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/cipher.h>
34 #include <crypto/internal/hash.h>
35 #include <crypto/internal/skcipher.h>
36 #include <crypto/scatterwalk.h>
37 #include <linux/module.h>
41 struct essiv_instance_ctx {
43 struct crypto_skcipher_spawn skcipher_spawn;
44 struct crypto_aead_spawn aead_spawn;
46 char essiv_cipher_name[CRYPTO_MAX_ALG_NAME];
47 char shash_driver_name[CRYPTO_MAX_ALG_NAME];
50 struct essiv_tfm_ctx {
52 struct crypto_skcipher *skcipher;
53 struct crypto_aead *aead;
55 struct crypto_cipher *essiv_cipher;
56 struct crypto_shash *hash;
60 struct essiv_aead_request_ctx {
61 struct scatterlist sg[4];
63 struct aead_request aead_req;
66 static int essiv_skcipher_setkey(struct crypto_skcipher *tfm,
67 const u8 *key, unsigned int keylen)
69 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
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);
81 err = crypto_shash_tfm_digest(tctx->hash, key, keylen, salt);
85 crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK);
86 crypto_cipher_set_flags(tctx->essiv_cipher,
87 crypto_skcipher_get_flags(tfm) &
89 return crypto_cipher_setkey(tctx->essiv_cipher, salt,
90 crypto_shash_digestsize(tctx->hash));
93 static int essiv_aead_setkey(struct crypto_aead *tfm, const u8 *key,
96 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
97 SHASH_DESC_ON_STACK(desc, tctx->hash);
98 struct crypto_authenc_keys keys;
99 u8 salt[HASH_MAX_DIGESTSIZE];
102 crypto_aead_clear_flags(tctx->u.aead, CRYPTO_TFM_REQ_MASK);
103 crypto_aead_set_flags(tctx->u.aead, crypto_aead_get_flags(tfm) &
104 CRYPTO_TFM_REQ_MASK);
105 err = crypto_aead_setkey(tctx->u.aead, key, keylen);
109 if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)
112 desc->tfm = tctx->hash;
113 err = crypto_shash_init(desc) ?:
114 crypto_shash_update(desc, keys.enckey, keys.enckeylen) ?:
115 crypto_shash_finup(desc, keys.authkey, keys.authkeylen, salt);
119 crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK);
120 crypto_cipher_set_flags(tctx->essiv_cipher, crypto_aead_get_flags(tfm) &
121 CRYPTO_TFM_REQ_MASK);
122 return crypto_cipher_setkey(tctx->essiv_cipher, salt,
123 crypto_shash_digestsize(tctx->hash));
126 static int essiv_aead_setauthsize(struct crypto_aead *tfm,
127 unsigned int authsize)
129 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
131 return crypto_aead_setauthsize(tctx->u.aead, authsize);
134 static void essiv_skcipher_done(struct crypto_async_request *areq, int err)
136 struct skcipher_request *req = areq->data;
138 skcipher_request_complete(req, err);
141 static int essiv_skcipher_crypt(struct skcipher_request *req, bool enc)
143 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
144 const struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
145 struct skcipher_request *subreq = skcipher_request_ctx(req);
147 crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
149 skcipher_request_set_tfm(subreq, tctx->u.skcipher);
150 skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen,
152 skcipher_request_set_callback(subreq, skcipher_request_flags(req),
153 essiv_skcipher_done, req);
155 return enc ? crypto_skcipher_encrypt(subreq) :
156 crypto_skcipher_decrypt(subreq);
159 static int essiv_skcipher_encrypt(struct skcipher_request *req)
161 return essiv_skcipher_crypt(req, true);
164 static int essiv_skcipher_decrypt(struct skcipher_request *req)
166 return essiv_skcipher_crypt(req, false);
169 static void essiv_aead_done(struct crypto_async_request *areq, int err)
171 struct aead_request *req = areq->data;
172 struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
174 if (err == -EINPROGRESS)
180 aead_request_complete(req, err);
183 static int essiv_aead_crypt(struct aead_request *req, bool enc)
185 struct crypto_aead *tfm = crypto_aead_reqtfm(req);
186 const struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
187 struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
188 struct aead_request *subreq = &rctx->aead_req;
189 struct scatterlist *src = req->src;
192 crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
195 * dm-crypt embeds the sector number and the IV in the AAD region, so
196 * we have to copy the converted IV into the right scatterlist before
200 if (req->src == req->dst || !enc) {
201 scatterwalk_map_and_copy(req->iv, req->dst,
202 req->assoclen - crypto_aead_ivsize(tfm),
203 crypto_aead_ivsize(tfm), 1);
205 u8 *iv = (u8 *)aead_request_ctx(req) + tctx->ivoffset;
206 int ivsize = crypto_aead_ivsize(tfm);
207 int ssize = req->assoclen - ivsize;
208 struct scatterlist *sg;
214 nents = sg_nents_for_len(req->src, ssize);
218 memcpy(iv, req->iv, ivsize);
219 sg_init_table(rctx->sg, 4);
221 if (unlikely(nents > 1)) {
223 * This is a case that rarely occurs in practice, but
224 * for correctness, we have to deal with it nonetheless.
