root/crypto/adiantum.c

DEFINITIONS

1. adiantum_setkey
2. le128_add
3. le128_sub
4. adiantum_hash_header
5. adiantum_hash_message
6. adiantum_finish
7. adiantum_streamcipher_done
8. adiantum_crypt
9. adiantum_encrypt
10. adiantum_decrypt
11. adiantum_init_tfm
12. adiantum_exit_tfm
13. adiantum_free_instance
14. adiantum_supported_algorithms
15. adiantum_create
16. adiantum_module_init
17. adiantum_module_exit

   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/skcipher.h>
  37 #include <crypto/nhpoly1305.h>
  38 #include <crypto/scatterwalk.h>
  39 #include <linux/module.h>
  40 
  41 #include "internal.h"
  42 
  43 /*
  44  * Size of right-hand part of input data, in bytes; also the size of the block
  45  * cipher's block size and the hash function's output.
  46  */
  47 #define BLOCKCIPHER_BLOCK_SIZE          16
  48 
  49 /* Size of the block cipher key (K_E) in bytes */
  50 #define BLOCKCIPHER_KEY_SIZE            32
  51 
  52 /* Size of the hash key (K_H) in bytes */
  53 #define HASH_KEY_SIZE           (POLY1305_BLOCK_SIZE + NHPOLY1305_KEY_SIZE)
  54 
  55 /*
  56  * The specification allows variable-length tweaks, but Linux's crypto API
  57  * currently only allows algorithms to support a single length.  The "natural"
  58  * tweak length for Adiantum is 16, since that fits into one Poly1305 block for
  59  * the best performance.  But longer tweaks are useful for fscrypt, to avoid
  60  * needing to derive per-file keys.  So instead we use two blocks, or 32 bytes.
  61  */
  62 #define TWEAK_SIZE              32
  63 
  64 struct adiantum_instance_ctx {
  65         struct crypto_skcipher_spawn streamcipher_spawn;
  66         struct crypto_spawn blockcipher_spawn;
  67         struct crypto_shash_spawn hash_spawn;
  68 };
  69 
  70 struct adiantum_tfm_ctx {
  71         struct crypto_skcipher *streamcipher;
  72         struct crypto_cipher *blockcipher;
  73         struct crypto_shash *hash;
  74         struct poly1305_key header_hash_key;
  75 };
  76 
  77 struct adiantum_request_ctx {
  78 
  79         /*
  80          * Buffer for right-hand part of data, i.e.
  81          *
  82          *    P_L => P_M => C_M => C_R when encrypting, or
  83          *    C_R => C_M => P_M => P_L when decrypting.
  84          *
  85          * Also used to build the IV for the stream cipher.
  86          */
  87         union {
  88                 u8 bytes[XCHACHA_IV_SIZE];
  89                 __le32 words[XCHACHA_IV_SIZE / sizeof(__le32)];
  90                 le128 bignum;   /* interpret as element of Z/(2^{128}Z) */
  91         } rbuf;
  92 
  93         bool enc; /* true if encrypting, false if decrypting */
  94 
  95         /*
  96          * The result of the Poly1305 ε-∆U hash function applied to
  97          * (bulk length, tweak)
  98          */
  99         le128 header_hash;
 100 
 101         /* Sub-requests, must be last */
 102         union {
 103                 struct shash_desc hash_desc;
 104                 struct skcipher_request streamcipher_req;
 105         } u;
 106 };
 107 
 108 /*
 109  * Given the XChaCha stream key K_S, derive the block cipher key K_E and the
 110  * hash key K_H as follows:
 111  *
 112  *     K_E || K_H || ... = XChaCha(key=K_S, nonce=1||0^191)
 113  *
 114  * Note that this denotes using bits from the XChaCha keystream, which here we
 115  * get indirectly by encrypting a buffer containing all 0's.
