Fixing Linux getrandom() in stable

[Michael Biebl]

Am 10.05.2018 um 00:46 schrieb Ben Hutchings:
> 1. Add entropy to the kernel during boot; either:
>    a. Improve systemd-random-seed
>    b. Recommend use of haveged
> 2. For each affected userland package, either:
>    a. Revert to using /dev/urandom
>    b. Tolerate a longer wait for getrandom() to return
> 
> I asked about haveged on Twitter, and got into a discussion with Jann
> Horn (who reported the original issue).  He pointed out that the
> systemd-random-seed service already saves and restores some random data
> between boots.  It currently doesn't tell the RNG that this should be
> treated as adding to available entropy, so it doesn't help to unblock
> getrandom().  It also doesn't fully protect against using the same
> saved data twice, which would be a prerequisite.

There is https://github.com/systemd/systemd/issues/4271 which seems
related. If there is further feedback from our side, this should
probably be added to the upstream bug report.

> The libbsd maintainer (Guillem Jover) favours option 2a.
> 
> One of the krb5 maintainers (Benjamin Kaduk) favours option 2b, and
> also proposed that systemd could provide a wait-for-rng-ready unit to
> support this.

What exactly would such a wait-for-rng-ready service do and how would it
solve this particular problem?

Michael

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