crypto/xts.c

   1 /* XTS: as defined in IEEE1619/D16
   2  *      http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
   3  *      (sector sizes which are not a multiple of 16 bytes are,
   4  *      however currently unsupported)
   5  *
   6  * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
   7  *
   8  * Based on ecb.c
   9  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
  10  *
  11  * This program is free software; you can redistribute it and/or modify it
  12  * under the terms of the GNU General Public License as published by the Free
  13  * Software Foundation; either version 2 of the License, or (at your option)
  14  * any later version.
  15  */
  16 #include <crypto/algapi.h>
  17 #include <linux/err.h>
  18 #include <linux/init.h>
  19 #include <linux/kernel.h>
  20 #include <linux/module.h>
  21 #include <linux/scatterlist.h>
  22 #include <linux/slab.h>
  23
  24 #include <crypto/xts.h>
  25 #include <crypto/b128ops.h>
  26 #include <crypto/gf128mul.h>
  27
  28 struct priv {
  29         struct crypto_cipher *child;
  30         struct crypto_cipher *tweak;
  31 };
  32
  33 static int setkey(struct crypto_tfm *parent, const u8 *key,
  34                   unsigned int keylen)
  35 {
  36         struct priv *ctx = crypto_tfm_ctx(parent);
  37         struct crypto_cipher *child = ctx->tweak;
  38         int err;
  39
  40         err = xts_check_key(parent, key, keylen);
  41         if (err)
  42                 return err;
  43
  44         /* we need two cipher instances: one to compute the initial 'tweak'
  45          * by encrypting the IV (usually the 'plain' iv) and the other
  46          * one to encrypt and decrypt the data */
  47
  48         /* tweak cipher, uses Key2 i.e. the second half of *key */
  49         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  50         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  51                                        CRYPTO_TFM_REQ_MASK);
  52         err = crypto_cipher_setkey(child, key + keylen/2, keylen/2);
  53         if (err)
  54                 return err;
  55
  56         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  57                                      CRYPTO_TFM_RES_MASK);
  58
  59         child = ctx->child;
  60
  61         /* data cipher, uses Key1 i.e. the first half of *key */
  62         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  63         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  64                                        CRYPTO_TFM_REQ_MASK);
  65         err = crypto_cipher_setkey(child, key, keylen/2);
  66         if (err)
  67                 return err;
  68
  69         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  70                                      CRYPTO_TFM_RES_MASK);
  71
  72         return 0;
  73 }
  74
  75 struct sinfo {
  76         be128 *t;
  77         struct crypto_tfm *tfm;
  78         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  79 };
  80
  81 static inline void xts_round(struct sinfo *s, void *dst, const void *src)
  82 {
  83         be128_xor(dst, s->t, src);              /* PP <- T xor P */
  84         s->fn(s->tfm, dst, dst);                /* CC <- E(Key1,PP) */
  85         be128_xor(dst, dst, s->t);              /* C <- T xor CC */
  86 }
  87
  88 static int crypt(struct blkcipher_desc *d,
  89                  struct blkcipher_walk *w, struct priv *ctx,
  90                  void (*tw)(struct crypto_tfm *, u8 *, const u8 *),
  91                  void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
  92 {
  93         int err;
  94         unsigned int avail;
  95         const int bs = XTS_BLOCK_SIZE;
  96         struct sinfo s = {
  97                 .tfm = crypto_cipher_tfm(ctx->child),
  98                 .fn = fn
  99         };
 100         u8 *wsrc;
 101         u8 *wdst;
 102
 103         err = blkcipher_walk_virt(d, w);
 104         if (!w->nbytes)
 105                 return err;
 106
 107         s.t = (be128 *)w->iv;
 108         avail = w->nbytes;
 109
 110         wsrc = w->src.virt.addr;
 111         wdst = w->dst.virt.addr;
 112
 113         /* calculate first value of T */
