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

On 05/29/2018 09:44 AM, Michal Privoznik wrote: > On 05/29/2018 03:38 PM, Martin Kletzander wrote: >> 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? > > That's exactly what I'm suggesting in my patches [1]. gnutls is widely > available (including Linux, Windows, *BSD, Mac Os X). However, before > doing that we need to fix virRandomBits() to actually call gnutls_rnd(). > > 1: https://www.redhat.com/archives/libvir-list/2018-May/msg02077.html > I have this faint recollection of one of the CI platform builds failing because something in the gnutls* family didn't exist there when I was making the changes to add the domain master secret code.... After a bit of digging, it seems it was a perhaps a CENTOS6 environment: https://www.redhat.com/archives/libvir-list/2016-April/msg00287.html and since IIUC that's not an issue any more....

John now if I could only figure out why my mail client seems to be dropping any patches with "crypto" in the subject line (I'm missing patches 2-4 and 10 from the series referenced above)...