summaryrefslogtreecommitdiff
path: root/crypto/adiantum.c
blob: c33ba22a66389cfdf06878d0bf288935ae5746c3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
// SPDX-License-Identifier: GPL-2.0
/*
 * Adiantum length-preserving encryption mode
 *
 * Copyright 2018 Google LLC
 */

/*
 * Adiantum is a tweakable, length-preserving encryption mode designed for fast
 * and secure disk encryption, especially on CPUs without dedicated crypto
 * instructions.  Adiantum encrypts each sector using the XChaCha12 stream
 * cipher, two passes of an ε-almost-∆-universal (ε-∆U) hash function based on
 * NH and Poly1305, and an invocation of the AES-256 block cipher on a single
 * 16-byte block.  See the paper for details:
 *
 *	Adiantum: length-preserving encryption for entry-level processors
 *      (https://eprint.iacr.org/2018/720.pdf)
 *
 * For flexibility, this implementation also allows other ciphers:
 *
 *	- Stream cipher: XChaCha12 or XChaCha20
 *	- Block cipher: any with a 128-bit block size and 256-bit key
 *
 * This implementation doesn't currently allow other ε-∆U hash functions, i.e.
 * HPolyC is not supported.  This is because Adiantum is ~20% faster than HPolyC
 * but still provably as secure, and also the ε-∆U hash function of HBSH is
 * formally defined to take two inputs (tweak, message) which makes it difficult
 * to wrap with the crypto_shash API.  Rather, some details need to be handled
 * here.  Nevertheless, if needed in the future, support for other ε-∆U hash
 * functions could be added here.
 */

#include <crypto/b128ops.h>
#include <crypto/chacha.h>
#include <crypto/internal/cipher.h>
#include <crypto/internal/hash.h>
#include <crypto/internal/poly1305.h>
#include <crypto/internal/skcipher.h>
#include <crypto/nhpoly1305.h>
#include <crypto/scatterwalk.h>
#include <linux/module.h>

/*
 * Size of right-hand part of input data, in bytes; also the size of the block
 * cipher's block size and the hash function's output.
 */
#define BLOCKCIPHER_BLOCK_SIZE		16

/* Size of the block cipher key (K_E) in bytes */
#define BLOCKCIPHER_KEY_SIZE		32

/* Size of the hash key (K_H) in bytes */
#define HASH_KEY_SIZE		(POLY1305_BLOCK_SIZE + NHPOLY1305_KEY_SIZE)

/*
 * The specification allows variable-length tweaks, but Linux's crypto API
 * currently only allows algorithms to support a single length.  The "natural"
 * tweak length for Adiantum is 16, since that fits into one Poly1305 block for
 * the best performance.  But longer tweaks are useful for fscrypt, to avoid
 * needing to derive per-file keys.  So instead we use two blocks, or 32 bytes.
 */
#define TWEAK_SIZE		32

struct adiantum_instance_ctx {
	struct crypto_skcipher_spawn streamcipher_spawn;
	struct crypto_cipher_spawn blockcipher_spawn;
	struct crypto_shash_spawn hash_spawn;
};

struct adiantum_tfm_ctx {
	struct crypto_skcipher *streamcipher;
	struct crypto_cipher *blockcipher;
	struct crypto_shash *hash;
	struct poly1305_core_key header_hash_key;
};

struct adiantum_request_ctx {

	/*
	 * Buffer for right-hand part of data, i.e.
	 *
	 *    P_L => P_M => C_M => C_R when encrypting, or
	 *    C_R => C_M => P_M => P_L when decrypting.
	 *
	 * Also used to build the IV for the stream cipher.
	 */
	union {
		u8 bytes[XCHACHA_IV_SIZE];
		__le32 words[XCHACHA_IV_SIZE / sizeof(__le32)];
		le128 bignum;	/* interpret as element of Z/(2^{128}Z) */
	} rbuf;

	bool enc; /* true if encrypting, false if decrypting */

	/*
	 * The result of the Poly1305 ε-∆U hash function applied to
	 * (bulk length, tweak)
	 */
	le128 header_hash;

