wps_pbc "alert" event?

John Finley john.finley at gmail.com
Wed Sep 17 22:06:23 EDT 2014


Hi,

I have my AP and device set up so at the moment I can do "wpa_cli wps_pbc"
and "hostapd_cli wps_pbc", and the pairing works as expected. The next step
I'm trying to get through might be a little odd.

What I want is for the button push on the device (wpa_cli wps_pbc) to be
noticed _automatically_ on the AP, such that I can prompt an operator to
accept the pairing or not. In other words, the only user-initiated action
to start a pairing will be the button push on the device, then software
should lead the user through the rest of it. Security is secondary to
simplicity.

So, I am trying to figure out how, on the AP side, I can get some kind of
event when the device tries to pair. The device does not know the SSID of
the AP - it is going to be quite trusting as far as whom it will pair with.

I attached an "action" to hostapd_cli, i.e. "hostapd_cli -a/my/script", and
all it does is log what it sees to a file. I don't see anything interesting
that comes out as an event when I initiate pairing on the device side. When
I initiate pairing on _both_ sides, I see events corresponding to the
pairing, but what I was hoping for is some kind of "please pair with me"
popping out when the device tries to pair.

Starting to grope around in the dark, I added some output on the AP side in
wps_hostapd.c::hostapd_wps_probe_req_rx, and can see probes coming in from
the device when I push the button, but they are dropped when
ieee802_11_vendor_ie_concat returns NULL. I have no idea if I'm in an
interesting place there or not.

So questions:
* Whether this is a bad idea or not, does it sound possible? (Either out of
the box, or with some tweaks to the code.)
* Is there information already available at the hostapd level that would
indicate there is a device out there that is trying to do wps_pbc pairing?
Some way to enable more "events"?
* If so, is there a way to get it sent to hostapd_cli so I can get an event?
* If not, is there some mechanism in wpa_supplicant that would let me do
something like append my own ie to a probe or anything special like that,
that would let me get some kind of signal from the device to hostapd so I
can proceed on the AP side?

I do not mind changing things if needed, but would like to start with a
feeling that there will be success in the end.

Sorry for the length. I do not mean to get free design input (or criticism
:). I'm just trying to figure out whether I need to start modifying code,
or if it already does what I want and I am just missing it.

Thanks,
John
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