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@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
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