crypto/adiantum.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Adiantum length-preserving encryption mode
   4  *
   5  * Copyright 2018 Google LLC
   6  */
   7
   8 /*
   9  * Adiantum is a tweakable, length-preserving encryption mode designed for fast
  10  * and secure disk encryption, especially on CPUs without dedicated crypto
  11  * instructions.  Adiantum encrypts each sector using the XChaCha12 stream
  12  * cipher, two passes of an ε-almost-∆-universal (ε-∆U) hash function based on
  13  * NH and Poly1305, and an invocation of the AES-256 block cipher on a single
  14  * 16-byte block.  See the paper for details:
  15  *
  16  *      Adiantum: length-preserving encryption for entry-level processors
  17  *      (https://eprint.iacr.org/2018/720.pdf)
  18  *
  19  * For flexibility, this implementation also allows other ciphers:
  20  *
  21  *      - Stream cipher: XChaCha12 or XChaCha20
  22  *      - Block cipher: any with a 128-bit block size and 256-bit key
  23  *
  24  * This implementation doesn't currently allow other ε-∆U hash functions, i.e.
  25  * HPolyC is not supported.  This is because Adiantum is ~20% faster than HPolyC
  26  * but still provably as secure, and also the ε-∆U hash function of HBSH is
  27  * formally defined to take two inputs (tweak, message) which makes it difficult
  28  * to wrap with the crypto_shash API.  Rather, some details need to be handled
  29  * here.  Nevertheless, if needed in the future, support for other ε-∆U hash
  30  * functions could be added here.
  31  */
  32
  33 #include <crypto/b128ops.h>
  34 #include <crypto/chacha.h>
  35 #include <crypto/internal/hash.h>
  36 #include <crypto/internal/poly1305.h>
  37 #include <crypto/internal/skcipher.h>
  38 #include <crypto/nhpoly1305.h>
  39 #include <crypto/scatterwalk.h>
  40 #include <linux/module.h>
  41
  42 /*
  43  * Size of right-hand part of input data, in bytes; also the size of the block
  44  * cipher's block size and the hash function's output.
  45  */
  46 #define BLOCKCIPHER_BLOCK_SIZE          16
  47
  48 /* Size of the block cipher key (K_E) in bytes */
  49 #define BLOCKCIPHER_KEY_SIZE            32
  50
  51 /* Size of the hash key (K_H) in bytes */
  52 #define HASH_KEY_SIZE           (POLY1305_BLOCK_SIZE + NHPOLY1305_KEY_SIZE)
  53
  54 /*
  55  * The specification allows variable-length tweaks, but Linux's crypto API
  56  * currently only allows algorithms to support a single length.  The "natural"
  57  * tweak length for Adiantum is 16, since that fits into one Poly1305 block for
  58  * the best performance.  But longer tweaks are useful for fscrypt, to avoid
  59  * needing to derive per-file keys.  So instead we use two blocks, or 32 bytes.
  60  */
  61 #define TWEAK_SIZE              32
  62
  63 struct adiantum_instance_ctx {
  64         struct crypto_skcipher_spawn streamcipher_spawn;
  65         struct crypto_cipher_spawn blockcipher_spawn;
  66         struct crypto_shash_spawn hash_spawn;
  67 };
  68
  69 struct adiantum_tfm_ctx {
  70         struct crypto_skcipher *streamcipher;
  71         struct crypto_cipher *blockcipher;
  72         struct crypto_shash *hash;
  73         struct poly1305_core_key header_hash_key;
  74 };
  75
  76 struct adiantum_request_ctx {
  77
  78         /*
  79          * Buffer for right-hand part of data, i.e.
  80          *
  81          *    P_L => P_M => C_M => C_R when encrypting, or
  82          *    C_R => C_M => P_M => P_L when decrypting.
  83          *
  84          * Also used to build the IV for the stream cipher.
