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Date: Fri, 20 Nov 2015 13:26:53 -0500 (EST)
From: cve-assign@...re.org
To: thoger@...hat.com
Cc: cve-assign@...re.org, oss-security@...ts.openwall.com
Subject: Re: LXDM X authentication issues

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> LXDM before 0.5.2 did not start X server with -auth parameter.
> Therefore any user able to connect to it (typically all local users)
> would have their X connections accepted.  The issue was fixed via:
> 
> http://git.lxde.org/gitweb/?p=lxde/lxdm.git;a=commit;h=e8f387089e241360bdc6955d3e479450722dcea3

>> pass xauth file to xserver command

It appears that this is the major finding. Use CVE-2015-8308.


> LXDM also defaults to not restarting X server between sessions, and
> does not change authentication cookies or remove xhost authorizations.
> This allows local user to be able to connect to the X server after they
> logged out. The 'reset' option in lxdm.conf controls whether X server
> is restarted on session user close.

This possibly can be included in CVE but, if so, the CVE ID would be
different. Is there any other information, e.g., why was there a
decision to make reset an optional behavior rather than a required
behavior? Is there a possible attack by a different local user, or is
the relevant attack that someone could steal the computer and recover
the authentication cookies (possibly violating an expectation of the
legitimate user who believed they were safely logged out)? Is the
behavior different from all major display managers?
http://wiki.lxde.org/en/LXDM says "LXDM is the lightweight display
manager ..." -- is the design tradeoff possibly different on a
low-resource machine where it's very expensive to restart the X server?

- -- 
CVE assignment team, MITRE CVE Numbering Authority
M/S M300
202 Burlington Road, Bedford, MA 01730 USA
[ PGP key available through http://cve.mitre.org/cve/request_id.html ]
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