Hiding Shutdown/reboot in logout dialog and possible security issue

Anders Bruun Olsen abo at dsl.dk
Thu Jul 10 12:21:32 UTC 2014


I am looking to build a new terminal server for remote desktops which will
be accessed through NoMachine Enterprise. Lubuntu and LXDE looks like a
nice fit, but I have run into a couple of issues.

I have a default install of Lubuntu 14.04 64-bit. I have created a
non-privileged user (no sudo rights). I have also installed NoMachine
Enterprise Server. First thing I discovered was what I would almost call a
security issue. When my non-privileged user is logged in remotely (with
Nomachine Enterprise Client), choosing shutdown in the logout dialog
actually does shut down the server. How can this user shut down the server,
without root access? I found out, that if I ensure lightdm isn't running
(nobody will login locally), my unprivileged user can't shut down the
server, but will be asked for the password to a privileged user, so I guess
this is an issue with lightdm. Is this really intended behavior?

Next up, I would like to hide the shutdown and reboot buttons in the logout
dialog. The only way I have been able to find by searching, is to actually
change the source code for lxsession-logout and recompile. Is there really
no other way to hide those buttons?

Anders Bruun Olsen
Det Danske Sprog- og Litteraturselskab
(Society for Danish Language and Literature)
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