 116  */
 117 static int adiantum_setkey(struct crypto_skcipher *tfm, const u8 *key,
 118                            unsigned int keylen)
 119 {
 120         struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 121         struct {
 122                 u8 iv[XCHACHA_IV_SIZE];
 123                 u8 derived_keys[BLOCKCIPHER_KEY_SIZE + HASH_KEY_SIZE];
 124                 struct scatterlist sg;
 125                 struct crypto_wait wait;
 126                 struct skcipher_request req; /* must be last */
 127         } *data;
 128         u8 *keyp;
 129         int err;
 130 
 131         /* Set the stream cipher key (K_S) */
 132         crypto_skcipher_clear_flags(tctx->streamcipher, CRYPTO_TFM_REQ_MASK);
 133         crypto_skcipher_set_flags(tctx->streamcipher,
 134                                   crypto_skcipher_get_flags(tfm) &
 135                                   CRYPTO_TFM_REQ_MASK);
 136         err = crypto_skcipher_setkey(tctx->streamcipher, key, keylen);
 137         crypto_skcipher_set_flags(tfm,
 138                                 crypto_skcipher_get_flags(tctx->streamcipher) &
 139                                 CRYPTO_TFM_RES_MASK);
 140         if (err)
 141                 return err;
 142 
 143         /* Derive the subkeys */
 144         data = kzalloc(sizeof(*data) +
 145                        crypto_skcipher_reqsize(tctx->streamcipher), GFP_KERNEL);
 146         if (!data)
 147                 return -ENOMEM;
 148         data->iv[0] = 1;
 149         sg_init_one(&data->sg, data->derived_keys, sizeof(data->derived_keys));
 150         crypto_init_wait(&data->wait);
 151         skcipher_request_set_tfm(&data->req, tctx->streamcipher);
 152         skcipher_request_set_callback(&data->req, CRYPTO_TFM_REQ_MAY_SLEEP |
 153                                                   CRYPTO_TFM_REQ_MAY_BACKLOG,
 154                                       crypto_req_done, &data->wait);
 155         skcipher_request_set_crypt(&data->req, &data->sg, &data->sg,
 156                                    sizeof(data->derived_keys), data->iv);
 157         err = crypto_wait_req(crypto_skcipher_encrypt(&data->req), &data->wait);
 158         if (err)
 159                 goto out;
 160         keyp = data->derived_keys;
 161 
 162         /* Set the block cipher key (K_E) */
 163         crypto_cipher_clear_flags(tctx->blockcipher, CRYPTO_TFM_REQ_MASK);
 164         crypto_cipher_set_flags(tctx->blockcipher,
 165                                 crypto_skcipher_get_flags(tfm) &
 166                                 CRYPTO_TFM_REQ_MASK);
 167         err = crypto_cipher_setkey(tctx->blockcipher, keyp,
 168                                    BLOCKCIPHER_KEY_SIZE);
 169         crypto_skcipher_set_flags(tfm,
 170                                   crypto_cipher_get_flags(tctx->blockcipher) &
 171                                   CRYPTO_TFM_RES_MASK);
 172         if (err)
 173                 goto out;
 174         keyp += BLOCKCIPHER_KEY_SIZE;
 175 
 176         /* Set the hash key (K_H) */
 177         poly1305_core_setkey(&tctx->header_hash_key, keyp);
 178         keyp += POLY1305_BLOCK_SIZE;
 179 
 180         crypto_shash_clear_flags(tctx->hash, CRYPTO_TFM_REQ_MASK);
 181         crypto_shash_set_flags(tctx->hash, crypto_skcipher_get_flags(tfm) &
 182                                            CRYPTO_TFM_REQ_MASK);
 183         err = crypto_shash_setkey(tctx->hash, keyp, NHPOLY1305_KEY_SIZE);
 184         crypto_skcipher_set_flags(tfm, crypto_shash_get_flags(tctx->hash) &
 185                                        CRYPTO_TFM_RES_MASK);
 186         keyp += NHPOLY1305_KEY_SIZE;
 187         WARN_ON(keyp != &data->derived_keys[ARRAY_SIZE(data->derived_keys)]);
 188 out:
 189         kzfree(data);
 190         return err;
 191 }
 192 
 193 /* Addition in Z/(2^{128}Z) */
 194 static inline void le128_add(le128 *r, const le128 *v1, const le128 *v2)
 195 {
 196         u64 x = le64_to_cpu(v1->b);