 114         tw(crypto_cipher_tfm(ctx->tweak), w->iv, w->iv);
 115
 116         goto first;
 117
 118         for (;;) {
 119                 do {
 120                         gf128mul_x_ble(s.t, s.t);
 121
 122 first:
 123                         xts_round(&s, wdst, wsrc);
 124
 125                         wsrc += bs;
 126                         wdst += bs;
 127                 } while ((avail -= bs) >= bs);
 128
 129                 err = blkcipher_walk_done(d, w, avail);
 130                 if (!w->nbytes)
 131                         break;
 132
 133                 avail = w->nbytes;
 134
 135                 wsrc = w->src.virt.addr;
 136                 wdst = w->dst.virt.addr;
 137         }
 138
 139         return err;
 140 }
 141
 142 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 143                    struct scatterlist *src, unsigned int nbytes)
 144 {
 145         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 146         struct blkcipher_walk w;
 147
 148         blkcipher_walk_init(&w, dst, src, nbytes);
 149         return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
 150                      crypto_cipher_alg(ctx->child)->cia_encrypt);
 151 }
 152
 153 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 154                    struct scatterlist *src, unsigned int nbytes)
 155 {
 156         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 157         struct blkcipher_walk w;
 158
 159         blkcipher_walk_init(&w, dst, src, nbytes);
 160         return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
 161                      crypto_cipher_alg(ctx->child)->cia_decrypt);
 162 }
 163
 164 int xts_crypt(struct blkcipher_desc *desc, struct scatterlist *sdst,
 165               struct scatterlist *ssrc, unsigned int nbytes,
 166               struct xts_crypt_req *req)
 167 {
 168         const unsigned int bsize = XTS_BLOCK_SIZE;
 169         const unsigned int max_blks = req->tbuflen / bsize;
 170         struct blkcipher_walk walk;
 171         unsigned int nblocks;
 172         be128 *src, *dst, *t;
 173         be128 *t_buf = req->tbuf;
 174         int err, i;
 175
 176         BUG_ON(max_blks < 1);
 177
 178         blkcipher_walk_init(&walk, sdst, ssrc, nbytes);
 179
 180         err = blkcipher_walk_virt(desc, &walk);
 181         nbytes = walk.nbytes;
 182         if (!nbytes)
 183                 return err;
 184
 185         nblocks = min(nbytes / bsize, max_blks);
 186         src = (be128 *)walk.src.virt.addr;
 187         dst = (be128 *)walk.dst.virt.addr;
 188
 189         /* calculate first value of T */
 190         req->tweak_fn(req->tweak_ctx, (u8 *)&t_buf[0], walk.iv);
 191
 192         i = 0;
 193         goto first;
 194
 195         for (;;) {
 196                 do {
 197                         for (i = 0; i < nblocks; i++) {
 198                                 gf128mul_x_ble(&t_buf[i], t);
 199 first:
 200                                 t = &t_buf[i];
 201
 202                                 /* PP <- T xor P */
 203                                 be128_xor(dst + i, t, src + i);
 204                         }
 205
 206                         /* CC <- E(Key2,PP) */
 207                         req->crypt_fn(req->crypt_ctx, (u8 *)dst,
 208                                       nblocks * bsize);
 209
 210                         /* C <- T xor CC */
 211                         for (i = 0; i < nblocks; i++)
 212                                 be128_xor(dst + i, dst + i, &t_buf[i]);
 213
 214                         src += nblocks;
 215                         dst += nblocks;
 216                         nbytes -= nblocks * bsize;
 217                         nblocks = min(nbytes / bsize, max_blks);
 218                 } while (nblocks > 0);
 219
 220                 *(be128 *)walk.iv = *t;
 221
 222                 err = blkcipher_walk_done(desc, &walk, nbytes);
 223                 nbytes = walk.nbytes;
 224                 if (!nbytes)
 225                         break;
 226
 227                 nblocks = min(nbytes / bsize, max_blks);
 228                 src = (be128 *)walk.src.virt.addr;
 229                 dst = (be128 *)walk.dst.virt.addr;
 230         }
 231
 232         return err;
 233 }
