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 u8 salt[HASH_MAX_DIGESTSIZE];
72 crypto_skcipher_clear_flags(tctx->u.skcipher, CRYPTO_TFM_REQ_MASK);
73 crypto_skcipher_set_flags(tctx->u.skcipher,
74 crypto_skcipher_get_flags(tfm) &
76 err = crypto_skcipher_setkey(tctx->u.skcipher, key, keylen);
80 err = crypto_shash_tfm_digest(tctx->hash, key, keylen, salt);
84 crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK);
85 crypto_cipher_set_flags(tctx->essiv_cipher,
86 crypto_skcipher_get_flags(tfm) &
88 return crypto_cipher_setkey(tctx->essiv_cipher, salt,
89 crypto_shash_digestsize(tctx->hash));
92 static int essiv_aead_setkey(struct crypto_aead *tfm, const u8 *key,
95 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
96 SHASH_DESC_ON_STACK(desc, tctx->hash);
97 struct crypto_authenc_keys keys;
98 u8 salt[HASH_MAX_DIGESTSIZE];
101 crypto_aead_clear_flags(tctx->u.aead, CRYPTO_TFM_REQ_MASK);
102 crypto_aead_set_flags(tctx->u.aead, crypto_aead_get_flags(tfm) &
103 CRYPTO_TFM_REQ_MASK);
104 err = crypto_aead_setkey(tctx->u.aead, key, keylen);
108 if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)
111 desc->tfm = tctx->hash;
112 err = crypto_shash_init(desc) ?:
113 crypto_shash_update(desc, keys.enckey, keys.enckeylen) ?:
114 crypto_shash_finup(desc, keys.authkey, keys.authkeylen, salt);
118 crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK);
119 crypto_cipher_set_flags(tctx->essiv_cipher, crypto_aead_get_flags(tfm) &
120 CRYPTO_TFM_REQ_MASK);
121 return crypto_cipher_setkey(tctx->essiv_cipher, salt,
122 crypto_shash_digestsize(tctx->hash));
125 static int essiv_aead_setauthsize(struct crypto_aead *tfm,
126 unsigned int authsize)
128 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
130 return crypto_aead_setauthsize(tctx->u.aead, authsize);
133 static void essiv_skcipher_done(struct crypto_async_request *areq, int err)
135 struct skcipher_request *req = areq->data;
137 skcipher_request_complete(req, err);
140 static int essiv_skcipher_crypt(struct skcipher_request *req, bool enc)
142 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
143 const struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
144 struct skcipher_request *subreq = skcipher_request_ctx(req);
146 crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
148 skcipher_request_set_tfm(subreq, tctx->u.skcipher);
149 skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen,
151 skcipher_request_set_callback(subreq, skcipher_request_flags(req),
152 essiv_skcipher_done, req);
154 return enc ? crypto_skcipher_encrypt(subreq) :
155 crypto_skcipher_decrypt(subreq);
158 static int essiv_skcipher_encrypt(struct skcipher_request *req)
160 return essiv_skcipher_crypt(req, true);
163 static int essiv_skcipher_decrypt(struct skcipher_request *req)
165 return essiv_skcipher_crypt(req, false);
168 static void essiv_aead_done(struct crypto_async_request *areq, int err)
170 struct aead_request *req = areq->data;
171 struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
173 if (err == -EINPROGRESS)
179 aead_request_complete(req, err);
182 static int essiv_aead_crypt(struct aead_request *req, bool enc)
184 struct crypto_aead *tfm = crypto_aead_reqtfm(req);
185 const struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
186 struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
187 struct aead_request *subreq = &rctx->aead_req;
188 struct scatterlist *src = req->src;
191 crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
194 * dm-crypt embeds the sector number and the IV in the AAD region, so
195 * we have to copy the converted IV into the right scatterlist before
199 if (req->src == req->dst || !enc) {
200 scatterwalk_map_and_copy(req->iv, req->dst,
201 req->assoclen - crypto_aead_ivsize(tfm),
202 crypto_aead_ivsize(tfm), 1);
204 u8 *iv = (u8 *)aead_request_ctx(req) + tctx->ivoffset;
205 int ivsize = crypto_aead_ivsize(tfm);
206 int ssize = req->assoclen - ivsize;
207 struct scatterlist *sg;
213 nents = sg_nents_for_len(req->src, ssize);
217 memcpy(iv, req->iv, ivsize);
218 sg_init_table(rctx->sg, 4);
220 if (unlikely(nents > 1)) {
222 * This is a case that rarely occurs in practice, but
223 * for correctness, we have to deal with it nonetheless.
