Question on IBSS + RSN

[Jouni Malinen]

On Fri, Jan 13, 2017 at 02:48:07PM -0800, Ben Greear wrote:
> Ok, seems I should focus on events around Authentication message then.

I was able to reproduce one related issue with mac80211_hwsim. This is a
bug that prevents wpa_supplicant from clearing the key when receiving
the Authentication frame from a peer. The patch below fixes that.
However, this resulted in hitting another issue within mac80211 where it
looks like the unicast frame from the re-joining STA gets lost in the RX
reorder buffer logic.. I'm not completely sure what causes that, but for
initial testing, using disable_ht=1 seemed to be a sufficient workaround
(i.e., disable QoS and reorder buffer logic for BA).


[PATCH] RSN IBSS: Fix TK clearing on Authentication frame RX

When wpa_supplicant was processing a received Authentication frame (seq
1) from a peer STA for which there was already a TK configured to the
driver, debug log claimed that the PTK gets cleared, but the actual
call to clear the key was actually dropped due to AUTH vs. SUPP set_key
selection. Fix this by explicitly clearing the TK in case it was set
and an Authentication frame (seq 1) is received.

This fixes some cases where EAPOL-Key frames were sent encrypted using
the old key when a peer STA restarted itself and lost the key and had to
re-join the IBSS. Previously, that state required timing out the 4-way
handshake and Deauthentication frame exchange to recover.

Signed-off-by: Jouni Malinen <j at w1.fi>
---
 wpa_supplicant/ibss_rsn.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/wpa_supplicant/ibss_rsn.c b/wpa_supplicant/ibss_rsn.c
index 53d7d57..c29d8d3 100644
--- a/wpa_supplicant/ibss_rsn.c
+++ b/wpa_supplicant/ibss_rsn.c
@@ -838,6 +838,18 @@ static void ibss_rsn_handle_auth_1_of_2(struct ibss_rsn *ibss_rsn,
 		   MAC2STR(addr));
 
 	if (peer &&
+	    peer->authentication_status & (IBSS_RSN_SET_PTK_SUPP |
+					   IBSS_RSN_SET_PTK_AUTH)) {
+		/* Clear the TK for this pair to allow recovery from the case
+		 * where the peer STA has restarted and lost its key while we
+		 * still have a pairwise key configured. */
+		wpa_printf(MSG_DEBUG, "RSN: Clear pairwise key for peer "
+			   MACSTR, MAC2STR(addr));
+		wpa_drv_set_key(ibss_rsn->wpa_s, WPA_ALG_NONE, addr, 0, 0,
+				NULL, 0, NULL, 0);
+	}
+
+	if (peer &&
 	    peer->authentication_status & IBSS_RSN_AUTH_EAPOL_BY_PEER) {
 		if (peer->own_auth_tx.sec) {
 			struct os_reltime now, diff;
-- 
2.7.4


-- 
Jouni Malinen                                            PGP id EFC895FA