226 rctx->assoc = kmalloc(ssize, GFP_ATOMIC);
230 scatterwalk_map_and_copy(rctx->assoc, req->src, 0,
232 sg_set_buf(rctx->sg, rctx->assoc, ssize);
234 sg_set_page(rctx->sg, sg_page(req->src), ssize,
238 sg_set_buf(rctx->sg + 1, iv, ivsize);
239 sg = scatterwalk_ffwd(rctx->sg + 2, req->src, req->assoclen);
240 if (sg != rctx->sg + 2)
241 sg_chain(rctx->sg, 3, sg);
246 aead_request_set_tfm(subreq, tctx->u.aead);
247 aead_request_set_ad(subreq, req->assoclen);
248 aead_request_set_callback(subreq, aead_request_flags(req),
249 essiv_aead_done, req);
250 aead_request_set_crypt(subreq, src, req->dst, req->cryptlen, req->iv);
252 err = enc ? crypto_aead_encrypt(subreq) :
253 crypto_aead_decrypt(subreq);
255 if (rctx->assoc && err != -EINPROGRESS && err != -EBUSY)
260 static int essiv_aead_encrypt(struct aead_request *req)
262 return essiv_aead_crypt(req, true);
265 static int essiv_aead_decrypt(struct aead_request *req)
267 return essiv_aead_crypt(req, false);
270 static int essiv_init_tfm(struct essiv_instance_ctx *ictx,
271 struct essiv_tfm_ctx *tctx)
273 struct crypto_cipher *essiv_cipher;
274 struct crypto_shash *hash;
277 essiv_cipher = crypto_alloc_cipher(ictx->essiv_cipher_name, 0, 0);
278 if (IS_ERR(essiv_cipher))
279 return PTR_ERR(essiv_cipher);
281 hash = crypto_alloc_shash(ictx->shash_driver_name, 0, 0);
284 goto err_free_essiv_cipher;
287 tctx->essiv_cipher = essiv_cipher;
292 err_free_essiv_cipher:
293 crypto_free_cipher(essiv_cipher);
297 static int essiv_skcipher_init_tfm(struct crypto_skcipher *tfm)
299 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
300 struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);
301 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
302 struct crypto_skcipher *skcipher;
305 skcipher = crypto_spawn_skcipher(&ictx->u.skcipher_spawn);
306 if (IS_ERR(skcipher))
307 return PTR_ERR(skcipher);
309 crypto_skcipher_set_reqsize(tfm, sizeof(struct skcipher_request) +
310 crypto_skcipher_reqsize(skcipher));
312 err = essiv_init_tfm(ictx, tctx);
314 crypto_free_skcipher(skcipher);
318 tctx->u.skcipher = skcipher;
322 static int essiv_aead_init_tfm(struct crypto_aead *tfm)
324 struct aead_instance *inst = aead_alg_instance(tfm);
325 struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);
326 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
327 struct crypto_aead *aead;
328 unsigned int subreq_size;
331 BUILD_BUG_ON(offsetofend(struct essiv_aead_request_ctx, aead_req) !=
332 sizeof(struct essiv_aead_request_ctx));
334 aead = crypto_spawn_aead(&ictx->u.aead_spawn);
336 return PTR_ERR(aead);
338 subreq_size = sizeof_field(struct essiv_aead_request_ctx, aead_req) +
339 crypto_aead_reqsize(aead);
341 tctx->ivoffset = offsetof(struct essiv_aead_request_ctx, aead_req) +
343 crypto_aead_set_reqsize(tfm, tctx->ivoffset + crypto_aead_ivsize(aead));
345 err = essiv_init_tfm(ictx, tctx);
347 crypto_free_aead(aead);
355 static void essiv_skcipher_exit_tfm(struct crypto_skcipher *tfm)
357 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
359 crypto_free_skcipher(tctx->u.skcipher);
360 crypto_free_cipher(tctx->essiv_cipher);
361 crypto_free_shash(tctx->hash);
364 static void essiv_aead_exit_tfm(struct crypto_aead *tfm)
366 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
368 crypto_free_aead(tctx->u.aead);
369 crypto_free_cipher(tctx->essiv_cipher);
370 crypto_free_shash(tctx->hash);
373 static void essiv_skcipher_free_instance(struct skcipher_instance *inst)
