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/internal/skcipher.h>
  17 #include <crypto/scatterwalk.h>
  18 #include <linux/err.h>
  19 #include <linux/init.h>
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <linux/scatterlist.h>
  23 #include <linux/slab.h>
  24
  25 #include <crypto/xts.h>
  26 #include <crypto/b128ops.h>
  27 #include <crypto/gf128mul.h>
  28
  29 struct priv {
  30         struct crypto_skcipher *child;
  31         struct crypto_cipher *tweak;
  32 };
  33
  34 struct xts_instance_ctx {
  35         struct crypto_skcipher_spawn spawn;
  36         char name[CRYPTO_MAX_ALG_NAME];
  37 };
  38
  39 struct rctx {
  40         le128 t;
  41         struct skcipher_request subreq;
  42 };
  43
  44 static int setkey(struct crypto_skcipher *parent, const u8 *key,
  45                   unsigned int keylen)
  46 {
  47         struct priv *ctx = crypto_skcipher_ctx(parent);
  48         struct crypto_skcipher *child;
  49         struct crypto_cipher *tweak;
  50         int err;
  51
  52         err = xts_verify_key(parent, key, keylen);
  53         if (err)
  54                 return err;
  55
  56         keylen /= 2;
  57
  58         /* we need two cipher instances: one to compute the initial 'tweak'
  59          * by encrypting the IV (usually the 'plain' iv) and the other
  60          * one to encrypt and decrypt the data */
  61
  62         /* tweak cipher, uses Key2 i.e. the second half of *key */
  63         tweak = ctx->tweak;
  64         crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
  65         crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
  66                                        CRYPTO_TFM_REQ_MASK);
  67         err = crypto_cipher_setkey(tweak, key + keylen, keylen);
  68         crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(tweak) &
  69                                           CRYPTO_TFM_RES_MASK);
  70         if (err)
  71                 return err;
  72
  73         /* data cipher, uses Key1 i.e. the first half of *key */
  74         child = ctx->child;
  75         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  76         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
  77                                          CRYPTO_TFM_REQ_MASK);
  78         err = crypto_skcipher_setkey(child, key, keylen);
  79         crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
  80                                           CRYPTO_TFM_RES_MASK);
  81
  82         return err;
  83 }
  84
  85 /*
  86  * We compute the tweak masks twice (both before and after the ECB encryption or
  87  * decryption) to avoid having to allocate a temporary buffer and/or make
  88  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
  89  * just doing the gf128mul_x_ble() calls again.
  90  */
  91 static int xor_tweak(struct skcipher_request *req, bool second_pass)
  92 {
  93         struct rctx *rctx = skcipher_request_ctx(req);
  94         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  95         const int bs = XTS_BLOCK_SIZE;
  96         struct skcipher_walk w;
  97         le128 t = rctx->t;
  98         int err;
  99
 100         if (second_pass) {
 101                 req = &rctx->subreq;
 102                 /* set to our TFM to enforce correct alignment: */
 103                 skcipher_request_set_tfm(req, tfm);
 104         }
 105         err = skcipher_walk_virt(&w, req, false);
 106
 107         while (w.nbytes) {
 108                 unsigned int avail = w.nbytes;
 109                 le128 *wsrc;
 110                 le128 *wdst;
 111
 112                 wsrc = w.src.virt.addr;
 113                 wdst = w.dst.virt.addr;
 114
 115                 do {
 116                         le128_xor(wdst++, &t, wsrc++);
 117                         gf128mul_x_ble(&t, &t);
 118                 } while ((avail -= bs) >= bs);
 119
 120                 err = skcipher_walk_done(&w, avail);
 121         }
 122
 123         return err;
 124 }
 125
 126 static int xor_tweak_pre(struct skcipher_request *req)
 127 {
 128         return xor_tweak(req, false);
 129 }
 130