 197         u64 y = le64_to_cpu(v2->b);
 198 
 199         r->b = cpu_to_le64(x + y);
 200         r->a = cpu_to_le64(le64_to_cpu(v1->a) + le64_to_cpu(v2->a) +
 201                            (x + y < x));
 202 }
 203 
 204 /* Subtraction in Z/(2^{128}Z) */
 205 static inline void le128_sub(le128 *r, const le128 *v1, const le128 *v2)
 206 {
 207         u64 x = le64_to_cpu(v1->b);
 208         u64 y = le64_to_cpu(v2->b);
 209 
 210         r->b = cpu_to_le64(x - y);
 211         r->a = cpu_to_le64(le64_to_cpu(v1->a) - le64_to_cpu(v2->a) -
 212                            (x - y > x));
 213 }
 214 
 215 /*
 216  * Apply the Poly1305 ε-∆U hash function to (bulk length, tweak) and save the
 217  * result to rctx->header_hash.  This is the calculation
 218  *
 219  *      H_T ← Poly1305_{K_T}(bin_{128}(|L|) || T)
 220  *
 221  * from the procedure in section 6.4 of the Adiantum paper.  The resulting value
 222  * is reused in both the first and second hash steps.  Specifically, it's added
 223  * to the result of an independently keyed ε-∆U hash function (for equal length
 224  * inputs only) taken over the left-hand part (the "bulk") of the message, to
 225  * give the overall Adiantum hash of the (tweak, left-hand part) pair.
 226  */
 227 static void adiantum_hash_header(struct skcipher_request *req)
 228 {
 229         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 230         const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 231         struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
 232         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 233         struct {
 234                 __le64 message_bits;
 235                 __le64 padding;
 236         } header = {
 237                 .message_bits = cpu_to_le64((u64)bulk_len * 8)
 238         };
 239         struct poly1305_state state;
 240 
 241         poly1305_core_init(&state);
 242 
 243         BUILD_BUG_ON(sizeof(header) % POLY1305_BLOCK_SIZE != 0);
 244         poly1305_core_blocks(&state, &tctx->header_hash_key,
 245                              &header, sizeof(header) / POLY1305_BLOCK_SIZE);
 246 
 247         BUILD_BUG_ON(TWEAK_SIZE % POLY1305_BLOCK_SIZE != 0);
 248         poly1305_core_blocks(&state, &tctx->header_hash_key, req->iv,
 249                              TWEAK_SIZE / POLY1305_BLOCK_SIZE);
 250 
 251         poly1305_core_emit(&state, &rctx->header_hash);
 252 }
 253 
 254 /* Hash the left-hand part (the "bulk") of the message using NHPoly1305 */
 255 static int adiantum_hash_message(struct skcipher_request *req,
 256                                  struct scatterlist *sgl, le128 *digest)
 257 {
 258         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 259         const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 260         struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
 261         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 262         struct shash_desc *hash_desc = &rctx->u.hash_desc;
 263         struct sg_mapping_iter miter;
 264         unsigned int i, n;
 265         int err;
 266 
 267         hash_desc->tfm = tctx->hash;
 268 
 269         err = crypto_shash_init(hash_desc);
 270         if (err)
 271                 return err;
 272 
 273         sg_miter_start(&miter, sgl, sg_nents(sgl),
 274                        SG_MITER_FROM_SG | SG_MITER_ATOMIC);
 275         for (i = 0; i < bulk_len; i += n) {
 276                 sg_miter_next(&miter);
 277                 n = min_t(unsigned int, miter.length, bulk_len - i);
 278                 err = crypto_shash_update(hash_desc, miter.addr, n);
 279                 if (err)
 280                         break;
 281         }
 282         sg_miter_stop(&miter);
 283         if (err)
 284                 return err;
 285 
 286         return crypto_shash_final(hash_desc, (u8 *)digest);
 287 }
 288 
 289 /* Continue Adiantum encryption/decryption after the stream cipher step */
 290 static int adiantum_finish(struct skcipher_request *req)
