MFP: Fix IGTK PN in group rekeying

IGTK get_seqnum needs to be skipped in the same way as GTK one when
rekeying group keys. Previously, the old PN value (the one from the
previous key) was indicated and that resulted in MMIE replay detection
at the station.

src/ap/wpa_auth.c

@@ -1535,7 +1535,8 @@ static u8 * ieee80211w_kde_add(struct wpa_state_machine *sm, u8 *pos)
 
 	igtk.keyid[0] = gsm->GN_igtk;
 	igtk.keyid[1] = 0;
-	if (wpa_auth_get_seqnum(sm->wpa_auth, NULL, gsm->GN_igtk, igtk.pn) < 0)
+	if (gsm->wpa_group_state != WPA_GROUP_SETKEYSDONE ||
+	    wpa_auth_get_seqnum(sm->wpa_auth, NULL, gsm->GN_igtk, igtk.pn) < 0)
 		os_memset(igtk.pn, 0, sizeof(igtk.pn));
 	os_memcpy(igtk.igtk, gsm->IGTK[gsm->GN_igtk - 4], WPA_IGTK_LEN);
 	pos = wpa_add_kde(pos, RSN_KEY_DATA_IGTK,