Re: [gdm-list] Face recognition for linux login ...

[Brian Cameron <Brian Cameron Sun COM>]

José:

All gdm GUI's run as the "gdm" user (refer to User/Group settings
in the GDM configuration).  The default values are gdm:gdm.

Note that GDM saves it's Xauthority cookies in /var/lib/gdm
(some distros may modify the servauthdir directory, but this is
the normal default for most distros so you shouldn't hardcode
this directory and make it configurable for your PAM module).
So you should be able to grab the Xauth cookie from here.  I
believe the file named .cookie is the cookie that the root user
can use when GDM is showing the GUI.

Since your PAM module code should be running as root, grabbing
and using the Xauth key for the gdm user should be possible to
do.

I hope this helps.  Let me know.

Brian

> First of all I have to introduce myself, I'm a Computer Vision
> researcher interested in human computer interaction. And
> I apologize if this is a bit off-topic (although it could not be).
>
> Some time ago I asked for advice in the gdm-list about
> implementing face recognition for linux login on gdm:
>
> http://mail.gnome.org/archives/gdm-list/2004-September/msg00001.html
>
> And Bob Doolittle sugested to implement such a thing as a PAM module:
>
> http://mail.gnome.org/archives/gdm-list/2004-September/msg00016.html
>
> Anyhow, we are now developing the face recognition driven linux login
> (on a master thesis) using a PAM module. The problem we have now is
> how to deal with the Xserver security (when using Xauthority) in order 
> to show
> a graphical window with the video aside the gdm login window.
>
> What we are doing is to fork a process in the PAM module to run
> the face recognition loop on the the child process. And when we try to show
> a simple graphical window the X server don't allow us to connect ... we
> are not even logged into the system and we are not using the rigth 
> Xauthority
> magic cookie !!
>
> And the question is, what is the unix user from which the gdm is running?
> what can we do to launch a window from a process aside the gdm login
> window?
>
> Please, answer me directly as I'm not in the list.
>
> Many thanks for any advice.
> Jose M. Buenaposada.