 291 {
 292         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 293         const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 294         struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
 295         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 296         le128 digest;
 297         int err;
 298 
 299         /* If decrypting, decrypt C_M with the block cipher to get P_M */
 300         if (!rctx->enc)
 301                 crypto_cipher_decrypt_one(tctx->blockcipher, rctx->rbuf.bytes,
 302                                           rctx->rbuf.bytes);
 303 
 304         /*
 305          * Second hash step
 306          *      enc: C_R = C_M - H_{K_H}(T, C_L)
 307          *      dec: P_R = P_M - H_{K_H}(T, P_L)
 308          */
 309         err = adiantum_hash_message(req, req->dst, &digest);
 310         if (err)
 311                 return err;
 312         le128_add(&digest, &digest, &rctx->header_hash);
 313         le128_sub(&rctx->rbuf.bignum, &rctx->rbuf.bignum, &digest);
 314         scatterwalk_map_and_copy(&rctx->rbuf.bignum, req->dst,
 315                                  bulk_len, BLOCKCIPHER_BLOCK_SIZE, 1);
 316         return 0;
 317 }
 318 
 319 static void adiantum_streamcipher_done(struct crypto_async_request *areq,
 320                                        int err)
 321 {
 322         struct skcipher_request *req = areq->data;
 323 
 324         if (!err)
 325                 err = adiantum_finish(req);
 326 
 327         skcipher_request_complete(req, err);
 328 }
 329 
 330 static int adiantum_crypt(struct skcipher_request *req, bool enc)
 331 {
 332         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 333         const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 334         struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
 335         const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
 336         unsigned int stream_len;
 337         le128 digest;
 338         int err;
 339 
 340         if (req->cryptlen < BLOCKCIPHER_BLOCK_SIZE)
 341                 return -EINVAL;
 342 
 343         rctx->enc = enc;
 344 
 345         /*
 346          * First hash step
 347          *      enc: P_M = P_R + H_{K_H}(T, P_L)
 348          *      dec: C_M = C_R + H_{K_H}(T, C_L)
 349          */
 350         adiantum_hash_header(req);
 351         err = adiantum_hash_message(req, req->src, &digest);
 352         if (err)
 353                 return err;
 354         le128_add(&digest, &digest, &rctx->header_hash);
 355         scatterwalk_map_and_copy(&rctx->rbuf.bignum, req->src,
 356                                  bulk_len, BLOCKCIPHER_BLOCK_SIZE, 0);
 357         le128_add(&rctx->rbuf.bignum, &rctx->rbuf.bignum, &digest);
 358 
 359         /* If encrypting, encrypt P_M with the block cipher to get C_M */
 360         if (enc)
 361                 crypto_cipher_encrypt_one(tctx->blockcipher, rctx->rbuf.bytes,
 362                                           rctx->rbuf.bytes);
 363 
 364         /* Initialize the rest of the XChaCha IV (first part is C_M) */
 365         BUILD_BUG_ON(BLOCKCIPHER_BLOCK_SIZE != 16);
 366         BUILD_BUG_ON(XCHACHA_IV_SIZE != 32);    /* nonce || stream position */
 367         rctx->rbuf.words[4] = cpu_to_le32(1);
 368         rctx->rbuf.words[5] = 0;
 369         rctx->rbuf.words[6] = 0;
 370         rctx->rbuf.words[7] = 0;
 371 
 372         /*
 373          * XChaCha needs to be done on all the data except the last 16 bytes;
 374          * for disk encryption that usually means 4080 or 496 bytes.  But ChaCha
 375          * implementations tend to be most efficient when passed a whole number
 376          * of 64-byte ChaCha blocks, or sometimes even a multiple of 256 bytes.
 377          * And here it doesn't matter whether the last 16 bytes are written to,
 378          * as the second hash step will overwrite them.  Thus, round the XChaCha
 379          * length up to the next 64-byte boundary if possible.
