Hiding Shutdown/reboot in logout dialog and possible security issue

Thu Jul 10 20:12:45 UTC 2014

Hi Nio,

The problem with going to the "real server guys" is that terminal servers
are sort of halfway between the server/desktop divide, so some things fall
on the desktop side, and some on the server side. This specific issue is
how to get lxsession-logout to not show the shutdown/reboot buttons, which
I would deem to belong on the desktop side of things. I may need to try the
LXDE guys directly if nobody is able to help here. I just thought I would
try the distro specific mailing list before going to the program specific
one :)

2014-07-10 18:13 GMT+02:00 Nio Wiklund <nio.wiklund at gmail.com>:

> Hi Anders,
>
> You can also ask in the Server Platforms Forum at
>
> http://ubuntuforums.org/forumdisplay.php?f=339
>
> where some real server guys will probably help you.
>
> Best regards/Nio
>
> 2014-07-10 16:07, Anders Bruun Olsen skrev:
> > Hi,
> >
> > Ehm.. a graphical desktop environment is sort of the point of a terminal
> > server. It provides remote desktops to users. It isn't for running a
> > graphical desktop on a locally attached screen :)
> > The issue here is two-fold:
> >
> > 1. If the graphical login-manager (lightdm) is running, all users who
> > login to a desktop remotely can shut down the entire machine. This is
> > not a good thing, but can be circumvented by killing off lightdm. This
> > is fine when you use something like Nomachine, which takes care of
> > spinning up a desktop session. But with LTSP you would probably run into
> > problems, since it depends on having a DM handling login and spinning up
> > desktop sessions. Although lightdm may be intelligent enough to actually
> > know when users are remote on LTSP, and will refuse to allow them to
> > shutdown the machine without proper rights. This may be a none-issue for
> > LTSP. I don't use LTSP, so I can't say for sure. With Nomachine it is an
> > issue.
> >
> > 2. Users can get confused when sitting in front of a thin client running
> > the nomachine client. They want to shut down for the day and choose the
> > shutdown menu on their Lubuntu desktop. Here the correct process is to
> > choose logout and then shut down the thin client when logout has
> > happened. But users don't usually think about the fact that this
> > connects to a remote desktop, so pressing the shutdown button in the
> > shutdown menu seems logical. They want to shut down their local machine.
> > Unfortunately that button is meant to shut down the terminal server.
> > When that does not work (they get the "access denied" message), most
> > users get confused and go ask it-support for help. I just want to
> > prevent this confusion, if possible :)
> >
> >
> >
> > 2014-07-10 14:53 GMT+02:00 Nio Wiklund <nio.wiklund at gmail.com
> > <mailto:nio.wiklund at gmail.com>>:
> >
> >     2014-07-10 14:21, Anders Bruun Olsen skrev:
> >     > Hi,
> >     >
> >     > 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?
> >
> >     I think it is made for desktop installation, where any user should be
> >     able to shut down the computer. But it is not suitable for a server.
> I'm
> >     glad you found a way to stop shutting it down with superuser
> privileges.
> >
> >     But, many people will discourage the use of a graphical desktop
> >     environment for a server. Do you really need it? Or maybe a simple
> >     window manager like Openbox or Fluxbox would do?
> >
> >     >
> >     > 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?
> >
> >     Sorry, I don't know this, but think other people can help you with
> it.
> >
> >     > --
> >     > Anders Bruun Olsen
> >     > It-ansvarlig
> >     > Det Danske Sprog- og Litteraturselskab
> >     > (Society for Danish Language and Literature)
> >     >
> >     >
> >
> >
> >     --
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> >
> >
> >
> >
> > --
> > Anders Bruun Olsen
> > It-ansvarlig
> > Det Danske Sprog- og Litteraturselskab
> > (Society for Danish Language and Literature)
>
>

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