WPS: As a workaround, pad zero-length device attributes

Some deployed WPS implementations fail to parse zero-length attributes.
As a workaround, send a null character if the device attribute string is
empty. This allows default values (empty strings) to be used without
interop issues.

diff --git a/src/wps/wps_dev_attr.c b/src/wps/wps_dev_attr.c
index 0d435ff..35f58d1 100644 (file)
--- a/src/wps/wps_dev_attr.c
+++ b/src/wps/wps_dev_attr.c
@@ -26,8 +26,18 @@ static int wps_build_manufacturer(struct wps_device_data *dev,
        wpa_printf(MSG_DEBUG, "WPS:  * Manufacturer");
        wpabuf_put_be16(msg, ATTR_MANUFACTURER);
        len = dev->manufacturer ? os_strlen(dev->manufacturer) : 0;
-       wpabuf_put_be16(msg, len);
-       wpabuf_put_data(msg, dev->manufacturer, len);
+       if (len == 0) {
+               /*
+                * Some deployed WPS implementations fail to parse zero-length
+                * attributes. As a workaround, send a null character if the
+                * device attribute string is empty.
+                */
+               wpabuf_put_be16(msg, 1);
+               wpabuf_put_u8(msg, '\0');
+       } else {
+               wpabuf_put_be16(msg, len);
+               wpabuf_put_data(msg, dev->manufacturer, len);
+       }
        return 0;
 }
 
@@ -39,8 +49,18 @@ static int wps_build_model_name(struct wps_device_data *dev,
        wpa_printf(MSG_DEBUG, "WPS:  * Model Name");
        wpabuf_put_be16(msg, ATTR_MODEL_NAME);
        len = dev->model_name ? os_strlen(dev->model_name) : 0;
-       wpabuf_put_be16(msg, len);
-       wpabuf_put_data(msg, dev->model_name, len);
+       if (len == 0) {
+               /*
+                * Some deployed WPS implementations fail to parse zero-length
+                * attributes. As a workaround, send a null character if the
+                * device attribute string is empty.
+                */
+               wpabuf_put_be16(msg, 1);
+               wpabuf_put_u8(msg, '\0');
+       } else {
+               wpabuf_put_be16(msg, len);
+               wpabuf_put_data(msg, dev->model_name, len);
+       }
        return 0;
 }
 
@@ -52,8 +72,18 @@ static int wps_build_model_number(struct wps_device_data *dev,
        wpa_printf(MSG_DEBUG, "WPS:  * Model Number");
        wpabuf_put_be16(msg, ATTR_MODEL_NUMBER);
        len = dev->model_number ? os_strlen(dev->model_number) : 0;
-       wpabuf_put_be16(msg, len);
-       wpabuf_put_data(msg, dev->model_number, len);
+       if (len == 0) {
+               /*
+                * Some deployed WPS implementations fail to parse zero-length
+                * attributes. As a workaround, send a null character if the
+                * device attribute string is empty.
+                */
+               wpabuf_put_be16(msg, 1);
+               wpabuf_put_u8(msg, '\0');
+       } else {
+               wpabuf_put_be16(msg, len);
+               wpabuf_put_data(msg, dev->model_number, len);
+       }
        return 0;
 }
 
@@ -65,8 +95,18 @@ static int wps_build_serial_number(struct wps_device_data *dev,
        wpa_printf(MSG_DEBUG, "WPS:  * Serial Number");
        wpabuf_put_be16(msg, ATTR_SERIAL_NUMBER);
        len = dev->serial_number ? os_strlen(dev->serial_number) : 0;
-       wpabuf_put_be16(msg, len);
-       wpabuf_put_data(msg, dev->serial_number, len);
+       if (len == 0) {
+               /*
+                * Some deployed WPS implementations fail to parse zero-length
+                * attributes. As a workaround, send a null character if the
+                * device attribute string is empty.
+                */
+               wpabuf_put_be16(msg, 1);
+               wpabuf_put_u8(msg, '\0');
+       } else {
+               wpabuf_put_be16(msg, len);
+               wpabuf_put_data(msg, dev->serial_number, len);
+       }
        return 0;
 }
 
@@ -91,8 +131,18 @@ static int wps_build_dev_name(struct wps_device_data *dev, struct wpabuf *msg)
        wpa_printf(MSG_DEBUG, "WPS:  * Device Name");
        wpabuf_put_be16(msg, ATTR_DEV_NAME);
        len = dev->device_name ? os_strlen(dev->device_name) : 0;
-       wpabuf_put_be16(msg, len);
-       wpabuf_put_data(msg, dev->device_name, len);
+       if (len == 0) {
+               /*
+                * Some deployed WPS implementations fail to parse zero-length
+                * attributes. As a workaround, send a null character if the
+                * device attribute string is empty.
+                */
+               wpabuf_put_be16(msg, 1);
+               wpabuf_put_u8(msg, '\0');
+       } else {
+               wpabuf_put_be16(msg, len);
+               wpabuf_put_data(msg, dev->device_name, len);
+       }
        return 0;
 }