Commit ba7d7433 authored by Eric Biggers's avatar Eric Biggers Committed by Herbert Xu
Browse files

crypto: hash - 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.

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.

Note: we can't set CRYPTO_TFM_NEED_KEY for OPTIONAL_KEY algorithms, so
->setkey() for those must nevertheless be atomic.  That's fine for now
since only the crc32 and crc32c algorithms set OPTIONAL_KEY, and it's
not intended that OPTIONAL_KEY be used much.

[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: 9fa68f62 ("crypto: hash - prevent using keyed hashes without setting key")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 6b476662

crypto/ahash.c

+19 −9
Original line number Diff line number Diff line
@@ -190,6 +190,21 @@ static int ahash_setkey_unaligned(struct crypto_ahash *tfm, const u8 *key, 
	return ret;

}



static int ahash_nosetkey(struct crypto_ahash *tfm, const u8 *key,

			  unsigned int keylen)

{

	return -ENOSYS;

}



static void ahash_set_needkey(struct crypto_ahash *tfm)

{

	const struct hash_alg_common *alg = crypto_hash_alg_common(tfm);



	if (tfm->setkey != ahash_nosetkey &&

	    !(alg->base.cra_flags & CRYPTO_ALG_OPTIONAL_KEY))

		crypto_ahash_set_flags(tfm, CRYPTO_TFM_NEED_KEY);

}



int crypto_ahash_setkey(struct crypto_ahash *tfm, const u8 *key,

			unsigned int keylen)

{
@@ -201,20 +216,16 @@ int crypto_ahash_setkey(struct crypto_ahash *tfm, const u8 *key, 
	else

		err = tfm->setkey(tfm, key, keylen);



	if (err)

	if (unlikely(err)) {

		ahash_set_needkey(tfm);

		return err;

	}



	crypto_ahash_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);

	return 0;

}

EXPORT_SYMBOL_GPL(crypto_ahash_setkey);



static int ahash_nosetkey(struct crypto_ahash *tfm, const u8 *key,

			  unsigned int keylen)

{

	return -ENOSYS;

}



static inline unsigned int ahash_align_buffer_size(unsigned len,

						   unsigned long mask)

{
@@ -489,8 +500,7 @@ static int crypto_ahash_init_tfm(struct crypto_tfm *tfm) 


	if (alg->setkey) {

		hash->setkey = alg->setkey;

		if (!(alg->halg.base.cra_flags & CRYPTO_ALG_OPTIONAL_KEY))

			crypto_ahash_set_flags(hash, CRYPTO_TFM_NEED_KEY);

		ahash_set_needkey(hash);

	}



	return 0;

crypto/shash.c

+13 −5
Original line number Diff line number Diff line
@@ -53,6 +53,13 @@ static int shash_setkey_unaligned(struct crypto_shash *tfm, const u8 *key, 
	return err;

}



static void shash_set_needkey(struct crypto_shash *tfm, struct shash_alg *alg)

{

	if (crypto_shash_alg_has_setkey(alg) &&

	    !(alg->base.cra_flags & CRYPTO_ALG_OPTIONAL_KEY))

		crypto_shash_set_flags(tfm, CRYPTO_TFM_NEED_KEY);

}



int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,

			unsigned int keylen)

{
@@ -65,8 +72,10 @@ int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key, 
	else

		err = shash->setkey(tfm, key, keylen);



	if (err)

	if (unlikely(err)) {

		shash_set_needkey(tfm, shash);

		return err;

	}



	crypto_shash_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);

	return 0;
@@ -373,6 +382,7 @@ int crypto_init_shash_ops_async(struct crypto_tfm *tfm) 
	crt->final = shash_async_final;

	crt->finup = shash_async_finup;

	crt->digest = shash_async_digest;

	if (crypto_shash_alg_has_setkey(alg))

		crt->setkey = shash_async_setkey;



	crypto_ahash_set_flags(crt, crypto_shash_get_flags(shash) &
@@ -395,9 +405,7 @@ static int crypto_shash_init_tfm(struct crypto_tfm *tfm) 


	hash->descsize = alg->descsize;



	if (crypto_shash_alg_has_setkey(alg) &&

	    !(alg->base.cra_flags & CRYPTO_ALG_OPTIONAL_KEY))

		crypto_shash_set_flags(hash, CRYPTO_TFM_NEED_KEY);

	shash_set_needkey(hash, alg);



	return 0;

}

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