oss-security - Re: CVE request: lightdm-gtk-greeter - local DOS due to NULL pointer dereference

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Message-ID: <20140107200954.GB6284@scapa.corsac.net>
Date: Tue, 7 Jan 2014 21:09:54 +0100
From: Yves-Alexis Perez <corsac@...ian.org>
To: oss-security@...ts.openwall.com
Cc: LightDM Mailing List <lightdm@...ts.freedesktop.org>,
	Robert Ancell <robert.ancell@...il.com>
Subject: Re: CVE request: lightdm-gtk-greeter - local DOS due
 to NULL pointer dereference

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On Tue, Jan 07, 2014 at 11:47:31AM +0100, Guido Berhoerster wrote:
> Hi,
> 
> an openSUSE user discovered that it is trivial to crash
> lightdm-gtk-greeter by entering an empty username due to a NULL
> pointer dereference. When a greeter crashes the lightdm daemon
> exits.
> This constitutes a local denial of service which can be triggered
> by any unprivileged attacker requiring the intervention of an
> administrator to restart lightdm. It affects all versions of
> lightdm-gtk-greeter.

I've just checked in Debian Wheezy (lightdm 1.2.2, lightdm-gtk-greeter
1.1.6), and a crashed greeter (because of that NULL username) doesn't
lead to a lightdm exit.

I'm not sure what was the reason for changing that (if there's a
reason), but it might be a problem in itself.

Regards,
- -- 
Yves-Alexis Perez
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