  85          */
  86         union {
  87                 u8 bytes[XCHACHA_IV_SIZE];
  88                 __le32 words[XCHACHA_IV_SIZE / sizeof(__le32)];
  89                 le128 bignum;   /* interpret as element of Z/(2^{128}Z) */
  90         } rbuf;
  91
  92         bool enc; /* true if encrypting, false if decrypting */
  93
  94         /*
  95          * The result of the Poly1305 ε-∆U hash function applied to
  96          * (bulk length, tweak)
  97          */
  98         le128 header_hash;
  99
 100         /* Sub-requests, must be last */
 101         union {
 102                 struct shash_desc hash_desc;
 103                 struct skcipher_request streamcipher_req;
 104         } u;
 105 };
 106
 107 /*
 108  * Given the XChaCha stream key K_S, derive the block cipher key K_E and the
 109  * hash key K_H as follows:
 110  *
 111  *     K_E || K_H || ... = XChaCha(key=K_S, nonce=1||0^191)
 112  *
 113  * Note that this denotes using bits from the XChaCha keystream, which here we
 114  * get indirectly by encrypting a buffer containing all 0's.
 115  */
 116 static int adiantum_setkey(struct crypto_skcipher *tfm, const u8 *key,
 117                            unsigned int keylen)
 118 {
 119         struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 120         struct {
 121                 u8 iv[XCHACHA_IV_SIZE];
 122                 u8 derived_keys[BLOCKCIPHER_KEY_SIZE + HASH_KEY_SIZE];
 123                 struct scatterlist sg;
 124                 struct crypto_wait wait;
 125                 struct skcipher_request req; /* must be last */
 126         } *data;
 127         u8 *keyp;
 128         int err;
 129
 130         /* Set the stream cipher key (K_S) */
 131         crypto_skcipher_clear_flags(tctx->streamcipher, CRYPTO_TFM_REQ_MASK);
 132         crypto_skcipher_set_flags(tctx->streamcipher,
 133                                   crypto_skcipher_get_flags(tfm) &
 134                                   CRYPTO_TFM_REQ_MASK);
 135         err = crypto_skcipher_setkey(tctx->streamcipher, key, keylen);
 136         if (err)
 137                 return err;
 138
 139         /* Derive the subkeys */
 140         data = kzalloc(sizeof(*data) +
 141                        crypto_skcipher_reqsize(tctx->streamcipher), GFP_KERNEL);
 142         if (!data)
 143                 return -ENOMEM;
 144         data->iv[0] = 1;
 145         sg_init_one(&data->sg, data->derived_keys, sizeof(data->derived_keys));
 146         crypto_init_wait(&data->wait);
 147         skcipher_request_set_tfm(&data->req, tctx->streamcipher);
 148         skcipher_request_set_callback(&data->req, CRYPTO_TFM_REQ_MAY_SLEEP |
 149                                                   CRYPTO_TFM_REQ_MAY_BACKLOG,
 150                                       crypto_req_done, &data->wait);
 151         skcipher_request_set_crypt(&data->req, &data->sg, &data->sg,
 152                                    sizeof(data->derived_keys), data->iv);
 153         err = crypto_wait_req(crypto_skcipher_encrypt(&data->req), &data->wait);
 154         if (err)
 155                 goto out;
 156         keyp = data->derived_keys;
 157
 158         /* Set the block cipher key (K_E) */
 159         crypto_cipher_clear_flags(tctx->blockcipher, CRYPTO_TFM_REQ_MASK);
 160         crypto_cipher_set_flags(tctx->blockcipher,
 161                                 crypto_skcipher_get_flags(tfm) &
 162                                 CRYPTO_TFM_REQ_MASK);
 163         err = crypto_cipher_setkey(tctx->blockcipher, keyp,
 164                                    BLOCKCIPHER_KEY_SIZE);
 165         if (err)
 166                 goto out;
 167         keyp += BLOCKCIPHER_KEY_SIZE;
 168
 169         /* Set the hash key (K_H) */
 170         poly1305_core_setkey(&tctx->header_hash_key, keyp);
 171         keyp += POLY1305_BLOCK_SIZE;
 172
 173         crypto_shash_clear_flags(tctx->hash, CRYPTO_TFM_REQ_MASK);
 174         crypto_shash_set_flags(tctx->hash, crypto_skcipher_get_flags(tfm) &
 175                                            CRYPTO_TFM_REQ_MASK);