375 struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);
377 crypto_drop_skcipher(&ictx->u.skcipher_spawn);
381 static void essiv_aead_free_instance(struct aead_instance *inst)
383 struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);
385 crypto_drop_aead(&ictx->u.aead_spawn);
389 static bool parse_cipher_name(char *essiv_cipher_name, const char *cra_name)
394 /* find the last opening parens */
395 p = strrchr(cra_name, '(');
399 /* find the first closing parens in the tail of the string */
405 if (len >= CRYPTO_MAX_ALG_NAME)
408 memcpy(essiv_cipher_name, p, len);
409 essiv_cipher_name[len] = '\0';
413 static bool essiv_supported_algorithms(const char *essiv_cipher_name,
414 struct shash_alg *hash_alg,
417 struct crypto_alg *alg;
420 alg = crypto_alg_mod_lookup(essiv_cipher_name,
421 CRYPTO_ALG_TYPE_CIPHER,
422 CRYPTO_ALG_TYPE_MASK);
426 if (hash_alg->digestsize < alg->cra_cipher.cia_min_keysize ||
427 hash_alg->digestsize > alg->cra_cipher.cia_max_keysize)
430 if (ivsize != alg->cra_blocksize)
433 if (crypto_shash_alg_needs_key(hash_alg))
443 static int essiv_create(struct crypto_template *tmpl, struct rtattr **tb)
445 struct crypto_attr_type *algt;
446 const char *inner_cipher_name;
447 const char *shash_name;
448 struct skcipher_instance *skcipher_inst = NULL;
449 struct aead_instance *aead_inst = NULL;
450 struct crypto_instance *inst;
451 struct crypto_alg *base, *block_base;
452 struct essiv_instance_ctx *ictx;
453 struct skcipher_alg *skcipher_alg = NULL;
454 struct aead_alg *aead_alg = NULL;
455 struct crypto_alg *_hash_alg;
456 struct shash_alg *hash_alg;
462 algt = crypto_get_attr_type(tb);
464 return PTR_ERR(algt);
466 inner_cipher_name = crypto_attr_alg_name(tb[1]);
467 if (IS_ERR(inner_cipher_name))
468 return PTR_ERR(inner_cipher_name);
470 shash_name = crypto_attr_alg_name(tb[2]);
471 if (IS_ERR(shash_name))
472 return PTR_ERR(shash_name);
474 type = algt->type & algt->mask;
475 mask = crypto_algt_inherited_mask(algt);
478 case CRYPTO_ALG_TYPE_SKCIPHER:
479 skcipher_inst = kzalloc(sizeof(*skcipher_inst) +
480 sizeof(*ictx), GFP_KERNEL);
483 inst = skcipher_crypto_instance(skcipher_inst);
484 base = &skcipher_inst->alg.base;
485 ictx = crypto_instance_ctx(inst);
487 /* Symmetric cipher, e.g., "cbc(aes)" */
488 err = crypto_grab_skcipher(&ictx->u.skcipher_spawn, inst,
489 inner_cipher_name, 0, mask);
492 skcipher_alg = crypto_spawn_skcipher_alg(&ictx->u.skcipher_spawn);
493 block_base = &skcipher_alg->base;
494 ivsize = crypto_skcipher_alg_ivsize(skcipher_alg);
497 case CRYPTO_ALG_TYPE_AEAD:
498 aead_inst = kzalloc(sizeof(*aead_inst) +
499 sizeof(*ictx), GFP_KERNEL);
502 inst = aead_crypto_instance(aead_inst);
503 base = &aead_inst->alg.base;
504 ictx = crypto_instance_ctx(inst);
506 /* AEAD cipher, e.g., "authenc(hmac(sha256),cbc(aes))" */
507 err = crypto_grab_aead(&ictx->u.aead_spawn, inst,
508 inner_cipher_name, 0, mask);
511 aead_alg = crypto_spawn_aead_alg(&ictx->u.aead_spawn);
512 block_base = &aead_alg->base;
513 if (!strstarts(block_base->cra_name, "authenc(")) {
514 pr_warn("Only authenc() type AEADs are supported by ESSIV\n");
516 goto out_drop_skcipher;
518 ivsize = aead_alg->ivsize;
525 if (!parse_cipher_name(ictx->essiv_cipher_name, block_base->cra_name)) {
526 pr_warn("Failed to parse ESSIV cipher name from skcipher cra_name\n");
528 goto out_drop_skcipher;
531 /* Synchronous hash, e.g., "sha256" */
532 _hash_alg = crypto_alg_mod_lookup(shash_name,
533 CRYPTO_ALG_TYPE_SHASH,
