From security-advisories@FreeBSD.org Tue Mar 13 18:23:57 2001 From: FreeBSD Security Advisories To: BUGTRAQ@SECURITYFOCUS.COM Date: Mon, 12 Mar 2001 15:47:59 -0800 Subject: [BUGTRAQ] FreeBSD Security Advisory FreeBSD-SA-01:29.rwhod -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-01:29 Security Advisory FreeBSD, Inc. Topic: rwhod allows remote denial of service Category: core Module: rwhod Announced: 2001-03-12 Credits: Mark Huizer Affects: All released versions of FreeBSD 3.x, 4.x. FreeBSD 3.5-STABLE prior to the correction date. FreeBSD 4.2-STABLE prior to the correction date. Corrected: 2000-12-23 (FreeBSD 3.5-STABLE) 2000-12-22 (FreeBSD 4.2-STABLE) FreeBSD only: NO I. Background rwhod(8) is a server which implements the rwho protocol, which communicates information on system uptime and logged-in users between machines on a network. II. Problem Description Malformed packets sent to the rwhod daemon could cause it to crash, thereby denying service to clients if rwhod is not run under a watchdog process which causes it to automatically restart in the event of a failure. The rwhod daemon is not run in this way in the default invocation from /etc/rc.conf using the rwhod_enable variable. All versions of FreeBSD 3.x and 4.x prior to the correction date including 3.5.1-RELEASE and 4.2-RELEASE are vulnerable to this problem, if they have been configued to run rwhod (this is not enabled by default). III. Impact Remote users can cause the rwhod daemon to crash, denying service to clients. IV. Workaround Implement packet filtering at perimeter firewalls or on the local machine using ipfw(8)/ipf(8) to prevent untrusted users from connecting to the rwhod service. The rwhod daemon listens on UDP port 513 by default. V. Solution Upgrade your vulnerable FreeBSD system to 3.5-STABLE or 4.2-STABLE after the respective correction dates. To patch your present system: download the relevant patch from the below location, and execute the following commands as root: # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:29/rwhod.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:29/rwhod.patch.asc This patch has been verified to apply to FreeBSD 4.2-RELEASE and FreeBSD 3.5.1-RELEASE. It may or may not apply to older releases. Verify the detached PGP signature using your PGP utility. # cd /usr/src/usr.sbin/rwhod # patch -p < /path/to/patch # make depend && make all install Kill and restart rwhod to cause the changes to take effect. If you have started rwhod with non-standard options (e.g. by setting rwhod_flags in /etc/rc.conf) then the below command will need to be modified appropriately. # killall -KILL rwhod # /usr/sbin/rwhod -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.4 (FreeBSD) Comment: For info see http://www.gnupg.org iQCVAwUBOq1fmlUuHi5z0oilAQG05QP/bQpUXpXc+X3/k/jbqgxjNOXwfzYRwNph trCjRBKDKZrBGvlS2mTSbyisn6Rcv5PhigVAmU7sllrrXmYDCuMjNoMQqIhRwMax ojaklsg6F8rX3zNwUlaQp45ZYiJ9Zi34kkRRnZQ5oAFciS6I/3tYnP9t0Sedbbsi V/na+hI/Gtk= =TskQ -----END PGP SIGNATURE-----