GNU bug report logs - #23605
/dev/urandom not seeded across reboots

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From: Leo Famulari <leo <at> famulari.name>
To: Taylan Ulrich Bayırlı/Kammer <taylanbayirli <at> gmail.com>
Cc: 23605 <at> debbugs.gnu.org
Subject: bug#23605: /dev/urandom not seeded across reboots
Date: Tue, 24 May 2016 12:16:17 -0400

On Tue, May 24, 2016 at 09:05:21AM +0200, Taylan Ulrich Bayırlı/Kammer wrote:
> Leo Famulari <leo <at> famulari.name> writes:
> > Does anyone have advice about the service? Am I wrong that we need to
> > seed /dev/urandom to make it work properly?
> 
> Yes, this is necessary under Linux if you want urandom to be random
> enough immediately after boot, and all the distros do it as part of
> their init.
> 
> There's also an interesting implication here about the very first time
> you boot the system and don't have a urandom seed file from the last
> shutdown yet.  I don't know how this is typically handled, given that
> for instance it's quite possible that a user might generate SSH keys
> shortly after their first boot of a system.

When I boot a GuixSD VM for the first time [0], it requires me to dance
on the keyboard until it has collected ~200 bits of entropy. I assumed
this is to properly bootstrap the CSPRNG in /dev/urandom, but I'm not
sure.

[0] I don't remember if I had to do this on bare metal.

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