225 rctx->assoc = kmalloc(ssize, GFP_ATOMIC);
229 scatterwalk_map_and_copy(rctx->assoc, req->src, 0,
231 sg_set_buf(rctx->sg, rctx->assoc, ssize);
233 sg_set_page(rctx->sg, sg_page(req->src), ssize,
237 sg_set_buf(rctx->sg + 1, iv, ivsize);
238 sg = scatterwalk_ffwd(rctx->sg + 2, req->src, req->assoclen);
239 if (sg != rctx->sg + 2)
240 sg_chain(rctx->sg, 3, sg);
245 aead_request_set_tfm(subreq, tctx->u.aead);
246 aead_request_set_ad(subreq, req->assoclen);
247 aead_request_set_callback(subreq, aead_request_flags(req),
248 essiv_aead_done, req);
249 aead_request_set_crypt(subreq, src, req->dst, req->cryptlen, req->iv);
251 err = enc ? crypto_aead_encrypt(subreq) :
252 crypto_aead_decrypt(subreq);
254 if (rctx->assoc && err != -EINPROGRESS && err != -EBUSY)
259 static int essiv_aead_encrypt(struct aead_request *req)
261 return essiv_aead_crypt(req, true);
264 static int essiv_aead_decrypt(struct aead_request *req)
266 return essiv_aead_crypt(req, false);
269 static int essiv_init_tfm(struct essiv_instance_ctx *ictx,
270 struct essiv_tfm_ctx *tctx)
272 struct crypto_cipher *essiv_cipher;
273 struct crypto_shash *hash;
276 essiv_cipher = crypto_alloc_cipher(ictx->essiv_cipher_name, 0, 0);
277 if (IS_ERR(essiv_cipher))
278 return PTR_ERR(essiv_cipher);
280 hash = crypto_alloc_shash(ictx->shash_driver_name, 0, 0);
283 goto err_free_essiv_cipher;
286 tctx->essiv_cipher = essiv_cipher;
291 err_free_essiv_cipher:
292 crypto_free_cipher(essiv_cipher);
296 static int essiv_skcipher_init_tfm(struct crypto_skcipher *tfm)
298 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
299 struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);
300 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
301 struct crypto_skcipher *skcipher;
304 skcipher = crypto_spawn_skcipher(&ictx->u.skcipher_spawn);
305 if (IS_ERR(skcipher))
306 return PTR_ERR(skcipher);
308 crypto_skcipher_set_reqsize(tfm, sizeof(struct skcipher_request) +
309 crypto_skcipher_reqsize(skcipher));
311 err = essiv_init_tfm(ictx, tctx);
313 crypto_free_skcipher(skcipher);
317 tctx->u.skcipher = skcipher;
321 static int essiv_aead_init_tfm(struct crypto_aead *tfm)
323 struct aead_instance *inst = aead_alg_instance(tfm);
324 struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);
325 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
326 struct crypto_aead *aead;
327 unsigned int subreq_size;
330 BUILD_BUG_ON(offsetofend(struct essiv_aead_request_ctx, aead_req) !=
331 sizeof(struct essiv_aead_request_ctx));
333 aead = crypto_spawn_aead(&ictx->u.aead_spawn);
335 return PTR_ERR(aead);
337 subreq_size = sizeof_field(struct essiv_aead_request_ctx, aead_req) +
338 crypto_aead_reqsize(aead);
340 tctx->ivoffset = offsetof(struct essiv_aead_request_ctx, aead_req) +
342 crypto_aead_set_reqsize(tfm, tctx->ivoffset + crypto_aead_ivsize(aead));
344 err = essiv_init_tfm(ictx, tctx);
346 crypto_free_aead(aead);
354 static void essiv_skcipher_exit_tfm(struct crypto_skcipher *tfm)
356 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
358 crypto_free_skcipher(tctx->u.skcipher);
359 crypto_free_cipher(tctx->essiv_cipher);
360 crypto_free_shash(tctx->hash);
363 static void essiv_aead_exit_tfm(struct crypto_aead *tfm)
365 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
367 crypto_free_aead(tctx->u.aead);
368 crypto_free_cipher(tctx->essiv_cipher);
369 crypto_free_shash(tctx->hash);
372 static void essiv_skcipher_free_instance(struct skcipher_instance *inst)