534 CRYPTO_ALG_TYPE_MASK | mask);
535 if (IS_ERR(_hash_alg)) {
536 err = PTR_ERR(_hash_alg);
537 goto out_drop_skcipher;
539 hash_alg = __crypto_shash_alg(_hash_alg);
541 /* Check the set of algorithms */
542 if (!essiv_supported_algorithms(ictx->essiv_cipher_name, hash_alg,
544 pr_warn("Unsupported essiv instantiation: essiv(%s,%s)\n",
545 block_base->cra_name, hash_alg->base.cra_name);
550 /* record the driver name so we can instantiate this exact algo later */
551 strscpy(ictx->shash_driver_name, hash_alg->base.cra_driver_name,
552 CRYPTO_MAX_ALG_NAME);
554 /* Instance fields */
557 if (snprintf(base->cra_name, CRYPTO_MAX_ALG_NAME,
558 "essiv(%s,%s)", block_base->cra_name,
559 hash_alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
561 if (snprintf(base->cra_driver_name, CRYPTO_MAX_ALG_NAME,
562 "essiv(%s,%s)", block_base->cra_driver_name,
563 hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
567 * hash_alg wasn't gotten via crypto_grab*(), so we need to inherit its
570 base->cra_flags |= (hash_alg->base.cra_flags &
571 CRYPTO_ALG_INHERITED_FLAGS);
572 base->cra_blocksize = block_base->cra_blocksize;
573 base->cra_ctxsize = sizeof(struct essiv_tfm_ctx);
574 base->cra_alignmask = block_base->cra_alignmask;
575 base->cra_priority = block_base->cra_priority;
577 if (type == CRYPTO_ALG_TYPE_SKCIPHER) {
578 skcipher_inst->alg.setkey = essiv_skcipher_setkey;
579 skcipher_inst->alg.encrypt = essiv_skcipher_encrypt;
580 skcipher_inst->alg.decrypt = essiv_skcipher_decrypt;
581 skcipher_inst->alg.init = essiv_skcipher_init_tfm;
582 skcipher_inst->alg.exit = essiv_skcipher_exit_tfm;
584 skcipher_inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(skcipher_alg);
585 skcipher_inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(skcipher_alg);
586 skcipher_inst->alg.ivsize = ivsize;
587 skcipher_inst->alg.chunksize = crypto_skcipher_alg_chunksize(skcipher_alg);
588 skcipher_inst->alg.walksize = crypto_skcipher_alg_walksize(skcipher_alg);
590 skcipher_inst->free = essiv_skcipher_free_instance;
592 err = skcipher_register_instance(tmpl, skcipher_inst);
594 aead_inst->alg.setkey = essiv_aead_setkey;
595 aead_inst->alg.setauthsize = essiv_aead_setauthsize;
596 aead_inst->alg.encrypt = essiv_aead_encrypt;
597 aead_inst->alg.decrypt = essiv_aead_decrypt;
598 aead_inst->alg.init = essiv_aead_init_tfm;
599 aead_inst->alg.exit = essiv_aead_exit_tfm;
601 aead_inst->alg.ivsize = ivsize;
602 aead_inst->alg.maxauthsize = crypto_aead_alg_maxauthsize(aead_alg);
603 aead_inst->alg.chunksize = crypto_aead_alg_chunksize(aead_alg);
605 aead_inst->free = essiv_aead_free_instance;
607 err = aead_register_instance(tmpl, aead_inst);
613 crypto_mod_put(_hash_alg);
617 crypto_mod_put(_hash_alg);
619 if (type == CRYPTO_ALG_TYPE_SKCIPHER)
620 crypto_drop_skcipher(&ictx->u.skcipher_spawn);
622 crypto_drop_aead(&ictx->u.aead_spawn);
624 kfree(skcipher_inst);
629 /* essiv(cipher_name, shash_name) */
630 static struct crypto_template essiv_tmpl = {
632 .create = essiv_create,
633 .module = THIS_MODULE,
636 static int __init essiv_module_init(void)
638 return crypto_register_template(&essiv_tmpl);
641 static void __exit essiv_module_exit(void)
643 crypto_unregister_template(&essiv_tmpl);
646 subsys_initcall(essiv_module_init);
647 module_exit(essiv_module_exit);
649 MODULE_DESCRIPTION("ESSIV skcipher/aead wrapper for block encryption");
650 MODULE_LICENSE("GPL v2");
651 MODULE_ALIAS_CRYPTO("essiv");
652 MODULE_IMPORT_NS(CRYPTO_INTERNAL);