1 // SPDX-License-Identifier: GPL-2.0
3 * ESSIV skcipher and aead template for block encryption
5 * This template encapsulates the ESSIV IV generation algorithm used by
6 * dm-crypt and fscrypt, which converts the initial vector for the skcipher
7 * used for block encryption, by encrypting it using the hash of the
8 * skcipher key as encryption key. Usually, the input IV is a 64-bit sector
9 * number in LE representation zero-padded to the size of the IV, but this
10 * is not assumed by this driver.
12 * The typical use of this template is to instantiate the skcipher
13 * 'essiv(cbc(aes),sha256)', which is the only instantiation used by
14 * fscrypt, and the most relevant one for dm-crypt. However, dm-crypt
15 * also permits ESSIV to be used in combination with the authenc template,
16 * e.g., 'essiv(authenc(hmac(sha256),cbc(aes)),sha256)', in which case
17 * we need to instantiate an aead that accepts the same special key format
18 * as the authenc template, and deals with the way the encrypted IV is
19 * embedded into the AAD area of the aead request. This means the AEAD
20 * flavor produced by this template is tightly coupled to the way dm-crypt
23 * Copyright (c) 2019 Linaro, Ltd. <ard.biesheuvel@linaro.org>
26 * adiantum length-preserving encryption mode
28 * Copyright 2018 Google LLC
31 #include <crypto/authenc.h>
32 #include <crypto/internal/aead.h>
33 #include <crypto/internal/hash.h>
34 #include <crypto/internal/skcipher.h>
35 #include <crypto/scatterwalk.h>
36 #include <linux/module.h>
40 struct essiv_instance_ctx {
42 struct crypto_skcipher_spawn skcipher_spawn;
43 struct crypto_aead_spawn aead_spawn;
45 char essiv_cipher_name[CRYPTO_MAX_ALG_NAME];
46 char shash_driver_name[CRYPTO_MAX_ALG_NAME];
49 struct essiv_tfm_ctx {
51 struct crypto_skcipher *skcipher;
52 struct crypto_aead *aead;
54 struct crypto_cipher *essiv_cipher;
55 struct crypto_shash *hash;
59 struct essiv_aead_request_ctx {
60 struct scatterlist sg[4];
62 struct aead_request aead_req;
65 static int essiv_skcipher_setkey(struct crypto_skcipher *tfm,
66 const u8 *key, unsigned int keylen)
68 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
69 SHASH_DESC_ON_STACK(desc, tctx->hash);
70 u8 salt[HASH_MAX_DIGESTSIZE];
73 crypto_skcipher_clear_flags(tctx->u.skcipher, CRYPTO_TFM_REQ_MASK);
74 crypto_skcipher_set_flags(tctx->u.skcipher,
75 crypto_skcipher_get_flags(tfm) &
77 err = crypto_skcipher_setkey(tctx->u.skcipher, key, keylen);
78 crypto_skcipher_set_flags(tfm,
79 crypto_skcipher_get_flags(tctx->u.skcipher) &
84 desc->tfm = tctx->hash;
85 err = crypto_shash_digest(desc, key, keylen, salt);
89 crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK);
90 crypto_cipher_set_flags(tctx->essiv_cipher,
91 crypto_skcipher_get_flags(tfm) &
93 err = crypto_cipher_setkey(tctx->essiv_cipher, salt,
94 crypto_shash_digestsize(tctx->hash));
95 crypto_skcipher_set_flags(tfm,
96 crypto_cipher_get_flags(tctx->essiv_cipher) &
102 static int essiv_aead_setkey(struct crypto_aead *tfm, const u8 *key,
105 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
106 SHASH_DESC_ON_STACK(desc, tctx->hash);
107 struct crypto_authenc_keys keys;
108 u8 salt[HASH_MAX_DIGESTSIZE];
111 crypto_aead_clear_flags(tctx->u.aead, CRYPTO_TFM_REQ_MASK);
112 crypto_aead_set_flags(tctx->u.aead, crypto_aead_get_flags(tfm) &
113 CRYPTO_TFM_REQ_MASK);
114 err = crypto_aead_setkey(tctx->u.aead, key, keylen);