 131 static int xor_tweak_post(struct skcipher_request *req)
 132 {
 133         return xor_tweak(req, true);
 134 }
 135
 136 static void crypt_done(struct crypto_async_request *areq, int err)
 137 {
 138         struct skcipher_request *req = areq->data;
 139
 140         if (!err) {
 141                 struct rctx *rctx = skcipher_request_ctx(req);
 142
 143                 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 144                 err = xor_tweak_post(req);
 145         }
 146
 147         skcipher_request_complete(req, err);
 148 }
 149
 150 static void init_crypt(struct skcipher_request *req)
 151 {
 152         struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 153         struct rctx *rctx = skcipher_request_ctx(req);
 154         struct skcipher_request *subreq = &rctx->subreq;
 155
 156         skcipher_request_set_tfm(subreq, ctx->child);
 157         skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
 158         skcipher_request_set_crypt(subreq, req->dst, req->dst,
 159                                    req->cryptlen, NULL);
 160
 161         /* calculate first value of T */
 162         crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
 163 }
 164
 165 static int encrypt(struct skcipher_request *req)
 166 {
 167         struct rctx *rctx = skcipher_request_ctx(req);
 168         struct skcipher_request *subreq = &rctx->subreq;
 169
 170         init_crypt(req);
 171         return xor_tweak_pre(req) ?:
 172                 crypto_skcipher_encrypt(subreq) ?:
 173                 xor_tweak_post(req);
 174 }
 175
 176 static int decrypt(struct skcipher_request *req)
 177 {
 178         struct rctx *rctx = skcipher_request_ctx(req);
 179         struct skcipher_request *subreq = &rctx->subreq;
 180
 181         init_crypt(req);
 182         return xor_tweak_pre(req) ?:
 183                 crypto_skcipher_decrypt(subreq) ?:
 184                 xor_tweak_post(req);
 185 }
 186
 187 static int init_tfm(struct crypto_skcipher *tfm)
 188 {
 189         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 190         struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
 191         struct priv *ctx = crypto_skcipher_ctx(tfm);
 192         struct crypto_skcipher *child;
 193         struct crypto_cipher *tweak;
 194
 195         child = crypto_spawn_skcipher(&ictx->spawn);
 196         if (IS_ERR(child))
 197                 return PTR_ERR(child);
 198
 199         ctx->child = child;
 200
 201         tweak = crypto_alloc_cipher(ictx->name, 0, 0);
 202         if (IS_ERR(tweak)) {
 203                 crypto_free_skcipher(ctx->child);
 204                 return PTR_ERR(tweak);
 205         }
 206
 207         ctx->tweak = tweak;
 208
 209         crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
 210                                          sizeof(struct rctx));
 211
 212         return 0;
 213 }
 214
 215 static void exit_tfm(struct crypto_skcipher *tfm)
 216 {
 217         struct priv *ctx = crypto_skcipher_ctx(tfm);
 218
 219         crypto_free_skcipher(ctx->child);
 220         crypto_free_cipher(ctx->tweak);
 221 }
 222
 223 static void free(struct skcipher_instance *inst)
 224 {
 225         crypto_drop_skcipher(skcipher_instance_ctx(inst));
 226         kfree(inst);
 227 }
 228
 229 static int create(struct crypto_template *tmpl, struct rtattr **tb)
 230 {
 231         struct skcipher_instance *inst;
 232         struct crypto_attr_type *algt;
 233         struct xts_instance_ctx *ctx;
 234         struct skcipher_alg *alg;
 235         const char *cipher_name;
 236         u32 mask;
 237         int err;
 238
 239         algt = crypto_get_attr_type(tb);
 240         if (IS_ERR(algt))
 241                 return PTR_ERR(algt);
 242
 243         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 244                 return -EINVAL;
 245
 246         cipher_name = crypto_attr_alg_name(tb[1]);
 247         if (IS_ERR(cipher_name))
 248                 return PTR_ERR(cipher_name);
 249
 250         inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
 251         if (!inst)
 252                 return -ENOMEM;
