crypto/xts.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* XTS: as defined in IEEE1619/D16
   3  *      http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
   4  *
   5  * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
   6  *
   7  * Based on ecb.c
   8  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   9  */
  10 #include <crypto/internal/skcipher.h>
  11 #include <crypto/scatterwalk.h>
  12 #include <linux/err.h>
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/scatterlist.h>
  17 #include <linux/slab.h>
  18
  19 #include <crypto/xts.h>
  20 #include <crypto/b128ops.h>
  21 #include <crypto/gf128mul.h>
  22
  23 struct priv {
  24         struct crypto_skcipher *child;
  25         struct crypto_cipher *tweak;
  26 };
  27
  28 struct xts_instance_ctx {
  29         struct crypto_skcipher_spawn spawn;
  30         char name[CRYPTO_MAX_ALG_NAME];
  31 };
  32
  33 struct rctx {
  34         le128 t;
  35         struct scatterlist *tail;
  36         struct scatterlist sg[2];
  37         struct skcipher_request subreq;
  38 };
  39
  40 static int setkey(struct crypto_skcipher *parent, const u8 *key,
  41                   unsigned int keylen)
  42 {
  43         struct priv *ctx = crypto_skcipher_ctx(parent);
  44         struct crypto_skcipher *child;
  45         struct crypto_cipher *tweak;
  46         int err;
  47
  48         err = xts_verify_key(parent, key, keylen);
  49         if (err)
  50                 return err;
  51
  52         keylen /= 2;
  53
  54         /* we need two cipher instances: one to compute the initial 'tweak'
  55          * by encrypting the IV (usually the 'plain' iv) and the other
  56          * one to encrypt and decrypt the data */
  57
  58         /* tweak cipher, uses Key2 i.e. the second half of *key */
  59         tweak = ctx->tweak;
  60         crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
  61         crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
  62                                        CRYPTO_TFM_REQ_MASK);
  63         err = crypto_cipher_setkey(tweak, key + keylen, keylen);
  64         if (err)
  65                 return err;
  66
  67         /* data cipher, uses Key1 i.e. the first half of *key */
  68         child = ctx->child;
  69         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  70         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
  71                                          CRYPTO_TFM_REQ_MASK);
  72         return crypto_skcipher_setkey(child, key, keylen);
  73 }
  74
  75 /*
  76  * We compute the tweak masks twice (both before and after the ECB encryption or
  77  * decryption) to avoid having to allocate a temporary buffer and/or make
  78  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
  79  * just doing the gf128mul_x_ble() calls again.
  80  */
  81 static int xor_tweak(struct skcipher_request *req, bool second_pass, bool enc)
  82 {
  83         struct rctx *rctx = skcipher_request_ctx(req);
  84         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  85         const bool cts = (req->cryptlen % XTS_BLOCK_SIZE);
  86         const int bs = XTS_BLOCK_SIZE;
  87         struct skcipher_walk w;
  88         le128 t = rctx->t;
  89         int err;
  90
  91         if (second_pass) {
  92                 req = &rctx->subreq;
  93                 /* set to our TFM to enforce correct alignment: */
  94                 skcipher_request_set_tfm(req, tfm);
  95         }
  96         err = skcipher_walk_virt(&w, req, false);
  97
  98         while (w.nbytes) {
  99                 unsigned int avail = w.nbytes;
 100                 le128 *wsrc;
 101                 le128 *wdst;
 102
 103                 wsrc = w.src.virt.addr;
 104                 wdst = w.dst.virt.addr;
 105
 106                 do {
 107                         if (unlikely(cts) &&
 108                             w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) {
 109                                 if (!enc) {
 110                                         if (second_pass)
 111                                                 rctx->t = t;
 112                                         gf128mul_x_ble(&t, &t);
 113                                 }
 114                                 le128_xor(wdst, &t, wsrc);
 115                                 if (enc && second_pass)
 116                                         gf128mul_x_ble(&rctx->t, &t);
 117                                 skcipher_walk_done(&w, avail - bs);
 118                                 return 0;
 119                         }
 120
 121                         le128_xor(wdst++, &t, wsrc++);
 122                         gf128mul_x_ble(&t, &t);
 123                 } while ((avail -= bs) >= bs);
 124
 125                 err = skcipher_walk_done(&w, avail);
 126         }
 127
 128         return err;
 129 }
 130
 131 static int xor_tweak_pre(struct skcipher_request *req, bool enc)
 132 {
 133         return xor_tweak(req, false, enc);
 134 }
 135
 136 static int xor_tweak_post(struct skcipher_request *req, bool enc)
 137 {
 138         return xor_tweak(req, true, enc);
 139 }
 140
 141 static void cts_done(struct crypto_async_request *areq, int err)
 142 {
 143         struct skcipher_request *req = areq->data;
 144         le128 b;
 145
 146         if (!err) {
 147                 struct rctx *rctx = skcipher_request_ctx(req);
 148
 149                 scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
 150                 le128_xor(&b, &rctx->t, &b);
 151                 scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
 152         }
 153
 154         skcipher_request_complete(req, err);
