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/slab.h>
  21
  22 struct crypto_rfc3686_ctx {
  23         struct crypto_skcipher *child;
  24         u8 nonce[CTR_RFC3686_NONCE_SIZE];
  25 };
  26
  27 struct crypto_rfc3686_req_ctx {
  28         u8 iv[CTR_RFC3686_BLOCK_SIZE];
  29         struct skcipher_request subreq CRYPTO_MINALIGN_ATTR;
  30 };
  31
  32 static void crypto_ctr_crypt_final(struct skcipher_walk *walk,
  33                                    struct crypto_cipher *tfm)
  34 {
  35         unsigned int bsize = crypto_cipher_blocksize(tfm);
  36         unsigned long alignmask = crypto_cipher_alignmask(tfm);
  37         u8 *ctrblk = walk->iv;
  38         u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
  39         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
  40         u8 *src = walk->src.virt.addr;
  41         u8 *dst = walk->dst.virt.addr;
  42         unsigned int nbytes = walk->nbytes;
  43
  44         crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
  45         crypto_xor_cpy(dst, keystream, src, nbytes);
  46
  47         crypto_inc(ctrblk, bsize);
  48 }
  49
  50 static int crypto_ctr_crypt_segment(struct skcipher_walk *walk,
  51                                     struct crypto_cipher *tfm)
  52 {
  53         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  54                    crypto_cipher_alg(tfm)->cia_encrypt;
  55         unsigned int bsize = crypto_cipher_blocksize(tfm);
  56         u8 *ctrblk = walk->iv;
  57         u8 *src = walk->src.virt.addr;
  58         u8 *dst = walk->dst.virt.addr;
  59         unsigned int nbytes = walk->nbytes;
  60
  61         do {
  62                 /* create keystream */
  63                 fn(crypto_cipher_tfm(tfm), dst, ctrblk);
  64                 crypto_xor(dst, src, bsize);
  65
  66                 /* increment counter in counterblock */
  67                 crypto_inc(ctrblk, bsize);
  68
  69                 src += bsize;
  70                 dst += bsize;
  71         } while ((nbytes -= bsize) >= bsize);
  72
  73         return nbytes;
  74 }
  75
  76 static int crypto_ctr_crypt_inplace(struct skcipher_walk *walk,
  77                                     struct crypto_cipher *tfm)
  78 {
  79         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  80                    crypto_cipher_alg(tfm)->cia_encrypt;
  81         unsigned int bsize = crypto_cipher_blocksize(tfm);
  82         unsigned long alignmask = crypto_cipher_alignmask(tfm);
  83         unsigned int nbytes = walk->nbytes;
  84         u8 *ctrblk = walk->iv;
  85         u8 *src = walk->src.virt.addr;
  86         u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
  87         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
  88
  89         do {
  90                 /* create keystream */
  91                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
  92                 crypto_xor(src, keystream, bsize);
  93
  94                 /* increment counter in counterblock */
  95                 crypto_inc(ctrblk, bsize);
  96
  97                 src += bsize;
  98         } while ((nbytes -= bsize) >= bsize);
  99
 100         return nbytes;
 101 }
 102
 103 static int crypto_ctr_crypt(struct skcipher_request *req)
 104 {
 105         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 106         struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
 107         const unsigned int bsize = crypto_cipher_blocksize(cipher);
 108         struct skcipher_walk walk;
 109         unsigned int nbytes;
 110         int err;
 111
 112         err = skcipher_walk_virt(&walk, req, false);
 113
 114         while (walk.nbytes >= bsize) {
 115                 if (walk.src.virt.addr == walk.dst.virt.addr)
 116                         nbytes = crypto_ctr_crypt_inplace(&walk, cipher);
 117                 else
 118                         nbytes = crypto_ctr_crypt_segment(&walk, cipher);
 119
 120                 err = skcipher_walk_done(&walk, nbytes);
 121         }
 122
 123         if (walk.nbytes) {
 124                 crypto_ctr_crypt_final(&walk, cipher);
 125                 err = skcipher_walk_done(&walk, 0);
 126         }
 127
 128         return err;
 129 }
 130
 131 static int crypto_ctr_create(struct crypto_template *tmpl, struct rtattr **tb)
 132 {
 133         struct skcipher_instance *inst;
 134         struct crypto_alg *alg;
 135         int err;
 136
 137         inst = skcipher_alloc_instance_simple(tmpl, tb, &alg);
 138         if (IS_ERR(inst))
 139                 return PTR_ERR(inst);
 140
 141         /* Block size must be >= 4 bytes. */
 142         err = -EINVAL;
 143         if (alg->cra_blocksize < 4)
 144                 goto out_free_inst;
 145
 146         /* If this is false we'd fail the alignment of crypto_inc. */
 147         if (alg->cra_blocksize % 4)
 148                 goto out_free_inst;
 149
 150         /* CTR mode is a stream cipher. */
 151         inst->alg.base.cra_blocksize = 1;
 152
 153         /*
 154          * To simplify the implementation, configure the skcipher walk to only
 155          * give a partial block at the very end, never earlier.
