From ce8614a312ef750bb60677bb13680cb27d1c284b Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Fri, 29 Dec 2017 10:00:46 -0600 Subject: crypto: algapi - convert cra_refcnt to refcount_t Reference counters should use refcount_t rather than atomic_t, since the refcount_t implementation can prevent overflows, reducing the exploitability of reference leak bugs. crypto_alg.cra_refcount is a reference counter with the usual semantics, so switch it over to refcount_t. Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- include/linux/crypto.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/crypto.h b/include/linux/crypto.h index 78508ca4b108..231e59f90d32 100644 --- a/include/linux/crypto.h +++ b/include/linux/crypto.h @@ -447,7 +447,7 @@ struct crypto_alg { unsigned int cra_alignmask; int cra_priority; - atomic_t cra_refcnt; + refcount_t cra_refcnt; char cra_name[CRYPTO_MAX_ALG_NAME]; char cra_driver_name[CRYPTO_MAX_ALG_NAME]; -- cgit v1.2.3 From a208fa8f33031b9e0aba44c7d1b7e68eb0cbd29e Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Wed, 3 Jan 2018 11:16:26 -0800 Subject: crypto: hash - annotate algorithms taking optional key We need to consistently enforce that keyed hashes cannot be used without setting the key. To do this we need a reliable way to determine whether a given hash algorithm is keyed or not. AF_ALG currently does this by checking for the presence of a ->setkey() method. However, this is actually slightly broken because the CRC-32 algorithms implement ->setkey() but can also be used without a key. (The CRC-32 "key" is not actually a cryptographic key but rather represents the initial state. If not overridden, then a default initial state is used.) Prepare to fix this by introducing a flag CRYPTO_ALG_OPTIONAL_KEY which indicates that the algorithm has a ->setkey() method, but it is not required to be called. Then set it on all the CRC-32 algorithms. The same also applies to the Adler-32 implementation in Lustre. Also, the cryptd and mcryptd templates have to pass through the flag from their underlying algorithm. Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- include/linux/crypto.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux') diff --git a/include/linux/crypto.h b/include/linux/crypto.h index 231e59f90d32..d2e33a90825b 100644 --- a/include/linux/crypto.h +++ b/include/linux/crypto.h @@ -106,6 +106,12 @@ */ #define CRYPTO_ALG_INTERNAL 0x00002000 +/* + * Set if the algorithm has a ->setkey() method but can be used without + * calling it first, i.e. there is a default key. + */ +#define CRYPTO_ALG_OPTIONAL_KEY 0x00004000 + /* * Transform masks and values (for crt_flags). */ -- cgit v1.2.3 From 9fa68f620041be04720d0cbfb1bd3ddfc6310b24 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Wed, 3 Jan 2018 11:16:27 -0800 Subject: crypto: hash - prevent using keyed hashes without setting key Currently, almost none of the keyed hash algorithms check whether a key has been set before proceeding. Some algorithms are okay with this and will effectively just use a key of all 0's or some other bogus default. However, others will severely break, as demonstrated using "hmac(sha3-512-generic)", the unkeyed use of which causes a kernel crash via a (potentially exploitable) stack buffer overflow. A while ago, this problem was solved for AF_ALG by pairing each hash transform with a 'has_key' bool. However, there are still other places in the kernel where userspace can specify an arbitrary hash algorithm by name, and the kernel uses it as unkeyed hash without checking whether it is really unkeyed. Examples of this include: - KEYCTL_DH_COMPUTE, via the KDF extension - dm-verity - dm-crypt, via the ESSIV support - dm-integrity, via the "internal hash" mode with no key given - drbd (Distributed Replicated Block Device) This bug is especially bad for KEYCTL_DH_COMPUTE as that requires no privileges to call. Fix the bug for all users by adding a flag CRYPTO_TFM_NEED_KEY to the ->crt_flags of each hash transform that indicates whether the transform still needs to be keyed or not. Then, make the hash init, import, and digest functions return -ENOKEY if the key is still needed. The new flag also replaces the 'has_key' bool which algif_hash was previously using, thereby simplifying the algif_hash implementation. Reported-by: syzbot Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- include/linux/crypto.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/crypto.h b/include/linux/crypto.h index d2e33a90825b..7e6e84cf6383 100644 --- a/include/linux/crypto.h +++ b/include/linux/crypto.h @@ -115,6 +115,8 @@ /* * Transform masks and values (for crt_flags). */ +#define CRYPTO_TFM_NEED_KEY 0x00000001 + #define CRYPTO_TFM_REQ_MASK 0x000fff00 #define CRYPTO_TFM_RES_MASK 0xfff00000 -- cgit v1.2.3