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dm crypt: convert essiv from ahash to shash 

In preparing to remove all stack VLA usage from the kernel[1], remove
the discouraged use of AHASH_REQUEST_ON_STACK in favor of the smaller
SHASH_DESC_ON_STACK by converting from ahash-wrapped-shash to direct
shash.  The stack allocation will be made a fixed size in a later patch
to the crypto subsystem.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Kees Cook 2018-07-15 20:59:12 -07:00 committed by Mike Snitzer
parent c7329eff72
commit c07c88f54f
1 changed files with 14 additions and 17 deletions
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31
drivers/md/dm-crypt.c
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@ -99,7 +99,7 @@ struct crypt_iv_operations {
};
struct iv_essiv_private {
struct crypto_ahash *hash_tfm;
struct crypto_shash *hash_tfm;
u8 *salt;
};
@ -327,25 +327,22 @@ static int crypt_iv_plain64be_gen(struct crypt_config *cc, u8 *iv,
static int crypt_iv_essiv_init(struct crypt_config *cc)
{
struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
AHASH_REQUEST_ON_STACK(req, essiv->hash_tfm);
struct scatterlist sg;
SHASH_DESC_ON_STACK(desc, essiv->hash_tfm);
struct crypto_cipher *essiv_tfm;
int err;
sg_init_one(&sg, cc->key, cc->key_size);
ahash_request_set_tfm(req, essiv->hash_tfm);
ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
ahash_request_set_crypt(req, &sg, essiv->salt, cc->key_size);
desc->tfm = essiv->hash_tfm;
desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
err = crypto_ahash_digest(req);
ahash_request_zero(req);
err = crypto_shash_digest(desc, cc->key, cc->key_size, essiv->salt);
shash_desc_zero(desc);
if (err)
return err;
essiv_tfm = cc->iv_private;
err = crypto_cipher_setkey(essiv_tfm, essiv->salt,
crypto_ahash_digestsize(essiv->hash_tfm));
crypto_shash_digestsize(essiv->hash_tfm));
if (err)
return err;
@ -356,7 +353,7 @@ static int crypt_iv_essiv_init(struct crypt_config *cc)
static int crypt_iv_essiv_wipe(struct crypt_config *cc)
{
struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
unsigned salt_size = crypto_ahash_digestsize(essiv->hash_tfm);
unsigned salt_size = crypto_shash_digestsize(essiv->hash_tfm);
struct crypto_cipher *essiv_tfm;
int r, err = 0;
@ -408,7 +405,7 @@ static void crypt_iv_essiv_dtr(struct crypt_config *cc)
struct crypto_cipher *essiv_tfm;
struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
crypto_free_ahash(essiv->hash_tfm);
crypto_free_shash(essiv->hash_tfm);
essiv->hash_tfm = NULL;
kzfree(essiv->salt);
@ -426,7 +423,7 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
const char *opts)
{
struct crypto_cipher *essiv_tfm = NULL;
struct crypto_ahash *hash_tfm = NULL;
struct crypto_shash *hash_tfm = NULL;
u8 *salt = NULL;
int err;
@ -436,14 +433,14 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
}
/* Allocate hash algorithm */
hash_tfm = crypto_alloc_ahash(opts, 0, CRYPTO_ALG_ASYNC);
hash_tfm = crypto_alloc_shash(opts, 0, 0);
if (IS_ERR(hash_tfm)) {
ti->error = "Error initializing ESSIV hash";
err = PTR_ERR(hash_tfm);
goto bad;
}
salt = kzalloc(crypto_ahash_digestsize(hash_tfm), GFP_KERNEL);
salt = kzalloc(crypto_shash_digestsize(hash_tfm), GFP_KERNEL);
if (!salt) {
ti->error = "Error kmallocing salt storage in ESSIV";
err = -ENOMEM;
@ -454,7 +451,7 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
cc->iv_gen_private.essiv.hash_tfm = hash_tfm;
essiv_tfm = alloc_essiv_cipher(cc, ti, salt,
crypto_ahash_digestsize(hash_tfm));
crypto_shash_digestsize(hash_tfm));
if (IS_ERR(essiv_tfm)) {
crypt_iv_essiv_dtr(cc);
return PTR_ERR(essiv_tfm);
@ -465,7 +462,7 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
bad:
if (hash_tfm && !IS_ERR(hash_tfm))
crypto_free_ahash(hash_tfm);
crypto_free_shash(hash_tfm);
kfree(salt);
return err;
}