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1// SPDX-License-Identifier: GPL-2.02/*3 * ESSIV skcipher and aead template for block encryption4 *5 * This template encapsulates the ESSIV IV generation algorithm used by6 * dm-crypt and fscrypt, which converts the initial vector for the skcipher7 * used for block encryption, by encrypting it using the hash of the8 * skcipher key as encryption key. Usually, the input IV is a 64-bit sector9 * number in LE representation zero-padded to the size of the IV, but this10 * is not assumed by this driver.11 *12 * The typical use of this template is to instantiate the skcipher13 * 'essiv(cbc(aes),sha256)', which is the only instantiation used by14 * fscrypt, and the most relevant one for dm-crypt. However, dm-crypt15 * also permits ESSIV to be used in combination with the authenc template,16 * e.g., 'essiv(authenc(hmac(sha256),cbc(aes)),sha256)', in which case17 * we need to instantiate an aead that accepts the same special key format18 * as the authenc template, and deals with the way the encrypted IV is19 * embedded into the AAD area of the aead request. This means the AEAD20 * flavor produced by this template is tightly coupled to the way dm-crypt21 * happens to use it.22 *23 * Copyright (c) 2019 Linaro, Ltd. <ard.biesheuvel@linaro.org>24 *25 * Heavily based on:26 * adiantum length-preserving encryption mode27 *28 * Copyright 2018 Google LLC29 */30 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>38 39#include "internal.h"40 41struct essiv_instance_ctx {42 union {43 struct crypto_skcipher_spawn skcipher_spawn;44 struct crypto_aead_spawn aead_spawn;45 } u;46 char essiv_cipher_name[CRYPTO_MAX_ALG_NAME];47 char shash_driver_name[CRYPTO_MAX_ALG_NAME];48};49 50struct essiv_tfm_ctx {51 union {52 struct crypto_skcipher *skcipher;53 struct crypto_aead *aead;54 } u;55 struct crypto_cipher *essiv_cipher;56 struct crypto_shash *hash;57 int ivoffset;58};59 60struct essiv_aead_request_ctx {61 struct scatterlist sg[4];62 u8 *assoc;63 struct aead_request aead_req;64};65 66static int essiv_skcipher_setkey(struct crypto_skcipher *tfm,67 const u8 *key, unsigned int keylen)68{69 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);70 u8 salt[HASH_MAX_DIGESTSIZE];71 int err;72 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) &76 CRYPTO_TFM_REQ_MASK);77 err = crypto_skcipher_setkey(tctx->u.skcipher, key, keylen);78 if (err)79 return err;80 81 err = crypto_shash_tfm_digest(tctx->hash, key, keylen, salt);82 if (err)83 return err;84 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) &88 CRYPTO_TFM_REQ_MASK);89 return crypto_cipher_setkey(tctx->essiv_cipher, salt,90 crypto_shash_digestsize(tctx->hash));91}92 93static int essiv_aead_setkey(struct crypto_aead *tfm, const u8 *key,94 unsigned int keylen)95{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];100 int err;101 102 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);106 if (err)107 return err;108 109 if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)110 return -EINVAL;111 112 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);116 if (err)117 return err;118 119 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));124}125 126static int essiv_aead_setauthsize(struct crypto_aead *tfm,127 unsigned int authsize)128{129 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);130 131 return crypto_aead_setauthsize(tctx->u.aead, authsize);132}133 134static void essiv_skcipher_done(void *data, int err)135{136 struct skcipher_request *req = data;137 138 skcipher_request_complete(req, err);139}140 141static int essiv_skcipher_crypt(struct skcipher_request *req, bool enc)142{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);146 147 crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);148 149 skcipher_request_set_tfm(subreq, tctx->u.skcipher);150 skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen,151 req->iv);152 skcipher_request_set_callback(subreq, skcipher_request_flags(req),153 essiv_skcipher_done, req);154 155 return enc ? crypto_skcipher_encrypt(subreq) :156 crypto_skcipher_decrypt(subreq);157}158 159static int essiv_skcipher_encrypt(struct