 234 EXPORT_SYMBOL_GPL(xts_crypt);
 235
 236 static int init_tfm(struct crypto_tfm *tfm)
 237 {
 238         struct crypto_cipher *cipher;
 239         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 240         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 241         struct priv *ctx = crypto_tfm_ctx(tfm);
 242         u32 *flags = &tfm->crt_flags;
 243
 244         cipher = crypto_spawn_cipher(spawn);
 245         if (IS_ERR(cipher))
 246                 return PTR_ERR(cipher);
 247
 248         if (crypto_cipher_blocksize(cipher) != XTS_BLOCK_SIZE) {
 249                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 250                 crypto_free_cipher(cipher);
 251                 return -EINVAL;
 252         }
 253
 254         ctx->child = cipher;
 255
 256         cipher = crypto_spawn_cipher(spawn);
 257         if (IS_ERR(cipher)) {
 258                 crypto_free_cipher(ctx->child);
 259                 return PTR_ERR(cipher);
 260         }
 261
 262         /* this check isn't really needed, leave it here just in case */
 263         if (crypto_cipher_blocksize(cipher) != XTS_BLOCK_SIZE) {
 264                 crypto_free_cipher(cipher);
 265                 crypto_free_cipher(ctx->child);
 266                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 267                 return -EINVAL;
 268         }
 269
 270         ctx->tweak = cipher;
 271
 272         return 0;
 273 }
 274
 275 static void exit_tfm(struct crypto_tfm *tfm)
 276 {
 277         struct priv *ctx = crypto_tfm_ctx(tfm);
 278         crypto_free_cipher(ctx->child);
 279         crypto_free_cipher(ctx->tweak);
 280 }
 281
 282 static struct crypto_instance *alloc(struct rtattr **tb)
 283 {
 284         struct crypto_instance *inst;
 285         struct crypto_alg *alg;
 286         int err;
 287
 288         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 289         if (err)
 290                 return ERR_PTR(err);
 291
 292         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 293                                   CRYPTO_ALG_TYPE_MASK);
 294         if (IS_ERR(alg))
 295                 return ERR_CAST(alg);
 296
 297         inst = crypto_alloc_instance("xts", alg);
 298         if (IS_ERR(inst))
 299                 goto out_put_alg;
 300
 301         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 302         inst->alg.cra_priority = alg->cra_priority;
 303         inst->alg.cra_blocksize = alg->cra_blocksize;
 304
 305         if (alg->cra_alignmask < 7)
 306                 inst->alg.cra_alignmask = 7;
 307         else
 308                 inst->alg.cra_alignmask = alg->cra_alignmask;
 309
 310         inst->alg.cra_type = &crypto_blkcipher_type;
 311
 312         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 313         inst->alg.cra_blkcipher.min_keysize =
 314                 2 * alg->cra_cipher.cia_min_keysize;
 315         inst->alg.cra_blkcipher.max_keysize =
 316                 2 * alg->cra_cipher.cia_max_keysize;
 317
 318         inst->alg.cra_ctxsize = sizeof(struct priv);
 319
 320         inst->alg.cra_init = init_tfm;
 321         inst->alg.cra_exit = exit_tfm;
 322
 323         inst->alg.cra_blkcipher.setkey = setkey;
 324         inst->alg.cra_blkcipher.encrypt = encrypt;
 325         inst->alg.cra_blkcipher.decrypt = decrypt;
 326
 327 out_put_alg:
 328         crypto_mod_put(alg);
 329         return inst;
 330 }
 331
 332 static void free(struct crypto_instance *inst)
 333 {
 334         crypto_drop_spawn(crypto_instance_ctx(inst));
 335         kfree(inst);
 336 }
 337
 338 static struct crypto_template crypto_tmpl = {
 339         .name = "xts",
 340         .alloc = alloc,
 341         .free = free,
 342         .module = THIS_MODULE,
 343 };
 344
 345 static int __init crypto_module_init(void)
 346 {
 347         return crypto_register_template(&crypto_tmpl);
 348 }
 349
 350 static void __exit crypto_module_exit(void)
 351 {
 352         crypto_unregister_template(&crypto_tmpl);
 353 }
 354
 355 module_init(crypto_module_init);
 356 module_exit(crypto_module_exit);
 357
 358 MODULE_LICENSE("GPL");
 359 MODULE_DESCRIPTION("XTS block cipher mode");
 360 MODULE_ALIAS_CRYPTO("xts");