diff options
Diffstat (limited to 'crypto/essiv.c')
| -rw-r--r-- | crypto/essiv.c | 663 |
1 files changed, 663 insertions, 0 deletions
diff --git a/crypto/essiv.c b/crypto/essiv.c new file mode 100644 index 000000000000..a8befc8fb06e --- /dev/null +++ b/crypto/essiv.c @@ -0,0 +1,663 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * ESSIV skcipher and aead template for block encryption + * + * This template encapsulates the ESSIV IV generation algorithm used by + * dm-crypt and fscrypt, which converts the initial vector for the skcipher + * used for block encryption, by encrypting it using the hash of the + * skcipher key as encryption key. Usually, the input IV is a 64-bit sector + * number in LE representation zero-padded to the size of the IV, but this + * is not assumed by this driver. + * + * The typical use of this template is to instantiate the skcipher + * 'essiv(cbc(aes),sha256)', which is the only instantiation used by + * fscrypt, and the most relevant one for dm-crypt. However, dm-crypt + * also permits ESSIV to be used in combination with the authenc template, + * e.g., 'essiv(authenc(hmac(sha256),cbc(aes)),sha256)', in which case + * we need to instantiate an aead that accepts the same special key format + * as the authenc template, and deals with the way the encrypted IV is + * embedded into the AAD area of the aead request. This means the AEAD + * flavor produced by this template is tightly coupled to the way dm-crypt + * happens to use it. + * + * Copyright (c) 2019 Linaro, Ltd. <[email protected]> + * + * Heavily based on: + * adiantum length-preserving encryption mode + * + * Copyright 2018 Google LLC + */ + +#include <crypto/authenc.h> +#include <crypto/internal/aead.h> +#include <crypto/internal/hash.h> +#include <crypto/internal/skcipher.h> +#include <crypto/scatterwalk.h> +#include <linux/module.h> + +#include "internal.h" + +struct essiv_instance_ctx { + union { + struct crypto_skcipher_spawn skcipher_spawn; + struct crypto_aead_spawn aead_spawn; + } u; + char essiv_cipher_name[CRYPTO_MAX_ALG_NAME]; + char shash_driver_name[CRYPTO_MAX_ALG_NAME]; +}; + +struct essiv_tfm_ctx { + union { + struct crypto_skcipher *skcipher; + struct crypto_aead *aead; + } u; + struct crypto_cipher *essiv_cipher; + struct crypto_shash *hash; + int ivoffset; +}; + +struct essiv_aead_request_ctx { + struct scatterlist sg[4]; + u8 *assoc; + struct aead_request aead_req; +}; + +static int essiv_skcipher_setkey(struct crypto_skcipher *tfm, + const u8 *key, unsigned int keylen) +{ + struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); + SHASH_DESC_ON_STACK(desc, tctx->hash); + u8 salt[HASH_MAX_DIGESTSIZE]; + int err; + + crypto_skcipher_clear_flags(tctx->u.skcipher, CRYPTO_TFM_REQ_MASK); + crypto_skcipher_set_flags(tctx->u.skcipher, + crypto_skcipher_get_flags(tfm) & + CRYPTO_TFM_REQ_MASK); + err = crypto_skcipher_setkey(tctx->u.skcipher, key, keylen); + crypto_skcipher_set_flags(tfm, + crypto_skcipher_get_flags(tctx->u.skcipher) & + CRYPTO_TFM_RES_MASK); + if (err) + return err; + + desc->tfm = tctx->hash; + err = crypto_shash_digest(desc, key, keylen, salt); + if (err) + return err; + + crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK); + crypto_cipher_set_flags(tctx->essiv_cipher, + crypto_skcipher_get_flags(tfm) & + CRYPTO_TFM_REQ_MASK); + err = crypto_cipher_setkey(tctx->essiv_cipher, salt, + crypto_shash_digestsize(tctx->hash)); + crypto_skcipher_set_flags(tfm, + crypto_cipher_get_flags(tctx->essiv_cipher) & + CRYPTO_TFM_RES_MASK); + + return err; +} + +static int essiv_aead_setkey(struct crypto_aead *tfm, const u8 *key, + unsigned int keylen) +{ + struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm); + SHASH_DESC_ON_STACK(desc, tctx->hash); + struct crypto_authenc_keys keys; + u8 salt[HASH_MAX_DIGESTSIZE]; + int err; + + crypto_aead_clear_flags(tctx->u.aead, CRYPTO_TFM_REQ_MASK); + crypto_aead_set_flags(tctx->u.aead, crypto_aead_get_flags(tfm) & + CRYPTO_TFM_REQ_MASK); + err = crypto_aead_setkey(tctx->u.aead, key, keylen); + crypto_aead_set_flags(tfm, crypto_aead_get_flags(tctx->u.aead) & + CRYPTO_TFM_RES_MASK); + if (err) + return err; + + if (crypto_authenc_extractkeys(&keys, key, keylen) != 0) { + crypto_aead_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN); + return -EINVAL; + } + + desc->tfm = tctx->hash; + err = crypto_shash_init(desc) ?: + crypto_shash_update(desc, keys.enckey, keys.enckeylen) ?: + crypto_shash_finup(desc, keys.authkey, keys.authkeylen, salt); + if (err) + return err; + + crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK); + crypto_cipher_set_flags(tctx->essiv_cipher, crypto_aead_get_flags(tfm) & + CRYPTO_TFM_REQ_MASK); + err = crypto_cipher_setkey(tctx->essiv_cipher, salt, + crypto_shash_digestsize(tctx->hash)); + crypto_aead_set_flags(tfm, crypto_cipher_get_flags(tctx->essiv_cipher) & + CRYPTO_TFM_RES_MASK); + + return err; +} + +static int essiv_aead_setauthsize(struct crypto_aead *tfm, + unsigned int authsize) +{ + struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm); + + return crypto_aead_setauthsize(tctx->u.aead, authsize); +} + +static void essiv_skcipher_done(struct crypto_async_request *areq, int err) +{ + struct skcipher_request *req = areq->data; + + skcipher_request_complete(req, err); +} + +static int essiv_skcipher_crypt(struct skcipher_request *req, bool enc) +{ + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); + const struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); + struct skcipher_request *subreq = skcipher_request_ctx(req); + + crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv); + + skcipher_request_set_tfm(subreq, tctx->u.skcipher); + skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen, + req->iv); + skcipher_request_set_callback(subreq, skcipher_request_flags(req), + essiv_skcipher_done, req); + + return enc ? crypto_skcipher_encrypt(subreq) : + crypto_skcipher_decrypt(subreq); +} + +static int essiv_skcipher_encrypt(struct skcipher_request *req) +{ + return essiv_skcipher_crypt(req, true); +} + +static int essiv_skcipher_decrypt(struct skcipher_request *req) +{ + return essiv_skcipher_crypt(req, false); +} + +static void essiv_aead_done(struct crypto_async_request *areq, int err) +{ + struct aead_request *req = areq->data; + struct essiv_aead_request_ctx *rctx = aead_request_ctx(req); + + if (rctx->assoc) + kfree(rctx->assoc); + aead_request_complete(req, err); +} + +static int essiv_aead_crypt(struct