crypto/cbc.c

   1 /*
   2  * CBC: Cipher Block Chaining mode
   3  *
   4  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   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 <linux/err.h>
  15 #include <linux/init.h>
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/scatterlist.h>
  19 #include <linux/slab.h>
  20
  21 struct crypto_cbc_ctx {
  22         struct crypto_cipher *child;
  23         void (*xor)(u8 *dst, const u8 *src, unsigned int bs);
  24 };
  25
  26 static int crypto_cbc_setkey(struct crypto_tfm *parent, const u8 *key,
  27                              unsigned int keylen)
  28 {
  29         struct crypto_cbc_ctx *ctx = crypto_tfm_ctx(parent);
  30         struct crypto_cipher *child = ctx->child;
  31         int err;
  32
  33         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  34         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  35                                        CRYPTO_TFM_REQ_MASK);
  36         err = crypto_cipher_setkey(child, key, keylen);
  37         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  38                                      CRYPTO_TFM_RES_MASK);
  39         return err;
  40 }
  41
  42 static int crypto_cbc_encrypt_segment(struct blkcipher_desc *desc,
  43                                       struct blkcipher_walk *walk,
  44                                       struct crypto_cipher *tfm,
  45                                       void (*xor)(u8 *, const u8 *,
  46                                                   unsigned int))
  47 {
  48         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  49                 crypto_cipher_alg(tfm)->cia_encrypt;
  50         int bsize = crypto_cipher_blocksize(tfm);
  51         unsigned int nbytes = walk->nbytes;
  52         u8 *src = walk->src.virt.addr;
  53         u8 *dst = walk->dst.virt.addr;
  54         u8 *iv = walk->iv;
  55
  56         do {
  57                 xor(iv, src, bsize);
  58                 fn(crypto_cipher_tfm(tfm), dst, iv);
  59                 memcpy(iv, dst, bsize);
  60
  61                 src += bsize;
  62                 dst += bsize;
  63         } while ((nbytes -= bsize) >= bsize);
  64
  65         return nbytes;
  66 }
  67
  68 static int crypto_cbc_encrypt_inplace(struct blkcipher_desc *desc,
  69                                       struct blkcipher_walk *walk,
  70                                       struct crypto_cipher *tfm,
  71                                       void (*xor)(u8 *, const u8 *,
  72                                                   unsigned int))
  73 {
  74         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  75                 crypto_cipher_alg(tfm)->cia_encrypt;
  76         int bsize = crypto_cipher_blocksize(tfm);
  77         unsigned int nbytes = walk->nbytes;
  78         u8 *src = walk->src.virt.addr;
  79         u8 *iv = walk->iv;
  80
  81         do {
  82                 xor(src, iv, bsize);
  83                 fn(crypto_cipher_tfm(tfm), src, src);
  84                 iv = src;
  85
  86                 src += bsize;
  87         } while ((nbytes -= bsize) >= bsize);
  88
  89         memcpy(walk->iv, iv, bsize);
  90
  91         return nbytes;
  92 }
  93
  94 static int crypto_cbc_encrypt(struct blkcipher_desc *desc,
  95                               struct scatterlist *dst, struct scatterlist *src,
  96                               unsigned int nbytes)
  97 {
  98         struct blkcipher_walk walk;
  99         struct crypto_blkcipher *tfm = desc->tfm;
 100         struct crypto_cbc_ctx *ctx = crypto_blkcipher_ctx(tfm);
 101         struct crypto_cipher *child = ctx->child;
 102         void (*xor)(u8 *, const u8 *, unsigned int bs) = ctx->xor;
 103         int err;
 104
 105         blkcipher_walk_init(&walk, dst, src, nbytes);
 106         err = blkcipher_walk_virt(desc, &walk);
 107
 108         while ((nbytes = walk.nbytes)) {
 109                 if (walk.src.virt.addr == walk.dst.virt.addr)
 110                         nbytes = crypto_cbc_encrypt_inplace(desc, &walk, child,
 111                                                             xor);
 112                 else
