From owner-freebsd-current Thu Oct 26 12:49:51 2000 Delivered-To: freebsd-current@freebsd.org Received: from dt051n37.san.rr.com (dt051n37.san.rr.com [204.210.32.55]) by hub.freebsd.org (Postfix) with ESMTP id D20CD37B479; Thu, 26 Oct 2000 12:49:48 -0700 (PDT) Received: from slave (Studded@slave [10.0.0.1]) by dt051n37.san.rr.com (8.9.3/8.9.3) with ESMTP id MAA15584; Thu, 26 Oct 2000 12:49:47 -0700 (PDT) (envelope-from DougB@gorean.org) Date: Thu, 26 Oct 2000 12:49:47 -0700 (PDT) From: Doug Barton X-Sender: doug@dt051n37.san.rr.com To: John Baldwin Cc: Rod Taylor , markm@FreeBSD.org, current@FreeBSD.org Subject: Re: entropy reseeding is totally broken In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Thu, 26 Oct 2000, John Baldwin wrote: > > How about when I hit the reset button? That case SHOULD be taken care > > of too! Would it not be possible to sample /dev/random to store the > > entropy every hour or so that the system runs? Atleast that way you > > would be guarenteed to have something. > > And if a malicious user on your machine grabs the saved entropy file > and then reboots your machine using some exploit of some sort? Granted > neither of these tasks may be easy, and it could be done in such a way > that the first requires root access. I stated this same objection until I actually attended Mark's presentation at the 'con. The yarrow algorithm uses an encrypted hash for the entropy on the way in, and encrypts the output on the way out. This would make it extremely difficult to guess the state at reboot, even if we weren't picking up new entropy sources during the boot process. Pending Mark's approval, I'd like to suggest we add a cron job to dump X k of data from /dev/random to a file (/boot/.periodic_entropy maybe?) and use that, AND ${entropy_file:/var/db/entropy} to reseed at boot, and only do the "long, annoying" failover process if neither file exists. The only remaining questions would be how many k of data to dump how often. Doug -- "The dead cannot be seduced." - Kai, "Lexx" Do YOU Yahoo!? To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message