From f96121b6afdbd22a665a1ae7a928131f3ed3f3d4 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Tue, 5 Sep 2017 14:54:54 +0200 Subject: [PATCH] mac80211: accept key reinstall without changing anything 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. Change-Id: Ie3402dce344b6471a2a213722eef66da8f14f4f9 Signed-off-by: Johannes Berg --- net/mac80211/key.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/net/mac80211/key.c b/net/mac80211/key.c index 635d0972b688..c07d74bbbbf1 100644 --- a/net/mac80211/key.c +++ b/net/mac80211/key.c @@ -3,6 +3,8 @@ * Copyright 2005-2006, Devicescape Software, Inc. * Copyright 2006-2007 Jiri Benc * Copyright 2007-2008 Johannes Berg + * Copyright 2013-2014 Intel Mobile Communications GmbH + * Copyright 2015-2017 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 @@ -464,9 +466,6 @@ int ieee80211_key_link(struct ieee80211_key *key, 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); @@ -477,6 +476,21 @@ int ieee80211_key_link(struct ieee80211_key *key, 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); @@ -489,6 +503,7 @@ int ieee80211_key_link(struct ieee80211_key *key, if (ret) ieee80211_key_free(key, true); + out: mutex_unlock(&sdata->local->key_mtx); return ret;