[libvirt] [libvirt-users] virRandomBits - not very random

[Martin Kletzander]

On Fri, May 25, 2018 at 09:37:44AM -0500, Eric Blake wrote:
>On 05/25/2018 09:17 AM, Michal Privoznik wrote:
>
>>>> We should probably seed it with data from /dev/urandom, and/or the new
>>>> Linux getrandom() syscall (or BSD equivalent).
>>
>> I'm not quite sure that right after reboot there's going to be enough
>> entropy. Every service that's starting wants some random bits. But it's
>> probably better than what we have now.
>
>Here's where we left things last time it came up:
>
>https://www.redhat.com/archives/libvir-list/2014-December/msg00573.html
>
>If gnutls has an interface that will give us random bits
>(gnutls_key_generate() in 3.0, perhaps), we should use THAT for all of
>our random bits (and forget about a seed), except when we are mocking
>things in our testsuite, and need a deterministic PRNG from a
>deterministic seed.
>
>If not (including if we are not linked with gnutls), then we should
>prefer the new Linux syscall but fall back to /dev/urandom for JUST
>enough bits for a seed; once we're seeded, stick with using our existing
>PRNG for all future bits (after all, we aren't trying to generate
>cryptographically secure keys using virRandomBits - and the places where
>we DO need crypto-strong randomness such as setting up TLS migration is
>where we are relying on gnutls to provide it rather than virRandomBits).
>
>So at this point, it's just a matter of someone writing the patches.
>

Actually, do we need to have a fallback at all?  Can't we just drop all the
gross parts of the code the conditionally compile based on GNUTLS support?  Why
don't we have gnutls required?

>--
>Eric Blake, Principal Software Engineer
>Red Hat, Inc.           +1-919-301-3266
>Virtualization:  qemu.org | libvirt.org
>
>--
>libvir-list mailing list
>libvir-list at redhat.com
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