crypto/hctr2.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * HCTR2 length-preserving encryption mode
   4  *
   5  * Copyright 2021 Google LLC
   6  */
   7
   8
   9 /*
  10  * HCTR2 is a length-preserving encryption mode that is efficient on
  11  * processors with instructions to accelerate AES and carryless
  12  * multiplication, e.g. x86 processors with AES-NI and CLMUL, and ARM
  13  * processors with the ARMv8 crypto extensions.
  14  *
  15  * For more details, see the paper: "Length-preserving encryption with HCTR2"
  16  * (https://eprint.iacr.org/2021/1441.pdf)
  17  */
  18
  19 #include <crypto/internal/cipher.h>
  20 #include <crypto/internal/hash.h>
  21 #include <crypto/internal/skcipher.h>
  22 #include <crypto/polyval.h>
  23 #include <crypto/scatterwalk.h>
  24 #include <linux/module.h>
  25
  26 #define BLOCKCIPHER_BLOCK_SIZE          16
  27
  28 /*
  29  * The specification allows variable-length tweaks, but Linux's crypto API
  30  * currently only allows algorithms to support a single length.  The "natural"
  31  * tweak length for HCTR2 is 16, since that fits into one POLYVAL block for
  32  * the best performance.  But longer tweaks are useful for fscrypt, to avoid
  33  * needing to derive per-file keys.  So instead we use two blocks, or 32 bytes.
  34  */
  35 #define TWEAK_SIZE              32
  36
  37 struct hctr2_instance_ctx {
  38         struct crypto_cipher_spawn blockcipher_spawn;
  39         struct crypto_skcipher_spawn xctr_spawn;
  40         struct crypto_shash_spawn polyval_spawn;
  41 };
  42
  43 struct hctr2_tfm_ctx {
  44         struct crypto_cipher *blockcipher;
  45         struct crypto_skcipher *xctr;
  46         struct crypto_shash *polyval;
  47         u8 L[BLOCKCIPHER_BLOCK_SIZE];
  48         int hashed_tweak_offset;
  49         /*
  50          * This struct is allocated with extra space for two exported hash
  51          * states.  Since the hash state size is not known at compile-time, we
  52          * can't add these to the struct directly.
  53          *
  54          * hashed_tweaklen_divisible;
  55          * hashed_tweaklen_remainder;
  56          */
  57 };
  58
  59 struct hctr2_request_ctx {
  60         u8 first_block[BLOCKCIPHER_BLOCK_SIZE];
  61         u8 xctr_iv[BLOCKCIPHER_BLOCK_SIZE];
  62         struct scatterlist *bulk_part_dst;
  63         struct scatterlist *bulk_part_src;
  64         struct scatterlist sg_src[2];
  65         struct scatterlist sg_dst[2];
  66         /*
  67          * Sub-request sizes are unknown at compile-time, so they need to go
  68          * after the members with known sizes.
  69          */
  70         union {
  71                 struct shash_desc hash_desc;
  72                 struct skcipher_request xctr_req;
  73         } u;
  74         /*
  75          * This struct is allocated with extra space for one exported hash
  76          * state.  Since the hash state size is not known at compile-time, we
  77          * can't add it to the struct directly.
  78          *
  79          * hashed_tweak;
  80          */
  81 };
  82
  83 static inline u8 *hctr2_hashed_tweaklen(const struct hctr2_tfm_ctx *tctx,
  84                                         bool has_remainder)
  85 {
  86         u8 *p = (u8 *)tctx + sizeof(*tctx);
  87
  88         if (has_remainder) /* For messages not a multiple of block length */
  89                 p += crypto_shash_statesize(tctx->polyval);
  90         return p;
  91 }
  92
  93 static inline u8 *hctr2_hashed_tweak(const struct hctr2_tfm_ctx *tctx,
  94                                      struct hctr2_request_ctx *rctx)
  95 {
  96         return (u8 *)rctx + tctx->hashed_tweak_offset;
  97 }
  98
  99 /*
 100  * The input data for each HCTR2 hash step begins with a 16-byte block that
 101  * contains the tweak length and a flag that indicates whether the input is evenly
 102  * divisible into blocks.  Since this implementation only supports one tweak
 103  * length, we precompute the two hash states resulting from hashing the two
 104  * possible values of this initial block.  This reduces by one block the amount of
 105  * data that needs to be hashed for each encryption/decryption
 106  *
 107  * These precomputed hashes are stored in hctr2_tfm_ctx.
