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Re: [Qemu-devel] [libvirt] RFC: virtio-rng and /dev/urandom
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-devel] [libvirt] RFC: virtio-rng and /dev/urandom |
Date: |
Fri, 15 Apr 2016 12:54:56 +0100 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
On Fri, Apr 15, 2016 at 12:46:46PM +0100, Richard W.M. Jones wrote:
> On Fri, Apr 15, 2016 at 06:41:34AM -0400, Cole Robinson wrote:
> > Libvirt currently rejects using host /dev/urandom as an input source for a
> > virtio-rng device. The only accepted sources are /dev/random and /dev/hwrng.
> > This is the result of discussions on qemu-devel around when the feature was
> > first added (2013). Examples:
> >
> > http://lists.gnu.org/archive/html/qemu-devel/2012-09/msg02387.html
> > https://lists.gnu.org/archive/html/qemu-devel/2013-03/threads.html#00023
> >
> > libvirt's rejection of /dev/urandom has generated some complaints from
> > users:
> >
> > https://bugzilla.redhat.com/show_bug.cgi?id=1074464
> > * cited: http://www.2uo.de/myths-about-urandom/
> > http://www.redhat.com/archives/libvir-list/2016-March/msg01062.html
> > http://www.redhat.com/archives/libvir-list/2016-April/msg00186.html
> >
> > I think it's worth having another discussion about this, at least with a
> > recent argument in one place so we can put it to bed. I'm CCing a bunch of
> > people. I think the questions are:
> >
> > 1) is the original recommendation to never use virtio-rng+/dev/urandom
> > correct?
> >
> > 2) regardless of #1, should we continue to reject that config in libvirt?
>
> There was a lot of internal-to-Red Hat discussion on this which I
> can't reproduce here unfortunately. However the crux of it was that
> it's quite safe to read enormous amounts from /dev/urandom, even
> without adding any entropy at all, and use those numbers for
> cryptographic purposes.
I should clarify I mean: *after* the pool has been initialized with
sufficient entropy in the first place (which happens very early in
boot), you can then read almost indefinitely.
Rich.
> Steve: can we disclose the research that was done into this? If so
> can you summarise the results for us?
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
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--
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- [Qemu-devel] RFC: virtio-rng and /dev/urandom, Cole Robinson, 2016/04/15
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, Richard W.M. Jones, 2016/04/15
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, Eric Blake, 2016/04/15
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, Hubert Kario, 2016/04/15
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, H. Peter Anvin, 2016/04/15
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, H. Peter Anvin, 2016/04/15
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, Paolo Bonzini, 2016/04/16
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, H. Peter Anvin, 2016/04/17
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, H. Peter Anvin, 2016/04/17
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, Hubert Kario, 2016/04/18
- Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, Hubert Kario, 2016/04/18