 176         err = crypto_shash_setkey(tctx->hash, keyp, NHPOLY1305_KEY_SIZE);
 177         keyp += NHPOLY1305_KEY_SIZE;
 178         WARN_ON(keyp != &data->derived_keys[ARRAY_SIZE(data->derived_keys)]);
 179 out:
 180         kzfree(data);
 181         return err;
 182 }
 183
 184 /* Addition in Z/(2^{128}Z) */
 185 static inline void le128_add(le128 *r, const le128 *v1, const le128 *v2)
 186 {
 187         u64 x = le64_to_cpu(v1->b);
 188         u64 y = le64_to_cpu(v2->b);
 189
 190         r->b = cpu_to_le64(x + y);
 191         r->a = cpu_to_le64(le64_to_cpu(v1->a) + le64_to_cpu(v2->a) +
 192                            (x + y < x));
 193 }
 194
 195 /* Subtraction in Z/(2^{128}Z) */
 196 static inline void le128_sub(le128 *r, const le128 *v1, const le128 *v2)
 197 {
 198         u64 x = le64_to_cpu(v1->b);
 199         u64 y = le64_to_cpu(v2->b);
 200
 201         r->b = cpu_to_le64(x - y);
 202         r->a = cpu_to_le64(le64_to_cpu(v1->a) - le64_to_cpu(v2->a) -
 203                            (x - y > x));
 204 }
 205
 206 /*
 207  * Apply the Poly1305 ε-∆U hash function to (bulk length, tweak) and save the
 208  * result to rctx->header_hash.  This is the calculation
 209  *
 210  *      H_T ← Poly1305_{K_T}(bin_{128}(|L|) || T)
 211  *
 212  * from the procedure in section 6.4 of the Adiantum paper.  The resulting value
 213  * is reused in both the first and second hash steps.  Specifically, it's added
 214  * to the result of an independently keyed ε-∆U hash function (for equal length
 215  * inputs only) taken over the left-hand part (the "bulk") of the message, to
 216  * give the overall Adiantum hash of the (tweak, left-hand part) pair.
 217  */
 218 static void adiantum_hash_header(struct skcipher_request *req)
 219 {
 220         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 221         const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 222         struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
 223         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 224         struct {
 225                 __le64 message_bits;
 226                 __le64 padding;
 227         } header = {
 228                 .message_bits = cpu_to_le64((u64)bulk_len * 8)
 229         };
 230         struct poly1305_state state;
 231
 232         poly1305_core_init(&state);
 233
 234         BUILD_BUG_ON(sizeof(header) % POLY1305_BLOCK_SIZE != 0);
 235         poly1305_core_blocks(&state, &tctx->header_hash_key,
 236                              &header, sizeof(header) / POLY1305_BLOCK_SIZE, 1);
 237
 238         BUILD_BUG_ON(TWEAK_SIZE % POLY1305_BLOCK_SIZE != 0);
 239         poly1305_core_blocks(&state, &tctx->header_hash_key, req->iv,
 240                              TWEAK_SIZE / POLY1305_BLOCK_SIZE, 1);
 241
 242         poly1305_core_emit(&state, NULL, &rctx->header_hash);
 243 }
 244
 245 /* Hash the left-hand part (the "bulk") of the message using NHPoly1305 */
 246 static int adiantum_hash_message(struct skcipher_request *req,
 247                                  struct scatterlist *sgl, le128 *digest)
 248 {
 249         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 250         const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 251         struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
 252         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 253         struct shash_desc *hash_desc = &rctx->u.hash_desc;
 254         struct sg_mapping_iter miter;
 255         unsigned int i, n;
 256         int err;
 257
 258         hash_desc->tfm = tctx->hash;
 259
 260         err = crypto_shash_init(hash_desc);
 261         if (err)
 262                 return err;
 263
 264         sg_miter_start(&miter, sgl, sg_nents(sgl),
 265                        SG_MITER_FROM_SG | SG_MITER_ATOMIC);
 266         for (i = 0; i < bulk_len; i += n) {
 267                 sg_miter_next(&miter);
 268                 n = min_t(unsigned int, miter.length, bulk_len - i);
 269                 err = crypto_shash_update(hash_desc, miter.addr, n);
 270                 if (err)