374 struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);
376 crypto_drop_skcipher(&ictx->u.skcipher_spawn);
380 static void essiv_aead_free_instance(struct aead_instance *inst)
382 struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);
384 crypto_drop_aead(&ictx->u.aead_spawn);
388 static bool parse_cipher_name(char *essiv_cipher_name, const char *cra_name)
393 /* find the last opening parens */
394 p = strrchr(cra_name, '(');
398 /* find the first closing parens in the tail of the string */
404 if (len >= CRYPTO_MAX_ALG_NAME)
407 memcpy(essiv_cipher_name, p, len);
408 essiv_cipher_name[len] = '\0';
412 static bool essiv_supported_algorithms(const char *essiv_cipher_name,
413 struct shash_alg *hash_alg,
416 struct crypto_alg *alg;
419 alg = crypto_alg_mod_lookup(essiv_cipher_name,
420 CRYPTO_ALG_TYPE_CIPHER,
421 CRYPTO_ALG_TYPE_MASK);
425 if (hash_alg->digestsize < alg->cra_cipher.cia_min_keysize ||
426 hash_alg->digestsize > alg->cra_cipher.cia_max_keysize)
429 if (ivsize != alg->cra_blocksize)
432 if (crypto_shash_alg_needs_key(hash_alg))
442 static int essiv_create(struct crypto_template *tmpl, struct rtattr **tb)
444 struct crypto_attr_type *algt;
445 const char *inner_cipher_name;
446 const char *shash_name;
447 struct skcipher_instance *skcipher_inst = NULL;
448 struct aead_instance *aead_inst = NULL;
449 struct crypto_instance *inst;
450 struct crypto_alg *base, *block_base;
451 struct essiv_instance_ctx *ictx;
452 struct skcipher_alg *skcipher_alg = NULL;
453 struct aead_alg *aead_alg = NULL;
454 struct crypto_alg *_hash_alg;
455 struct shash_alg *hash_alg;
461 algt = crypto_get_attr_type(tb);
463 return PTR_ERR(algt);
465 inner_cipher_name = crypto_attr_alg_name(tb[1]);
466 if (IS_ERR(inner_cipher_name))
467 return PTR_ERR(inner_cipher_name);
469 shash_name = crypto_attr_alg_name(tb[2]);
470 if (IS_ERR(shash_name))
471 return PTR_ERR(shash_name);
473 type = algt->type & algt->mask;
474 mask = crypto_algt_inherited_mask(algt);
477 case CRYPTO_ALG_TYPE_SKCIPHER:
478 skcipher_inst = kzalloc(sizeof(*skcipher_inst) +
479 sizeof(*ictx), GFP_KERNEL);
482 inst = skcipher_crypto_instance(skcipher_inst);
483 base = &skcipher_inst->alg.base;
484 ictx = crypto_instance_ctx(inst);
486 /* Symmetric cipher, e.g., "cbc(aes)" */
487 err = crypto_grab_skcipher(&ictx->u.skcipher_spawn, inst,
488 inner_cipher_name, 0, mask);
491 skcipher_alg = crypto_spawn_skcipher_alg(&ictx->u.skcipher_spawn);
492 block_base = &skcipher_alg->base;
493 ivsize = crypto_skcipher_alg_ivsize(skcipher_alg);
496 case CRYPTO_ALG_TYPE_AEAD:
497 aead_inst = kzalloc(sizeof(*aead_inst) +
498 sizeof(*ictx), GFP_KERNEL);
501 inst = aead_crypto_instance(aead_inst);
502 base = &aead_inst->alg.base;
503 ictx = crypto_instance_ctx(inst);
505 /* AEAD cipher, e.g., "authenc(hmac(sha256),cbc(aes))" */
506 err = crypto_grab_aead(&ictx->u.aead_spawn, inst,
507 inner_cipher_name, 0, mask);
510 aead_alg = crypto_spawn_aead_alg(&ictx->u.aead_spawn);
511 block_base = &aead_alg->base;
512 if (!strstarts(block_base->cra_name, "authenc(")) {
513 pr_warn("Only authenc() type AEADs are supported by ESSIV\n");
515 goto out_drop_skcipher;
517 ivsize = aead_alg->ivsize;
524 if (!parse_cipher_name(ictx->essiv_cipher_name, block_base->cra_name)) {
525 pr_warn("Failed to parse ESSIV cipher name from skcipher cra_name\n");
527 goto out_drop_skcipher;
530 /* Synchronous hash, e.g., "sha256" */
531 _hash_alg = crypto_alg_mod_lookup(shash_name,