115 crypto_aead_set_flags(tfm, crypto_aead_get_flags(tctx->u.aead) &
116 CRYPTO_TFM_RES_MASK);
120 if (crypto_authenc_extractkeys(&keys, key, keylen) != 0) {
121 crypto_aead_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
125 desc->tfm = tctx->hash;
126 err = crypto_shash_init(desc) ?:
127 crypto_shash_update(desc, keys.enckey, keys.enckeylen) ?:
128 crypto_shash_finup(desc, keys.authkey, keys.authkeylen, salt);
132 crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK);
133 crypto_cipher_set_flags(tctx->essiv_cipher, crypto_aead_get_flags(tfm) &
134 CRYPTO_TFM_REQ_MASK);
135 err = crypto_cipher_setkey(tctx->essiv_cipher, salt,
136 crypto_shash_digestsize(tctx->hash));
137 crypto_aead_set_flags(tfm, crypto_cipher_get_flags(tctx->essiv_cipher) &
138 CRYPTO_TFM_RES_MASK);
143 static int essiv_aead_setauthsize(struct crypto_aead *tfm,
144 unsigned int authsize)
146 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
148 return crypto_aead_setauthsize(tctx->u.aead, authsize);
151 static void essiv_skcipher_done(struct crypto_async_request *areq, int err)
153 struct skcipher_request *req = areq->data;
155 skcipher_request_complete(req, err);
158 static int essiv_skcipher_crypt(struct skcipher_request *req, bool enc)
160 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
161 const struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
162 struct skcipher_request *subreq = skcipher_request_ctx(req);
164 crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
166 skcipher_request_set_tfm(subreq, tctx->u.skcipher);
167 skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen,
169 skcipher_request_set_callback(subreq, skcipher_request_flags(req),
170 essiv_skcipher_done, req);
172 return enc ? crypto_skcipher_encrypt(subreq) :
173 crypto_skcipher_decrypt(subreq);
176 static int essiv_skcipher_encrypt(struct skcipher_request *req)
178 return essiv_skcipher_crypt(req, true);
181 static int essiv_skcipher_decrypt(struct skcipher_request *req)
183 return essiv_skcipher_crypt(req, false);
186 static void essiv_aead_done(struct crypto_async_request *areq, int err)
188 struct aead_request *req = areq->data;
189 struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
191 if (err == -EINPROGRESS)
197 aead_request_complete(req, err);
200 static int essiv_aead_crypt(struct aead_request *req, bool enc)
202 struct crypto_aead *tfm = crypto_aead_reqtfm(req);
203 const struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
204 struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
205 struct aead_request *subreq = &rctx->aead_req;
206 struct scatterlist *src = req->src;
209 crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
212 * dm-crypt embeds the sector number and the IV in the AAD region, so
213 * we have to copy the converted IV into the right scatterlist before
217 if (req->src == req->dst || !enc) {
218 scatterwalk_map_and_copy(req->iv, req->dst,
219 req->assoclen - crypto_aead_ivsize(tfm),
220 crypto_aead_ivsize(tfm), 1);
222 u8 *iv = (u8 *)aead_request_ctx(req) + tctx->ivoffset;
223 int ivsize = crypto_aead_ivsize(tfm);
224 int ssize = req->assoclen - ivsize;
225 struct scatterlist *sg;
231 nents = sg_nents_for_len(req->src, ssize);
235 memcpy(iv, req->iv, ivsize);
236 sg_init_table(rctx->sg, 4);
238 if (unlikely(nents > 1)) {
240 * This is a case that rarely occurs in practice, but
241 * for correctness, we have to deal with it nonetheless.