	/* Sub-requests, must be last */
	union {
		struct shash_desc hash_desc;
		struct skcipher_request streamcipher_req;
	} u;
};

/*
 * Given the XChaCha stream key K_S, derive the block cipher key K_E and the
 * hash key K_H as follows:
 *
 *     K_E || K_H || ... = XChaCha(key=K_S, nonce=1||0^191)
 *
 * Note that this denotes using bits from the XChaCha keystream, which here we
 * get indirectly by encrypting a buffer containing all 0's.
 */
static int adiantum_setkey(struct crypto_skcipher *tfm, const u8 *key,
			   unsigned int keylen)
{
	struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
	struct {
		u8 iv[XCHACHA_IV_SIZE];
		u8 derived_keys[BLOCKCIPHER_KEY_SIZE + HASH_KEY_SIZE];
		struct scatterlist sg;
		struct crypto_wait wait;
		struct skcipher_request req; /* must be last */
	} *data;
	u8 *keyp;
	int err;

	/* Set the stream cipher key (K_S) */
	crypto_skcipher_clear_flags(tctx->streamcipher, CRYPTO_TFM_REQ_MASK);
	crypto_skcipher_set_flags(tctx->streamcipher,
				  crypto_skcipher_get_flags(tfm) &
				  CRYPTO_TFM_REQ_MASK);
	err = crypto_skcipher_setkey(tctx->streamcipher, key, keylen);
	if (err)
		return err;

	/* Derive the subkeys */
	data = kzalloc(sizeof(*data) +
		       crypto_skcipher_reqsize(tctx->streamcipher), GFP_KERNEL);
	if (!data)
		return -ENOMEM;
	data->iv[0] = 1;
	sg_init_one(&data->sg, data->derived_keys, sizeof(data->derived_keys));
	crypto_init_wait(&data->wait);
	skcipher_request_set_tfm(&data->req, tctx->streamcipher);
	skcipher_request_set_callback(&data->req, CRYPTO_TFM_REQ_MAY_SLEEP |
						  CRYPTO_TFM_REQ_MAY_BACKLOG,
				      crypto_req_done, &data->wait);
	skcipher_request_set_crypt(&data->req, &data->sg, &data->sg,
				   sizeof(data->derived_keys), data->iv);
	err = crypto_wait_req(crypto_skcipher_encrypt(&data->req), &data->wait);
	if (err)
		goto out;
	keyp = data->derived_keys;

	/* Set the block cipher key (K_E) */
	crypto_cipher_clear_flags(tctx->blockcipher, CRYPTO_TFM_REQ_MASK);
	crypto_cipher_set_flags(tctx->blockcipher,
				crypto_skcipher_get_flags(tfm) &
				CRYPTO_TFM_REQ_MASK);
	err = crypto_cipher_setkey(tctx->blockcipher, keyp,
				   BLOCKCIPHER_KEY_SIZE);
	if (err)
		goto out;
	keyp += BLOCKCIPHER_KEY_SIZE;

	/* Set the hash key (K_H) */
	poly1305_core_setkey(&tctx->header_hash_key, keyp);
	keyp += POLY1305_BLOCK_SIZE;

	crypto_shash_clear_flags(tctx->hash, CRYPTO_TFM_REQ_MASK);
	crypto_shash_set_flags(tctx->hash, crypto_skcipher_get_flags(tfm) &
					   CRYPTO_TFM_REQ_MASK);
	err = crypto_shash_setkey(tctx->hash, keyp, NHPOLY1305_KEY_SIZE);
	keyp += NHPOLY1305_KEY_SIZE;
	WARN_ON(keyp != &data->derived_keys[ARRAY_SIZE(data->derived_keys)]);
out:
	kfree_sensitive(data);
	return err;
}

/* Addition in Z/(2^{128}Z) */
static inline void le128_add(le128 *r, const le128 *v1, const le128 *v2)
{
	u64 x = le64_to_cpu(v1->b);
	u64 y = le64_to_cpu(v2->b);

	r->b = cpu_to_le64(x + y);
	r->a = cpu_to_le64(le64_to_cpu(v1->a) + le64_to_cpu(v2->a) +
			   (x + y < x));
}

