[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom |
Date: |
Fri, 15 Apr 2016 12:46:46 +0100 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
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.
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
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v
- [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 <=
- 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