 271                         break;
 272         }
 273         sg_miter_stop(&miter);
 274         if (err)
 275                 return err;
 276
 277         return crypto_shash_final(hash_desc, (u8 *)digest);
 278 }
 279
 280 /* Continue Adiantum encryption/decryption after the stream cipher step */
 281 static int adiantum_finish(struct skcipher_request *req)
 282 {
 283         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 284         const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 285         struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
 286         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 287         le128 digest;
 288         int err;
 289
 290         /* If decrypting, decrypt C_M with the block cipher to get P_M */
 291         if (!rctx->enc)
 292                 crypto_cipher_decrypt_one(tctx->blockcipher, rctx->rbuf.bytes,
 293                                           rctx->rbuf.bytes);
 294
 295         /*
 296          * Second hash step
 297          *      enc: C_R = C_M - H_{K_H}(T, C_L)
 298          *      dec: P_R = P_M - H_{K_H}(T, P_L)
 299          */
 300         err = adiantum_hash_message(req, req->dst, &digest);
 301         if (err)
 302                 return err;
 303         le128_add(&digest, &digest, &rctx->header_hash);
 304         le128_sub(&rctx->rbuf.bignum, &rctx->rbuf.bignum, &digest);
 305         scatterwalk_map_and_copy(&rctx->rbuf.bignum, req->dst,
 306                                  bulk_len, BLOCKCIPHER_BLOCK_SIZE, 1);
 307         return 0;
 308 }
 309
 310 static void adiantum_streamcipher_done(struct crypto_async_request *areq,
 311                                        int err)
 312 {
 313         struct skcipher_request *req = areq->data;
 314
 315         if (!err)
 316                 err = adiantum_finish(req);
 317
 318         skcipher_request_complete(req, err);
 319 }
 320
 321 static int adiantum_crypt(struct skcipher_request *req, bool enc)
 322 {
 323         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 324         const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 325         struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
 326         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 327         unsigned int stream_len;
 328         le128 digest;
 329         int err;
 330
 331         if (req->cryptlen < BLOCKCIPHER_BLOCK_SIZE)
 332                 return -EINVAL;
 333
 334         rctx->enc = enc;
 335
 336         /*
 337          * First hash step
 338          *      enc: P_M = P_R + H_{K_H}(T, P_L)
 339          *      dec: C_M = C_R + H_{K_H}(T, C_L)
 340          */
 341         adiantum_hash_header(req);
 342         err = adiantum_hash_message(req, req->src, &digest);
 343         if (err)
 344                 return err;
 345         le128_add(&digest, &digest, &rctx->header_hash);
 346         scatterwalk_map_and_copy(&rctx->rbuf.bignum, req->src,
 347                                  bulk_len, BLOCKCIPHER_BLOCK_SIZE, 0);
 348         le128_add(&rctx->rbuf.bignum, &rctx->rbuf.bignum, &digest);
 349
 350         /* If encrypting, encrypt P_M with the block cipher to get C_M */
 351         if (enc)
 352                 crypto_cipher_encrypt_one(tctx->blockcipher, rctx->rbuf.bytes,
 353                                           rctx->rbuf.bytes);
 354
 355         /* Initialize the rest of the XChaCha IV (first part is C_M) */
 356         BUILD_BUG_ON(BLOCKCIPHER_BLOCK_SIZE != 16);
 357         BUILD_BUG_ON(XCHACHA_IV_SIZE != 32);    /* nonce || stream position */
 358         rctx->rbuf.words[4] = cpu_to_le32(1);
 359         rctx->rbuf.words[5] = 0;
 360         rctx->rbuf.words[6] = 0;
 361         rctx->rbuf.words[7] = 0;
 362
 363         /*
 364          * XChaCha needs to be done on all the data except the last 16 bytes;
 365          * for disk encryption that usually means 4080 or 496 bytes.  But ChaCha
 366          * implementations tend to be most efficient when passed a whole number
 367          * of 64-byte ChaCha blocks, or sometimes even a multiple of 256 bytes.
