----------------------------------------------------------------------------- CA-93:03 CERT Advisory February 3, 1993 SunOS File/Directory Permissions ----------------------------------------------------------------------------- The default permissions on a number of files and directories in SunOS 4.1, 4.1.1, 4.1.2, and 4.1.3 are set incorrectly. These problems are relevant for the sun3, sun3x, sun4, sun4c, and sun4m architectures. They have been fixed in SunOS 5.0. (Note that SunOS 5.0 is the operating system included in the Solaris 2.0 software distribution.) An updated patch to reset these permissions is available from Sun. CERT has seen an increasing number of attackers exploit these problems on systems and we encourage sites to consider installing this patch. ----------------------------------------------------------------------------- I. Description File permissions on numerous files were set incorrectly in the distribution tape of 4.1.x. A typical example is that a file which should have been owned by "root" was set to be owned by "bin". Not all sites will need or want to install the patch for this problem. The decision of what user id should own most system files and directories depends on the administrative practices of the site. It is quite reasonable to run a system where the majority of files are owned by "bin" as long as the entire system is run in a manner consistent with that practice. As distributed, the SunOS configuration expects most system files to be owned by "root". The fact that some are not creates security problems. Therefore, sites that are running the SunOS versions listed above as distributed should install the patch described below. Sites that have made an informed choice to configure their system differently may instead want to review the patch script and consider which, if any, of the changes should be made on their system. II. Impact Depending on the specific configuration of the local site, the default permissions may allow local users to gain "root" access. III. Solution 1) Sun has provided a script to reset file and directory permissions to their correct values. The script is available in Sun's Patch #100103 version 11. This patch can be obtained via local Sun Answer Centers worldwide as well as through anonymous FTP from the ftp.uu.net (137.39.1.9) system in the /systems/sun/sun-dist directory. Patch ID Filename Checksum 100103-11 100103-11.tar.Z 19847 6 Please note that Sun Microsystems sometimes updates patch files. If you find that the checksum is different please contact Sun Microsystems or CERT for verification. 2) Uncompress the file, extract the contents of the tar archive, and review the README file. % uncompress 100103-11.tar.Z % tar xfv 100103-11.tar % cat README 3) This patch will reset the group ownership of certain files to either "staff" or "bin". Make sure you have entries in the "/etc/group" file for these accounts. % grep '^staff:' /etc/group % grep '^bin:' /etc/group If you do not have both of these you will need to either add the missing account(s) or modify the patch script (4.1secure.sh) to reflect group ownerships appropriate for your site. (Note that the security problems are fixed by the ownerships and mode bits specified in the patch - not by the group ownerships. Therefore, changing the group ownerships does not invalidate the patch.) 4) As "root", run the patch script. # sh 4.1secure.sh This patch fixes Sun BugId's 1046817, 1047044, 1048142, 1054480, 1037153, 1039292, and 1042662. 5) The patch script will set "/usr/kvm/crash" to mode 02700 owned by "root". While this is not insecure, since only "root" can run the program, CERT recommends that the setgid bit be removed to prevent abuse if world execute permission were to be added some time later. As "root", make "/usr/kvm/crash" not a set-group-id program. # chmod 755 /usr/kvm/crash --------------------------------------------------------------------------- If you believe that your system has been compromised, contact the CERT Coordination Center or your representative in FIRST (Forum of Incident Response and Security Teams). Internet E-mail: cert@cert.org Telephone: 412-268-7090 (24-hour hotline) CERT personnel answer 7:30 a.m.-6:00 p.m. EST(GMT-5)/EDT(GMT-4), on call for emergencies during other hours. CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh, PA 15213-3890 Past advisories, information about FIRST representatives, and other information related to computer security are available for anonymous FTP from cert.org (192.88.209.5).