[libvirt] RFC: virtio-rng and /dev/urandom
Cole Robinson
crobinso at redhat.com
Wed Apr 20 22:21:24 UTC 2016
On 04/15/2016 06:41 AM, 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?
>
Even though there's still a debate about whether use of /dev/urandom here is
sensible, several people suggested removing the libvirt path restriction, and
nobody really spoke up to defend it. So I've posted a patch to fully drop
libvirt's rng path whitelist:
http://www.redhat.com/archives/libvir-list/2016-April/msg01362.html
- Cole
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