/* Subtraction in Z/(2^{128}Z) */
static inline void le128_sub(le128 *r, const le128 *v1, const le128 *v2)
{
	u64 x = le64_to_cpu(v1->b);
	u64 y = le64_to_cpu(v2->b);

	r->b = cpu_to_le64(x - y);
	r->a = cpu_to_le64(le64_to_cpu(v1->a) - le64_to_cpu(v2->a) -
			   (x - y > x));
}

/*
 * Apply the Poly1305 ε-∆U hash function to (bulk length, tweak) and save the
 * result to rctx->header_hash.  This is the calculation
 *
 *	H_T ← Poly1305_{K_T}(bin_{128}(|L|) || T)
 *
 * from the procedure in section 6.4 of the Adiantum paper.  The resulting value
 * is reused in both the first and second hash steps.  Specifically, it's added
 * to the result of an independently keyed ε-∆U hash function (for equal length
 * inputs only) taken over the left-hand part (the "bulk") of the message, to
 * give the overall Adiantum hash of the (tweak, left-hand part) pair.
 */
static void adiantum_hash_header(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
	struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
	const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
	struct {
		__le64 message_bits;
		__le64 padding;
	} header = {
		.message_bits = cpu_to_le64((u64)bulk_len * 8)
	};
	struct poly1305_state state;

	poly1305_core_init(&state);

	BUILD_BUG_ON(sizeof(header) % POLY1305_BLOCK_SIZE != 0);
	poly1305_core_blocks(&state, &tctx->header_hash_key,
			     &header, sizeof(header) / POLY1305_BLOCK_SIZE, 1);

	BUILD_BUG_ON(TWEAK_SIZE % POLY1305_BLOCK_SIZE != 0);
	poly1305_core_blocks(&state, &tctx->header_hash_key, req->iv,
			     TWEAK_SIZE / POLY1305_BLOCK_SIZE, 1);

	poly1305_core_emit(&state, NULL, &rctx->header_hash);
}

/* Hash the left-hand part (the "bulk") of the message using NHPoly1305 */
static int adiantum_hash_message(struct skcipher_request *req,
				 struct scatterlist *sgl, le128 *digest)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
	struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
	const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
	struct shash_desc *hash_desc = &rctx->u.hash_desc;
	struct sg_mapping_iter miter;
	unsigned int i, n;
	int err;

	hash_desc->tfm = tctx->hash;

	err = crypto_shash_init(hash_desc);
	if (err)
		return err;

	sg_miter_start(&miter, sgl, sg_nents(sgl),
		       SG_MITER_FROM_SG | SG_MITER_ATOMIC);
	for (i = 0; i < bulk_len; i += n) {
		sg_miter_next(&miter);
		n = min_t(unsigned int, miter.length, bulk_len - i);
		err = crypto_shash_update(hash_desc, miter.addr, n);
		if (err)
			break;
	}
	sg_miter_stop(&miter);
	if (err)
		return err;

	return crypto_shash_final(hash_desc, (u8 *)digest);
}

/* Continue Adiantum encryption/decryption after the stream cipher step */
static int adiantum_finish(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
	struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
	const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
	le128 digest;
	int err;

	/* If decrypting, decrypt C_M with the block cipher to get P_M */
	if (!rctx->enc)
		crypto_cipher_decrypt_one(tctx->blockcipher, rctx->rbuf.bytes,
					  rctx->rbuf.bytes);