 253
 254         ctx = skcipher_instance_ctx(inst);
 255
 256         crypto_set_skcipher_spawn(&ctx->spawn, skcipher_crypto_instance(inst));
 257
 258         mask = crypto_requires_off(algt->type, algt->mask,
 259                                    CRYPTO_ALG_NEED_FALLBACK |
 260                                    CRYPTO_ALG_ASYNC);
 261
 262         err = crypto_grab_skcipher(&ctx->spawn, cipher_name, 0, mask);
 263         if (err == -ENOENT) {
 264                 err = -ENAMETOOLONG;
 265                 if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
 266                              cipher_name) >= CRYPTO_MAX_ALG_NAME)
 267                         goto err_free_inst;
 268
 269                 err = crypto_grab_skcipher(&ctx->spawn, ctx->name, 0, mask);
 270         }
 271
 272         if (err)
 273                 goto err_free_inst;
 274
 275         alg = crypto_skcipher_spawn_alg(&ctx->spawn);
 276
 277         err = -EINVAL;
 278         if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
 279                 goto err_drop_spawn;
 280
 281         if (crypto_skcipher_alg_ivsize(alg))
 282                 goto err_drop_spawn;
 283
 284         err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
 285                                   &alg->base);
 286         if (err)
 287                 goto err_drop_spawn;
 288
 289         err = -EINVAL;
 290         cipher_name = alg->base.cra_name;
 291
 292         /* Alas we screwed up the naming so we have to mangle the
 293          * cipher name.
 294          */
 295         if (!strncmp(cipher_name, "ecb(", 4)) {
 296                 unsigned len;
 297
 298                 len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
 299                 if (len < 2 || len >= sizeof(ctx->name))
 300                         goto err_drop_spawn;
 301
 302                 if (ctx->name[len - 1] != ')')
 303                         goto err_drop_spawn;
 304
 305                 ctx->name[len - 1] = 0;
 306
 307                 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 308                              "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) {
 309                         err = -ENAMETOOLONG;
 310                         goto err_drop_spawn;
 311                 }
 312         } else
 313                 goto err_drop_spawn;
 314
 315         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 316         inst->alg.base.cra_priority = alg->base.cra_priority;
 317         inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
 318         inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 319                                        (__alignof__(u64) - 1);
 320
 321         inst->alg.ivsize = XTS_BLOCK_SIZE;
 322         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
 323         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
 324
 325         inst->alg.base.cra_ctxsize = sizeof(struct priv);
 326
 327         inst->alg.init = init_tfm;
 328         inst->alg.exit = exit_tfm;
 329
 330         inst->alg.setkey = setkey;
 331         inst->alg.encrypt = encrypt;
 332         inst->alg.decrypt = decrypt;
 333
 334         inst->free = free;
 335
 336         err = skcipher_register_instance(tmpl, inst);
 337         if (err)
 338                 goto err_drop_spawn;
 339
 340 out:
 341         return err;
 342
 343 err_drop_spawn:
 344         crypto_drop_skcipher(&ctx->spawn);
 345 err_free_inst:
 346         kfree(inst);
 347         goto out;
 348 }
 349
 350 static struct crypto_template crypto_tmpl = {
 351         .name = "xts",
 352         .create = create,
 353         .module = THIS_MODULE,
 354 };
 355
 356 static int __init crypto_module_init(void)
 357 {
 358         return crypto_register_template(&crypto_tmpl);
 359 }
 360
 361 static void __exit crypto_module_exit(void)
 362 {
 363         crypto_unregister_template(&crypto_tmpl);
 364 }
 365
 366 subsys_initcall(crypto_module_init);
 367 module_exit(crypto_module_exit);
 368
 369 MODULE_LICENSE("GPL");
 370 MODULE_DESCRIPTION("XTS block cipher mode");
 371 MODULE_ALIAS_CRYPTO("xts");