Re: [libvirt] Notes from the KVM Forum relevant to libvirt

On Tue, Aug 23, 2011 at 4:31 PM, Daniel P. Berrange <berrange(a)redhat.com&gt; wrote: > On Tue, Aug 23, 2011 at 04:24:46PM +0100, Stefan Hajnoczi wrote: >> On Tue, Aug 23, 2011 at 12:15 PM, Daniel P. Berrange >> <berrange(a)redhat.com&gt; wrote: >> > I was at the KVM Forum / LinuxCon last week and there were many >> > interesting things discussed which are relevant to ongoing libvirt >> > development. Here was the list that caught my attention. If I have >> > missed any, fill in the gaps.... >> > >> >  - Sandbox/container KVM.  The Solaris port of KVM puts QEMU inside >> >   a zone so that an exploit of QEMU can't escape into the full OS. >> >   Containers are Linux's parallel of Zones, and while not nearly as >> >   secure yet, it would still be worth using more containers support >> >   to confine QEMU. >> >> Can you elaborate on why Linux containers are "not nearly as secure" >> [as Solaris Zones]? > > Mostly because the Linux namespace functionality is far from complete, > notably lacking proper UID/GID/capability separation, and UID/GID > virtualization wrt filesystems. The longer answer is here: > >   https://wiki.ubuntu.com/UserNamespace > > So at this time you can't build a secure container on Linux, relying > just on DAC alone. You have to add in a MAC layer ontop of the container > to get full security benefits, which obviously defeats the point of > using the container as a backup for failure in the MAC layer. Thanks, that is interesting. I still don't understand why that is a problem. Linux containers (lxc) uses a different pid namespace (no ptrace worries), file system root (restricted to a subdirectory tree), forbids most device nodes, etc. Why does the user namespace matter for security in this case?

I think it matters when giving multiple containers access to the same file system. Is that what you'd like to do for libvirt?