Entropy collection in sshd (was Re: Entropy and DSA key)

[Ed Phillips]

On Tue, 6 Nov 2001, Gert Doering wrote:

> Date: Tue, 6 Nov 2001 20:57:01 +0100
> From: Gert Doering <gert at greenie.muc.de>
> To: Ed Phillips <ed at UDel.Edu>,
>      Lutz Jaenicke <Lutz.Jaenicke at aet.TU-Cottbus.DE>
> Cc: OpenSSH Development <openssh-unix-dev at mindrot.org>
> Subject: Re: Entropy collection in sshd (was Re: Entropy and DSA key)
>
> Hi,
>
> On Tue, Nov 06, 2001 at 12:48:53PM -0500, Ed Phillips wrote:
> > I'm not following you... the problem of "it takes 2 freakin minutes to get
> > logged into my SS1+" is a direct result of entropy collection performed by
> > sshd.
>
> No, it's not.  I use NetBSD on a Sparc LX with /dev/random, and ssh takes
> still 2 minutes - the delay is NOT caused by the random number generation
> but by slow crypto on ancient Sparc hardware.  ssh protocol 1 is much
> quicker (and also needs random).
>
> See the thread on slow connections that happened here about three days
> ago.

Later in my message that you quoted - you can see my detailed explanation
about how if you truss sshd (or what the syslog in DEBUG mode), you can
actually see it running prng commands, which takes a long time (waiting
for the commands to gather up enough bytes of entropy).  In my case, this
is further confounded by the fact that individual commands were taking
longer than the default timeout of 200 millisec.

I agree, the ancient Sparc hardware isn't really up to the crypto, but my
guess is that in our case it would still be able to provide a shell in
under 30 seconds if it didn't have to run a bunch of commands (does it
actually stop running commands if it gets enough entropy - or does it run
the whole set each time it needs entropy?).

	Ed

Ed Phillips <ed at udel.edu> University of Delaware (302) 831-6082
Systems Programmer III, Network and Systems Services
finger -l ed at polycut.nss.udel.edu for PGP public key