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// 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. <ard.biesheuvel@linaro.org>
*
* Heavily based on:
* adiantum length-preserving encryption mode
*
* Copyright 2018 Google LLC
*/
#include <crypto/authenc.h>
#include <crypto/internal/aead.h>
#include <crypto/internal/cipher.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);
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);
if (err)
return err;
err = crypto_shash_tfm_digest(tctx->hash, 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);
return crypto_cipher_setkey(tctx->essiv_cipher, salt,
crypto_shash_digestsize(tctx->hash));
}
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);
if (err)
return err;
if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)
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);
return crypto_cipher_setkey(tctx->essiv_cipher, salt,
crypto_shash_digestsize(tctx->hash));
}
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);
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 = sizeof_field(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_needs_key(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;
u32 mask;
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;
mask = crypto_algt_inherited_mask(algt);
switch (type) {
case CRYPTO_ALG_TYPE_SKCIPHER:
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)" */
err = crypto_grab_skcipher(&ictx->u.skcipher_spawn, inst,
inner_cipher_name, 0, 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))" */
err = crypto_grab_aead(&ictx->u.aead_spawn, inst,
inner_cipher_name, 0, 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 | 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;
/*
* hash_alg wasn't gotten via crypto_grab*(), so we need to inherit its
* flags manually.
*/
base->cra_flags |= (hash_alg->base.cra_flags &
CRYPTO_ALG_INHERITED_FLAGS);
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_SKCIPHER) {
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_SKCIPHER)
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");
MODULE_IMPORT_NS(CRYPTO_INTERNAL);