	/*
	 * Second hash step
	 *	enc: C_R = C_M - H_{K_H}(T, C_L)
	 *	dec: P_R = P_M - H_{K_H}(T, P_L)
	 */
	err = adiantum_hash_message(req, req->dst, &digest);
	if (err)
		return err;
	le128_add(&digest, &digest, &rctx->header_hash);
	le128_sub(&rctx->rbuf.bignum, &rctx->rbuf.bignum, &digest);
	scatterwalk_map_and_copy(&rctx->rbuf.bignum, req->dst,
				 bulk_len, BLOCKCIPHER_BLOCK_SIZE, 1);
	return 0;
}

static void adiantum_streamcipher_done(void *data, int err)
{
	struct skcipher_request *req = data;

	if (!err)
		err = adiantum_finish(req);

	skcipher_request_complete(req, err);
}

static int adiantum_crypt(struct skcipher_request *req, bool enc)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	const struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
	struct adiantum_request_ctx *rctx = skcipher_request_ctx(req);
	const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
	unsigned int stream_len;
	le128 digest;
	int err;

	if (req->cryptlen < BLOCKCIPHER_BLOCK_SIZE)
		return -EINVAL;

	rctx->enc = enc;

	/*
	 * First hash step
	 *	enc: P_M = P_R + H_{K_H}(T, P_L)
	 *	dec: C_M = C_R + H_{K_H}(T, C_L)
	 */
	adiantum_hash_header(req);
	err = adiantum_hash_message(req, req->src, &digest);
	if (err)
		return err;
	le128_add(&digest, &digest, &rctx->header_hash);
	scatterwalk_map_and_copy(&rctx->rbuf.bignum, req->src,
				 bulk_len, BLOCKCIPHER_BLOCK_SIZE, 0);
	le128_add(&rctx->rbuf.bignum, &rctx->rbuf.bignum, &digest);

	/* If encrypting, encrypt P_M with the block cipher to get C_M */
	if (enc)
		crypto_cipher_encrypt_one(tctx->blockcipher, rctx->rbuf.bytes,
					  rctx->rbuf.bytes);

	/* Initialize the rest of the XChaCha IV (first part is C_M) */
	BUILD_BUG_ON(BLOCKCIPHER_BLOCK_SIZE != 16);
	BUILD_BUG_ON(XCHACHA_IV_SIZE != 32);	/* nonce || stream position */
	rctx->rbuf.words[4] = cpu_to_le32(1);
	rctx->rbuf.words[5] = 0;
	rctx->rbuf.words[6] = 0;
	rctx->rbuf.words[7] = 0;

	/*
	 * XChaCha needs to be done on all the data except the last 16 bytes;
	 * for disk encryption that usually means 4080 or 496 bytes.  But ChaCha
	 * implementations tend to be most efficient when passed a whole number
	 * of 64-byte ChaCha blocks, or sometimes even a multiple of 256 bytes.
	 * And here it doesn't matter whether the last 16 bytes are written to,
	 * as the second hash step will overwrite them.  Thus, round the XChaCha
	 * length up to the next 64-byte boundary if possible.
	 */
	stream_len = bulk_len;
	if (round_up(stream_len, CHACHA_BLOCK_SIZE) <= req->cryptlen)
		stream_len = round_up(stream_len, CHACHA_BLOCK_SIZE);

	skcipher_request_set_tfm(&rctx->u.streamcipher_req, tctx->streamcipher);
	skcipher_request_set_crypt(&rctx->u.streamcipher_req, req->src,
				   req->dst, stream_len, &rctx->rbuf);
	skcipher_request_set_callback(&rctx->u.streamcipher_req,
				      req->base.flags,
				      adiantum_streamcipher_done, req);
	return crypto_skcipher_encrypt(&rctx->u.streamcipher_req) ?:
		adiantum_finish(req);
}

static int adiantum_encrypt(struct skcipher_request *req)
{
	return adiantum_crypt(req, true);
}

static int adiantum_decrypt(struct skcipher_request *req)
{
	return adiantum_crypt(req, false);
}

static int adiantum_init_tfm(struct crypto_skcipher *tfm)
{
	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	struct adiantum_instance_ctx *ictx = skcipher_instance_ctx(inst);
	struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
	struct crypto_skcipher *streamcipher;
	struct crypto_cipher *blockcipher;
	struct crypto_shash *hash;
	unsigned int subreq_size;
	int err;