 155 }
 156
 157 static int cts_final(struct skcipher_request *req,
 158                      int (*crypt)(struct skcipher_request *req))
 159 {
 160         struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 161         int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1);
 162         struct rctx *rctx = skcipher_request_ctx(req);
 163         struct skcipher_request *subreq = &rctx->subreq;
 164         int tail = req->cryptlen % XTS_BLOCK_SIZE;
 165         le128 b[2];
 166         int err;
 167
 168         rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst,
 169                                       offset - XTS_BLOCK_SIZE);
 170
 171         scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
 172         memcpy(b + 1, b, tail);
 173         scatterwalk_map_and_copy(b, req->src, offset, tail, 0);
 174
 175         le128_xor(b, &rctx->t, b);
 176
 177         scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1);
 178
 179         skcipher_request_set_tfm(subreq, ctx->child);
 180         skcipher_request_set_callback(subreq, req->base.flags, cts_done, req);
 181         skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail,
 182                                    XTS_BLOCK_SIZE, NULL);
 183
 184         err = crypt(subreq);
 185         if (err)
 186                 return err;
 187
 188         scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
 189         le128_xor(b, &rctx->t, b);
 190         scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
 191
 192         return 0;
 193 }
 194
 195 static void encrypt_done(struct crypto_async_request *areq, int err)
 196 {
 197         struct skcipher_request *req = areq->data;
 198
 199         if (!err) {
 200                 struct rctx *rctx = skcipher_request_ctx(req);
 201
 202                 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 203                 err = xor_tweak_post(req, true);
 204
 205                 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
 206                         err = cts_final(req, crypto_skcipher_encrypt);
 207                         if (err == -EINPROGRESS)
 208                                 return;
 209                 }
 210         }
 211
 212         skcipher_request_complete(req, err);
 213 }
 214
 215 static void decrypt_done(struct crypto_async_request *areq, int err)
 216 {
 217         struct skcipher_request *req = areq->data;
 218
 219         if (!err) {
 220                 struct rctx *rctx = skcipher_request_ctx(req);
 221
 222                 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 223                 err = xor_tweak_post(req, false);
 224
 225                 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
 226                         err = cts_final(req, crypto_skcipher_decrypt);
 227                         if (err == -EINPROGRESS)
 228                                 return;
 229                 }
 230         }
 231
 232         skcipher_request_complete(req, err);
 233 }
 234
 235 static int init_crypt(struct skcipher_request *req, crypto_completion_t compl)
 236 {
 237         struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 238         struct rctx *rctx = skcipher_request_ctx(req);
 239         struct skcipher_request *subreq = &rctx->subreq;
 240
 241         if (req->cryptlen < XTS_BLOCK_SIZE)
 242                 return -EINVAL;
 243
 244         skcipher_request_set_tfm(subreq, ctx->child);
 245         skcipher_request_set_callback(subreq, req->base.flags, compl, req);
 246         skcipher_request_set_crypt(subreq, req->dst, req->dst,
 247                                    req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL);
 248
 249         /* calculate first value of T */
 250         crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
 251
 252         return 0;
 253 }
 254
 255 static int encrypt(struct skcipher_request *req)
 256 {
 257         struct rctx *rctx = skcipher_request_ctx(req);
 258         struct skcipher_request *subreq = &rctx->subreq;
 259         int err;
 260
 261         err = init_crypt(req, encrypt_done) ?:
 262               xor_tweak_pre(req, true) ?:
 263               crypto_skcipher_encrypt(subreq) ?:
 264               xor_tweak_post(req, true);
 265
 266         if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
 267                 return err;
 268
 269         return cts_final(req, crypto_skcipher_encrypt);
 270 }
 271
 272 static int decrypt(struct skcipher_request *req)
 273 {
 274         struct rctx *rctx = skcipher_request_ctx(req);
 275         struct skcipher_request *subreq = &rctx->subreq;
 276         int err;
 277
 278         err = init_crypt(req, decrypt_done) ?:
 279               xor_tweak_pre(req, false) ?:
 280               crypto_skcipher_decrypt(subreq) ?:
 281               xor_tweak_post(req, false);
 282
 283         if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
 284                 return err;
 285
 286         return cts_final(req, crypto_skcipher_decrypt);
 287 }
 288
 289 static int init_tfm(struct crypto_skcipher *tfm)
 290 {
 291         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 292         struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
 293         struct priv *ctx = crypto_skcipher_ctx(tfm);
 294         struct crypto_skcipher *child;
 295         struct crypto_cipher *tweak;
 296
 297         child = crypto_spawn_skcipher(&ictx->spawn);
 298         if (IS_ERR(child))
 299                 return PTR_ERR(child);
 300
 301         ctx->child = child;
 302
 303         tweak = crypto_alloc_cipher(ictx->name, 0, 0);
 304         if (IS_ERR(tweak)) {