 108  */
 109 static int hctr2_hash_tweaklen(struct hctr2_tfm_ctx *tctx, bool has_remainder)
 110 {
 111         SHASH_DESC_ON_STACK(shash, tfm->polyval);
 112         __le64 tweak_length_block[2];
 113         int err;
 114
 115         shash->tfm = tctx->polyval;
 116         memset(tweak_length_block, 0, sizeof(tweak_length_block));
 117
 118         tweak_length_block[0] = cpu_to_le64(TWEAK_SIZE * 8 * 2 + 2 + has_remainder);
 119         err = crypto_shash_init(shash);
 120         if (err)
 121                 return err;
 122         err = crypto_shash_update(shash, (u8 *)tweak_length_block,
 123                                   POLYVAL_BLOCK_SIZE);
 124         if (err)
 125                 return err;
 126         return crypto_shash_export(shash, hctr2_hashed_tweaklen(tctx, has_remainder));
 127 }
 128
 129 static int hctr2_setkey(struct crypto_skcipher *tfm, const u8 *key,
 130                         unsigned int keylen)
 131 {
 132         struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 133         u8 hbar[BLOCKCIPHER_BLOCK_SIZE];
 134         int err;
 135
 136         crypto_cipher_clear_flags(tctx->blockcipher, CRYPTO_TFM_REQ_MASK);
 137         crypto_cipher_set_flags(tctx->blockcipher,
 138                                 crypto_skcipher_get_flags(tfm) &
 139                                 CRYPTO_TFM_REQ_MASK);
 140         err = crypto_cipher_setkey(tctx->blockcipher, key, keylen);
 141         if (err)
 142                 return err;
 143
 144         crypto_skcipher_clear_flags(tctx->xctr, CRYPTO_TFM_REQ_MASK);
 145         crypto_skcipher_set_flags(tctx->xctr,
 146                                   crypto_skcipher_get_flags(tfm) &
 147                                   CRYPTO_TFM_REQ_MASK);
 148         err = crypto_skcipher_setkey(tctx->xctr, key, keylen);
 149         if (err)
 150                 return err;
 151
 152         memset(hbar, 0, sizeof(hbar));
 153         crypto_cipher_encrypt_one(tctx->blockcipher, hbar, hbar);
 154
 155         memset(tctx->L, 0, sizeof(tctx->L));
 156         tctx->L[0] = 0x01;
 157         crypto_cipher_encrypt_one(tctx->blockcipher, tctx->L, tctx->L);
 158
 159         crypto_shash_clear_flags(tctx->polyval, CRYPTO_TFM_REQ_MASK);
 160         crypto_shash_set_flags(tctx->polyval, crypto_skcipher_get_flags(tfm) &
 161                                CRYPTO_TFM_REQ_MASK);
 162         err = crypto_shash_setkey(tctx->polyval, hbar, BLOCKCIPHER_BLOCK_SIZE);
 163         if (err)
 164                 return err;
 165         memzero_explicit(hbar, sizeof(hbar));
 166
 167         return hctr2_hash_tweaklen(tctx, true) ?: hctr2_hash_tweaklen(tctx, false);
 168 }
 169
 170 static int hctr2_hash_tweak(struct skcipher_request *req)
 171 {
 172         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 173         const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 174         struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
 175         struct shash_desc *hash_desc = &rctx->u.hash_desc;
 176         int err;
 177         bool has_remainder = req->cryptlen % POLYVAL_BLOCK_SIZE;
 178
 179         hash_desc->tfm = tctx->polyval;
 180         err = crypto_shash_import(hash_desc, hctr2_hashed_tweaklen(tctx, has_remainder));
 181         if (err)
 182                 return err;
 183         err = crypto_shash_update(hash_desc, req->iv, TWEAK_SIZE);
 184         if (err)
 185                 return err;
 186
 187         // Store the hashed tweak, since we need it when computing both
 188         // H(T || N) and H(T || V).
