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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2001.114 -- FreeBSD-SA-01:29.rwhod rwhod allows remote denial of service 13 March 2001 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: rwhod Vendor: FreeBSD Operating System: FreeBSD BSD Impact: Denial of Service Access Required: Remote - --------------------------BEGIN INCLUDED TEXT-------------------- - -----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 <xaa@xaa.iae.nl> 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----- - --------------------------END INCLUDED TEXT-------------------- This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to use any or all of this information is the responsibility of each user or organisation, and should be done so in accordance with site policies and procedures. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the original authors to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for emergencies. -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBOq4Mtih9+71yA2DNAQFqEgP/YIMUJDDf4WlZIYBmnyYxgiQIHiAlM2zT o7jAPTcEAGiLwnmCk9hOWy3PiA/vklYrgFA3k6PFTCJ4pErBNMP10Mj0NMhA3lsJ /tH5BcLOzrXBu2oL3En60qPN7GEXsy3MOKKQ9FbyxHjkLhoUKNLbLdL4slkPVynZ Zm0Fh/kPFBk= =7Kyy -----END PGP SIGNATURE-----