[systemd-devel] Delaying (SSH) key generation until the urandom pool is initialized

[Leonid Isaev]

Hi Florian,

	Let me see if I understand you... First, where did you get the logs
from: syslog or journald? 

On Wed, 30 Apr 2014 14:02:11 +0200
Florian Weimer <fweimer at redhat.com> wrote:

> [...]
>
> Using /dev/urandom for key generation is fine once its pool is seeded.

Are you concerned that the PRNG is not seeded properly and hence the keys are
cryptographically weak?

I thought that openssh uses openssl which in turn has its own PRNG that is
seeded from /dev/random and /dev/urandom.
 
> Using existing key generation algorithms with /dev/random instead does 
> not work because they consume too much entropy and can block for 
> significantly more time than just a few minutes.

Entropy is not a problem if you run a daemon like haveged.

Indeed, archlinux iso images provide a service which generate 2048 bit gpg keys
(for package signing) on each boot with no delay (and gpg uses /dev/random).

Moreover, I run ssh-keygen on-boot to generate a volatile key for the root
account, and the order of services appears to be correct (taken from journal -o
verbose):

11:46:15.252713 CDT -- random: nonblocking pool is initialized
11:46:15.970371 CDT -- haveged is operational
11:46:17.576259 CDT -- ssh-keygen exits

Cheers,
L.

-- 
Leonid Isaev
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