Re: FW: Possible flaw in XFree?

From: Michael Jennings (mej@kainx.org)
Date: 06/30/02


Date: Sat, 29 Jun 2002 18:21:38 -0400
From: Michael Jennings <mej@kainx.org>
To: vuln-dev@securityfocus.com

On Saturday, 29 June 2002, at 16:38:03 (-0700),
Nick Lange wrote:

> Which once again leads us back to a point that perhaps more people
> would agree with, the option should *not* be enabled by default
> precisely for the annoyance/information loss factor. First off, any
> user can kill off any other user's session (provided they have
> access to the hardware running the session) which can lead to
> potential data loss for any running applications. This could be
> done out of malice, etc.

If we're talking about Ctrl-Alt-Backspace killing an X session on
XFree86 started by startx or the like, then we're talking about an X
session running on the main console of a system. Given that fact,
said malicious user could just as easily power off the system. Or
unplug it. Or any number of other actions allowed by physical access
to a workstation/server.

This all gets back to the "security of a system to which an attacker
has physical access" thread that has been hashed out many times
before. I suggest dropping this silliness and consulting a mailing
list archive near you.

If a user starts X using startx and fails to employ the "exec"
technique mentioned earlier, this user should not walk away from
his/her terminal. If this user does so, this user is an idiot. The
Zap key sequence is a good feature, and the rest of us should not be
made to suffer on account of the idiocy of the few.

Michael

-- 
Michael Jennings (a.k.a. KainX)  http://www.kainx.org/  <mej@kainx.org>
n+1, Inc., http://www.nplus1.net/         Author, Eterm (www.eterm.org)
-----------------------------------------------------------------------
 "I have gotten into the habit of recording important meetings.  One
  never knows when an inconvenient truth will fall between the cracks
  and vanish."               -- Ambassador Londo Mollari, Babylon Five



Relevant Pages

  • Re: Removing System Consoles from Fedora
    ... How does one make a login attempt without intending to? ... unauthorized persons who might otherwise have physical access to the ... How is that different when logging on to a X session? ... access to a host, how is removing console sessions going to stop me ...
    (Fedora)
  • RE: How reliable is CDO?
    ... You get null reference exception on session object, because you called logon and logoff so frequently that leads to Logon function failure. ... defense code to protect ourselves from this scenario, so I suggest you add code to check if Outbox is null or not, or move following 3 lines out of while loop. ...
    (microsoft.public.win32.programmer.messaging)
  • Re: redirection if session object is nothing
    ... How do you actually check whether the Session has expired in ... if you do a response.redirect in this event, that leads ... to an infinite state, a kind of infinite loop trying to do multiple ...
    (microsoft.public.dotnet.framework.aspnet)