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Date: Wed, 15 Apr 2015 11:05:58 -0500
From: Tyler Hicks <tyhicks@...onical.com>
To: Tavis Ormandy <taviso@...gle.com>
Cc: oss-security@...ts.openwall.com,
Assign a CVE Identifier <cve-assign@...re.org>,
security <security@...ntu.com>,
Stéphane Graber <stgraber@...ntu.com>
Subject: Re: Re: Problems in automatic crash analysis
frameworks
On 2015-04-14 17:16:08, Tyler Hicks wrote:
> On 2015-04-14 14:10:12, Tavis Ormandy wrote:
> > On Tue, Apr 14, 2015 at 2:08 PM, Tavis Ormandy <taviso@...gle.com> wrote:
> > > On Tue, Apr 14, 2015 at 1:35 PM, Tavis Ormandy <taviso@...gle.com> wrote:
> > >> On Tue, Apr 14, 2015 at 9:02 AM, Marc Deslauriers
> > >> <marc.deslauriers@...onical.com> wrote:
> > >>> Hi,
> > >>>
> > >>> On 2015-04-14 11:55 AM, cve-assign@...re.org wrote:
> > >>>> This is mostly a question for the persons who assigned CVE-2015-1318
> > >>>> and CVE-2015-1862. Should these CVE assignments be interpreted to
> > >>>> mean:
> > >>>>
> > >>>> CVE-2015-1318 - in Apport, an unprivileged user can use a
> > >>>> namespace-based attack because there is an execve by
> > >>>> root after a chroot into a user-specified directory
> > >>>
> > >>> Yes, I assigned CVE-2015-1318 to that specific issue in Apport.
> > >>>
> > >>> Marc.
> > >>
> > >> It looks like this is the patch for Apport:
> > >>
> > >> http://bazaar.launchpad.net/~apport-hackers/apport/trunk/revision/2943#data/apport
> > >>
> > >> It's far more complicated than I expected, and not obviously correct.
> > >> It could probably use some review, I'll think about it today.
> > >>
> > >> Tavis.
> > >
> > > Wait, my first thought is that it's not obvious to me that
> > > /proc/net/unix is guaranteed to be newline delimited, newline is a
> > > perfectly valid name in a filename, no?
> > >
> > >>>> import socket
> > >>>> socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind('test\ntest')
> > >>>> sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
> > >>>> sock.bind('/tmp/foo\nbar')
> > >>>> sock.listen(1)
> > >
> > > $ grep -A1 foo /proc/net/unix
> > > 0000000000000000: 00000002 00000000 00010000 0001 01 4772228 /tmp/foo
> > > bar
> >
> > And with complete control over this line, it seems like it's game over.
> >
> > container = lxc.Container(path[-2], real_path)
> >
> > I'm calling this re-broken.
>
> I've pointed Stéphane Graber to your analysis (and put him on cc). He's
> working on a fix.
>
> Even though it isn't clear if all of the checks added in revision 2943
> can be bypassed, it is worth coming up with another approach.
Hi Tavis - We've opened a bug to track the issue that you discovered:
https://launchpad.net/bugs/1444518
Stéphane has prepared a patch that is more resilient to a malicious
/proc/net/unix:
https://launchpadlibrarian.net/203372380/apport.diff
Any feedback that you have would be appreciated. Thanks again!
Tyler
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