[PATCH] greeter ignores 'autologin-session'

[Roland Tapken]

When lightdm is configured with with 'autologin-user-timeout' > 0
any configured 'autologin-session' will be ignored and the autologin-user
will be logged in with the last used session instead (read from
/var/lib/lightdm/.cache/lightdm-gtk-greeter/state).

Example 1:

    autologin-user=foo
    autologin-user-timeout=0
    autologin-session=fluxbox

This works as intended, as the autologin is handled directly by 'lightdm'.

Example 2:

    autologin-user=foo
    autologin-user-timeout=10
    autologin-session=fluxbox

Now the autologin must be handled by the greeter, and this results
into starting the (last) selected session, which must not be the
same as the configured 'autologin-session'.

The fix is to explicitly set the session before doing the autologin.
But since the greeter hints doesn't give us any information about the
'autologin-session' a second patch to lightdm is also required).
However, since the attached patch to lightdm-gtk-greeter will just
keep the current behaviour if the second patch hasn't been applied
to lightdm it would be save to merge this anytime.

[Roland Tapken (cybso)]

Complementary bug report for lightdm:

https://bugs.launchpad.net/lightdm/+bug/1707187

[Roland Tapken (cybso)]

This might even be a security problem if the autologin user isn't expected to start with anything else but the configured autologin session, e.g. on a public kiosk system where the kiosk mode is automatically (re-)started after a few seconds.

[Roland Tapken (cybso)]

Nobody wants to have a look into this, despite of a working patch given?

[Robert Ancell (robert-ancell)]

This may be a bug in LightDM if the GTK+ greeter doesn't explicitly set the session for autologins, see bug 1718565.

[Sean Davis (bluesabre)]

Thanks for the patch! Applied to trunk.