 189         return crypto_shash_export(hash_desc, hctr2_hashed_tweak(tctx, rctx));
 190 }
 191
 192 static int hctr2_hash_message(struct skcipher_request *req,
 193                               struct scatterlist *sgl,
 194                               u8 digest[POLYVAL_DIGEST_SIZE])
 195 {
 196         static const u8 padding[BLOCKCIPHER_BLOCK_SIZE] = { 0x1 };
 197         struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
 198         struct shash_desc *hash_desc = &rctx->u.hash_desc;
 199         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 200         struct sg_mapping_iter miter;
 201         unsigned int remainder = bulk_len % BLOCKCIPHER_BLOCK_SIZE;
 202         int i;
 203         int err = 0;
 204         int n = 0;
 205
 206         sg_miter_start(&miter, sgl, sg_nents(sgl),
 207                        SG_MITER_FROM_SG | SG_MITER_ATOMIC);
 208         for (i = 0; i < bulk_len; i += n) {
 209                 sg_miter_next(&miter);
 210                 n = min_t(unsigned int, miter.length, bulk_len - i);
 211                 err = crypto_shash_update(hash_desc, miter.addr, n);
 212                 if (err)
 213                         break;
 214         }
 215         sg_miter_stop(&miter);
 216
 217         if (err)
 218                 return err;
 219
 220         if (remainder) {
 221                 err = crypto_shash_update(hash_desc, padding,
 222                                           BLOCKCIPHER_BLOCK_SIZE - remainder);
 223                 if (err)
 224                         return err;
 225         }
 226         return crypto_shash_final(hash_desc, digest);
 227 }
 228
 229 static int hctr2_finish(struct skcipher_request *req)
 230 {
 231         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 232         const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 233         struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
 234         u8 digest[POLYVAL_DIGEST_SIZE];
 235         struct shash_desc *hash_desc = &rctx->u.hash_desc;
 236         int err;
 237
 238         // U = UU ^ H(T || V)
 239         // or M = MM ^ H(T || N)
 240         hash_desc->tfm = tctx->polyval;
 241         err = crypto_shash_import(hash_desc, hctr2_hashed_tweak(tctx, rctx));
 242         if (err)
 243                 return err;
 244         err = hctr2_hash_message(req, rctx->bulk_part_dst, digest);
 245         if (err)
 246                 return err;
 247         crypto_xor(rctx->first_block, digest, BLOCKCIPHER_BLOCK_SIZE);
 248
 249         // Copy U (or M) into dst scatterlist
 250         scatterwalk_map_and_copy(rctx->first_block, req->dst,
 251                                  0, BLOCKCIPHER_BLOCK_SIZE, 1);
 252         return 0;
 253 }
 254
 255 static void hctr2_xctr_done(void *data, int err)
 256 {
 257         struct skcipher_request *req = data;
 258
 259         if (!err)
 260                 err = hctr2_finish(req);
 261
 262         skcipher_request_complete(req, err);
 263 }
 264
 265 static int hctr2_crypt(struct skcipher_request *req, bool enc)
 266 {
 267         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 268         const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 269         struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
 270         u8 digest[POLYVAL_DIGEST_SIZE];
 271         int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 272         int err;
 273
 274         // Requests must be at least one block
 275         if (req->cryptlen < BLOCKCIPHER_BLOCK_SIZE)
 276                 return -EINVAL;
 277
 278         // Copy M (or U) into a temporary buffer
 279         scatterwalk_map_and_copy(rctx->first_block, req->src,
 280                                  0, BLOCKCIPHER_BLOCK_SIZE, 0);
 281
 282         // Create scatterlists for N and V
 283         rctx->bulk_part_src = scatterwalk_ffwd(rctx->sg_src, req->src,
 284                                                BLOCKCIPHER_BLOCK_SIZE);
 285         rctx->bulk_part_dst = scatterwalk_ffwd(rctx->sg_dst, req->dst,
 286                                                BLOCKCIPHER_BLOCK_SIZE);
 287
 288         // MM = M ^ H(T || N)
 289         // or UU = U ^ H(T || V)
 290         err = hctr2_hash_tweak(req);
