Patch "mac80211: accept key reinstall without changing anything" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

mac80211: accept key reinstall without changing anything

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mac80211-accept-key-reinstall-without-changing-anything.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Johannes Berg <[email protected]>
Date: Tue, 5 Sep 2017 14:54:54 +0200
Subject: mac80211: accept key reinstall without changing anything

From: Johannes Berg <[email protected]>

commit fdf7cb4185b60c68e1a75e61691c4afdc15dea0e upstream.

When a key is reinstalled we can reset the replay counters etc. which can lead to nonce reuse and/or replay detection being impossible, breaking security properties, as described in the "KRACK attacks".

In particular, CVE-2017-13080 applies to GTK rekeying that happened in firmware while the host is in D3, with the second part of the attack being done after the host wakes up. In this case, the wpa_supplicant mitigation isn't sufficient since wpa_supplicant doesn't know the GTK material.

In case this happens, simply silently accept the new key coming from userspace but don't take any action on it since it's the same key; this keeps the PN replay counters intact.

---
 net/mac80211/key.c |   20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

@@ -4,6 +4,7 @@
  * Copyright 2006-2007	Jiri Benc <[email protected]>
  * Copyright 2007-2008	Johannes Berg <[email protected]>
  * Copyright 2013-2014  Intel Mobile Communications GmbH
+ * Copyright 2017	Intel Deutschland GmbH
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as

@@ -617,9 +618,6 @@ int ieee80211_key_link(struct ieee80211_
 
 	pairwise = key->conf.flags & IEEE80211_KEY_FLAG_PAIRWISE;
 	idx = key->conf.keyidx;
-	key->local = sdata->local;
-	key->sdata = sdata;
-	key->sta = sta;
 
 	mutex_lock(&sdata->local->key_mtx);
 

@@ -630,6 +628,21 @@ int ieee80211_key_link(struct ieee80211_
 	else
 		old_key = key_mtx_dereference(sdata->local, sdata->keys[idx]);
 
+	/*
+	 * Silently accept key re-installation without really installing the
+	 * 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)) {
+		ieee80211_key_free_unused(key);
+		ret = 0;
+		goto out;
+	}
+
+	key->local = sdata->local;
+	key->sdata = sdata;
+	key->sta = sta;
+
 	increment_tailroom_need_count(sdata);
 
 	ieee80211_key_replace(sdata, sta, pairwise, old_key, key);

@@ -645,6 +658,7 @@ int ieee80211_key_link(struct ieee80211_
 		ret = 0;
 	}
 
+ out:
 	mutex_unlock(&sdata->local->key_mtx);
 
 	return ret;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/mac80211-use-constant-time-comparison-with-keys.patch queue-4.4/mac80211-don-t-compare-tkip-tx-mic-key-in-reinstall-prevention.patch queue-4.4/mac80211-accept-key-reinstall-without-changing-anything.patch