linux-kernel - [PATCH 3.16 127/133] mac80211: use constant time comparison with keys

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Message-ID: <lsq.1511315893.35951821@decadent.org.uk>
Date:   Wed, 22 Nov 2017 01:58:13 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Johannes Berg" <johannes.berg@...el.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH 3.16 127/133] mac80211: use constant time comparison with keys

3.16.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Jason A. Donenfeld" <Jason@...c4.com>

commit 2bdd713b92a9cade239d3c7d15205a09f556624d upstream.

Otherwise we risk leaking information via timing side channel.

Fixes: fdf7cb4185b6 ("mac80211: accept key reinstall without changing anything")
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/mac80211/key.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/mac80211/key.c
+++ b/net/mac80211/key.c
@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/export.h>
 #include <net/mac80211.h>
+#include <crypto/algapi.h>
 #include <asm/unaligned.h>
 #include "ieee80211_i.h"
 #include "driver-ops.h"
@@ -503,7 +504,7 @@ int ieee80211_key_link(struct ieee80211_
 	 * new version of the key to avoid nonce reuse or replay issues.
 	 */
 	if (old_key && key->conf.keylen == old_key->conf.keylen &&
-	    !memcmp(key->conf.key, old_key->conf.key, key->conf.keylen)) {
+	    !crypto_memneq(key->conf.key, old_key->conf.key, key->conf.keylen)) {
 		ieee80211_key_free_unused(key);
 		ret = 0;
 		goto out;