 291         if (err)
 292                 return err;
 293         err = hctr2_hash_message(req, rctx->bulk_part_src, digest);
 294         if (err)
 295                 return err;
 296         crypto_xor(digest, rctx->first_block, BLOCKCIPHER_BLOCK_SIZE);
 297
 298         // UU = E(MM)
 299         // or MM = D(UU)
 300         if (enc)
 301                 crypto_cipher_encrypt_one(tctx->blockcipher, rctx->first_block,
 302                                           digest);
 303         else
 304                 crypto_cipher_decrypt_one(tctx->blockcipher, rctx->first_block,
 305                                           digest);
 306
 307         // S = MM ^ UU ^ L
 308         crypto_xor(digest, rctx->first_block, BLOCKCIPHER_BLOCK_SIZE);
 309         crypto_xor_cpy(rctx->xctr_iv, digest, tctx->L, BLOCKCIPHER_BLOCK_SIZE);
 310
 311         // V = XCTR(S, N)
 312         // or N = XCTR(S, V)
 313         skcipher_request_set_tfm(&rctx->u.xctr_req, tctx->xctr);
 314         skcipher_request_set_crypt(&rctx->u.xctr_req, rctx->bulk_part_src,
 315                                    rctx->bulk_part_dst, bulk_len,
 316                                    rctx->xctr_iv);
 317         skcipher_request_set_callback(&rctx->u.xctr_req,
 318                                       req->base.flags,
 319                                       hctr2_xctr_done, req);
 320         return crypto_skcipher_encrypt(&rctx->u.xctr_req) ?:
 321                 hctr2_finish(req);
 322 }
 323
 324 static int hctr2_encrypt(struct skcipher_request *req)
 325 {
 326         return hctr2_crypt(req, true);
 327 }
 328
 329 static int hctr2_decrypt(struct skcipher_request *req)
 330 {
 331         return hctr2_crypt(req, false);
 332 }
 333
 334 static int hctr2_init_tfm(struct crypto_skcipher *tfm)
 335 {
 336         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 337         struct hctr2_instance_ctx *ictx = skcipher_instance_ctx(inst);
 338         struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 339         struct crypto_skcipher *xctr;
 340         struct crypto_cipher *blockcipher;
 341         struct crypto_shash *polyval;
 342         unsigned int subreq_size;
 343         int err;
 344
 345         xctr = crypto_spawn_skcipher(&ictx->xctr_spawn);
 346         if (IS_ERR(xctr))
 347                 return PTR_ERR(xctr);
 348
 349         blockcipher = crypto_spawn_cipher(&ictx->blockcipher_spawn);
 350         if (IS_ERR(blockcipher)) {
 351                 err = PTR_ERR(blockcipher);
 352                 goto err_free_xctr;
 353         }
 354
 355         polyval = crypto_spawn_shash(&ictx->polyval_spawn);
 356         if (IS_ERR(polyval)) {
 357                 err = PTR_ERR(polyval);
 358                 goto err_free_blockcipher;
 359         }
 360
 361         tctx->xctr = xctr;
 362         tctx->blockcipher = blockcipher;
 363         tctx->polyval = polyval;
 364
 365         BUILD_BUG_ON(offsetofend(struct hctr2_request_ctx, u) !=
 366                                  sizeof(struct hctr2_request_ctx));
 367         subreq_size = max(sizeof_field(struct hctr2_request_ctx, u.hash_desc) +
 368                           crypto_shash_descsize(polyval),
 369                           sizeof_field(struct hctr2_request_ctx, u.xctr_req) +
 370                           crypto_skcipher_reqsize(xctr));
 371
 372         tctx->hashed_tweak_offset = offsetof(struct hctr2_request_ctx, u) +
 373                                     subreq_size;
 374         crypto_skcipher_set_reqsize(tfm, tctx->hashed_tweak_offset +
 375                                     crypto_shash_statesize(polyval));
 376         return 0;
 377
 378 err_free_blockcipher:
 379         crypto_free_cipher(blockcipher);
 380 err_free_xctr:
 381         crypto_free_skcipher(xctr);
 382         return err;
 383 }
 384
 385 static void hctr2_exit_tfm(struct crypto_skcipher *tfm)
 386 {
 387         struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 388
 389         crypto_free_cipher(tctx->blockcipher);
 390         crypto_free_skcipher(tctx->xctr);
 391         crypto_free_shash(tctx->polyval);
 392 }
 393
 394 static void hctr2_free_instance(struct skcipher_instance *inst)
 395 {
