OWE: Reuse own DH private key in AP if STA tries OWE association again

This is a workaround for mac80211 behavior of retransmitting the
Association Request frames multiple times if the link layer retries
(i.e., seq# remains same) fail. The mac80211 initiated retransmission
will use a different seq# and as such, will go through duplicate
detection. If we were to change our DH key for that attempt, there would
be two different DH shared secrets and the STA would likely select the
wrong one.

Signed-off-by: Jouni Malinen <j@w1.fi>

diff --git a/src/ap/ieee802_11.c b/src/ap/ieee802_11.c
index c722242ebdb0dc502615c91bc2991f04cb653152..15fdcbd621e8bf9c6bee78cb717eca0b2327d9cc 100644 (file)
--- a/src/ap/ieee802_11.c
+++ b/src/ap/ieee802_11.c
@@ -4186,8 +4186,21 @@ static u16 owe_process_assoc_req(struct hostapd_data *hapd,
        else
                return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
 
-       crypto_ecdh_deinit(sta->owe_ecdh);
-       sta->owe_ecdh = crypto_ecdh_init(group);
+       if (sta->owe_group == group && sta->owe_ecdh) {
+               /* This is a workaround for mac80211 behavior of retransmitting
+                * the Association Request frames multiple times if the link
+                * layer retries (i.e., seq# remains same) fail. The mac80211
+                * initiated retransmission will use a different seq# and as
+                * such, will go through duplicate detection. If we were to
+                * change our DH key for that attempt, there would be two
+                * different DH shared secrets and the STA would likely select
+                * the wrong one. */
+               wpa_printf(MSG_DEBUG,
+                          "OWE: Try to reuse own previous DH key since the STA tried to go through OWE association again");
+       } else {
+               crypto_ecdh_deinit(sta->owe_ecdh);
+               sta->owe_ecdh = crypto_ecdh_init(group);
+       }
        if (!sta->owe_ecdh)
                return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
        sta->owe_group = group;