__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN FreeBSD periodic Uses Insecure Temporary Files February 1, 2001 16:00 GMT Number L-037 ______________________________________________________________________________ PROBLEM: A vulnerability has been found in periodic that causes temporary files with insecure file names to be used in the system's temporary directory. PLATFORM: FreeBSD 4.1-STABLE after 2000-09-20, 4.1.1-RELEASE, and 4.1.1-STABLE prior to 2000-11-11. The problem was corrected prior to the release of FreeBSD 4.2. DAMAGE: By default, periodic is normally called by cron for daily, weekly, and monthly maintenance. Because these scripts run as root, an attacker may potentially corrupt any file on the system. SOLUTION: Upgrade the vulnerable FreeBSD system to 4.1.1-STABLE after the correction date or patch your present system. Refer to section V. of this bulletin for additional information. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. A malicious local user could cause ASSESSMENT: arbitrary files on the system to be corrupted. ______________________________________________________________________________ [****** Start FreeBSD Advisory ******] ============================================================================= FreeBSD-SA-01:12 Security Advisory FreeBSD, Inc. Topic: periodic uses insecure temporary files [REVISED] Category: core Module: periodic Announced: 2001-01-29 Revised: 2001-01-29 Credits: David Lary Affects: FreeBSD 4.1-STABLE after 2000-09-20, 4.1.1-RELEASE, and 4.1.1-STABLE prior to the correction date. No FreeBSD 3.x versions are affected. Corrected: 2000-11-11 FreeBSD only: Yes 0. Revision History v1.0 2001-01-29 Initial release v1.1 2001-01-29 Correctly credit original problem reporter I. Background periodic is a program to run periodic system functions. II. Problem Description A vulnerability was inadvertently introduced into periodic that caused temporary files with insecure file names to be used in the system's temporary directory. This may allow a malicious local user to cause arbitrary files on the system to be corrupted. By default, periodic is normally called by cron for daily, weekly, and monthly maintenance. Because these scripts run as root, an attacker may potentially corrupt any file on the system. FreeBSD 4.1-STABLE after 2000-09-20, 4.1.1-RELEASE, and 4.1.1-STABLE prior to the correction date are vulnerable. The problem was corrected prior to the release of FreeBSD 4.2. III. Impact Malicious local users can cause arbitrary files on the system to be corrupted. IV. Workaround Do not allow periodic to be used in untrusted multi-user environments. Disable the normal periodic system maintenance scripts by either commenting-out or removing the periodic entries in /etc/crontab. V. Solution One of the following: 1) Upgrade the vulnerable FreeBSD system to 4.1.1-STABLE after the correction date. 2) Affected FreeBSD 4.x systems prior to the correction date: Download the patch and the detached PGP signature from the following locations, and verify the signature using your PGP utility. ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:12/periodic.patch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:12/periodic.patch.asc Execute the following commands as root: # cd /usr/src/usr.sbin/periodic # patch -p < /path/to/patch # make depend && make all install [****** End FreeBSD Advisory ******] ______________________________________________________________________________ CIAC wishes to acknowledge the contributions of FreeBSD for 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 (DOE) and the emergency backup response team for the National Institutes of Health (NIH). 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, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@llnl.gov Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ (or http://ciac.llnl.gov -- they're the same machine) Anonymous FTP: ftp.ciac.org (or ciac.llnl.gov -- they're the same machine) PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. 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 via WWW at http://www.first.org/. 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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