From: Eric Biggers <ebiggers@xxxxxxxxxx>
In public_key_verify_signature(), if akcipher_request_alloc() fails, we
return -ENOMEM. But that error code was set 25 lines above, and by
accident someone could easily insert new code in between that assigns to
'ret', which would introduce a signature verification bypass. Make the
code clearer by moving the -ENOMEM down to where it is used.
Additionally, the callers of public_key_verify_signature() only consider
a negative return value to be an error. This means that if any positive
return value is accidentally introduced deeper in the call stack (e.g.
'return EBADMSG' instead of 'return -EBADMSG' somewhere in RSA),
signature verification will be bypassed. Make things more robust by
having public_key_verify_signature() warn about positive errors and
translate them into -EINVAL.
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
crypto/asymmetric_keys/public_key.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
index bc3035ef27a2..de996586762a 100644
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -73,7 +73,7 @@ int public_key_verify_signature(const struct public_key *pkey,
char alg_name_buf[CRYPTO_MAX_ALG_NAME];
void *output;
unsigned int outlen;
- int ret = -ENOMEM;
+ int ret;
pr_devel("==>%s()\n", __func__);
@@ -99,6 +99,7 @@ int public_key_verify_signature(const struct public_key *pkey,
if (IS_ERR(tfm))
return PTR_ERR(tfm);
+ ret = -ENOMEM;
req = akcipher_request_alloc(tfm, GFP_KERNEL);
if (!req)
goto error_free_tfm;
@@ -127,7 +128,7 @@ int public_key_verify_signature(const struct public_key *pkey,
* signature and returns that to us.
*/
ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
- if (ret < 0)
+ if (ret)
goto out_free_output;
/* Do the actual verification step. */
@@ -142,6 +143,8 @@ int public_key_verify_signature(const struct public_key *pkey,
error_free_tfm:
crypto_free_akcipher(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
+ if (WARN_ON_ONCE(ret > 0))
+ ret = -EINVAL;
return ret;
}
EXPORT_SYMBOL_GPL(public_key_verify_signature);
--
2.15.0
