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/cipher.h>
  11 #include <crypto/internal/skcipher.h>
  12 #include <crypto/scatterwalk.h>
  13 #include <linux/err.h>
  14 #include <linux/init.h>
  15 #include <linux/kernel.h>
  16 #include <linux/module.h>
  17 #include <linux/scatterlist.h>
  18 #include <linux/slab.h>
  19
  20 #include <crypto/xts.h>
  21 #include <crypto/b128ops.h>
  22 #include <crypto/gf128mul.h>
  23
  24 struct xts_tfm_ctx {
  25         struct crypto_skcipher *child;
  26         struct crypto_cipher *tweak;
  27 };
  28
  29 struct xts_instance_ctx {
  30         struct crypto_skcipher_spawn spawn;
  31         char name[CRYPTO_MAX_ALG_NAME];
  32 };
  33
  34 struct xts_request_ctx {
  35         le128 t;
  36         struct scatterlist *tail;
  37         struct scatterlist sg[2];
  38         struct skcipher_request subreq;
  39 };
  40
  41 static int xts_setkey(struct crypto_skcipher *parent, const u8 *key,
  42                       unsigned int keylen)
  43 {
  44         struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(parent);
  45         struct crypto_skcipher *child;
  46         struct crypto_cipher *tweak;
  47         int err;
  48
  49         err = xts_verify_key(parent, key, keylen);
  50         if (err)
  51                 return err;
  52
  53         keylen /= 2;
  54
  55         /* we need two cipher instances: one to compute the initial 'tweak'
  56          * by encrypting the IV (usually the 'plain' iv) and the other
  57          * one to encrypt and decrypt the data */
  58
  59         /* tweak cipher, uses Key2 i.e. the second half of *key */
  60         tweak = ctx->tweak;
  61         crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
  62         crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
  63                                        CRYPTO_TFM_REQ_MASK);
  64         err = crypto_cipher_setkey(tweak, key + keylen, keylen);
  65         if (err)
  66                 return err;
  67
  68         /* data cipher, uses Key1 i.e. the first half of *key */
  69         child = ctx->child;
  70         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  71         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
  72                                          CRYPTO_TFM_REQ_MASK);
  73         return crypto_skcipher_setkey(child, key, keylen);
  74 }
  75
  76 /*
  77  * We compute the tweak masks twice (both before and after the ECB encryption or
  78  * decryption) to avoid having to allocate a temporary buffer and/or make
  79  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
  80  * just doing the gf128mul_x_ble() calls again.
  81  */
  82 static int xts_xor_tweak(struct skcipher_request *req, bool second_pass,
  83                          bool enc)
  84 {
  85         struct xts_request_ctx *rctx = skcipher_request_ctx(req);
  86         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  87         const bool cts = (req->cryptlen % XTS_BLOCK_SIZE);
  88         const int bs = XTS_BLOCK_SIZE;
  89         struct skcipher_walk w;
  90         le128 t = rctx->t;
  91         int err;
  92
  93         if (second_pass) {
  94                 req = &rctx->subreq;
  95                 /* set to our TFM to enforce correct alignment: */
  96                 skcipher_request_set_tfm(req, tfm);
  97         }
  98         err = skcipher_walk_virt(&w, req, false);
  99
 100         while (w.nbytes) {
 101                 unsigned int avail = w.nbytes;
 102                 le128 *wsrc;
 103                 le128 *wdst;
 104
 105                 wsrc = w.src.virt.addr;
 106                 wdst = w.dst.virt.addr;
 107
 108                 do {
 109                         if (unlikely(cts) &&
 110                             w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) {
 111                                 if (!enc) {
 112                                         if (second_pass)
 113                                                 rctx->t = t;
 114                                         gf128mul_x_ble(&t, &t);
 115                                 }
 116                                 le128_xor(wdst, &t, wsrc);
 117                                 if (enc && second_pass)
 118                                         gf128mul_x_ble(&rctx->t, &t);
 119                                 skcipher_walk_done(&w, avail - bs);
 120                                 return 0;
 121                         }
 122
 123                         le128_xor(wdst++, &t, wsrc++);
 124                         gf128mul_x_ble(&t, &t);
 125                 } while ((avail -= bs) >= bs);
 126
 127                 err = skcipher_walk_done(&w, avail);
 128         }
 129
 130         return err;
 131 }
 132
 133 static int xts_xor_tweak_pre(struct skcipher_request *req, bool enc)
 134 {
 135         return xts_xor_tweak(req, false, enc);
 136 }
 137
 138 static int xts_xor_tweak_post(struct skcipher_request *req, bool enc)