 305                 crypto_free_skcipher(ctx->child);
 306                 return PTR_ERR(tweak);
 307         }
 308
 309         ctx->tweak = tweak;
 310
 311         crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
 312                                          sizeof(struct rctx));
 313
 314         return 0;
 315 }
 316
 317 static void exit_tfm(struct crypto_skcipher *tfm)
 318 {
 319         struct priv *ctx = crypto_skcipher_ctx(tfm);
 320
 321         crypto_free_skcipher(ctx->child);
 322         crypto_free_cipher(ctx->tweak);
 323 }
 324
 325 static void free(struct skcipher_instance *inst)
 326 {
 327         crypto_drop_skcipher(skcipher_instance_ctx(inst));
 328         kfree(inst);
 329 }
 330
 331 static int create(struct crypto_template *tmpl, struct rtattr **tb)
 332 {
 333         struct skcipher_instance *inst;
 334         struct crypto_attr_type *algt;
 335         struct xts_instance_ctx *ctx;
 336         struct skcipher_alg *alg;
 337         const char *cipher_name;
 338         u32 mask;
 339         int err;
 340
 341         algt = crypto_get_attr_type(tb);
 342         if (IS_ERR(algt))
 343                 return PTR_ERR(algt);
 344
 345         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 346                 return -EINVAL;
 347
 348         cipher_name = crypto_attr_alg_name(tb[1]);
 349         if (IS_ERR(cipher_name))
 350                 return PTR_ERR(cipher_name);
 351
 352         inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
 353         if (!inst)
 354                 return -ENOMEM;
 355
 356         ctx = skcipher_instance_ctx(inst);
 357
 358         mask = crypto_requires_off(algt->type, algt->mask,
 359                                    CRYPTO_ALG_NEED_FALLBACK |
 360                                    CRYPTO_ALG_ASYNC);
 361
 362         err = crypto_grab_skcipher(&ctx->spawn, skcipher_crypto_instance(inst),
 363                                    cipher_name, 0, mask);
 364         if (err == -ENOENT) {
 365                 err = -ENAMETOOLONG;
 366                 if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
 367                              cipher_name) >= CRYPTO_MAX_ALG_NAME)
 368                         goto err_free_inst;
 369
 370                 err = crypto_grab_skcipher(&ctx->spawn,
 371                                            skcipher_crypto_instance(inst),
 372                                            ctx->name, 0, mask);
 373         }
 374
 375         if (err)
 376                 goto err_free_inst;
 377
 378         alg = crypto_skcipher_spawn_alg(&ctx->spawn);
 379
 380         err = -EINVAL;
 381         if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
 382                 goto err_free_inst;
 383
 384         if (crypto_skcipher_alg_ivsize(alg))
 385                 goto err_free_inst;
 386
 387         err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
 388                                   &alg->base);
 389         if (err)
 390                 goto err_free_inst;
 391
 392         err = -EINVAL;
 393         cipher_name = alg->base.cra_name;
 394
 395         /* Alas we screwed up the naming so we have to mangle the
 396          * cipher name.
 397          */
 398         if (!strncmp(cipher_name, "ecb(", 4)) {
 399                 unsigned len;
 400
 401                 len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
 402                 if (len < 2 || len >= sizeof(ctx->name))
 403                         goto err_free_inst;
 404
 405                 if (ctx->name[len - 1] != ')')
 406                         goto err_free_inst;
 407
 408                 ctx->name[len - 1] = 0;
 409
 410                 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 411                              "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) {
 412                         err = -ENAMETOOLONG;
 413                         goto err_free_inst;
 414                 }
 415         } else
 416                 goto err_free_inst;
 417
 418         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 419         inst->alg.base.cra_priority = alg->base.cra_priority;
 420         inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
 421         inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 422                                        (__alignof__(u64) - 1);
 423
 424         inst->alg.ivsize = XTS_BLOCK_SIZE;
 425         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
 426         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
 427
 428         inst->alg.base.cra_ctxsize = sizeof(struct priv);
 429
 430         inst->alg.init = init_tfm;
 431         inst->alg.exit = exit_tfm;
 432
 433         inst->alg.setkey = setkey;
 434         inst->alg.encrypt = encrypt;
 435         inst->alg.decrypt = decrypt;
 436
 437         inst->free = free;
 438
 439         err = skcipher_register_instance(tmpl, inst);
 440         if (err) {
 441 err_free_inst:
 442                 free(inst);
 443         }
 444         return err;
 445 }
 446
 447 static struct crypto_template crypto_tmpl = {
 448         .name = "xts",
 449         .create = create,
 450         .module = THIS_MODULE,
 451 };
 452
 453 static int __init crypto_module_init(void)
 454 {
 455         return crypto_register_template(&crypto_tmpl);
 456 }
 457
 458 static void __exit crypto_module_exit(void)
 459 {
 460         crypto_unregister_template(&crypto_tmpl);
 461 }
 462
 463 subsys_initcall(crypto_module_init);
 464 module_exit(crypto_module_exit);
 465
 466 MODULE_LICENSE("GPL");
 467 MODULE_DESCRIPTION("XTS block cipher mode");
 468 MODULE_ALIAS_CRYPTO("xts");