************************************************************************** Security Bulletin 9501 DISA Defense Communications System January 5, 1995 Published by: DDN Security Coordination Center (SCC@NIC.DDN.MIL) 1-(800) 365-3642 DEFENSE DATA NETWORK SECURITY BULLETIN The DDN SECURITY BULLETIN is distributed by the DDN SCC (Security Coordination Center) under DISA contract as a means of communicating information on network and host security exposures, fixes, and concerns to security and management personnel at DDN facilities. Back issues may be obtained via FTP (or Kermit) from NIC.DDN.MIL [192.112.36.5] using login="anonymous" and password="guest". The bulletin pathname is scc/ddn-security-yynn (where "yy" is the year the bulletin is issued and "nn" is a bulletin number, e.g. scc/ddn-security-9428). ************************************************************************** + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + ! ! ! The following important advisory was issued by the Automated ! ! Systems Security Incident Support Team (ASSIST) and is being ! ! relayed unedited via the Defense Information Systems Agency's ! ! Security Coordination Center distribution system as a means ! ! of providing DDN subscribers with useful security information. ! ! ! + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Automated Systems Security Incident Support Team _____ ___ ___ _____ ___ _____ | / /\ / \ / \ | / \ | | / Integritas / \ \___ \___ | \___ | | < et /____\ \ \ | \ | | \ Celeritas / \ \___/ \___/ __|__ \___/ | |_____\ <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Bulletin 94-41 Release date: 23 December 1994, 10:30 AM EST (GMT -4) SUBJECT: NFS Vulnerabilities. SUMMARY: Increase in reports of root compromises caused by intruders using tools to exploit a number of Network File System (NFS) vulnerabilities. BACKGROUND: There are tools being used by intruders to exploit a number of NFS vulnerabilities and gain unauthorized access to network resources. These tools and related information have been widely distributed on numerous Internet forums. IMPACT: Varies depending on vulnerabilities present. In the worst case users can gain unauthorized root access from a remote host. RECOMMENDED SOLUTION: A. Filter packets at your firewall/router. Filter TCP port 111, UDP port 111 (portmapper), TCP port 2049, and UDP port 2049 (nfsd). Consult your vendor or your firewall documentation for detailed instructions on how to configure these ports. These measures will prevent access to NFS at your site from outside your firewall, but it will not protect you from attacks launched from your local network, from behind your firewall. B. Use a portmapper that disallows proxy access. Be sure that you do this for every host that runs a portmapper. For Solaris, 2.x, use a version of rpcbind that disallows proxy access. A portmapper that disallows proxy access protects all hosts with the modified portmapper from attacks that originate either inside or outside your firewall. Because this security measure addresses only the portmapper vulnerability, we recommend combining it with measure A above. Wietse Venema has developed a portmapper that disallows proxy access. It is available by anonymous FTP from ftp.win.tue.nl:/pub/security/portmap_3.shar.Z assist.mil:/pub/tools/NFStools/portmap_3.shar.Z MD5 checksum: f6a3ad98772e7a402ddcdac277adc4a6 For Solaris systems, Venema has developed a version of rpcbind that does not allow proxy access. Solaris users should install this program, not the portmapper. Rpcbind is available by anonymous FTP from the same sites as the portmapper: ftp.win.tue.nl:/pub/security/rpcbind_1.1.tar.Z assist.mil:/pub/tools/NFStools/rpcbind_1.1.tar.Z MD5 checksum: 58437adcbea0a55e37d3a3211f72c08b C. Check the configuration of the /etc/exports files on your hosts. In particular: 1. Do *not* self-reference an NFS server in its own exports file. 2. Do not allow the exports file to contain a "localhost" entry. 3. Export file systems only to hosts that require them. 4. Export only to fully qualified hostnames. 5. Ensure that export lists do not exceed 256 characters. If you have aliases, the list should not exceed 256 characters *after* the aliases have been expanded. (See ASSIST Bulletin 94-03, Revised Patch for SunOS /usr/etc/rpc.mountd Vulnerability.) 6. Use the showmount(8) utility to check that exports are correct. 7. Wherever possible, mount file systems to be exported read only and export file systems read only. D. Ensure that your systems are current with patches and workarounds available from your vendor and identified in ASSIST bulletins. The following advisories address problems related to NFS: ASSIST Bulletin 92-30, Security problem in SunOS fsirand program ASSIST Bulletin 92-37, Revised patch for SunOS /usr/etc/rpc.mountd vulnerabilitity ASSIST Bulletin 92-56, Multiple SunOS vulnerabilities patched ASSIST Bulletin 93-22, Summary of SunOS and Solaris security patches. ASSIST Bulletin 94-03, Revised Patch for SunOS /usr/etc/rpc.mountd vulnerability Vendors may have additional patches not covered by this or previous bulletins, contact your vendor if you need additional information about vulnerabilities and patches. ASSIST would like to thank the CERT Coordination Center,Steve Bellovin, Casper Dik, Leendert van Doorn, and Wietse Venema for information contained in this bulletin. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ASSIST is an element of the Defense Information Systems Agency (DISA), Center for Information Systems Security (CISS), that provides service to the entire DoD community. Constituents of the DoD with questions about ASSIST or computer security security issues, can contact ASSIST using one of the methods listed below. Non-DoD organizations/institutions, contact the Forum of Incident Response and Security Teams (FIRST) (FIRST) representative. To obtain a list of FIRST member organizations and their constituencies send an email to docserver@first.org with an empty "subject" line and a message body containing the line "send first-contacts". ASSIST Information Resources: To be included in the distribution list for the ASSIST bulletins, send your Milnet (Internet) e-mail address to assist-request@assist.mil. Back issues of ASSIST bulletins, and other security related information, are available from the ASSIST BBS at 703-756-7993/1154 DSN 289-7993/1154, and through anonymous FTP from assist.mil (IP address 199.211.123.11). Note: assist.mil will only accept anonymous FTP connections from Milnet addresses that are registered with the NIC or DNS. ASSIST Contact Information: PHONE: 800-357-4231 (or 703-756-7974 DSN 289), duty hours are 06:00 to 22:30 EDT (GMT -4) Monday through Friday. During off duty hours, weekends and holidays, ASSIST can be reached via pager at 800-791- 4857. The page will be answered within 30 minutes, however if a quicker response is required, prefix the phone number with "999". ELECTRONIC MAIL: Send to assist@assist.mil. ASSIST BBS: Leave a message for the "sysop". Reference herein to any specific commercial product, process, or service by trade name, trademark manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or favoring by ASSIST. The views and opinions of authors expressed herein shall not be used for advertising or product endorsement purposes. **************************************************************************** * * * The point of contact for MILNET security-related incidents is the * * Security Coordination Center (SCC). * * * * E-mail address: SCC@NIC.DDN.MIL * * * * Telephone: 1-(800)-365-3642 * * * * NIC Help Desk personnel are available from 7:00 a.m.-7:00 p.m. EST, * * Monday through Friday except on federal holidays. * * * **************************************************************************** PLEASE NOTE: Some users outside of the DOD computing communities may receive DDN Security bulletins. If you are not part of the DOD community, please contact your agency's incident response team to report incidents. Your agency's team will coordinate with DOD. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained by sending email to docserver@first.org with an empty subject line and a message body containing the line: send first-contacts. This document was prepared as an service to the DOD community. Neither the United States Government nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government. The opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government, and shall not be used for advertising or product endorsement purposes.