Config Methods for Probe Response

Jouni Malinen j
Fri Mar 30 07:47:22 PDT 2012

On Fri, Mar 30, 2012 at 08:47:56PM +0900, Takashi Kawamoto wrote:
> I have a question for WPS implementation of hostapd.
> I can't understand why hostapd gets rid of Push Button related 
> attributes from Config Methods when building Probe Response.

That's explained in the comment there:

> [src/wps/wps_registrar.c]
> static int wps_build_probe_config_methods(struct wps_registrar *reg,
> 					  struct wpabuf *msg)
> {
> 	/*
> 	 * These are the methods that the AP supports as an Enrollee for adding
> 	 * external Registrars.
> 	 */
> 	methods = reg->wps->config_methods & ~WPS_CONFIG_PUSHBUTTON;

> Do anyone know which description in specification this implementation 
> conforms to? There seems to be no description which says Probe Response 
> should not include WPS IE with Config Methods without these attributes.

That comment is based on WSC v2.0 8.2.5 Probe Response table
("Configuration Methods corresponds to the methods the AP supports as an
Enrollee for adding external Registrars") and PushButton is not allowed
for that purpose as noted in 11.1 ("AP MUST NOT support using PBC to add
an external Registrar").

Jouni Malinen                                            PGP id EFC895FA

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