 396         struct hctr2_instance_ctx *ictx = skcipher_instance_ctx(inst);
 397
 398         crypto_drop_cipher(&ictx->blockcipher_spawn);
 399         crypto_drop_skcipher(&ictx->xctr_spawn);
 400         crypto_drop_shash(&ictx->polyval_spawn);
 401         kfree(inst);
 402 }
 403
 404 static int hctr2_create_common(struct crypto_template *tmpl,
 405                                struct rtattr **tb,
 406                                const char *xctr_name,
 407                                const char *polyval_name)
 408 {
 409         struct skcipher_alg_common *xctr_alg;
 410         u32 mask;
 411         struct skcipher_instance *inst;
 412         struct hctr2_instance_ctx *ictx;
 413         struct crypto_alg *blockcipher_alg;
 414         struct shash_alg *polyval_alg;
 415         char blockcipher_name[CRYPTO_MAX_ALG_NAME];
 416         int len;
 417         int err;
 418
 419         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
 420         if (err)
 421                 return err;
 422
 423         inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
 424         if (!inst)
 425                 return -ENOMEM;
 426         ictx = skcipher_instance_ctx(inst);
 427
 428         /* Stream cipher, xctr(block_cipher) */
 429         err = crypto_grab_skcipher(&ictx->xctr_spawn,
 430                                    skcipher_crypto_instance(inst),
 431                                    xctr_name, 0, mask);
 432         if (err)
 433                 goto err_free_inst;
 434         xctr_alg = crypto_spawn_skcipher_alg_common(&ictx->xctr_spawn);
 435
 436         err = -EINVAL;
 437         if (strncmp(xctr_alg->base.cra_name, "xctr(", 5))
 438                 goto err_free_inst;
 439         len = strscpy(blockcipher_name, xctr_alg->base.cra_name + 5,
 440                       sizeof(blockcipher_name));
 441         if (len < 1)
 442                 goto err_free_inst;
 443         if (blockcipher_name[len - 1] != ')')
 444                 goto err_free_inst;
 445         blockcipher_name[len - 1] = 0;
 446
 447         /* Block cipher, e.g. "aes" */
 448         err = crypto_grab_cipher(&ictx->blockcipher_spawn,
 449                                  skcipher_crypto_instance(inst),
 450                                  blockcipher_name, 0, mask);
 451         if (err)
 452                 goto err_free_inst;
 453         blockcipher_alg = crypto_spawn_cipher_alg(&ictx->blockcipher_spawn);
 454
 455         /* Require blocksize of 16 bytes */
 456         err = -EINVAL;
 457         if (blockcipher_alg->cra_blocksize != BLOCKCIPHER_BLOCK_SIZE)
 458                 goto err_free_inst;
 459
 460         /* Polyval ε-∆U hash function */
 461         err = crypto_grab_shash(&ictx->polyval_spawn,
 462                                 skcipher_crypto_instance(inst),
 463                                 polyval_name, 0, mask);
 464         if (err)
 465                 goto err_free_inst;
 466         polyval_alg = crypto_spawn_shash_alg(&ictx->polyval_spawn);
 467
 468         /* Ensure Polyval is being used */
 469         err = -EINVAL;
 470         if (strcmp(polyval_alg->base.cra_name, "polyval") != 0)
 471                 goto err_free_inst;
 472
 473         /* Instance fields */
 474
 475         err = -ENAMETOOLONG;
 476         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, "hctr2(%s)",
 477                      blockcipher_alg->cra_name) >= CRYPTO_MAX_ALG_NAME)
 478                 goto err_free_inst;
 479         if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 480                      "hctr2_base(%s,%s)",
 481                      xctr_alg->base.cra_driver_name,
 482                      polyval_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
 483                 goto err_free_inst;
 484
 485         inst->alg.base.cra_blocksize = BLOCKCIPHER_BLOCK_SIZE;
 486         inst->alg.base.cra_ctxsize = sizeof(struct hctr2_tfm_ctx) +
 487                                      polyval_alg->statesize * 2;
 488         inst->alg.base.cra_alignmask = xctr_alg->base.cra_alignmask;
 489         /*
 490          * The hash function is called twice, so it is weighted higher than the
 491          * xctr and blockcipher.
