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/b128ops.h>
  25 #include <crypto/gf128mul.h>
  26
  27 struct priv {
  28         struct crypto_cipher *child;
  29         struct crypto_cipher *tweak;
  30 };
  31
  32 static int setkey(struct crypto_tfm *parent, const u8 *key,
  33                   unsigned int keylen)
  34 {
  35         struct priv *ctx = crypto_tfm_ctx(parent);
  36         struct crypto_cipher *child = ctx->tweak;
  37         u32 *flags = &parent->crt_flags;
  38         int err;
  39
  40         /* key consists of keys of equal size concatenated, therefore
  41          * the length must be even */
  42         if (keylen % 2) {
  43                 /* tell the user why there was an error */
  44                 *flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
  45                 return -EINVAL;
  46         }
  47
  48         /* we need two cipher instances: one to compute the inital 'tweak'
  49          * by encrypting the IV (usually the 'plain' iv) and the other
  50          * one to encrypt and decrypt the data */
  51
  52         /* tweak cipher, uses Key2 i.e. the second half of *key */
  53         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  54         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  55                                        CRYPTO_TFM_REQ_MASK);
  56         err = crypto_cipher_setkey(child, key + keylen/2, keylen/2);
  57         if (err)
  58                 return err;
  59
  60         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  61                                      CRYPTO_TFM_RES_MASK);
  62
  63         child = ctx->child;
  64
  65         /* data cipher, uses Key1 i.e. the first half of *key */
  66         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  67         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  68                                        CRYPTO_TFM_REQ_MASK);
  69         err = crypto_cipher_setkey(child, key, keylen/2);
  70         if (err)
  71                 return err;
  72
  73         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  74                                      CRYPTO_TFM_RES_MASK);
  75
  76         return 0;
  77 }
  78
  79 struct sinfo {
  80         be128 *t;
  81         struct crypto_tfm *tfm;
  82         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  83 };
  84
  85 static inline void xts_round(struct sinfo *s, void *dst, const void *src)
  86 {
  87         be128_xor(dst, s->t, src);              /* PP <- T xor P */
  88         s->fn(s->tfm, dst, dst);                /* CC <- E(Key1,PP) */
  89         be128_xor(dst, dst, s->t);              /* C <- T xor CC */
  90 }
  91
  92 static int crypt(struct blkcipher_desc *d,
  93                  struct blkcipher_walk *w, struct priv *ctx,
  94                  void (*tw)(struct crypto_tfm *, u8 *, const u8 *),
  95                  void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
  96 {
  97         int err;
  98         unsigned int avail;
  99         const int bs = crypto_cipher_blocksize(ctx->child);
 100         struct sinfo s = {
 101                 .tfm = crypto_cipher_tfm(ctx->child),
 102                 .fn = fn
 103         };
 104         u8 *wsrc;
 105         u8 *wdst;
 106
 107         err = blkcipher_walk_virt(d, w);
 108         if (!w->nbytes)
 109                 return err;
 110
 111         s.t = (be128 *)w->iv;
 112         avail = w->nbytes;
 113
 114         wsrc = w->src.virt.addr;
 115         wdst = w->dst.virt.addr;
 116
 117         /* calculate first value of T */
 118         tw(crypto_cipher_tfm(ctx->tweak), w->iv, w->iv);
 119
 120         goto first;
 121
 122         for (;;) {
 123                 do {
 124                         gf128mul_x_ble(s.t, s.t);
 125
 126 first:
 127                         xts_round(&s, wdst, wsrc);
 128
 129                         wsrc += bs;
 130                         wdst += bs;
 131                 } while ((avail -= bs) >= bs);
 132
 133                 err = blkcipher_walk_done(d, w, avail);
 134                 if (!w->nbytes)
 135                         break;
 136
 137                 avail = w->nbytes;
 138
 139                 wsrc = w->src.virt.addr;
 140                 wdst = w->dst.virt.addr;
 141         }
 142
 143         return err;
 144 }
 145
 146 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 147                    struct scatterlist *src, unsigned int nbytes)
 148 {
 149         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 150         struct blkcipher_walk w;
 151
 152         blkcipher_walk_init(&w, dst, src, nbytes);
 153         return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