 113                         nbytes = crypto_cbc_encrypt_segment(desc, &walk, child,
 114                                                             xor);
 115                 err = blkcipher_walk_done(desc, &walk, nbytes);
 116         }
 117
 118         return err;
 119 }
 120
 121 static int crypto_cbc_decrypt_segment(struct blkcipher_desc *desc,
 122                                       struct blkcipher_walk *walk,
 123                                       struct crypto_cipher *tfm,
 124                                       void (*xor)(u8 *, const u8 *,
 125                                                   unsigned int))
 126 {
 127         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
 128                 crypto_cipher_alg(tfm)->cia_decrypt;
 129         int bsize = crypto_cipher_blocksize(tfm);
 130         unsigned int nbytes = walk->nbytes;
 131         u8 *src = walk->src.virt.addr;
 132         u8 *dst = walk->dst.virt.addr;
 133         u8 *iv = walk->iv;
 134
 135         do {
 136                 fn(crypto_cipher_tfm(tfm), dst, src);
 137                 xor(dst, iv, bsize);
 138                 iv = src;
 139
 140                 src += bsize;
 141                 dst += bsize;
 142         } while ((nbytes -= bsize) >= bsize);
 143
 144         memcpy(walk->iv, iv, bsize);
 145
 146         return nbytes;
 147 }
 148
 149 static int crypto_cbc_decrypt_inplace(struct blkcipher_desc *desc,
 150                                       struct blkcipher_walk *walk,
 151                                       struct crypto_cipher *tfm,
 152                                       void (*xor)(u8 *, const u8 *,
 153                                                   unsigned int))
 154 {
 155         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
 156                 crypto_cipher_alg(tfm)->cia_decrypt;
 157         int bsize = crypto_cipher_blocksize(tfm);
 158         unsigned long alignmask = crypto_cipher_alignmask(tfm);
 159         unsigned int nbytes = walk->nbytes;
 160         u8 *src = walk->src.virt.addr;
 161         u8 stack[bsize + alignmask];
 162         u8 *first_iv = (u8 *)ALIGN((unsigned long)stack, alignmask + 1);
 163
 164         memcpy(first_iv, walk->iv, bsize);
 165
 166         /* Start of the last block. */
 167         src += nbytes - nbytes % bsize - bsize;
 168         memcpy(walk->iv, src, bsize);
 169
 170         for (;;) {
 171                 fn(crypto_cipher_tfm(tfm), src, src);
 172                 if ((nbytes -= bsize) < bsize)
 173                         break;
 174                 xor(src, src - bsize, bsize);
 175                 src -= bsize;
 176         }
 177
 178         xor(src, first_iv, bsize);
 179
 180         return nbytes;
 181 }
 182
 183 static int crypto_cbc_decrypt(struct blkcipher_desc *desc,
 184                               struct scatterlist *dst, struct scatterlist *src,
 185                               unsigned int nbytes)
 186 {
 187         struct blkcipher_walk walk;
 188         struct crypto_blkcipher *tfm = desc->tfm;
 189         struct crypto_cbc_ctx *ctx = crypto_blkcipher_ctx(tfm);
 190         struct crypto_cipher *child = ctx->child;
 191         void (*xor)(u8 *, const u8 *, unsigned int bs) = ctx->xor;
 192         int err;
 193
 194         blkcipher_walk_init(&walk, dst, src, nbytes);
 195         err = blkcipher_walk_virt(desc, &walk);
 196
 197         while ((nbytes = walk.nbytes)) {
 198                 if (walk.src.virt.addr == walk.dst.virt.addr)
 199                         nbytes = crypto_cbc_decrypt_inplace(desc, &walk, child,
 200                                                             xor);
 201                 else
 202                         nbytes = crypto_cbc_decrypt_segment(desc, &walk, child,
 203                                                             xor);
 204                 err = blkcipher_walk_done(desc, &walk, nbytes);
 205         }
 206
 207         return err;
 208 }
 209
 210 static void xor_byte(u8 *a, const u8 *b, unsigned int bs)
 211 {
 212         do {
 213                 *a++ ^= *b++;
 214         } while (--bs);
 215 }
 216
 217 static void xor_quad(u8 *dst, const u8 *src, unsigned int bs)
 218 {
