Commit b1f6b4bf authored by Eric Biggers's avatar Eric Biggers Committed by Herbert Xu
Browse files

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: f8d33fac ("crypto: skcipher - prevent using skciphers without setting key")
Cc: <stable@vger.kernel.org> # v4.16+
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent ba7d7433

crypto/skcipher.c

+18 −9
Original line number Diff line number Diff line
@@ -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;

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