 368          * And here it doesn't matter whether the last 16 bytes are written to,
 369          * as the second hash step will overwrite them.  Thus, round the XChaCha
 370          * length up to the next 64-byte boundary if possible.
 371          */
 372         stream_len = bulk_len;
 373         if (round_up(stream_len, CHACHA_BLOCK_SIZE) <= req->cryptlen)
 374                 stream_len = round_up(stream_len, CHACHA_BLOCK_SIZE);
 375
 376         skcipher_request_set_tfm(&rctx->u.streamcipher_req, tctx->streamcipher);
 377         skcipher_request_set_crypt(&rctx->u.streamcipher_req, req->src,
 378                                    req->dst, stream_len, &rctx->rbuf);
 379         skcipher_request_set_callback(&rctx->u.streamcipher_req,
 380                                       req->base.flags,
 381                                       adiantum_streamcipher_done, req);
 382         return crypto_skcipher_encrypt(&rctx->u.streamcipher_req) ?:
 383                 adiantum_finish(req);
 384 }
 385
 386 static int adiantum_encrypt(struct skcipher_request *req)
 387 {
 388         return adiantum_crypt(req, true);
 389 }
 390
 391 static int adiantum_decrypt(struct skcipher_request *req)
 392 {
 393         return adiantum_crypt(req, false);
 394 }
 395
 396 static int adiantum_init_tfm(struct crypto_skcipher *tfm)
 397 {
 398         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 399         struct adiantum_instance_ctx *ictx = skcipher_instance_ctx(inst);
 400         struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 401         struct crypto_skcipher *streamcipher;
 402         struct crypto_cipher *blockcipher;
 403         struct crypto_shash *hash;
 404         unsigned int subreq_size;
 405         int err;
 406
 407         streamcipher = crypto_spawn_skcipher(&ictx->streamcipher_spawn);
 408         if (IS_ERR(streamcipher))
 409                 return PTR_ERR(streamcipher);
 410
 411         blockcipher = crypto_spawn_cipher(&ictx->blockcipher_spawn);
 412         if (IS_ERR(blockcipher)) {
 413                 err = PTR_ERR(blockcipher);
 414                 goto err_free_streamcipher;
 415         }
 416
 417         hash = crypto_spawn_shash(&ictx->hash_spawn);
 418         if (IS_ERR(hash)) {
 419                 err = PTR_ERR(hash);
 420                 goto err_free_blockcipher;
 421         }
 422
 423         tctx->streamcipher = streamcipher;
 424         tctx->blockcipher = blockcipher;
 425         tctx->hash = hash;
 426
 427         BUILD_BUG_ON(offsetofend(struct adiantum_request_ctx, u) !=
 428                      sizeof(struct adiantum_request_ctx));
 429         subreq_size = max(sizeof_field(struct adiantum_request_ctx,
 430                                        u.hash_desc) +
 431                           crypto_shash_descsize(hash),
 432                           sizeof_field(struct adiantum_request_ctx,
 433                                        u.streamcipher_req) +
 434                           crypto_skcipher_reqsize(streamcipher));
 435
 436         crypto_skcipher_set_reqsize(tfm,
 437                                     offsetof(struct adiantum_request_ctx, u) +
 438                                     subreq_size);
 439         return 0;
 440
 441 err_free_blockcipher:
 442         crypto_free_cipher(blockcipher);
 443 err_free_streamcipher:
 444         crypto_free_skcipher(streamcipher);
 445         return err;
 446 }
 447
 448 static void adiantum_exit_tfm(struct crypto_skcipher *tfm)
 449 {
 450         struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 451
 452         crypto_free_skcipher(tctx->streamcipher);
 453         crypto_free_cipher(tctx->blockcipher);
 454         crypto_free_shash(tctx->hash);
 455 }
 456
 457 static void adiantum_free_instance(struct skcipher_instance *inst)
 458 {
 459         struct adiantum_instance_ctx *ictx = skcipher_instance_ctx(inst);
 460
 461         crypto_drop_skcipher(&ictx->streamcipher_spawn);
 462         crypto_drop_cipher(&ictx->blockcipher_spawn);
 463         crypto_drop_shash(&ictx->hash_spawn);
 464         kfree(inst);
 465 }
 466
 467 /*
 468  * Check for a supported set of inner algorithms.