	streamcipher = crypto_spawn_skcipher(&ictx->streamcipher_spawn);
	if (IS_ERR(streamcipher))
		return PTR_ERR(streamcipher);

	blockcipher = crypto_spawn_cipher(&ictx->blockcipher_spawn);
	if (IS_ERR(blockcipher)) {
		err = PTR_ERR(blockcipher);
		goto err_free_streamcipher;
	}

	hash = crypto_spawn_shash(&ictx->hash_spawn);
	if (IS_ERR(hash)) {
		err = PTR_ERR(hash);
		goto err_free_blockcipher;
	}

	tctx->streamcipher = streamcipher;
	tctx->blockcipher = blockcipher;
	tctx->hash = hash;

	BUILD_BUG_ON(offsetofend(struct adiantum_request_ctx, u) !=
		     sizeof(struct adiantum_request_ctx));
	subreq_size = max(sizeof_field(struct adiantum_request_ctx,
				       u.hash_desc) +
			  crypto_shash_descsize(hash),
			  sizeof_field(struct adiantum_request_ctx,
				       u.streamcipher_req) +
			  crypto_skcipher_reqsize(streamcipher));

	crypto_skcipher_set_reqsize(tfm,
				    offsetof(struct adiantum_request_ctx, u) +
				    subreq_size);
	return 0;

err_free_blockcipher:
	crypto_free_cipher(blockcipher);
err_free_streamcipher:
	crypto_free_skcipher(streamcipher);
	return err;
}

static void adiantum_exit_tfm(struct crypto_skcipher *tfm)
{
	struct adiantum_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);

	crypto_free_skcipher(tctx->streamcipher);
	crypto_free_cipher(tctx->blockcipher);
	crypto_free_shash(tctx->hash);
}

static void adiantum_free_instance(struct skcipher_instance *inst)
{
	struct adiantum_instance_ctx *ictx = skcipher_instance_ctx(inst);

	crypto_drop_skcipher(&ictx->streamcipher_spawn);
	crypto_drop_cipher(&ictx->blockcipher_spawn);
	crypto_drop_shash(&ictx->hash_spawn);
	kfree(inst);
}

/*
 * Check for a supported set of inner algorithms.
 * See the comment at the beginning of this file.
 */
static bool adiantum_supported_algorithms(struct skcipher_alg *streamcipher_alg,
					  struct crypto_alg *blockcipher_alg,
					  struct shash_alg *hash_alg)
{
	if (strcmp(streamcipher_alg->base.cra_name, "xchacha12") != 0 &&
	    strcmp(streamcipher_alg->base.cra_name, "xchacha20") != 0)
		return false;

	if (blockcipher_alg->cra_cipher.cia_min_keysize > BLOCKCIPHER_KEY_SIZE ||
	    blockcipher_alg->cra_cipher.cia_max_keysize < BLOCKCIPHER_KEY_SIZE)
		return false;
	if (blockcipher_alg->cra_blocksize != BLOCKCIPHER_BLOCK_SIZE)
		return false;

	if (strcmp(hash_alg->base.cra_name, "nhpoly1305") != 0)
		return false;

	return true;
}

static int adiantum_create(struct crypto_template *tmpl, struct rtattr **tb)
{
	u32 mask;
	const char *nhpoly1305_name;
	struct skcipher_instance *inst;
	struct adiantum_instance_ctx *ictx;
	struct skcipher_alg *streamcipher_alg;
	struct crypto_alg *blockcipher_alg;
	struct shash_alg *hash_alg;
	int err;

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
	if (err)
		return err;

	inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
	if (!inst)
		return -ENOMEM;
	ictx = skcipher_instance_ctx(inst);

	/* Stream cipher, e.g. "xchacha12" */
	err = crypto_grab_skcipher(&ictx->streamcipher_spawn,
				   skcipher_crypto_instance(inst),
				   crypto_attr_alg_name(tb[1]), 0, mask);
	if (err)
		goto err_free_inst;
	streamcipher_alg = crypto_spawn_skcipher_alg(&ictx->streamcipher_spawn);

