Date: Tue, 18 Feb 2003 13:41:12 +0000 From: Ian Watkinson <ian.watkinson@ehsbrann.com> To: freebsd-hackers@freebsd.org Subject: DHCP Client DoS Message-ID: <20030218134112.GA93504@marvin.penguinpowered.org.uk>
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Hi all, 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. If you remove the schg flag from resolv.conf, this problem does not happen. This has been tested from a FreeBSD 5 client against a Windows NT server and a FreeBSD 4.7 server with the same results. -- Ian Watkinson To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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