From ba7d7433a0e998c902132bd47330e355a1eaa894 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 6 Jan 2019 18:47:42 -0800 Subject: [PATCH] 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: 9fa68f620041 ("crypto: hash - prevent using keyed hashes without setting key") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- crypto/ahash.c | 28 +++++++++++++++++++--------- crypto/shash.c | 18 +++++++++++++----- 2 files changed, 32 insertions(+), 14 deletions(-) diff --git a/crypto/ahash.c b/crypto/ahash.c index 5d320a811f75..ca0d3e281fef 100644 --- a/crypto/ahash.c +++ b/crypto/ahash.c @@ -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; diff --git a/crypto/shash.c b/crypto/shash.c index 44d297b82a8f..40311ccad3fa 100644 --- a/crypto/shash.c +++ b/crypto/shash.c @@ -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; @@ -373,7 +382,8 @@ 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; - crt->setkey = shash_async_setkey; + if (crypto_shash_alg_has_setkey(alg)) + crt->setkey = shash_async_setkey; crypto_ahash_set_flags(crt, crypto_shash_get_flags(shash) & CRYPTO_TFM_NEED_KEY); @@ -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; } -- 2.30.2