 380          */
 381         stream_len = bulk_len;
 382         if (round_up(stream_len, CHACHA_BLOCK_SIZE) <= req->cryptlen)
 383                 stream_len = round_up(stream_len, CHACHA_BLOCK_SIZE);
 384 
 385         skcipher_request_set_tfm(&rctx->u.streamcipher_req, tctx->streamcipher);
 386         skcipher_request_set_crypt(&rctx->u.streamcipher_req, req->src,
 387                                    req->dst, stream_len, &rctx->rbuf);
 388         skcipher_request_set_callback(&rctx->u.streamcipher_req,
 389                                       req->base.flags,
 390                                       adiantum_streamcipher_done, req);
 391         return crypto_skcipher_encrypt(&rctx->u.streamcipher_req) ?:
 392                 adiantum_finish(req);
 393 }
 394 
 395 static int adiantum_encrypt(struct skcipher_request *req)
 396 {
 397         return adiantum_crypt(req, true);
 398 }
 399 
 400 static int adiantum_decrypt(struct skcipher_request *req)
 401 {
 402         return adiantum_crypt(req, false);
 403 }
 404 
 405 static int adiantum_init_tfm(struct crypto_skcipher *tfm)
 406 {
 407         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 408         struct adiantum_instance_ctx *ictx = skcipher_instance_ctx(inst);
 409         struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 410         struct crypto_skcipher *streamcipher;
 411         struct crypto_cipher *blockcipher;
 412         struct crypto_shash *hash;
 413         unsigned int subreq_size;
 414         int err;
 415 
 416         streamcipher = crypto_spawn_skcipher(&ictx->streamcipher_spawn);
 417         if (IS_ERR(streamcipher))
 418                 return PTR_ERR(streamcipher);
 419 
 420         blockcipher = crypto_spawn_cipher(&ictx->blockcipher_spawn);
 421         if (IS_ERR(blockcipher)) {
 422                 err = PTR_ERR(blockcipher);
 423                 goto err_free_streamcipher;
 424         }
 425 
 426         hash = crypto_spawn_shash(&ictx->hash_spawn);
 427         if (IS_ERR(hash)) {
 428                 err = PTR_ERR(hash);
 429                 goto err_free_blockcipher;
 430         }
 431 
 432         tctx->streamcipher = streamcipher;
 433         tctx->blockcipher = blockcipher;
 434         tctx->hash = hash;
 435 
 436         BUILD_BUG_ON(offsetofend(struct adiantum_request_ctx, u) !=
 437                      sizeof(struct adiantum_request_ctx));
 438         subreq_size = max(FIELD_SIZEOF(struct adiantum_request_ctx,
 439                                        u.hash_desc) +
 440                           crypto_shash_descsize(hash),
 441                           FIELD_SIZEOF(struct adiantum_request_ctx,
 442                                        u.streamcipher_req) +
 443                           crypto_skcipher_reqsize(streamcipher));
 444 
 445         crypto_skcipher_set_reqsize(tfm,
 446                                     offsetof(struct adiantum_request_ctx, u) +
 447                                     subreq_size);
 448         return 0;
 449 
 450 err_free_blockcipher:
 451         crypto_free_cipher(blockcipher);
 452 err_free_streamcipher:
 453         crypto_free_skcipher(streamcipher);
 454         return err;
 455 }
 456 
 457 static void adiantum_exit_tfm(struct crypto_skcipher *tfm)
 458 {
 459         struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
 460 
 461         crypto_free_skcipher(tctx->streamcipher);
 462         crypto_free_cipher(tctx->blockcipher);
 463         crypto_free_shash(tctx->hash);
 464 }
 465 
 466 static void adiantum_free_instance(struct skcipher_instance *inst)
 467 {
 468         struct adiantum_instance_ctx *ictx = skcipher_instance_ctx(inst);
 469 
 470         crypto_drop_skcipher(&ictx->streamcipher_spawn);
 471         crypto_drop_spawn(&ictx->blockcipher_spawn);
 472         crypto_drop_shash(&ictx->hash_spawn);
 473         kfree(inst);
 474 }
 475 
 476 /*
 477  * Check for a supported set of inner algorithms.
 478  * See the comment at the beginning of this file.