 154                      crypto_cipher_alg(ctx->child)->cia_encrypt);
 155 }
 156
 157 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 158                    struct scatterlist *src, unsigned int nbytes)
 159 {
 160         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 161         struct blkcipher_walk w;
 162
 163         blkcipher_walk_init(&w, dst, src, nbytes);
 164         return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
 165                      crypto_cipher_alg(ctx->child)->cia_decrypt);
 166 }
 167
 168 static int init_tfm(struct crypto_tfm *tfm)
 169 {
 170         struct crypto_cipher *cipher;
 171         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 172         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 173         struct priv *ctx = crypto_tfm_ctx(tfm);
 174         u32 *flags = &tfm->crt_flags;
 175
 176         cipher = crypto_spawn_cipher(spawn);
 177         if (IS_ERR(cipher))
 178                 return PTR_ERR(cipher);
 179
 180         if (crypto_cipher_blocksize(cipher) != 16) {
 181                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 182                 crypto_free_cipher(cipher);
 183                 return -EINVAL;
 184         }
 185
 186         ctx->child = cipher;
 187
 188         cipher = crypto_spawn_cipher(spawn);
 189         if (IS_ERR(cipher)) {
 190                 crypto_free_cipher(ctx->child);
 191                 return PTR_ERR(cipher);
 192         }
 193
 194         /* this check isn't really needed, leave it here just in case */
 195         if (crypto_cipher_blocksize(cipher) != 16) {
 196                 crypto_free_cipher(cipher);
 197                 crypto_free_cipher(ctx->child);
 198                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 199                 return -EINVAL;
 200         }
 201
 202         ctx->tweak = cipher;
 203
 204         return 0;
 205 }
 206
 207 static void exit_tfm(struct crypto_tfm *tfm)
 208 {
 209         struct priv *ctx = crypto_tfm_ctx(tfm);
 210         crypto_free_cipher(ctx->child);
 211         crypto_free_cipher(ctx->tweak);
 212 }
 213
 214 static struct crypto_instance *alloc(struct rtattr **tb)
 215 {
 216         struct crypto_instance *inst;
 217         struct crypto_alg *alg;
 218         int err;
 219
 220         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 221         if (err)
 222                 return ERR_PTR(err);
 223
 224         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 225                                   CRYPTO_ALG_TYPE_MASK);
 226         if (IS_ERR(alg))
 227                 return ERR_PTR(PTR_ERR(alg));
 228
 229         inst = crypto_alloc_instance("xts", alg);
 230         if (IS_ERR(inst))
 231                 goto out_put_alg;
 232
 233         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 234         inst->alg.cra_priority = alg->cra_priority;
 235         inst->alg.cra_blocksize = alg->cra_blocksize;
 236
 237         if (alg->cra_alignmask < 7)
 238                 inst->alg.cra_alignmask = 7;
 239         else
 240                 inst->alg.cra_alignmask = alg->cra_alignmask;
 241
 242         inst->alg.cra_type = &crypto_blkcipher_type;
 243
 244         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 245         inst->alg.cra_blkcipher.min_keysize =
 246                 2 * alg->cra_cipher.cia_min_keysize;
 247         inst->alg.cra_blkcipher.max_keysize =
 248                 2 * alg->cra_cipher.cia_max_keysize;
 249
 250         inst->alg.cra_ctxsize = sizeof(struct priv);
 251
 252         inst->alg.cra_init = init_tfm;
 253         inst->alg.cra_exit = exit_tfm;
 254
 255         inst->alg.cra_blkcipher.setkey = setkey;
 256         inst->alg.cra_blkcipher.encrypt = encrypt;
 257         inst->alg.cra_blkcipher.decrypt = decrypt;
 258
 259 out_put_alg:
 260         crypto_mod_put(alg);
 261         return inst;
 262 }
 263
 264 static void free(struct crypto_instance *inst)
 265 {
 266         crypto_drop_spawn(crypto_instance_ctx(inst));
 267         kfree(inst);
 268 }
 269
 270 static struct crypto_template crypto_tmpl = {
 271         .name = "xts",
 272         .alloc = alloc,
 273         .free = free,
 274         .module = THIS_MODULE,
 275 };
 276
 277 static int __init crypto_module_init(void)
 278 {
 279         return crypto_register_template(&crypto_tmpl);
 280 }
 281
 282 static void __exit crypto_module_exit(void)
 283 {
 284         crypto_unregister_template(&crypto_tmpl);
 285 }
 286
 287 module_init(crypto_module_init);
 288 module_exit(crypto_module_exit);
 289
 290 MODULE_LICENSE("GPL");
 291 MODULE_DESCRIPTION("XTS block cipher mode");