243 rctx->assoc = kmalloc(ssize, GFP_ATOMIC);
247 scatterwalk_map_and_copy(rctx->assoc, req->src, 0,
249 sg_set_buf(rctx->sg, rctx->assoc, ssize);
251 sg_set_page(rctx->sg, sg_page(req->src), ssize,
255 sg_set_buf(rctx->sg + 1, iv, ivsize);
256 sg = scatterwalk_ffwd(rctx->sg + 2, req->src, req->assoclen);
257 if (sg != rctx->sg + 2)
258 sg_chain(rctx->sg, 3, sg);
263 aead_request_set_tfm(subreq, tctx->u.aead);
264 aead_request_set_ad(subreq, req->assoclen);
265 aead_request_set_callback(subreq, aead_request_flags(req),
266 essiv_aead_done, req);
267 aead_request_set_crypt(subreq, src, req->dst, req->cryptlen, req->iv);
269 err = enc ? crypto_aead_encrypt(subreq) :
270 crypto_aead_decrypt(subreq);
272 if (rctx->assoc && err != -EINPROGRESS && err != -EBUSY)
277 static int essiv_aead_encrypt(struct aead_request *req)
279 return essiv_aead_crypt(req, true);
282 static int essiv_aead_decrypt(struct aead_request *req)
284 return essiv_aead_crypt(req, false);
287 static int essiv_init_tfm(struct essiv_instance_ctx *ictx,
288 struct essiv_tfm_ctx *tctx)
290 struct crypto_cipher *essiv_cipher;
291 struct crypto_shash *hash;
294 essiv_cipher = crypto_alloc_cipher(ictx->essiv_cipher_name, 0, 0);
295 if (IS_ERR(essiv_cipher))
296 return PTR_ERR(essiv_cipher);
298 hash = crypto_alloc_shash(ictx->shash_driver_name, 0, 0);
301 goto err_free_essiv_cipher;
304 tctx->essiv_cipher = essiv_cipher;
309 err_free_essiv_cipher:
310 crypto_free_cipher(essiv_cipher);
314 static int essiv_skcipher_init_tfm(struct crypto_skcipher *tfm)
316 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
317 struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);
318 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
319 struct crypto_skcipher *skcipher;
322 skcipher = crypto_spawn_skcipher(&ictx->u.skcipher_spawn);
323 if (IS_ERR(skcipher))
324 return PTR_ERR(skcipher);
326 crypto_skcipher_set_reqsize(tfm, sizeof(struct skcipher_request) +
327 crypto_skcipher_reqsize(skcipher));
329 err = essiv_init_tfm(ictx, tctx);
331 crypto_free_skcipher(skcipher);
335 tctx->u.skcipher = skcipher;
339 static int essiv_aead_init_tfm(struct crypto_aead *tfm)
341 struct aead_instance *inst = aead_alg_instance(tfm);
342 struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);
343 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
344 struct crypto_aead *aead;
345 unsigned int subreq_size;
348 BUILD_BUG_ON(offsetofend(struct essiv_aead_request_ctx, aead_req) !=
349 sizeof(struct essiv_aead_request_ctx));
351 aead = crypto_spawn_aead(&ictx->u.aead_spawn);
353 return PTR_ERR(aead);
355 subreq_size = FIELD_SIZEOF(struct essiv_aead_request_ctx, aead_req) +
356 crypto_aead_reqsize(aead);
358 tctx->ivoffset = offsetof(struct essiv_aead_request_ctx, aead_req) +
360 crypto_aead_set_reqsize(tfm, tctx->ivoffset + crypto_aead_ivsize(aead));
362 err = essiv_init_tfm(ictx, tctx);
364 crypto_free_aead(aead);
372 static void essiv_skcipher_exit_tfm(struct crypto_skcipher *tfm)
374 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
376 crypto_free_skcipher(tctx->u.skcipher);
377 crypto_free_cipher(tctx->essiv_cipher);
378 crypto_free_shash(tctx->hash);
381 static void essiv_aead_exit_tfm(struct crypto_aead *tfm)
383 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
385 crypto_free_aead(tctx->u.aead);
386 crypto_free_cipher(tctx->essiv_cipher);
387 crypto_free_shash(tctx->hash);
390 static void essiv_skcipher_free_instance(struct skcipher_instance *inst)
