[Lxc-users] Mitigating LXC Container Evasion?

[Michael H. Warfield]

On Sun, 2011-07-31 at 23:02 +0200, Olivier Mauras wrote: 
> That's where MAC system comes handy.

Was just reading up on that from your earlier post.  Very nice.  I see I
have some reading a research to do.  I posted a URL to an IBM paper in a
reply to your earlier post.

> -- 
> Sent from my Android phone with K-9 Mail. Please excuse my brevity.
> 
> "Michael H. Warfield" <mhw at WittsEnd.com> wrote:
> 
> On Sun, 2011-07-31 at 17:59 +0200, Robert Kawecki wrote: 
> > Dnia 2011-07-30, sob o godzinie 21:10 -0400, Matthew Franz pisze:
> > > Had seen some previous discussions before, but are there any ways to
> > > mitigate this design vulnerability?
> > > 
> > > http://blog.bofh.it/debian/id_413
> > > 
> > > Are there any workarounds?
> > > 
> > > Thanks,
> > > 
> > > - mdf
> > > 
> > 
> > The blog post explicitly mounts /sys... Why would you want your
> > container to even have the capability to mount anything?
> 
> Let's see... Where shall we start. If you're containerizing a
> "machine" or full system there's a laundry list of reasons you would
> want to. Maybe you want to mount an image, like a CD image or maybe an
> encrypted file system? Then, there's a variety of fuse file systems you
> might want access to for a variety of reasons.
> 
> Maybe you want to run a service, like bind's named in a bind mounted
> chrooted environment (default for running name servers on Fedora for
> some time now:
> 
> /var/named on /var/named/chroot/var/named type none (rw,bind)
> /var/named/etc/named.conf on /var/named/chroot/etc/named.conf type none (rw,bind)
> /etc/named.rfc1912.zones on /var/named/chroot/etc/named.rfc1912.zones type none (rw,bind)
> /etc/rndc.conf on /var/named/chroot/etc/rndc.conf type none (rw,bind)
> /etc/rndc.key on /var/named/chroot/etc/rndc.key type none (rw,bind)
> /usr/lib/bind on /var/named/chroot/usr/lib/bind type none (rw,bind)
> /etc/named.iscdlv.key on /var/named/chroot/etc/named.iscdlv.key type none (rw,bind)
> /etc/named.root.key on /var/named/chroot/etc/named.root.key type none (rw,bind)
> 
> That gets done by "service named start".
> 
> > If possible, drop CAP_SYS_ADMIN.
> 
> That's been proposed as a workaround for some of the remount problems we
> have to where a partition is suppose to be mounted ro but the container
> can remount it rw. I've actually tried that trick. Yeah, that was an
> epic failure.
> 
> Generally not possible in a generalized system container. Way too many
> things are impacted by CAP_SYS_ADMIN. Disabling that, you can't even
> set your own hostname in the container. You can't set crypto keys
> either. That's a sledge hammer approach that won't work in many if not
> most system containers. A simply application container? It might work
> in, depending on the application.
> 
> Check out "man capabilities" and scroll down to CAP_SYS_ADMIN and look
> at that laundry list under it (and I'm not totally sure that list is
> comprehensive in the man page either) and honestly say there are not
> reasons for a container wanting to do at least one or two of them (even
> given that every container I have sets its own hostname).
> 
> Gotta be a better answer than that.
> 
> Regards,
> Mike
> -- 
> Michael H. Warfield (AI4NB) | (770) 985-6132 | mhw at WittsEnd.com
> /\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/
> NIC whois: MHW9 | An optimist believes we live in the best of all
> PGP Key: 0x674627FF | possible worlds. A pessimist is sure of it!
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-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of it!
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