skcipher_request *req)160{161 return essiv_skcipher_crypt(req, true);162}163 164static int essiv_skcipher_decrypt(struct skcipher_request *req)165{166 return essiv_skcipher_crypt(req, false);167}168 169static void essiv_aead_done(void *data, int err)170{171 struct aead_request *req = data;172 struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);173 174 if (err == -EINPROGRESS)175 goto out;176 177 kfree(rctx->assoc);178 179out:180 aead_request_complete(req, err);181}182 183static int essiv_aead_crypt(struct aead_request *req, bool enc)184{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;190 int err;191 192 crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);193 194 /*195 * dm-crypt embeds the sector number and the IV in the AAD region, so196 * we have to copy the converted IV into the right scatterlist before197 * we pass it on.198 */199 rctx->assoc = NULL;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);204 } else {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;209 int nents;210 211 if (ssize < 0)212 return -EINVAL;213 214 nents = sg_nents_for_len(req->src, ssize);215 if (nents < 0)216 return -EINVAL;217 218 memcpy(iv, req->iv, ivsize);219 sg_init_table(rctx->sg, 4);220 221 if (unlikely(nents > 1)) {222 /*223 * This is a case that rarely occurs in practice, but224 * for correctness, we have to deal with it nonetheless.225 */226 rctx->assoc = kmalloc(ssize, GFP_ATOMIC);227 if (!rctx->assoc)228 return -ENOMEM;229 230 scatterwalk_map_and_copy(rctx->assoc, req->src, 0,231 ssize, 0);232 sg_set_buf(rctx->sg, rctx->assoc, ssize);233 } else {234 sg_set_page(rctx->sg, sg_page(req->src), ssize,235 req->src->offset);236 }237 238 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);242 243 src = rctx->sg;244 }245 246 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);251 252 err = enc ? crypto_aead_encrypt(subreq) :253 crypto_aead_decrypt(subreq);254 255 if (rctx->assoc && err != -EINPROGRESS && err != -EBUSY)256 kfree(rctx->assoc);257 return err;258}259 260static int essiv_aead_encrypt(struct aead_request *req)261{262 return essiv_aead_crypt(req, true);263}264 265static int essiv_aead_decrypt(struct aead_request *req)266{267 return essiv_aead_crypt(req, false);268}269 270static int essiv_init_tfm(struct essiv_instance_ctx *ictx,271 struct essiv_tfm_ctx *tctx)272{273 struct crypto_cipher *essiv_cipher;274 struct crypto_shash *hash;275 int err;276 277 essiv_cipher = crypto_alloc_cipher(ictx->essiv_cipher_name, 0, 0);278 if (IS_ERR(essiv_cipher))279 return PTR_ERR(essiv_cipher);280 281 hash = crypto_alloc_shash(ictx->shash_driver_name, 0, 0);282 if (IS_ERR(hash)) {283 err = PTR_ERR(hash);284 goto err_free_essiv_cipher;285 }286 287 tctx->essiv_cipher = essiv_cipher;288 tctx->hash = hash;289 290 return 0;291 292err_free_essiv_cipher:293 crypto_free_cipher(essiv_cipher);294 return err;295}296 297static int essiv_skcipher_init_tfm(struct crypto_skcipher *tfm)298{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;303 int err;304 305 skcipher = crypto_spawn_skcipher(&ictx->u.skcipher_spawn);306 if (IS_ERR(skcipher))307 return PTR_ERR(skcipher);308 309 crypto_skcipher_set_reqsize(tfm, sizeof(struct skcipher_request) +310 crypto_skcipher_reqsize(skcipher));311 312 err = essiv_init_tfm(ictx, tctx);313 if (err) {314 crypto_free_skcipher(skcipher);315 return err;316 }317 318 tctx->u.skcipher = skcipher;319 return 0;320}321 322static int essiv_aead_init_tfm(struct crypto_aead *tfm)323{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;329 int err;330 331 BUILD_BUG_ON(offsetofend(struct essiv_aead_request_ctx, aead_req) !