-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Incorrect Permissions on /tmp August 17, 1995 1200 PDT Number F-27 _______________________________________________________________________________ PROBLEM: A vulnerability exists in Solaris 2.x systems that allows a race condition to be exploited to gain root access. PLATFORM: Sun Solaris 2.x (SunOS 5.x) and Solaris 2.4x86 DAMAGE: Users logged into a system may gain unauthorized root privileges. SOLUTION: Use the workaround contained in this bulletin to modify the sticky bit on the /tmp directory. AVAILABILITY: See the workaround that is contained in this bulletin _______________________________________________________________________________ VULNERABILITY Unprivileged users who are logged on to a system can use this ASSESSMENT: vulnerability to gain unauthorized root privileges. An exploit program for this vulnerability has been published publically. CIAC advises that the workaround described below be performed immediately. _______________________________________________________________________________ CRITICAL Information on the Incorrect Permissions on /tmp CIAC has received information from the Australian Computer Emergency Response Team (AUSCERT) and from the bugtraq mailing list that a vulnerability has been identified in Solaris 2.x systems that allows a race condition to be exploited to gain root access. The basic problem is that the sticky bit is sometimes not set on the /tmp directory. This improper setting causes users to be able to access other user's files in the /tmp directory. Sun Microsystems has confirmed this vulnerability and is currently testing patches for this vulnerability. Patches from Sun Microsystems will be for Solaris 2.3, 2.4 and 2.4x86. Sun Microsystems expects to have patches available within about a week. This vulnerability has been fixed in the upcoming release of Solaris. Detailed Description ____________________ A race condition has been identified in at least one Solaris 2.x system program which can be exploited to gain root access if a user has access to the temporary files. Access to these temporary files may be obtained if the permissions on the /tmp and /var/tmp directories are set incorrectly. The permissions on the /tmp directory are often reset improperly by the system if tmpfs (which is mounting swap as /tmp) is in use. This vulnerability affects the Solaris 2.x (SunOS 5.x) systems. A vulnerability similar to this affected SunOS 4.1.x (Solaris 1.x) systems in the past. Therefore, CIAC recommends that these systems also be checked for the correct permissions. The remainder of this bulletin shows how to identify if this vulnerability exists on your system and additionally identifies commands to be used as a workaround to this vulnerability. Commands shown are for Solaris 2.x systems. Similar commands and configurations exist for SunOS 4.1.x users. To determine if you are running tmpfs, the following command can be used to verify if the filesystem for /tmp is swap: $ /usr/sbin/df -k /tmp Filesystem kbytes used avail capacity Mounted on swap 158728 28 158700 0% /tmp or look in the file /etc/vfstab for the configuration line: #device device mount FS fsck mount mount #to mount to fsck point type pass at boot options # swap - /tmp tmpfs - yes - If either of these two conditions exist, then you are running tmpfs and the system may automatically reset the permissions bits of /tmp at the next reboot. To verify if your configuration is vulnerable, the following command may be used: $ ls -ld /tmp drwxrwxrwt 5 root root 306 Aug 16 11:12 /tmp ^ ^ (Sticky bit is set -- system not currently vulnerable) $ ls -ld /tmp drwxrwxrwx 5 root root 306 Aug 16 11:12 /tmp ^ ^ (Sticky bit is not set -- system is vulnerable) If the sticky bit (t) is not set, then the system is vulnerable. WORKAROUNDS ___________ These workarounds have been verified with Sun Microsystems. Sun Microsystems expect a patch to be released in the near future. 