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 om 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         u32 *flags = &parent->crt_flags;
  39         int err;
  40
  41         /* key consists of keys of equal size concatenated, therefore
  42          * the length must be even */
  43         if (keylen % 2) {
  44                 /* tell the user why there was an error */
  45                 *flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
  46                 return -EINVAL;
  47         }
  48
  49         /* we need two cipher instances: one to compute the initial 'tweak'
  50          * by encrypting the IV (usually the 'plain' iv) and the other
  51          * one to encrypt and decrypt the data */
  52
  53         /* tweak cipher, uses Key2 i.e. the second half of *key */
  54         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  55         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  56                                        CRYPTO_TFM_REQ_MASK);
  57         err = crypto_cipher_setkey(child, key + keylen/2, keylen/2);
  58         if (err)
  59                 return err;
  60
  61         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  62                                      CRYPTO_TFM_RES_MASK);
  63
  64         child = ctx->child;
  65
  66         /* data cipher, uses Key1 i.e. the first half of *key */
  67         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  68         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  69                                        CRYPTO_TFM_REQ_MASK);
  70         err = crypto_cipher_setkey(child, key, keylen/2);
  71         if (err)
  72                 return err;
  73
  74         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  75                                      CRYPTO_TFM_RES_MASK);
  76
  77         return 0;
  78 }
  79
  80 struct sinfo {
  81         be128 *t;
  82         struct crypto_tfm *tfm;
  83         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  84 };
  85
  86 static inline void xts_round(struct sinfo *s, void *dst, const void *src)
  87 {
  88         be128_xor(dst, s->t, src);              /* PP <- T xor P */
  89         s->fn(s->tfm, dst, dst);                /* CC <- E(Key1,PP) */
  90         be128_xor(dst, dst, s->t);              /* C <- T xor CC */
  91 }
  92
  93 static int crypt(struct blkcipher_desc *d,
  94                  struct blkcipher_walk *w, struct priv *ctx,
  95                  void (*tw)(struct crypto_tfm *, u8 *, const u8 *),
  96                  void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
  97 {
  98         int err;
  99         unsigned int avail;
 100         const int bs = XTS_BLOCK_SIZE;
 101         struct sinfo s = {
 102                 .tfm = crypto_cipher_tfm(ctx->child),
 103                 .fn = fn
 104         };
 105         u8 *wsrc;
 106         u8 *wdst;
 107
 108         err = blkcipher_walk_virt(d, w);
 109         if (!w->nbytes)
 110                 return err;
 111
 112         s.t = (be128 *)w->iv;
 113         avail = w->nbytes;
 114
 115         wsrc = w->src.virt.addr;
 116         wdst = w->dst.virt.addr;
 117
 118         /* calculate first value of T */
 119         tw(crypto_cipher_tfm(ctx->tweak), w->iv, w->iv);
 120
 121         goto first;
 122
 123         for (;;) {
 124                 do {
 125                         gf128mul_x_ble(s.t, s.t);
 126
 127 first:
 128                         xts_round(&s, wdst, wsrc);
 129
 130                         wsrc += bs;
 131                         wdst += bs;
 132                 } while ((avail -= bs) >= bs);
 133
 134                 err = blkcipher_walk_done(d, w, avail);
 135                 if (!w->nbytes)
 136                         break;
 137
 138                 avail = w->nbytes;
 139
 140                 wsrc = w->src.virt.addr;
 141                 wdst = w->dst.virt.addr;
 142         }
 143
 144         return err;
 145 }
 146
 147 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 148                    struct scatterlist *src, unsigned int nbytes)
 149 {
 150         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 151         struct blkcipher_walk w;
 152
 153         blkcipher_walk_init(&w, dst, src, nbytes);
 154         return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
 155                      crypto_cipher_alg(ctx->child)->cia_encrypt);
 156 }
 157
 158 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 159                    struct scatterlist *src, unsigned int nbytes)
 160 {
 161         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 162         struct blkcipher_walk w;
 163
 164         blkcipher_walk_init(&w, dst, src, nbytes);
 165         return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
 166                      crypto_cipher_alg(ctx->child)->cia_decrypt);
 167 }
 168
 169 int xts_crypt(struct blkcipher_desc *desc, struct scatterlist *sdst,
 170               struct scatterlist *ssrc, unsigned int nbytes,
 171               struct xts_crypt_req *req)
 172 {
 173         const unsigned int bsize = XTS_BLOCK_SIZE;
 174         const unsigned int max_blks = req->tbuflen / bsize;
 175         struct blkcipher_walk walk;
 176         unsigned int nblocks;
 177         be128 *src, *dst, *t;
 178         be128 *t_buf = req->tbuf;
 179         int err, i;
 180
 181         BUG_ON(max_blks < 1);
 182
 183         blkcipher_walk_init(&walk, sdst, ssrc, nbytes);
 184
 185         err = blkcipher_walk_virt(desc, &walk);
 186         nbytes = walk.nbytes;
 187         if (!nbytes)
 188                 return err;
 189
 190         nblocks = min(nbytes / bsize, max_blks);
 191         src = (be128 *)walk.src.virt.addr;
 192         dst = (be128 *)walk.dst.virt.addr;
 193
 194         /* calculate first value of T */