532 CRYPTO_ALG_TYPE_SHASH,
533 CRYPTO_ALG_TYPE_MASK | mask);
534 if (IS_ERR(_hash_alg)) {
535 err = PTR_ERR(_hash_alg);
536 goto out_drop_skcipher;
538 hash_alg = __crypto_shash_alg(_hash_alg);
540 /* Check the set of algorithms */
541 if (!essiv_supported_algorithms(ictx->essiv_cipher_name, hash_alg,
543 pr_warn("Unsupported essiv instantiation: essiv(%s,%s)\n",
544 block_base->cra_name, hash_alg->base.cra_name);
549 /* record the driver name so we can instantiate this exact algo later */
550 strlcpy(ictx->shash_driver_name, hash_alg->base.cra_driver_name,
551 CRYPTO_MAX_ALG_NAME);
553 /* Instance fields */
556 if (snprintf(base->cra_name, CRYPTO_MAX_ALG_NAME,
557 "essiv(%s,%s)", block_base->cra_name,
558 hash_alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
560 if (snprintf(base->cra_driver_name, CRYPTO_MAX_ALG_NAME,
561 "essiv(%s,%s)", block_base->cra_driver_name,
562 hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
566 * hash_alg wasn't gotten via crypto_grab*(), so we need to inherit its
569 base->cra_flags |= (hash_alg->base.cra_flags &
570 CRYPTO_ALG_INHERITED_FLAGS);
571 base->cra_blocksize = block_base->cra_blocksize;
572 base->cra_ctxsize = sizeof(struct essiv_tfm_ctx);
573 base->cra_alignmask = block_base->cra_alignmask;
574 base->cra_priority = block_base->cra_priority;
576 if (type == CRYPTO_ALG_TYPE_SKCIPHER) {
577 skcipher_inst->alg.setkey = essiv_skcipher_setkey;
578 skcipher_inst->alg.encrypt = essiv_skcipher_encrypt;
579 skcipher_inst->alg.decrypt = essiv_skcipher_decrypt;
580 skcipher_inst->alg.init = essiv_skcipher_init_tfm;
581 skcipher_inst->alg.exit = essiv_skcipher_exit_tfm;
583 skcipher_inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(skcipher_alg);
584 skcipher_inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(skcipher_alg);
585 skcipher_inst->alg.ivsize = ivsize;
586 skcipher_inst->alg.chunksize = crypto_skcipher_alg_chunksize(skcipher_alg);
587 skcipher_inst->alg.walksize = crypto_skcipher_alg_walksize(skcipher_alg);
589 skcipher_inst->free = essiv_skcipher_free_instance;
591 err = skcipher_register_instance(tmpl, skcipher_inst);
593 aead_inst->alg.setkey = essiv_aead_setkey;
594 aead_inst->alg.setauthsize = essiv_aead_setauthsize;
595 aead_inst->alg.encrypt = essiv_aead_encrypt;
596 aead_inst->alg.decrypt = essiv_aead_decrypt;
597 aead_inst->alg.init = essiv_aead_init_tfm;
598 aead_inst->alg.exit = essiv_aead_exit_tfm;
600 aead_inst->alg.ivsize = ivsize;
601 aead_inst->alg.maxauthsize = crypto_aead_alg_maxauthsize(aead_alg);
602 aead_inst->alg.chunksize = crypto_aead_alg_chunksize(aead_alg);
604 aead_inst->free = essiv_aead_free_instance;
606 err = aead_register_instance(tmpl, aead_inst);
612 crypto_mod_put(_hash_alg);
616 crypto_mod_put(_hash_alg);
618 if (type == CRYPTO_ALG_TYPE_SKCIPHER)
619 crypto_drop_skcipher(&ictx->u.skcipher_spawn);
621 crypto_drop_aead(&ictx->u.aead_spawn);
623 kfree(skcipher_inst);
628 /* essiv(cipher_name, shash_name) */
629 static struct crypto_template essiv_tmpl = {
631 .create = essiv_create,
632 .module = THIS_MODULE,
635 static int __init essiv_module_init(void)
637 return crypto_register_template(&essiv_tmpl);
640 static void __exit essiv_module_exit(void)
642 crypto_unregister_template(&essiv_tmpl);
645 subsys_initcall(essiv_module_init);
646 module_exit(essiv_module_exit);
648 MODULE_DESCRIPTION("ESSIV skcipher/aead wrapper for block encryption");
649 MODULE_LICENSE("GPL v2");
650 MODULE_ALIAS_CRYPTO("essiv");