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Re: [Qemu-devel] [RFC] [PATCH 0/2] Sandboxing Qemu guests with Libseccom
Daniel P. Berrange
Re: [Qemu-devel] [RFC] [PATCH 0/2] Sandboxing Qemu guests with Libseccomp
Tue, 8 May 2012 15:27:23 +0100
On Tue, May 08, 2012 at 10:10:25AM -0400, Corey Bryant wrote:
> On 05/08/2012 07:32 AM, Stefano Stabellini wrote:
> >On Tue, 8 May 2012, Daniel P. Berrange wrote:
> >>On Fri, May 04, 2012 at 04:08:36PM -0300, Eduardo Otubo wrote:
> >>>Hello all,
> >>>This is the first effort to sandboxing Qemu guests using Libseccomp. The
> >>>patches that follows are pretty simple and straightforward. I added the
> >>>options and checks to the configure script and the basic calls to
> >>>libseccomp in
> >>>the main loop at vl.c. Details of each one are in the emails of the patch
> >>>This support limits the system call footprint of the entire QEMU process
> >>>to a
> >>>limited set of syscalls, those that we know QEMU uses. The idea is to
> >>>the allowable syscalls, therefore limiting the impact that an attacked
> >>>could have on the host system.
> >>What functionality has been lost by applying this seccomp filter ? I've not
> >>looked closely at the code, but it appears as if this blocks pretty much
> >>any kind of runtime device changes. ie no hotplug of any kind will work ?
> >Right, I was wondering the same thing: open is not on the list so adding
> >a new disk shouldn't be possible.
> >Regarding Xen, most of the hypercalls go through xc_* calls that are
> >ioctls on the privcmd device. Is it possible to add ioctl to the list?
> If the whitelist is complete there should be no functionality lost
> when using seccomp with QEMU. The idea (at least at this point) is
> to disallow the system calls that QEMU doesn't use. open and ioctl
> should be added to the whitelist.
Ok. So my next question is what is the benchmark for evaluating
whether this seccomp code provides any kind of meaningful security
improvement ? AFAICT, if you were allow open(), or indeed every
syscall any QEMU feature could possibly use, then there would be
little-to-no security benefit.
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Re: [Qemu-devel] [RFC] [PATCH 0/2] Sandboxing Qemu guests with Libseccomp, Daniel P. Berrange, 2012/05/08
- [Qemu-devel] [RFC] [PATCH 1/2] Adding support for libseccomp in configure, (continued)