 195         req->tweak_fn(req->tweak_ctx, (u8 *)&t_buf[0], walk.iv);
 196
 197         i = 0;
 198         goto first;
 199
 200         for (;;) {
 201                 do {
 202                         for (i = 0; i < nblocks; i++) {
 203                                 gf128mul_x_ble(&t_buf[i], t);
 204 first:
 205                                 t = &t_buf[i];
 206
 207                                 /* PP <- T xor P */
 208                                 be128_xor(dst + i, t, src + i);
 209                         }
 210
 211                         /* CC <- E(Key2,PP) */
 212                         req->crypt_fn(req->crypt_ctx, (u8 *)dst,
 213                                       nblocks * bsize);
 214
 215                         /* C <- T xor CC */
 216                         for (i = 0; i < nblocks; i++)
 217                                 be128_xor(dst + i, dst + i, &t_buf[i]);
 218
 219                         src += nblocks;
 220                         dst += nblocks;
 221                         nbytes -= nblocks * bsize;
 222                         nblocks = min(nbytes / bsize, max_blks);
 223                 } while (nblocks > 0);
 224
 225                 *(be128 *)walk.iv = *t;
 226
 227                 err = blkcipher_walk_done(desc, &walk, nbytes);
 228                 nbytes = walk.nbytes;
 229                 if (!nbytes)
 230                         break;
 231
 232                 nblocks = min(nbytes / bsize, max_blks);
 233                 src = (be128 *)walk.src.virt.addr;
 234                 dst = (be128 *)walk.dst.virt.addr;
 235         }
 236
 237         return err;
 238 }
 239 EXPORT_SYMBOL_GPL(xts_crypt);
 240
 241 static int init_tfm(struct crypto_tfm *tfm)
 242 {
 243         struct crypto_cipher *cipher;
 244         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 245         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 246         struct priv *ctx = crypto_tfm_ctx(tfm);
 247         u32 *flags = &tfm->crt_flags;
 248
 249         cipher = crypto_spawn_cipher(spawn);
 250         if (IS_ERR(cipher))
 251                 return PTR_ERR(cipher);
 252
 253         if (crypto_cipher_blocksize(cipher) != XTS_BLOCK_SIZE) {
 254                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 255                 crypto_free_cipher(cipher);
 256                 return -EINVAL;
 257         }
 258
 259         ctx->child = cipher;
 260
 261         cipher = crypto_spawn_cipher(spawn);
 262         if (IS_ERR(cipher)) {
 263                 crypto_free_cipher(ctx->child);
 264                 return PTR_ERR(cipher);
 265         }
 266
 267         /* this check isn't really needed, leave it here just in case */
 268         if (crypto_cipher_blocksize(cipher) != XTS_BLOCK_SIZE) {
 269                 crypto_free_cipher(cipher);
 270                 crypto_free_cipher(ctx->child);
 271                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 272                 return -EINVAL;
 273         }
 274
 275         ctx->tweak = cipher;
 276
 277         return 0;
 278 }
 279
 280 static void exit_tfm(struct crypto_tfm *tfm)
 281 {
 282         struct priv *ctx = crypto_tfm_ctx(tfm);
 283         crypto_free_cipher(ctx->child);
 284         crypto_free_cipher(ctx->tweak);
 285 }
 286
 287 static struct crypto_instance *alloc(struct rtattr **tb)
 288 {
 289         struct crypto_instance *inst;
 290         struct crypto_alg *alg;
 291         int err;
 292
 293         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 294         if (err)
 295                 return ERR_PTR(err);
 296
 297         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 298                                   CRYPTO_ALG_TYPE_MASK);
 299         if (IS_ERR(alg))
 300                 return ERR_CAST(alg);
 301
 302         inst = crypto_alloc_instance("xts", alg);
 303         if (IS_ERR(inst))
 304                 goto out_put_alg;
 305
 306         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 307         inst->alg.cra_priority = alg->cra_priority;
 308         inst->alg.cra_blocksize = alg->cra_blocksize;
 309
 310         if (alg->cra_alignmask < 7)
 311                 inst->alg.cra_alignmask = 7;
 312         else
 313                 inst->alg.cra_alignmask = alg->cra_alignmask;
 314
 315         inst->alg.cra_type = &crypto_blkcipher_type;
 316
 317         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 318         inst->alg.cra_blkcipher.min_keysize =
 319                 2 * alg->cra_cipher.cia_min_keysize;
 320         inst->alg.cra_blkcipher.max_keysize =
 321                 2 * alg->cra_cipher.cia_max_keysize;
 322
 323         inst->alg.cra_ctxsize = sizeof(struct priv);
 324
 325         inst->alg.cra_init = init_tfm;
 326         inst->alg.cra_exit = exit_tfm;
 327
 328         inst->alg.cra_blkcipher.setkey = setkey;
 329         inst->alg.cra_blkcipher.encrypt = encrypt;
 330         inst->alg.cra_blkcipher.decrypt = decrypt;
 331
 332 out_put_alg:
 333         crypto_mod_put(alg);
 334         return inst;
 335 }
 336
 337 static void free(struct crypto_instance *inst)
 338 {
 339         crypto_drop_spawn(crypto_instance_ctx(inst));
 340         kfree(inst);
 341 }
 342
 343 static struct crypto_template crypto_tmpl = {
 344         .name = "xts",
 345         .alloc = alloc,
 346         .free = free,
 347         .module = THIS_MODULE,
 348 };
 349
 350 static int __init crypto_module_init(void)
 351 {
 352         return crypto_register_template(&crypto_tmpl);
 353 }
 354
 355 static void __exit crypto_module_exit(void)
 356 {
 357         crypto_unregister_template(&crypto_tmpl);
 358 }
 359
 360 module_init(crypto_module_init);
 361 module_exit(crypto_module_exit);
 362
 363 MODULE_LICENSE("GPL");
 364 MODULE_DESCRIPTION("XTS block cipher mode");