 139 {
 140         return xts_xor_tweak(req, true, enc);
 141 }
 142
 143 static void xts_cts_done(struct crypto_async_request *areq, int err)
 144 {
 145         struct skcipher_request *req = areq->data;
 146         le128 b;
 147
 148         if (!err) {
 149                 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
 150
 151                 scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
 152                 le128_xor(&b, &rctx->t, &b);
 153                 scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
 154         }
 155
 156         skcipher_request_complete(req, err);
 157 }
 158
 159 static int xts_cts_final(struct skcipher_request *req,
 160                          int (*crypt)(struct skcipher_request *req))
 161 {
 162         const struct xts_tfm_ctx *ctx =
 163                 crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 164         int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1);
 165         struct xts_request_ctx *rctx = skcipher_request_ctx(req);
 166         struct skcipher_request *subreq = &rctx->subreq;
 167         int tail = req->cryptlen % XTS_BLOCK_SIZE;
 168         le128 b[2];
 169         int err;
 170
 171         rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst,
 172                                       offset - XTS_BLOCK_SIZE);
 173
 174         scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
 175         b[1] = b[0];
 176         scatterwalk_map_and_copy(b, req->src, offset, tail, 0);
 177
 178         le128_xor(b, &rctx->t, b);
 179
 180         scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1);
 181
 182         skcipher_request_set_tfm(subreq, ctx->child);
 183         skcipher_request_set_callback(subreq, req->base.flags, xts_cts_done,
 184                                       req);
 185         skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail,
 186                                    XTS_BLOCK_SIZE, NULL);
 187
 188         err = crypt(subreq);
 189         if (err)
 190                 return err;
 191
 192         scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
 193         le128_xor(b, &rctx->t, b);
 194         scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
 195
 196         return 0;
 197 }
 198
 199 static void xts_encrypt_done(struct crypto_async_request *areq, int err)
 200 {
 201         struct skcipher_request *req = areq->data;
 202
 203         if (!err) {
 204                 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
 205
 206                 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 207                 err = xts_xor_tweak_post(req, true);
 208
 209                 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
 210                         err = xts_cts_final(req, crypto_skcipher_encrypt);
 211                         if (err == -EINPROGRESS)
 212                                 return;
 213                 }
 214         }
 215
 216         skcipher_request_complete(req, err);
 217 }
 218
 219 static void xts_decrypt_done(struct crypto_async_request *areq, int err)
 220 {
 221         struct skcipher_request *req = areq->data;
 222
 223         if (!err) {
 224                 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
 225
 226                 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 227                 err = xts_xor_tweak_post(req, false);
 228
 229                 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
 230                         err = xts_cts_final(req, crypto_skcipher_decrypt);
 231                         if (err == -EINPROGRESS)
 232                                 return;
 233                 }
 234         }
 235
 236         skcipher_request_complete(req, err);
 237 }
 238
 239 static int xts_init_crypt(struct skcipher_request *req,
 240                           crypto_completion_t compl)
 241 {
 242         const struct xts_tfm_ctx *ctx =
 243                 crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 244         struct xts_request_ctx *rctx = skcipher_request_ctx(req);
 245         struct skcipher_request *subreq = &rctx->subreq;
 246
 247         if (req->cryptlen < XTS_BLOCK_SIZE)
 248                 return -EINVAL;
 249
 250         skcipher_request_set_tfm(subreq, ctx->child);
 251         skcipher_request_set_callback(subreq, req->base.flags, compl, req);
 252         skcipher_request_set_crypt(subreq, req->dst, req->dst,
 253                                    req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL);
 254
 255         /* calculate first value of T */
 256         crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
 257
 258         return 0;
 259 }
 260
 261 static int xts_encrypt(struct skcipher_request *req)
 262 {
 263         struct xts_request_ctx *rctx = skcipher_request_ctx(req);
 264         struct skcipher_request *subreq = &rctx->subreq;
 265         int err;