=332 sizeof(struct essiv_aead_request_ctx));333 334 aead = crypto_spawn_aead(&ictx->u.aead_spawn);335 if (IS_ERR(aead))336 return PTR_ERR(aead);337 338 subreq_size = sizeof_field(struct essiv_aead_request_ctx, aead_req) +339 crypto_aead_reqsize(aead);340 341 tctx->ivoffset = offsetof(struct essiv_aead_request_ctx, aead_req) +342 subreq_size;343 crypto_aead_set_reqsize(tfm, tctx->ivoffset + crypto_aead_ivsize(aead));344 345 err = essiv_init_tfm(ictx, tctx);346 if (err) {347 crypto_free_aead(aead);348 return err;349 }350 351 tctx->u.aead = aead;352 return 0;353}354 355static void essiv_skcipher_exit_tfm(struct crypto_skcipher *tfm)356{357 struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);358 359 crypto_free_skcipher(tctx->u.skcipher);360 crypto_free_cipher(tctx->essiv_cipher);361 crypto_free_shash(tctx->hash);362}363 364static void essiv_aead_exit_tfm(struct crypto_aead *tfm)365{366 struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);367 368 crypto_free_aead(tctx->u.aead);369 crypto_free_cipher(tctx->essiv_cipher);370 crypto_free_shash(tctx->hash);371}372 373static void essiv_skcipher_free_instance(struct skcipher_instance *inst)374{375 struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);376 377 crypto_drop_skcipher(&ictx->u.skcipher_spawn);378 kfree(inst);379}380 381static void essiv_aead_free_instance(struct aead_instance *inst)382{383 struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);384 385 crypto_drop_aead(&ictx->u.aead_spawn);386 kfree(inst);387}388 389static bool parse_cipher_name(char *essiv_cipher_name, const char *cra_name)390{391 const char *p, *q;392 int len;393 394 /* find the last opening parens */395 p = strrchr(cra_name, '(');396 if (!p++)397 return false;398 399 /* find the first closing parens in the tail of the string */400 q = strchr(p, ')');401 if (!q)402 return false;403 404 len = q - p;405 if (len >= CRYPTO_MAX_ALG_NAME)406 return false;407 408 memcpy(essiv_cipher_name, p, len);409 essiv_cipher_name[len] = '\0';410 return true;411}412 413static bool essiv_supported_algorithms(const char *essiv_cipher_name,414 struct shash_alg *hash_alg,415 int ivsize)416{417 struct crypto_alg *alg;418 bool ret = false;419 420 alg = crypto_alg_mod_lookup(essiv_cipher_name,421 CRYPTO_ALG_TYPE_CIPHER,422 CRYPTO_ALG_TYPE_MASK);423 if (IS_ERR(alg))424 return false;425 426 if (hash_alg->digestsize < alg->cra_cipher.cia_min_keysize ||427 hash_alg->digestsize > alg->cra_cipher.cia_max_keysize)428 goto out;429 430 if (ivsize != alg->cra_blocksize)431 goto out;432 433 if (crypto_shash_alg_needs_key(hash_alg))434 goto out;435 436 ret = true;437 438out:439 crypto_mod_put(alg);440 return ret;441}442 443static int essiv_create(struct crypto_template *tmpl, struct rtattr **tb)444{445 struct skcipher_alg_common *skcipher_alg = NULL;446 struct crypto_attr_type *algt;447 const char *inner_cipher_name;448 const char *shash_name;449 struct skcipher_instance *skcipher_inst = NULL;450 struct aead_instance *aead_inst = NULL;451 struct crypto_instance *inst;452 struct crypto_alg *base, *block_base;453 struct essiv_instance_ctx *ictx;454 struct aead_alg *aead_alg = NULL;455 struct crypto_alg *_hash_alg;456 struct shash_alg *hash_alg;457 int ivsize;458 u32 type;459 u32 mask;460 int err;461 462 algt = crypto_get_attr_type(tb);463 if (IS_ERR(algt))464 return PTR_ERR(algt);465 466 inner_cipher_name = crypto_attr_alg_name(tb[1]);467 if (IS_ERR(inner_cipher_name))468 return PTR_ERR(inner_cipher_name);469 470 shash_name = crypto_attr_alg_name(tb[2]);471 if (IS_ERR(shash_name))472 return PTR_ERR(shash_name);473 474 type = algt->type & algt->mask;475 mask = crypto_algt_inherited_mask(algt);476 477 switch (type) {478 case CRYPTO_ALG_TYPE_LSKCIPHER:479 skcipher_inst = kzalloc(sizeof(*skcipher_inst) +480 sizeof(*ictx), GFP_KERNEL);481 if (!skcipher_inst)482 return -ENOMEM;483 inst = skcipher_crypto_instance(skcipher_inst);484 base = &skcipher_inst->alg.base;485 ictx = crypto_instance_ctx(inst);486 487 /* Symmetric cipher, e.g., "cbc(aes)" */488 err = crypto_grab_skcipher(&ictx->u.skcipher_spawn, inst,489 inner_cipher_name, 0, mask);490 if (err)491 goto out_free_inst;492 skcipher_alg = crypto_spawn_skcipher_alg_common(493 &ictx->u.skcipher_spawn);494 block_base = &skcipher_alg->base;495 ivsize = skcipher_alg->ivsize;496 break;497 498 case CRYPTO_ALG_TYPE_AEAD:499 aead_inst = kzalloc(sizeof(*aead_inst) +500 sizeof(*ictx), GFP_KERNEL);501 if (!aead_inst)502 return -ENOMEM;503 inst = aead_crypto_instance(aead_inst);504 base = &aead_inst->alg.base;505 ictx = crypto_instance_ctx(inst);506 507 /* AEAD cipher, e.g., "authenc(hmac(sha256),cbc(aes))" */508 err = crypto_grab_aead(&ictx->u.aead_spawn, inst,509 inner_cipher_name, 0, mask);510 if (err)511 goto out_free_inst;512 aead_alg = crypto_spawn_aead_alg(&ictx->u.aead_spawn);513 block_base = &aead_alg->base;514 if (!strstarts(block_base->cra_name, "authenc(")) {515 pr_warn("Only authenc() type AEADs are supported by ESSIV\n");516 err = -EINVAL;517 goto out_drop_skcipher;518 }519 ivsize = aead_alg->ivsize;520 break;521 522 default:523 return -EINVAL;524 }525 526 if (!parse_cipher_name(ictx->essiv_cipher_name, block_base->cra_name)) {527 pr_warn("Failed to parse ESSIV cipher name from skcipher cra_name\n");528 err = -EINVAL;529 goto out_drop_skcipher;530 }531 532 /* Synchronous hash, e.g., "sha256" */533 _hash_alg = crypto_alg_mod_lookup(shash_name,534 CRYPTO_ALG_TYPE_SHASH,535 CRYPTO_ALG_TYPE_MASK | mask);536 if (IS_ERR(_hash_alg)) {537 err = PTR_ERR(_hash_alg);538 goto out_drop_skcipher;539 }540 hash_alg = __crypto_shash_alg(_hash_alg);541 542 /* Check the set of algorithms */543 if (!essiv_supported_algorithms(ictx->essiv_cipher_name, hash_alg,544 ivsize)) {545 pr_warn("Unsupported essiv instantiation: essiv(%s,%s)\n",546 block_base->cra_name, hash_alg->base.cra_name);547 err = -EINVAL;548 goto out_free_hash;549 }550 551 /* record the driver name so we can instantiate this exact algo later */552 strscpy(ictx->shash_driver_name, hash_alg->base.cra_driver_name,553 CRYPTO_MAX_ALG_NAME);554 555 /* Instance fields */556 557 err = -ENAMETOOLONG;558 if (snprintf(base->cra_name, CRYPTO_MAX_ALG_NAME,559 "essiv(%s,%s)", block_base->cra_name,560 hash_alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)561 goto out_free_hash;562 if (snprintf(base->cra_driver_name, CRYPTO_MAX_ALG_NAME,563 "essiv(%s,%s)", block_base->cra_driver_name,564 hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)565 goto out_free_hash;566 567 /*568 * hash_alg wasn't gotten via crypto_grab*(), so we need to inherit its569 * flags manually.570 */571 base->cra_flags |= (hash_alg->base.cra_flags &572 CRYPTO_ALG_INHERITED_FLAGS);573 base->cra_blocksize = block_base->cra_blocksize;574 base->cra_ctxsize = sizeof(struct essiv_tfm_ctx);575 base->cra_alignmask = block_base->cra_alignmask;576 base->cra_priority = block_base->cra_priority;577 578 if (type == CRYPTO_ALG_TYPE_LSKCIPHER) {579 skcipher_inst->alg.setkey = essiv_skcipher_setkey;580 skcipher_inst->alg.encrypt = essiv_skcipher_encrypt;581 skcipher_inst->alg.decrypt = essiv_skcipher_decrypt;582 skcipher_inst->alg.init = essiv_skcipher_init_tfm;583 skcipher_inst->alg.exit = essiv_skcipher_exit_tfm;584 585 skcipher_inst->alg.min_keysize = skcipher_alg->min_keysize;586 skcipher_inst->alg.max_keysize = skcipher_alg->max_keysize;587 skcipher_inst->alg.ivsize = ivsize;588 skcipher_inst->alg.chunksize = skcipher_alg->chunksize;589 590 skcipher_inst->free = essiv_skcipher_free_instance;591 592 err = skcipher_register_instance(tmpl, skcipher_inst);593 } else {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;600 601 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);604 605 aead_inst->free = essiv_aead_free_instance;606 607 err = aead_register_instance(tmpl, aead_inst);608 }609 610 if (err)611 goto out_free_hash;612 613 crypto_mod_put(_hash_alg);614 return 0;615 616out_free_hash:617 crypto_mod_put(_hash_alg);618out_drop_skcipher:619 if (type == CRYPTO_ALG_TYPE_LSKCIPHER)620 crypto_drop_skcipher(&ictx->u.skcipher_spawn);621 else622 crypto_drop_aead(&ictx->u.aead_spawn);623out_free_inst:624 kfree(skcipher_inst);625 kfree(aead_inst);626 return err;627}628 629/* essiv(cipher_name, shash_name) */630static struct crypto_template essiv_tmpl = {631 .name = "essiv",632 .create = essiv_create,633 .module = THIS_MODULE,634};635 636static int __init essiv_module_init(void)637{638 return crypto_register_template(&essiv_tmpl);639}640 641static void __exit essiv_module_exit(void)642{643 crypto_unregister_template(&essiv_tmpl);644}645 646subsys_initcall(essiv_module_init);647module_exit(essiv_module_exit);648 649MODULE_DESCRIPTION("ESSIV skcipher/aead wrapper for block encryption");650MODULE_LICENSE("GPL v2");651MODULE_ALIAS_CRYPTO("essiv");652MODULE_IMPORT_NS(CRYPTO_INTERNAL);653