 156          */
 157         inst->alg.chunksize = alg->cra_blocksize;
 158
 159         inst->alg.encrypt = crypto_ctr_crypt;
 160         inst->alg.decrypt = crypto_ctr_crypt;
 161
 162         err = skcipher_register_instance(tmpl, inst);
 163         if (err)
 164                 goto out_free_inst;
 165         goto out_put_alg;
 166
 167 out_free_inst:
 168         inst->free(inst);
 169 out_put_alg:
 170         crypto_mod_put(alg);
 171         return err;
 172 }
 173
 174 static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,
 175                                  const u8 *key, unsigned int keylen)
 176 {
 177         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(parent);
 178         struct crypto_skcipher *child = ctx->child;
 179         int err;
 180
 181         /* the nonce is stored in bytes at end of key */
 182         if (keylen < CTR_RFC3686_NONCE_SIZE)
 183                 return -EINVAL;
 184
 185         memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
 186                CTR_RFC3686_NONCE_SIZE);
 187
 188         keylen -= CTR_RFC3686_NONCE_SIZE;
 189
 190         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 191         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
 192                                          CRYPTO_TFM_REQ_MASK);
 193         err = crypto_skcipher_setkey(child, key, keylen);
 194         crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
 195                                           CRYPTO_TFM_RES_MASK);
 196
 197         return err;
 198 }
 199
 200 static int crypto_rfc3686_crypt(struct skcipher_request *req)
 201 {
 202         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 203         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 204         struct crypto_skcipher *child = ctx->child;
 205         unsigned long align = crypto_skcipher_alignmask(tfm);
 206         struct crypto_rfc3686_req_ctx *rctx =
 207                 (void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);
 208         struct skcipher_request *subreq = &rctx->subreq;
 209         u8 *iv = rctx->iv;
 210
 211         /* set up counter block */
 212         memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
 213         memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
 214
 215         /* initialize counter portion of counter block */
 216         *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
 217                 cpu_to_be32(1);
 218
 219         skcipher_request_set_tfm(subreq, child);
 220         skcipher_request_set_callback(subreq, req->base.flags,
 221                                       req->base.complete, req->base.data);
 222         skcipher_request_set_crypt(subreq, req->src, req->dst,
 223                                    req->cryptlen, iv);
 224
 225         return crypto_skcipher_encrypt(subreq);
 226 }
 227
 228 static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)
 229 {
 230         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 231         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 232         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 233         struct crypto_skcipher *cipher;
 234         unsigned long align;
 235         unsigned int reqsize;
 236
 237         cipher = crypto_spawn_skcipher(spawn);
 238         if (IS_ERR(cipher))
 239                 return PTR_ERR(cipher);
 240
 241         ctx->child = cipher;
 242
 243         align = crypto_skcipher_alignmask(tfm);
 244         align &= ~(crypto_tfm_ctx_alignment() - 1);
 245         reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
 246                   crypto_skcipher_reqsize(cipher);
 247         crypto_skcipher_set_reqsize(tfm, reqsize);
 248
 249         return 0;
 250 }
 251
 252 static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)
 253 {
 254         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 255
 256         crypto_free_skcipher(ctx->child);
 257 }
 258
 259 static void crypto_rfc3686_free(struct skcipher_instance *inst)
 260 {
 261         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 262
 263         crypto_drop_skcipher(spawn);
 264         kfree(inst);
 265 }
 266
 267 static int crypto_rfc3686_create(struct crypto_template *tmpl,
 268                                  struct rtattr **tb)
 269 {
 270         struct crypto_attr_type *algt;
 271         struct skcipher_instance *inst;