 266
 267         err = xts_init_crypt(req, xts_encrypt_done) ?:
 268               xts_xor_tweak_pre(req, true) ?:
 269               crypto_skcipher_encrypt(subreq) ?:
 270               xts_xor_tweak_post(req, true);
 271
 272         if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
 273                 return err;
 274
 275         return xts_cts_final(req, crypto_skcipher_encrypt);
 276 }
 277
 278 static int xts_decrypt(struct skcipher_request *req)
 279 {
 280         struct xts_request_ctx *rctx = skcipher_request_ctx(req);
 281         struct skcipher_request *subreq = &rctx->subreq;
 282         int err;
 283
 284         err = xts_init_crypt(req, xts_decrypt_done) ?:
 285               xts_xor_tweak_pre(req, false) ?:
 286               crypto_skcipher_decrypt(subreq) ?:
 287               xts_xor_tweak_post(req, false);
 288
 289         if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
 290                 return err;
 291
 292         return xts_cts_final(req, crypto_skcipher_decrypt);
 293 }
 294
 295 static int xts_init_tfm(struct crypto_skcipher *tfm)
 296 {
 297         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 298         struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
 299         struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
 300         struct crypto_skcipher *child;
 301         struct crypto_cipher *tweak;
 302
 303         child = crypto_spawn_skcipher(&ictx->spawn);
 304         if (IS_ERR(child))
 305                 return PTR_ERR(child);
 306
 307         ctx->child = child;
 308
 309         tweak = crypto_alloc_cipher(ictx->name, 0, 0);
 310         if (IS_ERR(tweak)) {
 311                 crypto_free_skcipher(ctx->child);
 312                 return PTR_ERR(tweak);
 313         }
 314
 315         ctx->tweak = tweak;
 316
 317         crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
 318                                          sizeof(struct xts_request_ctx));
 319
 320         return 0;
 321 }
 322
 323 static void xts_exit_tfm(struct crypto_skcipher *tfm)
 324 {
 325         struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
 326
 327         crypto_free_skcipher(ctx->child);
 328         crypto_free_cipher(ctx->tweak);
 329 }
 330
 331 static void xts_free_instance(struct skcipher_instance *inst)
 332 {
 333         struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
 334
 335         crypto_drop_skcipher(&ictx->spawn);
 336         kfree(inst);
 337 }
 338
 339 static int xts_create(struct crypto_template *tmpl, struct rtattr **tb)
 340 {
 341         struct skcipher_instance *inst;
 342         struct xts_instance_ctx *ctx;
 343         struct skcipher_alg *alg;
 344         const char *cipher_name;
 345         u32 mask;
 346         int err;
 347
 348         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
 349         if (err)
 350                 return err;
 351
 352         cipher_name = crypto_attr_alg_name(tb[1]);
 353         if (IS_ERR(cipher_name))
 354                 return PTR_ERR(cipher_name);
 355
 356         inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
 357         if (!inst)
 358                 return -ENOMEM;
 359
 360         ctx = skcipher_instance_ctx(inst);
 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_priority = alg->base.cra_priority;
 419         inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
 420         inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 421                                        (__alignof__(u64) - 1);
 422
 423         inst->alg.ivsize = XTS_BLOCK_SIZE;
 424         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
 425         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
 426
 427         inst->alg.base.cra_ctxsize = sizeof(struct xts_tfm_ctx);
 428
 429         inst->alg.init = xts_init_tfm;
 430         inst->alg.exit = xts_exit_tfm;
 431
 432         inst->alg.setkey = xts_setkey;
 433         inst->alg.encrypt = xts_encrypt;
 434         inst->alg.decrypt = xts_decrypt;
 435
 436         inst->free = xts_free_instance;
 437
 438         err = skcipher_register_instance(tmpl, inst);
 439         if (err) {
 440 err_free_inst:
 441                 xts_free_instance(inst);
 442         }
 443         return err;
 444 }
 445
 446 static struct crypto_template xts_tmpl = {
 447         .name = "xts",
 448         .create = xts_create,
 449         .module = THIS_MODULE,
 450 };
 451
 452 static int __init xts_module_init(void)
 453 {
 454         return crypto_register_template(&xts_tmpl);
 455 }
 456
 457 static void __exit xts_module_exit(void)
 458 {
 459         crypto_unregister_template(&xts_tmpl);
 460 }
 461
 462 subsys_initcall(xts_module_init);
 463 module_exit(xts_module_exit);
 464
 465 MODULE_LICENSE("GPL");
 466 MODULE_DESCRIPTION("XTS block cipher mode");
 467 MODULE_ALIAS_CRYPTO("xts");
 468 MODULE_IMPORT_NS(CRYPTO_INTERNAL);
 469 MODULE_SOFTDEP("pre: ecb");