WPS UPnP: Do not allow event subscriptions with URLs to other networks

The UPnP Device Architecture 2.0 specification errata ("UDA errata
16-04-2020.docx") addresses a problem with notifications being allowed
to go out to other domains by disallowing such cases. Do such filtering
for the notification callback URLs to avoid undesired connections to
external networks based on subscriptions that any device in the local
network could request when WPS support for external registrars is
enabled (the upnp_iface parameter in hostapd configuration).

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

src/wps/wps_er.c

@@ -1298,7 +1298,7 @@ wps_er_init(struct wps_context *wps, const char *ifname, const char *filter)
 			   "with %s", filter);
 	}
 	if (get_netif_info(er->ifname, &er->ip_addr, &er->ip_addr_text,
-			   er->mac_addr)) {
+			   NULL, er->mac_addr)) {
 		wpa_printf(MSG_INFO, "WPS UPnP: Could not get IP/MAC address "
 			   "for %s. Does it have IP address?", er->ifname);
 		wps_er_deinit(er, NULL, NULL);

src/wps/wps_upnp.c

@@ -303,6 +303,14 @@ static void subscr_addr_free_all(struct subscription *s)
 }
 
 
+static int local_network_addr(struct upnp_wps_device_sm *sm,
+			      struct sockaddr_in *addr)
+{
+	return (addr->sin_addr.s_addr & sm->netmask.s_addr) ==
+		(sm->ip_addr & sm->netmask.s_addr);
+}
+
+
 /* subscr_addr_add_url -- add address(es) for one url to subscription */
 static void subscr_addr_add_url(struct subscription *s, const char *url,
 				size_t url_len)
@@ -381,6 +389,7 @@ static void subscr_addr_add_url(struct subscription *s, const char *url,
 
 	for (rp = result; rp; rp = rp->ai_next) {
 		struct subscr_addr *a;
+		struct sockaddr_in *addr = (struct sockaddr_in *) rp->ai_addr;
 
 		/* Limit no. of address to avoid denial of service attack */
 		if (dl_list_len(&s->addr_list) >= MAX_ADDR_PER_SUBSCRIPTION) {
@@ -389,6 +398,13 @@ static void subscr_addr_add_url(struct subscription *s, const char *url,
 			break;
 		}
 
+		if (!local_network_addr(s->sm, addr)) {
+			wpa_printf(MSG_INFO,
+				   "WPS UPnP: Ignore a delivery URL that points to another network %s",
+				   inet_ntoa(addr->sin_addr));
+			continue;
+		}
+
 		a = os_zalloc(sizeof(*a) + alloc_len);
 		if (a == NULL)
 			break;
@@ -890,11 +906,12 @@ static int eth_get(const char *device, u8 ea[ETH_ALEN])
  * @net_if: Selected network interface name
  * @ip_addr: Buffer for returning IP address in network byte order
  * @ip_addr_text: Buffer for returning a pointer to allocated IP address text
+ * @netmask: Buffer for returning netmask or %NULL if not needed
  * @mac: Buffer for returning MAC address
  * Returns: 0 on success, -1 on failure
  */
 int get_netif_info(const char *net_if, unsigned *ip_addr, char **ip_addr_text,
-		   u8 mac[ETH_ALEN])
+		   struct in_addr *netmask, u8 mac[ETH_ALEN])
 {
 	struct ifreq req;
 	int sock = -1;
@@ -920,6 +937,19 @@ int get_netif_info(const char *net_if, unsigned *ip_addr, char **ip_addr_text,
 	in_addr.s_addr = *ip_addr;
 	os_snprintf(*ip_addr_text, 16, "%s", inet_ntoa(in_addr));
 
+	if (netmask) {
+		os_memset(&req, 0, sizeof(req));
+		os_strlcpy(req.ifr_name, net_if, sizeof(req.ifr_name));
+		if (ioctl(sock, SIOCGIFNETMASK, &req) < 0) {
+			wpa_printf(MSG_ERROR,
+				   "WPS UPnP: SIOCGIFNETMASK failed: %d (%s)",
+				   errno, strerror(errno));
+			goto fail;
+		}
+		addr = (struct sockaddr_in *) &req.ifr_netmask;
+		netmask->s_addr = addr->sin_addr.s_addr;
+	}
+
 #ifdef __linux__
 	os_strlcpy(req.ifr_name, net_if, sizeof(req.ifr_name));
 	if (ioctl(sock, SIOCGIFHWADDR, &req) < 0) {
@@ -1026,11 +1056,15 @@ static int upnp_wps_device_start(struct upnp_wps_device_sm *sm, char *net_if)
 
 	/* Determine which IP and mac address we're using */
 	if (get_netif_info(net_if, &sm->ip_addr, &sm->ip_addr_text,
-			   sm->mac_addr)) {
+			   &sm->netmask, sm->mac_addr)) {
 		wpa_printf(MSG_INFO, "WPS UPnP: Could not get IP/MAC address "
 			   "for %s. Does it have IP address?", net_if);
 		goto fail;
 	}
+	wpa_printf(MSG_DEBUG, "WPS UPnP: Local IP address %s netmask %s hwaddr "
+		   MACSTR,
+		   sm->ip_addr_text, inet_ntoa(sm->netmask),
+		   MAC2STR(sm->mac_addr));
 
 	/* Listen for incoming TCP connections so that others
 	 * can fetch our "xml files" from us.

src/wps/wps_upnp_i.h

@@ -128,6 +128,7 @@ struct upnp_wps_device_sm {
 	u8 mac_addr[ETH_ALEN]; /* mac addr of network i.f. we use */
 	char *ip_addr_text; /* IP address of network i.f. we use */
 	unsigned ip_addr; /* IP address of network i.f. we use (host order) */
+	struct in_addr netmask;
 	int multicast_sd; /* send multicast messages over this socket */
 	int ssdp_sd; /* receive discovery UPD packets on socket */
 	int ssdp_sd_registered; /* nonzero if we must unregister */
@@ -158,7 +159,7 @@ struct subscription * subscription_find(struct upnp_wps_device_sm *sm,
 					const u8 uuid[UUID_LEN]);
 void subscr_addr_delete(struct subscr_addr *a);
 int get_netif_info(const char *net_if, unsigned *ip_addr, char **ip_addr_text,
-		   u8 mac[ETH_ALEN]);
+		   struct in_addr *netmask, u8 mac[ETH_ALEN]);
 
 /* wps_upnp_ssdp.c */
 void msearchreply_state_machine_stop(struct advertisement_state_machine *a);