 272         struct skcipher_alg *alg;
 273         struct crypto_skcipher_spawn *spawn;
 274         const char *cipher_name;
 275         u32 mask;
 276
 277         int err;
 278
 279         algt = crypto_get_attr_type(tb);
 280         if (IS_ERR(algt))
 281                 return PTR_ERR(algt);
 282
 283         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 284                 return -EINVAL;
 285
 286         cipher_name = crypto_attr_alg_name(tb[1]);
 287         if (IS_ERR(cipher_name))
 288                 return PTR_ERR(cipher_name);
 289
 290         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 291         if (!inst)
 292                 return -ENOMEM;
 293
 294         mask = crypto_requires_sync(algt->type, algt->mask) |
 295                 crypto_requires_off(algt->type, algt->mask,
 296                                     CRYPTO_ALG_NEED_FALLBACK);
 297
 298         spawn = skcipher_instance_ctx(inst);
 299
 300         crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
 301         err = crypto_grab_skcipher(spawn, cipher_name, 0, mask);
 302         if (err)
 303                 goto err_free_inst;
 304
 305         alg = crypto_spawn_skcipher_alg(spawn);
 306
 307         /* We only support 16-byte blocks. */
 308         err = -EINVAL;
 309         if (crypto_skcipher_alg_ivsize(alg) != CTR_RFC3686_BLOCK_SIZE)
 310                 goto err_drop_spawn;
 311
 312         /* Not a stream cipher? */
 313         if (alg->base.cra_blocksize != 1)
 314                 goto err_drop_spawn;
 315
 316         err = -ENAMETOOLONG;
 317         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 318                      "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
 319                 goto err_drop_spawn;
 320         if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 321                      "rfc3686(%s)", alg->base.cra_driver_name) >=
 322             CRYPTO_MAX_ALG_NAME)
 323                 goto err_drop_spawn;
 324
 325         inst->alg.base.cra_priority = alg->base.cra_priority;
 326         inst->alg.base.cra_blocksize = 1;
 327         inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
 328
 329         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 330
 331         inst->alg.ivsize = CTR_RFC3686_IV_SIZE;
 332         inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
 333         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 334                                 CTR_RFC3686_NONCE_SIZE;
 335         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 336                                 CTR_RFC3686_NONCE_SIZE;
 337
 338         inst->alg.setkey = crypto_rfc3686_setkey;
 339         inst->alg.encrypt = crypto_rfc3686_crypt;
 340         inst->alg.decrypt = crypto_rfc3686_crypt;
 341
 342         inst->alg.base.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
 343
 344         inst->alg.init = crypto_rfc3686_init_tfm;
 345         inst->alg.exit = crypto_rfc3686_exit_tfm;
 346
 347         inst->free = crypto_rfc3686_free;
 348
 349         err = skcipher_register_instance(tmpl, inst);
 350         if (err)
 351                 goto err_drop_spawn;
 352
 353 out:
 354         return err;
 355
 356 err_drop_spawn:
 357         crypto_drop_skcipher(spawn);
 358 err_free_inst:
 359         kfree(inst);
 360         goto out;
 361 }
 362
 363 static struct crypto_template crypto_ctr_tmpls[] = {
 364         {
 365                 .name = "ctr",
 366                 .create = crypto_ctr_create,
 367                 .module = THIS_MODULE,
 368         }, {
 369                 .name = "rfc3686",
 370                 .create = crypto_rfc3686_create,
 371                 .module = THIS_MODULE,
 372         },
 373 };
 374
 375 static int __init crypto_ctr_module_init(void)
 376 {
 377         return crypto_register_templates(crypto_ctr_tmpls,
 378                                          ARRAY_SIZE(crypto_ctr_tmpls));
 379 }
 380
 381 static void __exit crypto_ctr_module_exit(void)
 382 {
 383         crypto_unregister_templates(crypto_ctr_tmpls,
 384                                     ARRAY_SIZE(crypto_ctr_tmpls));
 385 }
 386
 387 module_init(crypto_ctr_module_init);
 388 module_exit(crypto_ctr_module_exit);
 389
 390 MODULE_LICENSE("GPL");
 391 MODULE_DESCRIPTION("CTR block cipher mode of operation");
 392 MODULE_ALIAS_CRYPTO("rfc3686");
 393 MODULE_ALIAS_CRYPTO("ctr");