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crypto: skcipher - set CRYPTO_TFM_NEED_KEY if ->setkey() fails 

Some algorithms have a ->setkey() method that is not atomic, in the
sense that setting a key can fail after changes were already made to the
tfm context.  In this case, if a key was already set the tfm can end up
in a state that corresponds to neither the old key nor the new key.

For example, in lrw.c, if gf128mul_init_64k_bbe() fails due to lack of
memory, then priv::table will be left NULL.  After that, encryption with
that tfm will cause a NULL pointer dereference.

It's not feasible to make all ->setkey() methods atomic, especially ones
that have to key multiple sub-tfms.  Therefore, make the crypto API set
CRYPTO_TFM_NEED_KEY if ->setkey() fails and the algorithm requires a
key, to prevent the tfm from being used until a new key is set.

[Cc stable mainly because when introducing the NEED_KEY flag I changed
 AF_ALG to rely on it; and unlike in-kernel crypto API users, AF_ALG
 previously didn't have this problem.  So these "incompletely keyed"
 states became theoretically accessible via AF_ALG -- though, the
 opportunities for causing real mischief seem pretty limited.]

Fixes: f8d33fac84 ("crypto: skcipher - prevent using skciphers without setting key")
Cc: <stable@vger.kernel.org> # v4.16+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2019-01-06 18:47:43 -08:00 committed by Herbert Xu
parent ba7d7433a0
commit b1f6b4bf41
1 changed files with 18 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
crypto/skcipher.c
View File

@ -585,6 +585,12 @@ static unsigned int crypto_skcipher_extsize(struct crypto_alg *alg)
return crypto_alg_extsize(alg);
}
static void skcipher_set_needkey(struct crypto_skcipher *tfm)
{
if (tfm->keysize)
crypto_skcipher_set_flags(tfm, CRYPTO_TFM_NEED_KEY);
}
static int skcipher_setkey_blkcipher(struct crypto_skcipher *tfm,
const u8 *key, unsigned int keylen)
{
@ -598,8 +604,10 @@ static int skcipher_setkey_blkcipher(struct crypto_skcipher *tfm,
err = crypto_blkcipher_setkey(blkcipher, key, keylen);
crypto_skcipher_set_flags(tfm, crypto_blkcipher_get_flags(blkcipher) &
CRYPTO_TFM_RES_MASK);
if (err)
if (unlikely(err)) {
skcipher_set_needkey(tfm);
return err;
}
crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
return 0;
@ -677,8 +685,7 @@ static int crypto_init_skcipher_ops_blkcipher(struct crypto_tfm *tfm)
skcipher->ivsize = crypto_blkcipher_ivsize(blkcipher);
skcipher->keysize = calg->cra_blkcipher.max_keysize;
if (skcipher->keysize)
crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
skcipher_set_needkey(skcipher);
return 0;
}
@ -698,8 +705,10 @@ static int skcipher_setkey_ablkcipher(struct crypto_skcipher *tfm,
crypto_skcipher_set_flags(tfm,
crypto_ablkcipher_get_flags(ablkcipher) &
CRYPTO_TFM_RES_MASK);
if (err)
if (unlikely(err)) {
skcipher_set_needkey(tfm);
return err;
}
crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
return 0;
@ -776,8 +785,7 @@ static int crypto_init_skcipher_ops_ablkcipher(struct crypto_tfm *tfm)
sizeof(struct ablkcipher_request);
skcipher->keysize = calg->cra_ablkcipher.max_keysize;
if (skcipher->keysize)
crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
skcipher_set_needkey(skcipher);
return 0;
}
@ -820,8 +828,10 @@ static int skcipher_setkey(struct crypto_skcipher *tfm, const u8 *key,
else
err = cipher->setkey(tfm, key, keylen);
if (err)
if (unlikely(err)) {
skcipher_set_needkey(tfm);
return err;
}
crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
return 0;
@ -852,8 +862,7 @@ static int crypto_skcipher_init_tfm(struct crypto_tfm *tfm)
skcipher->ivsize = alg->ivsize;
skcipher->keysize = alg->max_keysize;
if (skcipher->keysize)
crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
skcipher_set_needkey(skcipher);
if (alg->exit)
skcipher->base.exit = crypto_skcipher_exit_tfm;