392 struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);
394 crypto_drop_skcipher(&ictx->u.skcipher_spawn);
398 static void essiv_aead_free_instance(struct aead_instance *inst)
400 struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);
402 crypto_drop_aead(&ictx->u.aead_spawn);
406 static bool parse_cipher_name(char *essiv_cipher_name, const char *cra_name)
411 /* find the last opening parens */
412 p = strrchr(cra_name, '(');
416 /* find the first closing parens in the tail of the string */
422 if (len >= CRYPTO_MAX_ALG_NAME)
425 memcpy(essiv_cipher_name, p, len);
426 essiv_cipher_name[len] = '\0';
430 static bool essiv_supported_algorithms(const char *essiv_cipher_name,
431 struct shash_alg *hash_alg,
434 struct crypto_alg *alg;
437 alg = crypto_alg_mod_lookup(essiv_cipher_name,
438 CRYPTO_ALG_TYPE_CIPHER,
439 CRYPTO_ALG_TYPE_MASK);
443 if (hash_alg->digestsize < alg->cra_cipher.cia_min_keysize ||
444 hash_alg->digestsize > alg->cra_cipher.cia_max_keysize)
447 if (ivsize != alg->cra_blocksize)
450 if (crypto_shash_alg_has_setkey(hash_alg))
460 static int essiv_create(struct crypto_template *tmpl, struct rtattr **tb)
462 struct crypto_attr_type *algt;
463 const char *inner_cipher_name;
464 const char *shash_name;
465 struct skcipher_instance *skcipher_inst = NULL;
466 struct aead_instance *aead_inst = NULL;
467 struct crypto_instance *inst;
468 struct crypto_alg *base, *block_base;
469 struct essiv_instance_ctx *ictx;
470 struct skcipher_alg *skcipher_alg = NULL;
471 struct aead_alg *aead_alg = NULL;
472 struct crypto_alg *_hash_alg;
473 struct shash_alg *hash_alg;
478 algt = crypto_get_attr_type(tb);
480 return PTR_ERR(algt);
482 inner_cipher_name = crypto_attr_alg_name(tb[1]);
483 if (IS_ERR(inner_cipher_name))
484 return PTR_ERR(inner_cipher_name);
486 shash_name = crypto_attr_alg_name(tb[2]);
487 if (IS_ERR(shash_name))
488 return PTR_ERR(shash_name);
490 type = algt->type & algt->mask;
493 case CRYPTO_ALG_TYPE_BLKCIPHER:
494 skcipher_inst = kzalloc(sizeof(*skcipher_inst) +
495 sizeof(*ictx), GFP_KERNEL);
498 inst = skcipher_crypto_instance(skcipher_inst);
499 base = &skcipher_inst->alg.base;
500 ictx = crypto_instance_ctx(inst);
502 /* Symmetric cipher, e.g., "cbc(aes)" */
503 crypto_set_skcipher_spawn(&ictx->u.skcipher_spawn, inst);
504 err = crypto_grab_skcipher(&ictx->u.skcipher_spawn,
505 inner_cipher_name, 0,
506 crypto_requires_sync(algt->type,
510 skcipher_alg = crypto_spawn_skcipher_alg(&ictx->u.skcipher_spawn);
511 block_base = &skcipher_alg->base;
512 ivsize = crypto_skcipher_alg_ivsize(skcipher_alg);
515 case CRYPTO_ALG_TYPE_AEAD:
516 aead_inst = kzalloc(sizeof(*aead_inst) +
517 sizeof(*ictx), GFP_KERNEL);
520 inst = aead_crypto_instance(aead_inst);
521 base = &aead_inst->alg.base;
522 ictx = crypto_instance_ctx(inst);
524 /* AEAD cipher, e.g., "authenc(hmac(sha256),cbc(aes))" */
525 crypto_set_aead_spawn(&ictx->u.aead_spawn, inst);
526 err = crypto_grab_aead(&ictx->u.aead_spawn,
527 inner_cipher_name, 0,
528 crypto_requires_sync(algt->type,
532 aead_alg = crypto_spawn_aead_alg(&ictx->u.aead_spawn);
533 block_base = &aead_alg->base;
534 if (!strstarts(block_base->cra_name, "authenc(")) {
535 pr_warn("Only authenc() type AEADs are supported by ESSIV\n");
537 goto out_drop_skcipher;
539 ivsize = aead_alg->ivsize;
546 if (!parse_cipher_name(ictx->essiv_cipher_name, block_base->cra_name)) {
547 pr_warn("Failed to parse ESSIV cipher name from skcipher cra_name\n");
549 goto out_drop_skcipher;
