From 8c07fa9eda13e835f3f968b2e1c9a8be3a851ff9 Mon Sep 17 00:00:00 2001
From: Jouni Malinen <j@w1.fi>
Date: Thu, 29 Aug 2019 11:52:04 +0300
Subject: [PATCH] AP: Silently ignore management frame from unexpected source
 address

Do not process any received Management frames with unexpected/invalid SA
so that we do not add any state for unexpected STA addresses or end up
sending out frames to unexpected destination. This prevents unexpected
sequences where an unprotected frame might end up causing the AP to send
out a response to another device and that other device processing the
unexpected response.

In particular, this prevents some potential denial of service cases
where the unexpected response frame from the AP might result in a
connected station dropping its association.

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

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[Retrieved from:
https://w1.fi/security/2019-7/0001-AP-Silently-ignore-management-frame-from-unexpected-.patch]
---
 src/ap/drv_callbacks.c | 13 +++++++++++++
 src/ap/ieee802_11.c    | 12 ++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/src/ap/drv_callbacks.c b/src/ap/drv_callbacks.c
index 31587685fe3b..34ca379edc3d 100644
--- a/src/ap/drv_callbacks.c
+++ b/src/ap/drv_callbacks.c
@@ -131,6 +131,19 @@ int hostapd_notif_assoc(struct hostapd_data *hapd, const u8 *addr,
 			   "hostapd_notif_assoc: Skip event with no address");
 		return -1;
 	}
+
+	if (is_multicast_ether_addr(addr) ||
+	    is_zero_ether_addr(addr) ||
+	    os_memcmp(addr, hapd->own_addr, ETH_ALEN) == 0) {
+		/* Do not process any frames with unexpected/invalid SA so that
+		 * we do not add any state for unexpected STA addresses or end
+		 * up sending out frames to unexpected destination. */
+		wpa_printf(MSG_DEBUG, "%s: Invalid SA=" MACSTR
+			   " in received indication - ignore this indication silently",
+			   __func__, MAC2STR(addr));
+		return 0;
+	}
+
 	random_add_randomness(addr, ETH_ALEN);
 
 	hostapd_logger(hapd, addr, HOSTAPD_MODULE_IEEE80211,
diff --git a/src/ap/ieee802_11.c b/src/ap/ieee802_11.c
index c85a28db44b7..e7065372e158 100644
--- a/src/ap/ieee802_11.c
+++ b/src/ap/ieee802_11.c
@@ -4626,6 +4626,18 @@ int ieee802_11_mgmt(struct hostapd_data *hapd, const u8 *buf, size_t len,
 	fc = le_to_host16(mgmt->frame_control);
 	stype = WLAN_FC_GET_STYPE(fc);
 
+	if (is_multicast_ether_addr(mgmt->sa) ||
+	    is_zero_ether_addr(mgmt->sa) ||
+	    os_memcmp(mgmt->sa, hapd->own_addr, ETH_ALEN) == 0) {
+		/* Do not process any frames with unexpected/invalid SA so that
+		 * we do not add any state for unexpected STA addresses or end
+		 * up sending out frames to unexpected destination. */
+		wpa_printf(MSG_DEBUG, "MGMT: Invalid SA=" MACSTR
+			   " in received frame - ignore this frame silently",
+			   MAC2STR(mgmt->sa));
+		return 0;
+	}
+
 	if (stype == WLAN_FC_STYPE_BEACON) {
 		handle_beacon(hapd, mgmt, len, fi);
 		return 1;
-- 
2.20.1