************************************************************************** Security Bulletin 9547 DISA Defense Communications System December 1, 1995 Published by: DISN Security Coordination Center (SCC@NIC.DDN.MIL) 1-(800) 365-3642 DEFENSE INFORMATION SYSTEM NETWORK SECURITY BULLETIN The DISN SECURITY BULLETIN is distributed by the DISN 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 DISN 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/sec-yynn (where "yy" is the year the bulletin is issued and "nn" is a bulletin number, e.g. scc/sec-9544.txt). These are also available at our WWW site, http://nic.ddn.mil. ************************************************************************** + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + ! ! ! 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 DISN subscribers with useful security information. ! ! ! + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + -----BEGIN PGP SIGNED MESSAGE----- <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Automated Systems Security Incident Support Team _____ ___ ___ _____ ___ _____ | / /\ / \ / \ | / \ | | / Integritas / \ \___ \___ | \___ | | < et /____\ \ \ | \ | | \ Celeritas / \ \___/ \___/ __|__ \___/ | |_____\ <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Bulletin 95-44 Release date: 30 November, 1995, 1:45 PM EDT (GMT -4) SUBJECT: SGI lp Vulnerability. SUMMARY: The default lp account created during SGI installation, as well as other default accounts, has no password. The lp account, which is used by the lp(1) program for remote printing, and other accounts are initially configured without passwords to provide easy "plug-and-play" install and operation. These password-less accounts are, however, well known by intruders and may allow unauthorized access to your system. BACKGROUND: The SGI IRIX system as distributed has some accounts without passwords. Among the accounts that are password-less is the lp account. This account is used in part by the lp(1) program to manage object and spooled data files in the /var/spool/lp directory (for IRIX 4.X, this directory is /usr/spool/lp). The account is created without a password because lp(1) uses rsh(1) to transfer files from print clients to print servers. In the documentation that SGI distributes with their systems, these password-less accounts are specifically addressed in the "IRIX Advanced Site and Server Administrative Guide" in the chapter on System Security. The documentation recommends disabling the login for the lp account and recommends that you create passwords for the following accounts immediately after installation is complete: demos, guest, lp, nuucp, root, tour, tutor, and 4Dgifts. The documentation includes guidelines for choosing good passwords. To determine if your system is vulnerable, execute the following command as root to display all accounts that have no password: # /bin/passwd -sa | /bin/awk '$2 == "NP" {print $0}' If this command displays any accounts, especially the lp account, then your system is vulnerable. To address this vulnerability, see the "RECOMMENDED SOLUTIONS" section below. IMPACT: Remote users can gain access to systems without providing authentication. The level of privilege gained depends on which account is used as the point of entry to the system. RECOMMENDED SOLUTIONS: Lock all accounts that do not have passwords as described in (1) below. See (2) below for info about how to re-enable print client to print server communication. (1). Lock each password-less account. Store the following script in, for example, /tmp/CheckPasswords and then run it as root on your machine to lock each password-less account. The password installed will not allow the accounts to be used as login accounts. See the passwd(1) manual page for more details. Note that this script only locks accounts on the local machine. If there are password-less accounts in NIS, those accounts will not be locked by this script. - ------------------------cut here--8<------------------------ #!/bin/sh for account in `/bin/passwd -sa | /bin/awk '$2 == "NP" {print $1}'` do /bin/echo Locked the $account account /bin/passwd -l $account done - ------------------------cut here--8<------------------------ The first time the script is run, it should display something similar to the following: # sh /tmp/CheckPasswords Locked the tutor account Locked the tour account Locked the lp account ... If the script locked an account, run the script again. This time it should produce no output because all password-less accounts have now been locked. (2). Re-enable print client to print server communication. SGI has verified that you can use the script in this section to re- enable the print client to print server communication. SGI has asked that it be made clear, however, that they do not have the resources to handle issues relating to the use of wrappers.) ASSIST recommends that in general the rlogin and rsh services be blocked at your Internet routers and turned off on all of your machines. If you have turned the rsh service off on your print server, you will need to turn it back on on that machine. If you decide to do this, we strongly recommend that you install and use a TCP/IP wrapper program to restrict the set of machines that can connect to your print server's rsh service. A TCP/IP wrapper program is available from ftp://assist.mil/pub/tools/network/tcp_wrappers_7.2.tar.Z MD5 (tcp_wrappers_7.2.tar.Z) = 883d00cbd2dedd9bfc783b7065740e74 Once the rsh service is turned on on your print server and a TCP/IP wrapper program installed and configured, you then need to define the set of machines that can communicate with your print server. For each IRIX system that controls a printer, the lp account needs to be changed to re-enable print client to print server communication. To do this, the lp account on each print server needs a .rhosts file in lp's home directory, typically /var/spool/lp (for IRIX 4.X, this directory is /usr/spool/lp). The owner and group of this file must be the same as that of the lp account. Its contents are lines of the form: print_client_name lp Each line identifies the name of the print client and indicates that the lp account is the account that is allowed to rsh from the print client to the print server. The following shows an example of configuring communication from a print client (named "client") to a print server. This configuration need only be done on a print server. The ping command is used to determine the print client's formal name according to whatever host resolution scheme is in place. That name is stored in the .rhosts file. The last two lines, the ping and the echo, need to be repeated for each client of a print server. # /bin/awk -F: '$1 == "lp" {print $0}' /etc/passwd lp:*LK*:9:9:Print Spooler Owner:/var/spool/lp:/bin/sh # cd `/bin/awk -F: '$1 == "lp" {print $6}' /etc/passwd` # /bin/touch .rhosts # /bin/chown lp .rhosts # /bin/chgrp lp .rhosts # /bin/chmod 600 .rhosts # /usr/etc/ping -c 1 client | /bin/awk '$1 == "PING" {print $2}' client.YourDomain # /bin/echo client.YourDomain lp >> .rhosts <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ASSIST would like to thank the CERT Coordination Center 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 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) 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 703-607-4710, 327-4710, 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. If your system is not registered, you must provide your MILNET IP address to ASSIST before access can be provided. ASSIST Contact Information: PHONE: 800-357-4231, COMM 703-607-4700, DSN 327-4700. ELECTRONIC MAIL: assist@assist.mil. ASSIST BBS: COMM 703-607-4710, DSN 327-4710, leave a message for the "sysop". FAX: COMM 703-607-4735, DSN 607-4735 ASSIST uses Pretty Good Privacy (PGP) 2.6.2 as the digital signature mechanism for bulletins. PGP 2.6.2 incorporates the RSAREF(tm) Cryptographic Toolkit under license from RSA Data Security, Inc. A copy of that license is available via anonymous FTP from net-dist.mit.edu (IP 18.72.0.3) in the file /pub/PGP/rsalicen.txt, and through the world wide web from http://net-dist.mit.edu/pgp.html. In accordance with the terms of that license, PGP 2.6.2 may be used for non-commercial purposes only. Instructions for downloading the PGP 2.6.2 software can also be obtained from net-dist.mit.edu in the pub/PGP/README file. PGP 2.6.2 and RSAREF may be subject to the export control laws of the United States of America as implemented by the United States Department of State Office of Defense Trade Controls. The PGP signature information will be attached to the end of ASSIST bulletins. 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. 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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.