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

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.

-- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list