From owner-freebsd-current Sat Jul 22 8:38: 4 2000 Delivered-To: freebsd-current@freebsd.org Received: from cypherpunks.ai (cypherpunks.ai [209.88.68.47]) by hub.freebsd.org (Postfix) with ESMTP id 5930037B9A1; Sat, 22 Jul 2000 08:38:00 -0700 (PDT) (envelope-from jeroen@vangelderen.org) Received: from vangelderen.org (grolsch.ai [209.88.68.214]) by cypherpunks.ai (Postfix) with ESMTP id 29E6852; Sat, 22 Jul 2000 11:37:58 -0400 (AST) Message-ID: <3979BFD6.9DFEE454@vangelderen.org> Date: Sat, 22 Jul 2000 11:37:58 -0400 From: "Jeroen C. van Gelderen" X-Mailer: Mozilla 4.73 [en] (X11; I; Linux 2.2.12 i386) X-Accept-Language: en MIME-Version: 1.0 To: Kris Kennaway Cc: Mark Murray , current@FreeBSD.ORG Subject: Re: randomdev entropy gathering is really weak References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Kris Kennaway wrote: > > On Fri, 21 Jul 2000, Mark Murray wrote: > > > Section 2.1, last paragraph: > > "If a system is shut down, and restarted, it is desirable to store some > > high-entropy data (such as the key) in non-volatile memory. This allows > > the PRNG to be restarted in an unguessable state at the next restart. We > > call this data the reseed file." > > I'm all for storing a sample at shutdown and using it to help seed the > PRNG at startup, but it shouldn't be the only seed used (for example, the > case where the system has never been shut down (cleanly) before and so has > no pre-existing seed file is a BIG corner case to consider since thats how > the system is at the time it first generates SSH keys after a fresh > install). > > It might be only an academic vulnerability, but if someone can read your > HD during the time the system is shut down then I'd prefer them not to > know the precise state when the system next starts up again. Yes, if they > can read they can probably also write, but it seems like a mistake when > there's nothing really gained by saving the complete state, as opposed to > an extract. Well, academic or not (not when you run financial transactioning systems on FreeBSD) you can edit rc.shutdown to not write out a seed file. You don't have to use it but it's good that it's there. Cheers, Jeroen -- Jeroen C. van Gelderen o _ _ _ jeroen@vangelderen.org _o /\_ _ \\o (_)\__/o (_) _< \_ _>(_) (_)/<_ \_| \ _|/' \/ (_)>(_) (_) (_) (_) (_)' _\o_ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message