From owner-freebsd-current Thu Oct 26 13:29:56 2000 Delivered-To: freebsd-current@freebsd.org Received: from grimreaper.grondar.za (adsl-63-206-96-212.dsl.snfc21.pacbell.net [63.206.96.212]) by hub.freebsd.org (Postfix) with ESMTP id B398937B479 for ; Thu, 26 Oct 2000 13:29:52 -0700 (PDT) Received: from grondar.za (mark@localhost [127.0.0.1]) by grimreaper.grondar.za (8.11.1/8.11.1) with ESMTP id e9QKTXM00442; Thu, 26 Oct 2000 13:29:40 -0700 (PDT) (envelope-from mark@grondar.za) Message-Id: <200010262029.e9QKTXM00442@grimreaper.grondar.za> To: Doug Barton Cc: current@FreeBSD.org Subject: Re: entropy reseeding is totally broken References: In-Reply-To: ; from Doug Barton "Thu, 26 Oct 2000 12:49:47 PDT." Date: Thu, 26 Oct 2000 13:29:33 -0700 From: Mark Murray Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > 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. There is an angle; an attacker can attack by replaying, but this requires strong privelige. > 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. I like that, but I'd like to see more than one file. This avoids the race where fsck may blat an incompletely written file after a (in)convenient crash. We are really headed towards saving state in the first swap partition (if there is one). On a related note, I'd like to see mergemaster rebuild /dev if it is not DEVFS (obviously taking into account user preferences in MAKEDEV.local). I believe that users are shootin their feet by not tracking /dev properly. M -- Mark Murray Join the anti-SPAM movement: http://www.cauce.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message