From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
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 5d320a811f750..ca0d3e281fefb 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 44d297b82a8fb..40311ccad3fae 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;
}
--
2.20.1