 479  */
 480 static bool adiantum_supported_algorithms(struct skcipher_alg *streamcipher_alg,
 481                                           struct crypto_alg *blockcipher_alg,
 482                                           struct shash_alg *hash_alg)
 483 {
 484         if (strcmp(streamcipher_alg->base.cra_name, "xchacha12") != 0 &&
 485             strcmp(streamcipher_alg->base.cra_name, "xchacha20") != 0)
 486                 return false;
 487 
 488         if (blockcipher_alg->cra_cipher.cia_min_keysize > BLOCKCIPHER_KEY_SIZE ||
 489             blockcipher_alg->cra_cipher.cia_max_keysize < BLOCKCIPHER_KEY_SIZE)
 490                 return false;
 491         if (blockcipher_alg->cra_blocksize != BLOCKCIPHER_BLOCK_SIZE)
 492                 return false;
 493 
 494         if (strcmp(hash_alg->base.cra_name, "nhpoly1305") != 0)
 495                 return false;
 496 
 497         return true;
 498 }
 499 
 500 static int adiantum_create(struct crypto_template *tmpl, struct rtattr **tb)
 501 {
 502         struct crypto_attr_type *algt;
 503         const char *streamcipher_name;
 504         const char *blockcipher_name;
 505         const char *nhpoly1305_name;
 506         struct skcipher_instance *inst;
 507         struct adiantum_instance_ctx *ictx;
 508         struct skcipher_alg *streamcipher_alg;
 509         struct crypto_alg *blockcipher_alg;
 510         struct crypto_alg *_hash_alg;
 511         struct shash_alg *hash_alg;
 512         int err;
 513 
 514         algt = crypto_get_attr_type(tb);
 515         if (IS_ERR(algt))
 516                 return PTR_ERR(algt);
 517 
 518         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 519                 return -EINVAL;
 520 
 521         streamcipher_name = crypto_attr_alg_name(tb[1]);
 522         if (IS_ERR(streamcipher_name))
 523                 return PTR_ERR(streamcipher_name);
 524 
 525         blockcipher_name = crypto_attr_alg_name(tb[2]);
 526         if (IS_ERR(blockcipher_name))
 527                 return PTR_ERR(blockcipher_name);
 528 
 529         nhpoly1305_name = crypto_attr_alg_name(tb[3]);
 530         if (nhpoly1305_name == ERR_PTR(-ENOENT))
 531                 nhpoly1305_name = "nhpoly1305";
 532         if (IS_ERR(nhpoly1305_name))
 533                 return PTR_ERR(nhpoly1305_name);
 534 
 535         inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
 536         if (!inst)
 537                 return -ENOMEM;
 538         ictx = skcipher_instance_ctx(inst);
 539 
 540         /* Stream cipher, e.g. "xchacha12" */
 541         crypto_set_skcipher_spawn(&ictx->streamcipher_spawn,
 542                                   skcipher_crypto_instance(inst));
 543         err = crypto_grab_skcipher(&ictx->streamcipher_spawn, streamcipher_name,
 544                                    0, crypto_requires_sync(algt->type,
 545                                                            algt->mask));
 546         if (err)
 547                 goto out_free_inst;
 548         streamcipher_alg = crypto_spawn_skcipher_alg(&ictx->streamcipher_spawn);
 549 
 550         /* Block cipher, e.g. "aes" */
 551         crypto_set_spawn(&ictx->blockcipher_spawn,
 552                          skcipher_crypto_instance(inst));
 553         err = crypto_grab_spawn(&ictx->blockcipher_spawn, blockcipher_name,
 554                                 CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_MASK);
 555         if (err)
 556                 goto out_drop_streamcipher;
 557         blockcipher_alg = ictx->blockcipher_spawn.alg;
 558 
 559         /* NHPoly1305 ε-∆U hash function */
 560         _hash_alg = crypto_alg_mod_lookup(nhpoly1305_name,
 561                                           CRYPTO_ALG_TYPE_SHASH,
 562                                           CRYPTO_ALG_TYPE_MASK);
 563         if (IS_ERR(_hash_alg)) {
 564                 err = PTR_ERR(_hash_alg);
 565                 goto out_drop_blockcipher;
 566         }
 567         hash_alg = __crypto_shash_alg(_hash_alg);
 568         err = crypto_init_shash_spawn(&ictx->hash_spawn, hash_alg,
 569                                       skcipher_crypto_instance(inst));
 570         if (err)
