[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom
From: |
H. Peter Anvin |
Subject: |
Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom |
Date: |
Fri, 15 Apr 2016 17:51:36 -0700 |
User-agent: |
K-9 Mail for Android |
On April 15, 2016 9:10:44 AM PDT, Hubert Kario <address@hidden> wrote:
>On Friday 15 April 2016 09:47:51 Eric Blake wrote:
>> On 04/15/2016 04:41 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#0
>> > 0023
>> >
>> > 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?
>> That I'm not sure about - and the answer may be context-dependent
>(for
>> example a FIPS user may care more than an ordinary user)
>
>/dev/urandom use is FIPS compliant, no FIPS-validated protocol or
>cryptographic primitive requires the "fresh" entropy provided by
>/dev/random. All primitives are designed to work with weaker entropy
>guarantees than what /dev/urandom provides.
So: using urandom for a seed makes sense, but "unplugging the drain" is a huge
waste of resources and provides absolutely zero value.
Also, I do not believe /dev/urandom is FIPS compliant. Finally, the refill
policy is different, so it is not really true the algorithm is the same.
All in all, other than a seed value it really doesn't make any sense. Of
course, none of this matters on newer Intel hardware ;)
--
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.
- [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 <=
- 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
Re: [Qemu-devel] [libvirt] RFC: virtio-rng and /dev/urandom, Yaniv Kaul, 2016/04/19
Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom, H. Peter Anvin, 2016/04/15