_SIZE);
 259
 260         keylen -= CTR_RFC3686_NONCE_SIZE;
 261
 262         crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 263         crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
 264                                           CRYPTO_TFM_REQ_MASK);
 265         err = crypto_blkcipher_setkey(child, key, keylen);
 266         crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
 267                                      CRYPTO_TFM_RES_MASK);
 268
 269         return err;
 270 }
 271
 272 static int crypto_rfc3686_crypt(struct blkcipher_desc *desc,
 273                                 struct scatterlist *dst,
 274                                 struct scatterlist *src, unsigned int nbytes)
 275 {
 276         struct crypto_blkcipher *tfm = desc->tfm;
 277         struct crypto_rfc3686_ctx *ctx = crypto_blkcipher_ctx(tfm);
 278         struct crypto_blkcipher *child = ctx->child;
 279         unsigned long alignmask = crypto_blkcipher_alignmask(tfm);
 280         u8 ivblk[CTR_RFC3686_BLOCK_SIZE + alignmask];
 281         u8 *iv = PTR_ALIGN(ivblk + 0, alignmask + 1);
 282         u8 *info = desc->info;
 283         int err;
 284
 285         /* set up counter block */
 286         memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
 287         memcpy(iv + CTR_RFC3686_NONCE_SIZE, info, CTR_RFC3686_IV_SIZE);
 288
 289         /* initialize counter portion of counter block */
 290         *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
 291                 cpu_to_be32(1);
 292
 293         desc->tfm = child;
 294         desc->info = iv;
 295         err = crypto_blkcipher_encrypt_iv(desc, dst, src, nbytes);
 296         desc->tfm = tfm;
 297         desc->info = info;
 298
 299         return err;
 300 }
 301
 302 static int crypto_rfc3686_init_tfm(struct crypto_tfm *tfm)
 303 {
 304         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 305         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 306         struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
 307         struct crypto_blkcipher *cipher;
 308
 309         cipher = crypto_spawn_blkcipher(spawn);
 310         if (IS_ERR(cipher))
 311                 return PTR_ERR(cipher);
 312
 313         ctx->child = cipher;
 314
 315         return 0;
 316 }
 317
 318 static void crypto_rfc3686_exit_tfm(struct crypto_tfm *tfm)
 319 {
 320         struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
 321
 322         crypto_free_blkcipher(ctx->child);
 323 }
 324
 325 static struct crypto_instance *crypto_rfc3686_alloc(struct rtattr **tb)
 326 {
 327         struct crypto_instance *inst;
 328         struct crypto_alg *alg;
 329         int err;
 330
 331         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 332         if (err)
 333                 return ERR_PTR(err);
 334
 335         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
 336                                   CRYPTO_ALG_TYPE_MASK);
 337         err = PTR_ERR(alg);
 338         if (IS_ERR(alg))
 339                 return ERR_PTR(err);
 340
 341         /* We only support 16-byte blocks. */
 342         err = -EINVAL;
 343         if (alg->cra_blkcipher.ivsize != CTR_RFC3686_BLOCK_SIZE)
 344                 goto out_put_alg;
 345
 346         /* Not a stream cipher? */
 347         if (alg->cra_blocksize != 1)
 348                 goto out_put_alg;
 349
 350         inst = crypto_alloc_instance("rfc3686", alg);
 351         if (IS_ERR(inst))
 352                 goto out;
 353
 354         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 355         inst->alg.cra_priority = alg->cra_priority;
 356         inst->alg.cra_blocksize = 1;
 357         inst->alg.cra_alignmask = alg->cra_alignmask;
 358         inst->alg.cra_type = &crypto_blkcipher_type;
 359
 360         inst->alg.cra_blkcipher.ivsize = CTR_RFC3686_IV_SIZE;
 361         inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize
 362                                               + CTR_RFC3686_NONCE_SIZE;
 363         inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize
 364                                               + CTR_RFC3686_NONCE_SIZE;
 365
 366         inst->alg.cra_blkcipher.geniv = "seqiv";
 367
 368         inst->alg.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
 369
 370         inst->alg.cra_init = crypto_rfc3686_init_tfm;
 371         inst->alg.cra_exit = crypto_rfc3686_exit_tfm;
 372
 373         inst->alg.cra_blkcipher.setkey = crypto_rfc3686_setkey;
 374         inst->alg.cra_blkcipher.encrypt = crypto_rfc3686_crypt;
 375         inst->alg.cra_blkcipher.decrypt = crypto_rfc3686_crypt;
 376
 377 out:
 378         crypto_mod_put(alg);
 379         return inst;
 380
 381 out_put_alg:
 382         inst = ERR_PTR(err);
 383         goto out;
 384 }
 385
 386 static struct crypto_template crypto_rfc3686_tmpl = {
 387         .name = "rfc3686",
 388         .alloc = crypto_rfc3686_alloc,
 389         .free = crypto_ctr_free,
 390         .module = THIS_MODULE,
 391 };
 392
 393 static int __init crypto_ctr_module_init(void)
 394 {
 395         int err;
 396
 397         err = crypto_register_template(&crypto_ctr_tmpl);
 398         if (err)
 399                 goto out;
 400
 401         err = crypto_register_template(&crypto_rfc3686_tmpl);
 402         if (err)
 403                 goto out_drop_ctr;
 404
 405 out:
 406         return err;
 407
 408 out_drop_ctr:
 409         crypto_unregister_template(&crypto_ctr_tmpl);
 410         goto out;
 411 }
 412
 413 static void __exit crypto_ctr_module_exit(void)
 414 {
 415         crypto_unregister_template(&crypto_rfc3686_tmpl);
 416         crypto_unregister_template(&crypto_ctr_tmpl);
 417 }
 418
 419 module_init(crypto_ctr_module_init);
 420 module_exit(crypto_ctr_module_exit);
 421
 422 MODULE_LICENSE("GPL");
 423 MODULE_DESCRIPTION("CTR Counter block mode");
 424 MODULE_ALIAS_CRYPTO("rfc3686");
 425 MODULE_ALIAS_CRYPTO("ctr");