aead_request *req, bool enc) +{ + struct crypto_aead *tfm = crypto_aead_reqtfm(req); + const struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm); + struct essiv_aead_request_ctx *rctx = aead_request_ctx(req); + struct aead_request *subreq = &rctx->aead_req; + struct scatterlist *src = req->src; + int err; + + crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv); + + /* + * dm-crypt embeds the sector number and the IV in the AAD region, so + * we have to copy the converted IV into the right scatterlist before + * we pass it on. + */ + rctx->assoc = NULL; + if (req->src == req->dst || !enc) { + scatterwalk_map_and_copy(req->iv, req->dst, + req->assoclen - crypto_aead_ivsize(tfm), + crypto_aead_ivsize(tfm), 1); + } else { + u8 *iv = (u8 *)aead_request_ctx(req) + tctx->ivoffset; + int ivsize = crypto_aead_ivsize(tfm); + int ssize = req->assoclen - ivsize; + struct scatterlist *sg; + int nents; + + if (ssize < 0) + return -EINVAL; + + nents = sg_nents_for_len(req->src, ssize); + if (nents < 0) + return -EINVAL; + + memcpy(iv, req->iv, ivsize); + sg_init_table(rctx->sg, 4); + + if (unlikely(nents > 1)) { + /* + * This is a case that rarely occurs in practice, but + * for correctness, we have to deal with it nonetheless. + */ + rctx->assoc = kmalloc(ssize, GFP_ATOMIC); + if (!rctx->assoc) + return -ENOMEM; + + scatterwalk_map_and_copy(rctx->assoc, req->src, 0, + ssize, 0); + sg_set_buf(rctx->sg, rctx->assoc, ssize); + } else { + sg_set_page(rctx->sg, sg_page(req->src), ssize, + req->src->offset); + } + + sg_set_buf(rctx->sg + 1, iv, ivsize); + sg = scatterwalk_ffwd(rctx->sg + 2, req->src, req->assoclen); + if (sg != rctx->sg + 2) + sg_chain(rctx->sg, 3, sg); + + src = rctx->sg; + } + + aead_request_set_tfm(subreq, tctx->u.aead); + aead_request_set_ad(subreq, req->assoclen); + aead_request_set_callback(subreq, aead_request_flags(req), + essiv_aead_done, req); + aead_request_set_crypt(subreq, src, req->dst, req->cryptlen, req->iv); + + err = enc ? crypto_aead_encrypt(subreq) : + crypto_aead_decrypt(subreq); + + if (rctx->assoc && err != -EINPROGRESS) + kfree(rctx->assoc); + return err; +} + +static int essiv_aead_encrypt(struct aead_request *req) +{ + return essiv_aead_crypt(req, true); +} + +static int essiv_aead_decrypt(struct aead_request *req) +{ + return essiv_aead_crypt(req, false); +} + +static int essiv_init_tfm(struct essiv_instance_ctx *ictx, + struct essiv_tfm_ctx *tctx) +{ + struct crypto_cipher *essiv_cipher; + struct crypto_shash *hash; + int err; + + essiv_cipher = crypto_alloc_cipher(ictx->essiv_cipher_name, 0, 0); + if (IS_ERR(essiv_cipher)) + return PTR_ERR(essiv_cipher); + + hash = crypto_alloc_shash(ictx->shash_driver_name, 0, 0); + if (IS_ERR(hash)) { + err = PTR_ERR(hash); + goto err_free_essiv_cipher; + } + + tctx->essiv_cipher = essiv_cipher; + tctx->hash = hash; + + return 0; + +err_free_essiv_cipher: + crypto_free_cipher(essiv_cipher); + return err; +} + +static int essiv_skcipher_init_tfm(struct crypto_skcipher *tfm) +{ + struct skcipher_instance *inst = skcipher_alg_instance(tfm); + struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst); + struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); + struct