	/* Block cipher, e.g. "aes" */
	err = crypto_grab_cipher(&ictx->blockcipher_spawn,
				 skcipher_crypto_instance(inst),
				 crypto_attr_alg_name(tb[2]), 0, mask);
	if (err)
		goto err_free_inst;
	blockcipher_alg = crypto_spawn_cipher_alg(&ictx->blockcipher_spawn);

	/* NHPoly1305 ε-∆U hash function */
	nhpoly1305_name = crypto_attr_alg_name(tb[3]);
	if (nhpoly1305_name == ERR_PTR(-ENOENT))
		nhpoly1305_name = "nhpoly1305";
	err = crypto_grab_shash(&ictx->hash_spawn,
				skcipher_crypto_instance(inst),
				nhpoly1305_name, 0, mask);
	if (err)
		goto err_free_inst;
	hash_alg = crypto_spawn_shash_alg(&ictx->hash_spawn);

	/* Check the set of algorithms */
	if (!adiantum_supported_algorithms(streamcipher_alg, blockcipher_alg,
					   hash_alg)) {
		pr_warn("Unsupported Adiantum instantiation: (%s,%s,%s)\n",
			streamcipher_alg->base.cra_name,
			blockcipher_alg->cra_name, hash_alg->base.cra_name);
		err = -EINVAL;
		goto err_free_inst;
	}

	/* Instance fields */

	err = -ENAMETOOLONG;
	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
		     "adiantum(%s,%s)", streamcipher_alg->base.cra_name,
		     blockcipher_alg->cra_name) >= CRYPTO_MAX_ALG_NAME)
		goto err_free_inst;
	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
		     "adiantum(%s,%s,%s)",
		     streamcipher_alg->base.cra_driver_name,
		     blockcipher_alg->cra_driver_name,
		     hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
		goto err_free_inst;

	inst->alg.base.cra_blocksize = BLOCKCIPHER_BLOCK_SIZE;
	inst->alg.base.cra_ctxsize = sizeof(struct adiantum_tfm_ctx);
	inst->alg.base.cra_alignmask = streamcipher_alg->base.cra_alignmask |
				       hash_alg->base.cra_alignmask;
	/*
	 * The block cipher is only invoked once per message, so for long
	 * messages (e.g. sectors for disk encryption) its performance doesn't
	 * matter as much as that of the stream cipher and hash function.  Thus,
	 * weigh the block cipher's ->cra_priority less.
	 */
	inst->alg.base.cra_priority = (4 * streamcipher_alg->base.cra_priority +
				       2 * hash_alg->base.cra_priority +
				       blockcipher_alg->cra_priority) / 7;

	inst->alg.setkey = adiantum_setkey;
	inst->alg.encrypt = adiantum_encrypt;
	inst->alg.decrypt = adiantum_decrypt;
	inst->alg.init = adiantum_init_tfm;
	inst->alg.exit = adiantum_exit_tfm;
	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(streamcipher_alg);
	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(streamcipher_alg);
	inst->alg.ivsize = TWEAK_SIZE;

	inst->free = adiantum_free_instance;

	err = skcipher_register_instance(tmpl, inst);
	if (err) {
err_free_inst:
		adiantum_free_instance(inst);
	}
	return err;
}

/* adiantum(streamcipher_name, blockcipher_name [, nhpoly1305_name]) */
static struct crypto_template adiantum_tmpl = {
	.name = "adiantum",
	.create = adiantum_create,
	.module = THIS_MODULE,
};

static int __init adiantum_module_init(void)
{
	return crypto_register_template(&adiantum_tmpl);
}

static void __exit adiantum_module_exit(void)
{
	crypto_unregister_template(&adiantum_tmpl);
}

subsys_initcall(adiantum_module_init);
module_exit(adiantum_module_exit);

MODULE_DESCRIPTION("Adiantum length-preserving encryption mode");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
MODULE_ALIAS_CRYPTO("adiantum");
MODULE_IMPORT_NS(CRYPTO_INTERNAL);