 571                 goto out_put_hash;
 572 
 573         /* Check the set of algorithms */
 574         if (!adiantum_supported_algorithms(streamcipher_alg, blockcipher_alg,
 575                                            hash_alg)) {
 576                 pr_warn("Unsupported Adiantum instantiation: (%s,%s,%s)\n",
 577                         streamcipher_alg->base.cra_name,
 578                         blockcipher_alg->cra_name, hash_alg->base.cra_name);
 579                 err = -EINVAL;
 580                 goto out_drop_hash;
 581         }
 582 
 583         /* Instance fields */
 584 
 585         err = -ENAMETOOLONG;
 586         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 587                      "adiantum(%s,%s)", streamcipher_alg->base.cra_name,
 588                      blockcipher_alg->cra_name) >= CRYPTO_MAX_ALG_NAME)
 589                 goto out_drop_hash;
 590         if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 591                      "adiantum(%s,%s,%s)",
 592                      streamcipher_alg->base.cra_driver_name,
 593                      blockcipher_alg->cra_driver_name,
 594                      hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
 595                 goto out_drop_hash;
 596 
 597         inst->alg.base.cra_flags = streamcipher_alg->base.cra_flags &
 598                                    CRYPTO_ALG_ASYNC;
 599         inst->alg.base.cra_blocksize = BLOCKCIPHER_BLOCK_SIZE;
 600         inst->alg.base.cra_ctxsize = sizeof(struct adiantum_tfm_ctx);
 601         inst->alg.base.cra_alignmask = streamcipher_alg->base.cra_alignmask |
 602                                        hash_alg->base.cra_alignmask;
 603         /*
 604          * The block cipher is only invoked once per message, so for long
 605          * messages (e.g. sectors for disk encryption) its performance doesn't
 606          * matter as much as that of the stream cipher and hash function.  Thus,
 607          * weigh the block cipher's ->cra_priority less.
 608          */
 609         inst->alg.base.cra_priority = (4 * streamcipher_alg->base.cra_priority +
 610                                        2 * hash_alg->base.cra_priority +
 611                                        blockcipher_alg->cra_priority) / 7;
 612 
 613         inst->alg.setkey = adiantum_setkey;
 614         inst->alg.encrypt = adiantum_encrypt;
 615         inst->alg.decrypt = adiantum_decrypt;
 616         inst->alg.init = adiantum_init_tfm;
 617         inst->alg.exit = adiantum_exit_tfm;
 618         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(streamcipher_alg);
 619         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(streamcipher_alg);
 620         inst->alg.ivsize = TWEAK_SIZE;
 621 
 622         inst->free = adiantum_free_instance;
 623 
 624         err = skcipher_register_instance(tmpl, inst);
 625         if (err)
 626                 goto out_drop_hash;
 627 
 628         crypto_mod_put(_hash_alg);
 629         return 0;
 630 
 631 out_drop_hash:
 632         crypto_drop_shash(&ictx->hash_spawn);
 633 out_put_hash:
 634         crypto_mod_put(_hash_alg);
 635 out_drop_blockcipher:
 636         crypto_drop_spawn(&ictx->blockcipher_spawn);
 637 out_drop_streamcipher:
 638         crypto_drop_skcipher(&ictx->streamcipher_spawn);
 639 out_free_inst:
 640         kfree(inst);
 641         return err;
 642 }
 643 
 644 /* adiantum(streamcipher_name, blockcipher_name [, nhpoly1305_name]) */
 645 static struct crypto_template adiantum_tmpl = {
 646         .name = "adiantum",
 647         .create = adiantum_create,
 648         .module = THIS_MODULE,
 649 };
 650 
 651 static int __init adiantum_module_init(void)
 652 {
 653         return crypto_register_template(&adiantum_tmpl);
 654 }
 655 
 656 static void __exit adiantum_module_exit(void)
 657 {
 658         crypto_unregister_template(&adiantum_tmpl);
 659 }
 660 
 661 subsys_initcall(adiantum_module_init);
 662 module_exit(adiantum_module_exit);
 663 
 664 MODULE_DESCRIPTION("Adiantum length-preserving encryption mode");
 665 MODULE_LICENSE("GPL v2");
 666 MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
 667 MODULE_ALIAS_CRYPTO("adiantum");