 469  * See the comment at the beginning of this file.
 470  */
 471 static bool adiantum_supported_algorithms(struct skcipher_alg *streamcipher_alg,
 472                                           struct crypto_alg *blockcipher_alg,
 473                                           struct shash_alg *hash_alg)
 474 {
 475         if (strcmp(streamcipher_alg->base.cra_name, "xchacha12") != 0 &&
 476             strcmp(streamcipher_alg->base.cra_name, "xchacha20") != 0)
 477                 return false;
 478
 479         if (blockcipher_alg->cra_cipher.cia_min_keysize > BLOCKCIPHER_KEY_SIZE ||
 480             blockcipher_alg->cra_cipher.cia_max_keysize < BLOCKCIPHER_KEY_SIZE)
 481                 return false;
 482         if (blockcipher_alg->cra_blocksize != BLOCKCIPHER_BLOCK_SIZE)
 483                 return false;
 484
 485         if (strcmp(hash_alg->base.cra_name, "nhpoly1305") != 0)
 486                 return false;
 487
 488         return true;
 489 }
 490
 491 static int adiantum_create(struct crypto_template *tmpl, struct rtattr **tb)
 492 {
 493         struct crypto_attr_type *algt;
 494         u32 mask;
 495         const char *nhpoly1305_name;
 496         struct skcipher_instance *inst;
 497         struct adiantum_instance_ctx *ictx;
 498         struct skcipher_alg *streamcipher_alg;
 499         struct crypto_alg *blockcipher_alg;
 500         struct shash_alg *hash_alg;
 501         int err;
 502
 503         algt = crypto_get_attr_type(tb);
 504         if (IS_ERR(algt))
 505                 return PTR_ERR(algt);
 506
 507         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 508                 return -EINVAL;
 509
 510         mask = crypto_requires_sync(algt->type, algt->mask);
 511
 512         inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
 513         if (!inst)
 514                 return -ENOMEM;
 515         ictx = skcipher_instance_ctx(inst);
 516
 517         /* Stream cipher, e.g. "xchacha12" */
 518         err = crypto_grab_skcipher(&ictx->streamcipher_spawn,
 519                                    skcipher_crypto_instance(inst),
 520                                    crypto_attr_alg_name(tb[1]), 0, mask);
 521         if (err)
 522                 goto err_free_inst;
 523         streamcipher_alg = crypto_spawn_skcipher_alg(&ictx->streamcipher_spawn);
 524
 525         /* Block cipher, e.g. "aes" */
 526         err = crypto_grab_cipher(&ictx->blockcipher_spawn,
 527                                  skcipher_crypto_instance(inst),
 528                                  crypto_attr_alg_name(tb[2]), 0, mask);
 529         if (err)
 530                 goto err_free_inst;
 531         blockcipher_alg = crypto_spawn_cipher_alg(&ictx->blockcipher_spawn);
 532
 533         /* NHPoly1305 ε-∆U hash function */
 534         nhpoly1305_name = crypto_attr_alg_name(tb[3]);
 535         if (nhpoly1305_name == ERR_PTR(-ENOENT))
 536                 nhpoly1305_name = "nhpoly1305";
 537         err = crypto_grab_shash(&ictx->hash_spawn,
 538                                 skcipher_crypto_instance(inst),
 539                                 nhpoly1305_name, 0, mask);
 540         if (err)
 541                 goto err_free_inst;
 542         hash_alg = crypto_spawn_shash_alg(&ictx->hash_spawn);
 543
 544         /* Check the set of algorithms */
 545         if (!adiantum_supported_algorithms(streamcipher_alg, blockcipher_alg,
 546                                            hash_alg)) {
 547                 pr_warn("Unsupported Adiantum instantiation: (%s,%s,%s)\n",