552 /* Synchronous hash, e.g., "sha256" */
553 _hash_alg = crypto_alg_mod_lookup(shash_name,
554 CRYPTO_ALG_TYPE_SHASH,
555 CRYPTO_ALG_TYPE_MASK);
556 if (IS_ERR(_hash_alg)) {
557 err = PTR_ERR(_hash_alg);
558 goto out_drop_skcipher;
560 hash_alg = __crypto_shash_alg(_hash_alg);
562 /* Check the set of algorithms */
563 if (!essiv_supported_algorithms(ictx->essiv_cipher_name, hash_alg,
565 pr_warn("Unsupported essiv instantiation: essiv(%s,%s)\n",
566 block_base->cra_name, hash_alg->base.cra_name);
571 /* record the driver name so we can instantiate this exact algo later */
572 strlcpy(ictx->shash_driver_name, hash_alg->base.cra_driver_name,
573 CRYPTO_MAX_ALG_NAME);
575 /* Instance fields */
578 if (snprintf(base->cra_name, CRYPTO_MAX_ALG_NAME,
579 "essiv(%s,%s)", block_base->cra_name,
580 hash_alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
582 if (snprintf(base->cra_driver_name, CRYPTO_MAX_ALG_NAME,
583 "essiv(%s,%s)", block_base->cra_driver_name,
584 hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
587 base->cra_flags = block_base->cra_flags & CRYPTO_ALG_ASYNC;
588 base->cra_blocksize = block_base->cra_blocksize;
589 base->cra_ctxsize = sizeof(struct essiv_tfm_ctx);
590 base->cra_alignmask = block_base->cra_alignmask;
591 base->cra_priority = block_base->cra_priority;
593 if (type == CRYPTO_ALG_TYPE_BLKCIPHER) {
594 skcipher_inst->alg.setkey = essiv_skcipher_setkey;
595 skcipher_inst->alg.encrypt = essiv_skcipher_encrypt;
596 skcipher_inst->alg.decrypt = essiv_skcipher_decrypt;
597 skcipher_inst->alg.init = essiv_skcipher_init_tfm;
598 skcipher_inst->alg.exit = essiv_skcipher_exit_tfm;
600 skcipher_inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(skcipher_alg);
601 skcipher_inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(skcipher_alg);
602 skcipher_inst->alg.ivsize = ivsize;
603 skcipher_inst->alg.chunksize = crypto_skcipher_alg_chunksize(skcipher_alg);
604 skcipher_inst->alg.walksize = crypto_skcipher_alg_walksize(skcipher_alg);
606 skcipher_inst->free = essiv_skcipher_free_instance;
608 err = skcipher_register_instance(tmpl, skcipher_inst);
610 aead_inst->alg.setkey = essiv_aead_setkey;
611 aead_inst->alg.setauthsize = essiv_aead_setauthsize;
612 aead_inst->alg.encrypt = essiv_aead_encrypt;
613 aead_inst->alg.decrypt = essiv_aead_decrypt;
614 aead_inst->alg.init = essiv_aead_init_tfm;
615 aead_inst->alg.exit = essiv_aead_exit_tfm;
617 aead_inst->alg.ivsize = ivsize;
618 aead_inst->alg.maxauthsize = crypto_aead_alg_maxauthsize(aead_alg);
619 aead_inst->alg.chunksize = crypto_aead_alg_chunksize(aead_alg);
621 aead_inst->free = essiv_aead_free_instance;
623 err = aead_register_instance(tmpl, aead_inst);
629 crypto_mod_put(_hash_alg);
633 crypto_mod_put(_hash_alg);
635 if (type == CRYPTO_ALG_TYPE_BLKCIPHER)
636 crypto_drop_skcipher(&ictx->u.skcipher_spawn);
638 crypto_drop_aead(&ictx->u.aead_spawn);
640 kfree(skcipher_inst);
645 /* essiv(cipher_name, shash_name) */
646 static struct crypto_template essiv_tmpl = {
648 .create = essiv_create,
649 .module = THIS_MODULE,
652 static int __init essiv_module_init(void)
654 return crypto_register_template(&essiv_tmpl);
657 static void __exit essiv_module_exit(void)
659 crypto_unregister_template(&essiv_tmpl);
662 subsys_initcall(essiv_module_init);
663 module_exit(essiv_module_exit);
665 MODULE_DESCRIPTION("ESSIV skcipher/aead wrapper for block encryption");
666 MODULE_LICENSE("GPL v2");
667 MODULE_ALIAS_CRYPTO("essiv");