sunrpc: use constant time memory comparison for mac
authorJason A. Donenfeld <Jason@zx2c4.com>
Sat, 10 Jun 2017 02:59:07 +0000 (04:59 +0200)
committerAnna Schumaker <Anna.Schumaker@Netapp.com>
Thu, 13 Jul 2017 20:00:14 +0000 (16:00 -0400)
Otherwise, we enable a MAC forgery via timing attack.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: linux-nfs@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
net/sunrpc/auth_gss/gss_krb5_crypto.c

index fb39284..12649c9 100644 (file)
@@ -34,6 +34,7 @@
  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  */
 
+#include <crypto/algapi.h>
 #include <crypto/hash.h>
 #include <crypto/skcipher.h>
 #include <linux/err.h>
@@ -927,7 +928,7 @@ gss_krb5_aes_decrypt(struct krb5_ctx *kctx, u32 offset, struct xdr_buf *buf,
        if (ret)
                goto out_err;
 
-       if (memcmp(pkt_hmac, our_hmac, kctx->gk5e->cksumlength) != 0) {
+       if (crypto_memneq(pkt_hmac, our_hmac, kctx->gk5e->cksumlength) != 0) {
                ret = GSS_S_BAD_SIG;
                goto out_err;
        }