 548                         streamcipher_alg->base.cra_name,
 549                         blockcipher_alg->cra_name, hash_alg->base.cra_name);
 550                 err = -EINVAL;
 551                 goto err_free_inst;
 552         }
 553
 554         /* Instance fields */
 555
 556         err = -ENAMETOOLONG;
 557         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 558                      "adiantum(%s,%s)", streamcipher_alg->base.cra_name,
 559                      blockcipher_alg->cra_name) >= CRYPTO_MAX_ALG_NAME)
 560                 goto err_free_inst;
 561         if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 562                      "adiantum(%s,%s,%s)",
 563                      streamcipher_alg->base.cra_driver_name,
 564                      blockcipher_alg->cra_driver_name,
 565                      hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
 566                 goto err_free_inst;
 567
 568         inst->alg.base.cra_flags = streamcipher_alg->base.cra_flags &
 569                                    CRYPTO_ALG_ASYNC;
 570         inst->alg.base.cra_blocksize = BLOCKCIPHER_BLOCK_SIZE;
 571         inst->alg.base.cra_ctxsize = sizeof(struct adiantum_tfm_ctx);
 572         inst->alg.base.cra_alignmask = streamcipher_alg->base.cra_alignmask |
 573                                        hash_alg->base.cra_alignmask;
 574         /*
 575          * The block cipher is only invoked once per message, so for long
 576          * messages (e.g. sectors for disk encryption) its performance doesn't
 577          * matter as much as that of the stream cipher and hash function.  Thus,
 578          * weigh the block cipher's ->cra_priority less.
 579          */
 580         inst->alg.base.cra_priority = (4 * streamcipher_alg->base.cra_priority +
 581                                        2 * hash_alg->base.cra_priority +
 582                                        blockcipher_alg->cra_priority) / 7;
 583
 584         inst->alg.setkey = adiantum_setkey;
 585         inst->alg.encrypt = adiantum_encrypt;
 586         inst->alg.decrypt = adiantum_decrypt;
 587         inst->alg.init = adiantum_init_tfm;
 588         inst->alg.exit = adiantum_exit_tfm;
 589         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(streamcipher_alg);
 590         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(streamcipher_alg);
 591         inst->alg.ivsize = TWEAK_SIZE;
 592
 593         inst->free = adiantum_free_instance;
 594
 595         err = skcipher_register_instance(tmpl, inst);
 596         if (err) {
 597 err_free_inst:
 598                 adiantum_free_instance(inst);
 599         }
 600         return err;
 601 }
 602
 603 /* adiantum(streamcipher_name, blockcipher_name [, nhpoly1305_name]) */
 604 static struct crypto_template adiantum_tmpl = {
 605         .name = "adiantum",
 606         .create = adiantum_create,
 607         .module = THIS_MODULE,
 608 };
 609
 610 static int __init adiantum_module_init(void)
 611 {
 612         return crypto_register_template(&adiantum_tmpl);
 613 }
 614
 615 static void __exit adiantum_module_exit(void)
 616 {
 617         crypto_unregister_template(&adiantum_tmpl);
 618 }
 619
 620 subsys_initcall(adiantum_module_init);
 621 module_exit(adiantum_module_exit);
 622
 623 MODULE_DESCRIPTION("Adiantum length-preserving encryption mode");
 624 MODULE_LICENSE("GPL v2");
 625 MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
 626 MODULE_ALIAS_CRYPTO("adiantum");