 219         u32 *a = (u32 *)dst;
 220         u32 *b = (u32 *)src;
 221
 222         do {
 223                 *a++ ^= *b++;
 224         } while ((bs -= 4));
 225 }
 226
 227 static void xor_64(u8 *a, const u8 *b, unsigned int bs)
 228 {
 229         ((u32 *)a)[0] ^= ((u32 *)b)[0];
 230         ((u32 *)a)[1] ^= ((u32 *)b)[1];
 231 }
 232
 233 static void xor_128(u8 *a, const u8 *b, unsigned int bs)
 234 {
 235         ((u32 *)a)[0] ^= ((u32 *)b)[0];
 236         ((u32 *)a)[1] ^= ((u32 *)b)[1];
 237         ((u32 *)a)[2] ^= ((u32 *)b)[2];
 238         ((u32 *)a)[3] ^= ((u32 *)b)[3];
 239 }
 240
 241 static int crypto_cbc_init_tfm(struct crypto_tfm *tfm)
 242 {
 243         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 244         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 245         struct crypto_cbc_ctx *ctx = crypto_tfm_ctx(tfm);
 246
 247         switch (crypto_tfm_alg_blocksize(tfm)) {
 248         case 8:
 249                 ctx->xor = xor_64;
 250                 break;
 251
 252         case 16:
 253                 ctx->xor = xor_128;
 254                 break;
 255
 256         default:
 257                 if (crypto_tfm_alg_blocksize(tfm) % 4)
 258                         ctx->xor = xor_byte;
 259                 else
 260                         ctx->xor = xor_quad;
 261         }
 262
 263         tfm = crypto_spawn_tfm(spawn);
 264         if (IS_ERR(tfm))
 265                 return PTR_ERR(tfm);
 266
 267         ctx->child = crypto_cipher_cast(tfm);
 268         return 0;
 269 }
 270
 271 static void crypto_cbc_exit_tfm(struct crypto_tfm *tfm)
 272 {
 273         struct crypto_cbc_ctx *ctx = crypto_tfm_ctx(tfm);
 274         crypto_free_cipher(ctx->child);
 275 }
 276
 277 static struct crypto_instance *crypto_cbc_alloc(void *param, unsigned int len)
 278 {
 279         struct crypto_instance *inst;
 280         struct crypto_alg *alg;
 281
 282         alg = crypto_get_attr_alg(param, len, CRYPTO_ALG_TYPE_CIPHER,
 283                                   CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC);
 284         if (IS_ERR(alg))
 285                 return ERR_PTR(PTR_ERR(alg));
 286
 287         inst = crypto_alloc_instance("cbc", alg);
 288         if (IS_ERR(inst))
 289                 goto out_put_alg;
 290
 291         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 292         inst->alg.cra_priority = alg->cra_priority;
 293         inst->alg.cra_blocksize = alg->cra_blocksize;
 294         inst->alg.cra_alignmask = alg->cra_alignmask;
 295         inst->alg.cra_type = &crypto_blkcipher_type;
 296
 297         if (!(alg->cra_blocksize % 4))
 298                 inst->alg.cra_alignmask |= 3;
 299         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 300         inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
 301         inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
 302
 303         inst->alg.cra_ctxsize = sizeof(struct crypto_cbc_ctx);
 304
 305         inst->alg.cra_init = crypto_cbc_init_tfm;
 306         inst->alg.cra_exit = crypto_cbc_exit_tfm;
 307
 308         inst->alg.cra_blkcipher.setkey = crypto_cbc_setkey;
 309         inst->alg.cra_blkcipher.encrypt = crypto_cbc_encrypt;
 310         inst->alg.cra_blkcipher.decrypt = crypto_cbc_decrypt;
 311
 312 out_put_alg:
 313         crypto_mod_put(alg);
 314         return inst;
 315 }
 316
 317 static void crypto_cbc_free(struct crypto_instance *inst)
 318 {
 319         crypto_drop_spawn(crypto_instance_ctx(inst));
 320         kfree(inst);
 321 }
 322
 323 static struct crypto_template crypto_cbc_tmpl = {
 324         .name = "cbc",
 325         .alloc = crypto_cbc_alloc,
 326         .free = crypto_cbc_free,
 327         .module = THIS_MODULE,
 328 };
 329
 330 static int __init crypto_cbc_module_init(void)
 331 {
 332         return crypto_register_template(&crypto_cbc_tmpl);
 333 }
 334
 335 static void __exit crypto_cbc_module_exit(void)
 336 {
 337         crypto_unregister_template(&crypto_cbc_tmpl);
 338 }
 339
 340 module_init(crypto_cbc_module_init);
 341 module_exit(crypto_cbc_module_exit);
 342
 343 MODULE_LICENSE("GPL");
 344 MODULE_DESCRIPTION("CBC block cipher algorithm");