Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [day] [month] [year] [list]
Date: Tue, 23 Aug 2011 11:32:09 +0200
From: Sebastian Krahmer <krahmer@...e.de>
To: oss-security@...ts.openwall.com
Cc: daniel.lezcano@...e.fr
Subject: lxc + fscaps


Hi Daniel, oss-sec,

I was checking the lxc container framework for some use-cases
and found that it supports usage of containers by users.
It is installed with file caps in this case. (and a lot
of caps indeed, so actually you have almost all caps distributed
across the binaries). Particular interesting of course is
cap_dac_override and it looks like most lxc- binaries are
not really prepared to handle such cases:

linux:~> /sbin/getcap /usr/local/bin/lxc-start
/usr/local/bin/lxc-start = cap_dac_override,cap_fowner,cap_setpcap,\
cap_net_admin,cap_net_raw,cap_sys_chroot,cap_sys_admin+ep
linux:~> /usr/local/bin/lxc-start -n foo -c /etc/foo /usr/bin/id
lxc-start: failed to spawn 'foo'
linux:~> ls -la /etc/foo
-rw------- 1 jim users 0 Aug 23 09:38 /etc/foo
linux:~>

That means you have a trivial root exploit if lxc is installed for users.
There is a lxc-setuid script too but I guess that the lxc binaries
are similarily not intended for such use.
I dont know whether any distributor ships lxc with file caps, but
probably the tools need some hardening if you want to allow
lxc for users at all. I checked the latest 0.7.5 version.

regards,
Sebastian


-- 

~ perl self.pl
~ $_='print"\$_=\47$_\47;eval"';eval
~ krahmer@...e.de - SuSE Security Team

---
SUSE LINUX Products GmbH,
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 16746 (AG Nürnberg)
Maxfeldstraße 5
90409 Nürnberg
Germany

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.