From owner-freebsd-hackers Tue Feb 18 7:11:12 2003 Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E0AB737B401 for ; Tue, 18 Feb 2003 07:11:10 -0800 (PST) Received: from atlas.informatik.rwth-aachen.de (atlas.Informatik.RWTH-Aachen.DE [137.226.194.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id B551F43F75 for ; Tue, 18 Feb 2003 07:11:09 -0800 (PST) (envelope-from stolz@i2.informatik.rwth-aachen.de) Received: from menelaos.informatik.rwth-aachen.de (menelaos.Informatik.RWTH-Aachen.DE [137.226.194.73]) by atlas.informatik.rwth-aachen.de (8.11.3/8.11.3/SuSE Linux 8.11.1-0.5) with ESMTP id h1IFB8W13556; Tue, 18 Feb 2003 16:11:08 +0100 Received: (from stolz@localhost) by menelaos.informatik.rwth-aachen.de (8.12.6/8.12.6/Submit) id h1IFBEeq002895; Tue, 18 Feb 2003 16:11:14 +0100 (CET) (envelope-from stolz) Date: Tue, 18 Feb 2003 16:11:14 +0100 From: Volker Stolz To: Ian Watkinson Cc: freebsd-hackers@freebsd.org Subject: Re: DHCP Client DoS Message-ID: <20030218151114.GA2873@i2.informatik.rwth-aachen.de> References: <20030218134112.GA93504@marvin.penguinpowered.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030218134112.GA93504@marvin.penguinpowered.org.uk> X-PGP-Key: finger vs@foldr.org X-PGP-Id: 0x3FD1B6B5 User-Agent: Mutt/1.5.3i Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG In local.freebsd-hackers, you wrote: > We've recently found a problem with dhclient that can DoS a DHCP > server. If you have schg flags set on /etc/resolv.conf to stop dhcp > overwriting your existing nameservers, the problem occurs. > Basically, the client just keeps rejecting the IP details it has > received from the server and requesting another. The server marks the > record as used, and moves onto the next one. Over the course of a couple > of minutes, you can pretty much mark an entire class C as in use. The problem of read-only resolv.conf is already documented in the PR database and I think recently somebody started thinking about a solution. Check http://www.freebsd.org/cgi/query-pr.cgi?pr=bin/38778 That the server runs out of IPs is his probably his own fault. It should be configured to not eat up all IPs when a host which already has obtained a lease requests another one but simply hand out the old one or deny the request... Stijn: Could you add your suggestion to the above PR? -- http://www-i2.informatik.rwth-aachen.de/stolz/ *** PGP *** S/MIME rage against the finite state machine To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message