1. Immediate Workaround The immediate workaround is to set the sticky bit on the /tmp directory using the following command as root: # /usr/bin/chmod 1777 /tmp Note that this command must be performed after each reboot if you are mounting swap as /tmp (using tmpfs). In addition, the ownership and group membership of the /tmp directory should be verified using ls -ld /tmp and if incorrect may be reset by issuing the following commands: # /usr/bin/chown root /tmp # /usr/bin/chgrp root /tmp 2. System Reboot workaround It is possible to perform these commands automatically at reboot by creating the following script as /etc/init.d/tmpfsfix: -------------------------8<--- cut here ---8<-------------------------------- #!/bin/sh if [ -d /tmp ] then /usr/bin/chmod 1777 /tmp /usr/bin/chgrp root /tmp /usr/bin/chown root /tmp fi # # end of script tmpfsfix -------------------------8<--- cut here ---8<-------------------------------- A symbolic link should be then be created called /etc/rc3.d/S79tmpfix which points to /etc/init.d/tmpfsfix by issuing the following command as root: # /usr/bin/ln -s /etc/init.d/tmpfsfix /etc/rc3.d/S79tmpfix 3. /var/tmp permissions The /var/tmp directory should be similarly checked and corrected. Note that this directory is not usually mounted as tmpfs, and therefore is not subject to automatic resetting of its permission bits on reboot. % ls -ld /var/tmp drwxrwxrwt 2 root 512 Aug 15 11:35 /var/tmp _______________________________________________________________________________ CIAC wishes to thank the AUSCERT team and Mark Graff of Sun Microsystems for providing the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy. CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE and DOE contractors, and CIAC can be contacted at: Voice: 510-422-8193 FAX: 510-423-8002 STU-III: 510-423-2604 E-mail: ciac@llnl.gov For emergencies and off-hour assistance, DOE and DOE contractor sites may contact CIAC 24-hours a day. During off hours (5PM - 8AM PST), call the CIAC voice number 510-422-8193 and leave a message, or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC duty person, and the secondary PIN number, 8550074 is for the CIAC Project Leader. Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://ciac.llnl.gov/ Anonymous FTP: ciac.llnl.gov (128.115.19.53) Modem access: (510) 423-4753 (14.4K baud) (510) 423-3331 (9600 baud) CIAC has several self-subscribing mailing lists for electronic publications: 1. 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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 account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, 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 or the University of California. 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CIAC BULLETINS ISSUED IN FY95 (Previous bulletins available from CIAC) (F-01) SGI IRIX serial_ports Vulnerability (F-02) Summary of HP Security Bulletins (F-03) Restricted Distribution (F-04) Security Vulnerabilities in DECnet/OSI for OpenVMS (F-05) SCO Unix at, login, prwarn, sadc, and pt_chmod Patches Available (F-06) Novell UnixWare sadc, urestore, and suid_exec Vulnerabilities (F-07) New and Revised HP Bulletins (F-08) Internet Address Spoofing and Hijacked Session Attacks (F-09) Unix /bin/mail Vulnerabilities (F-10) HP-UX Remote Watch (F-11) Unix NCSA httpd Vulnerability (F-12) Kerberos Telnet Encryption Vulnerability (F-13) Unix sendmail vulnerabilities (F-14) HP-UX Malicious Code Sequences (F-15) HP-UX "at" and "cron" vulnerabilities (F-16) SGI IRIX Desktop Permissions Tool Vulnerability (F-17) Limited Distribution (F-18) MPE/iX Vulnerabilities (F-19) Protecting HP-UX Systems Against SATAN (F-20) Security Administrator Tool for Analyzing Networks (SATAN) (F-21) Protecting SUN OS Systems Against SATAN (F-22) SATAN Password Disclosure (F-23) Protecting IBM AIX Systems Against SATAN (F-24) Protecting SGI IRIX Systems Against SATAN (F-25) Cisco IOS Router Software Vulnerability (F-26) OSF/DCE Security Hole CIAC NOTES ISSUED IN FY1995 (Previous Notes available from CIAC) 04c December 8, 1994 05d January 11, 1995 06 March 22, 1995 07 March 29, 1995 08 April 4, 1995 09 April 24, 1995 10a June 16, 1995 11 July, 31, 1995 -----BEGIN PGP SIGNATURE----- Version: 2.6.1 iQCVAwUBMDOoZrnzJzdsy3QZAQH3JwQA4aLdx+CVgFl0zXbtxUXDLPqI/9lalaLQ qgh1ec7ydoY6hW8l9JOkpf+TsTznTsw2WH4UBeej2Aia3e3Uq60g4FzhdpaG6TCq ZKaSaMxo3HixhEHEZYKDYKR6YtYUaDZzFhAKyrHv3CbsFddpWwHaBj7zGLDXqfKq EqhQckC5Z/U= =rpta -----END PGP SIGNATURE-----