WPS: Add special AP Setup Locked mode to allow read only ER

ap_setup_locked=2 can now be used to enable a special mode where
WPS ER can learn the current AP settings, but cannot change then.
In other words, the protocol is allowed to continue past M2, but
is stopped at M7 when AP is in this mode. WPS IE does not
advertise AP Setup Locked in this case to avoid interoperability
issues.

In wpa_supplicant, use ap_setup_locked=2 by default. Since the AP PIN
is disabled by default, this does not enable any new functionality
automatically. To allow the read-only ER to go through the protocol,
wps_ap_pin command needs to be used to enable the AP PIN.

src/wps/wps_enrollee.c

@@ -839,8 +839,15 @@ static enum wps_process_res wps_process_m2(struct wps_data *wps,
 		return WPS_CONTINUE;
 	}
 
+	/*
+	 * Stop here on an AP as an Enrollee if AP Setup is locked unless the
+	 * special locked mode is used to allow protocol run up to M7 in order
+	 * to support external Registrars that only learn the current AP
+	 * configuration without changing it.
+	 */
 	if (wps->wps->ap &&
-	    (wps->wps->ap_setup_locked || wps->dev_password == NULL)) {
+	    ((wps->wps->ap_setup_locked && wps->wps->ap_setup_locked != 2) ||
+	     wps->dev_password == NULL)) {
 		wpa_printf(MSG_DEBUG, "WPS: AP Setup is locked - refuse "
 			   "registration of a new Registrar");
 		wps->config_error = WPS_CFG_SETUP_LOCKED;
@@ -1045,6 +1052,19 @@ static enum wps_process_res wps_process_m8(struct wps_data *wps,
 		return WPS_CONTINUE;
 	}
 
+	if (wps->wps->ap && wps->wps->ap_setup_locked) {
+		/*
+		 * Stop here if special ap_setup_locked == 2 mode allowed the
+		 * protocol to continue beyond M2. This allows ER to learn the
+		 * current AP settings without changing them.
+		 */
+		wpa_printf(MSG_DEBUG, "WPS: AP Setup is locked - refuse "
+			   "registration of a new Registrar");
+		wps->config_error = WPS_CFG_SETUP_LOCKED;
+		wps->state = SEND_WSC_NACK;
+		return WPS_CONTINUE;
+	}
+
 	decrypted = wps_decrypt_encr_settings(wps, attr->encr_settings,
 					      attr->encr_settings_len);
 	if (decrypted == NULL) {

src/wps/wps_registrar.c

@@ -392,7 +392,7 @@ static void wps_registrar_free_pending_m2(struct wps_context *wps)
 static int wps_build_ap_setup_locked(struct wps_context *wps,
 				     struct wpabuf *msg)
 {
-	if (wps->ap_setup_locked) {
+	if (wps->ap_setup_locked && wps->ap_setup_locked != 2) {
 		wpa_printf(MSG_DEBUG, "WPS:  * AP Setup Locked");
 		wpabuf_put_be16(msg, ATTR_AP_SETUP_LOCKED);
 		wpabuf_put_be16(msg, 1);

wpa_supplicant/ap.c

@@ -161,7 +161,7 @@ static int wpa_supplicant_conf_ap(struct wpa_supplicant *wpa_s,
 	 */
 	bss->eap_server = 1;
 	bss->wps_state = 2;
-	bss->ap_setup_locked = 1;
+	bss->ap_setup_locked = 2;
 	if (wpa_s->conf->config_methods)
 		bss->config_methods = os_strdup(wpa_s->conf->config_methods);
 	if (wpa_s->conf->device_type)