[xgk]dm hackery.

[Ken D'Ambrosio]

Steven W. Orr wrote:

> scenario #1: In this case, the system is not configured to run a
> graphic login. User Freddy logs in in text mode and then runs startx.
> While running his session, he locks the monitor using xlock. He walks
> away and Boris Badinoff comes along. BB types "Ctl-Alt-F1" and is
> taken to the text window that is running X. He then types Ctl-C and
> has commandeered the text login and can do anything that that account
> allows. Thank you xlock.

I used to do that during acquisitions at Cisco; I'd do a ^Z, background
it, kill xlock, and leave some esoteric message on the screen, and then
re-start xlock.  I also found that some tweaking of how you start startx
will make everything okay, something along the lines of
nohup startx & exit
They can still get to the console, but are greeted with a login prompt.

>
> scenario #2: In this case, the computer is configured to run at
> runlevel 5 and Freddy logs in on a graphic login (i.e., xdm, kdm,
> etc...). BB comes along and hits Ctl-Alt-F1 and gets taken to the
> mgetty prompt for screen1. BB (or is it me) is stuck.
>
> Is it possible for BB to be able to do anything with the machine
> (short of sticking a cd in and rebooting) in scenario 2 to get control
> of that user's account?

No.  Bear in mind a couple of things:
1) <ctl><alt><del> or some magic SysRq key sequences will allow you to
reboot, whereupon a smart enough BB will know tricks about grub and LILO
that allow him to crack the machine.  <ctl><alt><del> can be disabled in
/etc/inittab, but I believe a kernel re-compile is required for magic
SysRq stuff.

2) Physical access == ownership.  If someone can work uninterrupted for,
say, 10 minutes -- even with BIOS passwords enabled -- they can 0\/\/n
the machine.  If this is the sort of person you're truly worried about,
putting the box in a kiosk, getting a real caselock, etc., are the only
real ways to keep someone with time (but, hopefully, not bolt cutters,
Dremmels, etc.) out.

-Ken