crypto_skcipher *skcipher; + int err; + + skcipher = crypto_spawn_skcipher(&ictx->u.skcipher_spawn); + if (IS_ERR(skcipher)) + return PTR_ERR(skcipher); + + crypto_skcipher_set_reqsize(tfm, sizeof(struct skcipher_request) + + crypto_skcipher_reqsize(skcipher)); + + err = essiv_init_tfm(ictx, tctx); + if (err) { + crypto_free_skcipher(skcipher); + return err; + } + + tctx->u.skcipher = skcipher; + return 0; +} + +static int essiv_aead_init_tfm(struct crypto_aead *tfm) +{ + struct aead_instance *inst = aead_alg_instance(tfm); + struct essiv_instance_ctx *ictx = aead_instance_ctx(inst); + struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm); + struct crypto_aead *aead; + unsigned int subreq_size; + int err; + + BUILD_BUG_ON(offsetofend(struct essiv_aead_request_ctx, aead_req) != + sizeof(struct essiv_aead_request_ctx)); + + aead = crypto_spawn_aead(&ictx->u.aead_spawn); + if (IS_ERR(aead)) + return PTR_ERR(aead); + + subreq_size = FIELD_SIZEOF(struct essiv_aead_request_ctx, aead_req) + + crypto_aead_reqsize(aead); + + tctx->ivoffset = offsetof(struct essiv_aead_request_ctx, aead_req) + + subreq_size; + crypto_aead_set_reqsize(tfm, tctx->ivoffset + crypto_aead_ivsize(aead)); + + err = essiv_init_tfm(ictx, tctx); + if (err) { + crypto_free_aead(aead); + return err; + } + + tctx->u.aead = aead; + return 0; +} + +static void essiv_skcipher_exit_tfm(struct crypto_skcipher *tfm) +{ + struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); + + crypto_free_skcipher(tctx->u.skcipher); + crypto_free_cipher(tctx->essiv_cipher); + crypto_free_shash(tctx->hash); +} + +static void essiv_aead_exit_tfm(struct crypto_aead *tfm) +{ + struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm); + + crypto_free_aead(tctx->u.aead); + crypto_free_cipher(tctx->essiv_cipher); + crypto_free_shash(tctx->hash); +} + +static void essiv_skcipher_free_instance(struct skcipher_instance *inst) +{ + struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst); + + crypto_drop_skcipher(&ictx->u.skcipher_spawn); + kfree(inst); +} + +static void essiv_aead_free_instance(struct aead_instance *inst) +{ + struct essiv_instance_ctx *ictx = aead_instance_ctx(inst); + + crypto_drop_aead(&ictx->u.aead_spawn); + kfree(inst); +} + +static bool parse_cipher_name(char *essiv_cipher_name, const char *cra_name) +{ + const char *p, *q; + int len; + + /* find the last opening parens */ + p = strrchr(cra_name, '('); + if (!p++) + return false; + + /* find the first closing parens in the tail of the string */ + q = strchr(p, ')'); + if (!q) + return false; + + len = q - p; + if (len >= CRYPTO_MAX_ALG_NAME) + return false; + + memcpy(essiv_cipher_name, p, len); + essiv_cipher_name[len] = '\0'; + return true; +} + +static bool essiv_supported_algorithms(const char *essiv_cipher_name, + struct shash_alg *hash_alg, + int ivsize) +{ + struct crypto_alg *alg; + bool ret = false; + + alg = crypto_alg_mod_lookup(essiv_cipher_name, + CRYPTO_ALG_TYPE_CIPHER, + CRYPTO_ALG_TYPE_MASK); + if (IS_ERR(alg)) + return false; + + if (hash_alg->digestsize < alg->cra_cipher.cia_min_keysize || + hash_alg->digestsize > alg->cra_cipher.cia_max_keysize) + goto out; + + if (ivsize != alg->cra_blocksize) + goto out; + + if (crypto_shash_alg_has_setkey(hash_alg)) + goto out; + + ret = true; + +out: + crypto_mod_put(alg); + return ret; +} + +static int essiv_create(struct crypto_template *tmpl, struct rtattr **tb) +{ + struct crypto_attr_type *algt; + const char *inner_cipher_name; + const char *shash_name; + struct skcipher_instance *skcipher_inst = NULL; + struct aead_instance *aead_inst = NULL; + struct crypto_instance *inst; + struct crypto_alg *base, *block_base; + struct essiv_instance_ctx *ictx; + struct skcipher_alg *skcipher_alg = NULL; + struct aead_alg *aead_alg = NULL; + struct crypto_alg *_hash_alg; + struct shash_alg *hash_alg; + int ivsize; + u32 type; + int err; + + algt = crypto_get_attr_type(tb); + if (IS_ERR(algt)) + return PTR_ERR(algt); + + inner_cipher_name = crypto_attr_alg_name(tb[1]); + if (IS_ERR(inner_cipher_name)) + return PTR_ERR(inner_cipher_name); + + shash_name = crypto_attr_alg_name(tb[2]); + if (IS_ERR(shash_name)) + return PTR_ERR(shash_name); + + type = algt->type & algt->mask; + + switch (type) { + case CRYPTO_ALG_TYPE_BLKCIPHER: + skcipher_inst = kzalloc(sizeof(*skcipher_inst) + + sizeof(*ictx), GFP_KERNEL); + if (!skcipher_inst) + return -ENOMEM; + inst = skcipher_crypto_instance(skcipher_inst); + base = &skcipher_inst->alg.base; + ictx = crypto_instance_ctx(inst); + + /* Symmetric cipher, e.g., "cbc(aes)" */ + crypto_set_skcipher_spawn(&ictx->u.skcipher_spawn, inst); + err = crypto_grab_skcipher(&ictx->u.skcipher_spawn, + inner_cipher_name, 0, + crypto_requires_sync(algt->type, + algt->mask)); + if (err) + goto out_free_inst; + skcipher_alg = crypto_spawn_skcipher_alg(&ictx->u.skcipher_spawn); + block_base = &skcipher_alg->base; + ivsize = crypto_skcipher_alg_ivsize(skcipher_alg); + break; + + case CRYPTO_ALG_TYPE_AEAD: + aead_inst = kzalloc(sizeof(*aead_inst) + + sizeof(*ictx), GFP_KERNEL); + if (!aead_inst) + return -ENOMEM; + inst = aead_crypto_instance(aead_inst); + base = &aead_inst->alg.base; + ictx = crypto_instance_ctx(inst); + + /* AEAD cipher, e.g., "authenc(hmac(sha256),cbc(aes))" */ + crypto_set_aead_spawn(&ictx->u.aead_spawn, inst); + err = crypto_grab_aead(&ictx->u.aead_spawn, + inner_cipher_name, 0, + crypto_requires_sync(algt->type, + algt->mask)); + if (err) + goto out_free_inst; + aead_alg = crypto_spawn_aead_alg(&ictx->u.aead_spawn); + block_base = &aead_alg->base; + if (!strstarts(block_base->cra_name, "authenc(")) { + pr_warn("Only authenc() type AEADs are supported by ESSIV\n"); + err = -EINVAL; + goto out_drop_skcipher; + } + ivsize = aead_alg->ivsize; + break; + + default: + return -EINVAL; + } + + if (!parse_cipher_name(ictx->essiv_cipher_name, block_base->cra_name)) { + pr_warn("Failed to parse ESSIV cipher name from skcipher cra_name\n"); + err = -EINVAL; + goto out_drop_skcipher; + } + + /* Synchronous hash, e.g., "sha256" */ + _hash_alg = crypto_alg_mod_lookup(shash_name, + CRYPTO_ALG_TYPE_SHASH, + CRYPTO_ALG_TYPE_MASK); + if (IS_ERR(_hash_alg)) { + err = PTR_ERR(_hash_alg); + goto out_drop_skcipher; + } + hash_alg = __crypto_shash_alg(_hash_alg); + + /* Check the set of algorithms */ + if (!essiv_supported_algorithms(ictx->essiv_cipher_name, hash_alg, + ivsize)) { + pr_warn("Unsupported essiv instantiation: essiv(%s,%s)\n", + block_base->cra_name, hash_alg->base.cra_name); + err = -EINVAL; + goto out_free_hash; + } + + /* record the driver name so we can instantiate this exact algo later */ + strlcpy(ictx->shash_driver_name, hash_alg->base.cra_driver_name, + CRYPTO_MAX_ALG_NAME); + + /* Instance fields */ + + err = -ENAMETOOLONG; + if (snprintf(base->cra_name, CRYPTO_MAX_ALG_NAME, + "essiv(%s,%s)", block_base->cra_name, + hash_alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME) + goto out_free_hash; + if (snprintf(base->cra_driver_name, CRYPTO_MAX_ALG_NAME, + "essiv(%s,%s)", block_base->cra_driver_name, + hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME) + goto out_free_hash; + + base->cra_flags = block_base->cra_flags & CRYPTO_ALG_ASYNC; + base->cra_blocksize = block_base->cra_blocksize; + base->cra_ctxsize = sizeof(struct essiv_tfm_ctx); + base->cra_alignmask = block_base->cra_alignmask; + base->cra_priority = block_base->cra_priority; + + if (type == CRYPTO_ALG_TYPE_BLKCIPHER) { + skcipher_inst->alg.setkey = essiv_skcipher_setkey; + skcipher_inst->alg.encrypt = essiv_skcipher_encrypt; + skcipher_inst->alg.decrypt = essiv_skcipher_decrypt; + skcipher_inst->alg.init = essiv_skcipher_init_tfm; + skcipher_inst->alg.exit = essiv_skcipher_exit_tfm; + + skcipher_inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(skcipher_alg); + skcipher_inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(skcipher_alg); + skcipher_inst->alg.ivsize = ivsize; + skcipher_inst->alg.chunksize = crypto_skcipher_alg_chunksize(skcipher_alg); + skcipher_inst->alg.walksize = crypto_skcipher_alg_walksize(skcipher_alg); + + skcipher_inst->free = essiv_skcipher_free_instance; + + err = skcipher_register_instance(tmpl, skcipher_inst); + } else { + aead_inst->alg.setkey = essiv_aead_setkey; + aead_inst->alg.setauthsize = essiv_aead_setauthsize; + aead_inst->alg.encrypt = essiv_aead_encrypt; + aead_inst->alg.decrypt = essiv_aead_decrypt; + aead_inst->alg.init = essiv_aead_init_tfm; + aead_inst->alg.exit = essiv_aead_exit_tfm; + + aead_inst->alg.ivsize = ivsize; + aead_inst->alg.maxauthsize = crypto_aead_alg_maxauthsize(aead_alg); + aead_inst->alg.chunksize = crypto_aead_alg_chunksize(aead_alg); + + aead_inst->free = essiv_aead_free_instance; + + err = aead_register_instance(tmpl, aead_inst); + } + + if (err) + goto out_free_hash; + + crypto_mod_put(_hash_alg); + return 0; + +out_free_hash: + crypto_mod_put(_hash_alg); +out_drop_skcipher: + if (type == CRYPTO_ALG_TYPE_BLKCIPHER) + crypto_drop_skcipher(&ictx->u.skcipher_spawn); + else + crypto_drop_aead(&ictx->u.aead_spawn); +out_free_inst: + kfree(skcipher_inst); + kfree(aead_inst); + return err; +} + +/* essiv(cipher_name, shash_name) */ +static struct crypto_template essiv_tmpl = { + .name = "essiv", + .create = essiv_create, + .module = THIS_MODULE, +}; + +static int __init essiv_module_init(void) +{ + return crypto_register_template(&essiv_tmpl); +} + +static void __exit essiv_module_exit(void) +{ + crypto_unregister_template(&essiv_tmpl); +} + +subsys_initcall(essiv_module_init); +module_exit(essiv_module_exit); + +MODULE_DESCRIPTION("ESSIV skcipher/aead wrapper for block encryption"); +MODULE_LICENSE("GPL v2"); +MODULE_ALIAS_CRYPTO("essiv"); |