 492          */
 493         inst->alg.base.cra_priority = (2 * xctr_alg->base.cra_priority +
 494                                        4 * polyval_alg->base.cra_priority +
 495                                        blockcipher_alg->cra_priority) / 7;
 496
 497         inst->alg.setkey = hctr2_setkey;
 498         inst->alg.encrypt = hctr2_encrypt;
 499         inst->alg.decrypt = hctr2_decrypt;
 500         inst->alg.init = hctr2_init_tfm;
 501         inst->alg.exit = hctr2_exit_tfm;
 502         inst->alg.min_keysize = xctr_alg->min_keysize;
 503         inst->alg.max_keysize = xctr_alg->max_keysize;
 504         inst->alg.ivsize = TWEAK_SIZE;
 505
 506         inst->free = hctr2_free_instance;
 507
 508         err = skcipher_register_instance(tmpl, inst);
 509         if (err) {
 510 err_free_inst:
 511                 hctr2_free_instance(inst);
 512         }
 513         return err;
 514 }
 515
 516 static int hctr2_create_base(struct crypto_template *tmpl, struct rtattr **tb)
 517 {
 518         const char *xctr_name;
 519         const char *polyval_name;
 520
 521         xctr_name = crypto_attr_alg_name(tb[1]);
 522         if (IS_ERR(xctr_name))
 523                 return PTR_ERR(xctr_name);
 524
 525         polyval_name = crypto_attr_alg_name(tb[2]);
 526         if (IS_ERR(polyval_name))
 527                 return PTR_ERR(polyval_name);
 528
 529         return hctr2_create_common(tmpl, tb, xctr_name, polyval_name);
 530 }
 531
 532 static int hctr2_create(struct crypto_template *tmpl, struct rtattr **tb)
 533 {
 534         const char *blockcipher_name;
 535         char xctr_name[CRYPTO_MAX_ALG_NAME];
 536
 537         blockcipher_name = crypto_attr_alg_name(tb[1]);
 538         if (IS_ERR(blockcipher_name))
 539                 return PTR_ERR(blockcipher_name);
 540
 541         if (snprintf(xctr_name, CRYPTO_MAX_ALG_NAME, "xctr(%s)",
 542                     blockcipher_name) >= CRYPTO_MAX_ALG_NAME)
 543                 return -ENAMETOOLONG;
 544
 545         return hctr2_create_common(tmpl, tb, xctr_name, "polyval");
 546 }
 547
 548 static struct crypto_template hctr2_tmpls[] = {
 549         {
 550                 /* hctr2_base(xctr_name, polyval_name) */
 551                 .name = "hctr2_base",
 552                 .create = hctr2_create_base,
 553                 .module = THIS_MODULE,
 554         }, {
 555                 /* hctr2(blockcipher_name) */
 556                 .name = "hctr2",
 557                 .create = hctr2_create,
 558                 .module = THIS_MODULE,
 559         }
 560 };
 561
 562 static int __init hctr2_module_init(void)
 563 {
 564         return crypto_register_templates(hctr2_tmpls, ARRAY_SIZE(hctr2_tmpls));
 565 }
 566
 567 static void __exit hctr2_module_exit(void)
 568 {
 569         return crypto_unregister_templates(hctr2_tmpls,
 570                                            ARRAY_SIZE(hctr2_tmpls));
 571 }
 572
 573 subsys_initcall(hctr2_module_init);
 574 module_exit(hctr2_module_exit);
 575
 576 MODULE_DESCRIPTION("HCTR2 length-preserving encryption mode");
 577 MODULE_LICENSE("GPL v2");
 578 MODULE_ALIAS_CRYPTO("hctr2");
 579 MODULE_IMPORT_NS("CRYPTO_INTERNAL");