-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN HP-UX ppl Core Dump Vulnerability February 18, 1997 22:00 GMT Number H-32 ______________________________________________________________________________ PROBLEM: A vulnerability exists in the ppl(1) program. PLATFORM: HP-UX 9.x and 10.x DAMAGE: This vulnerability may allow local users to gain root privileges. SOLUTION: Until patches are available, take the steps outlined in section 3 as soon as possible. ______________________________________________________________________________ VULNERABILITY Exploit details involving this vulnerability have been made ASSESSMENT: publicly available. ______________________________________________________________________________ [ Start AUSCERT Advisory ] =========================================================================== AA-97.07 AUSCERT Advisory HP-UX ppl core dump vulnerability 18 February 1997 Last Revised: -- - ---------------------------------------------------------------------------- AUSCERT has received information that a vulnerability exists in the ppl(1) program under HP-UX 9.x and 10.x. This vulnerability may allow local users to gain root privileges. Exploit information involving this vulnerability has been made publicly available. The patches listed in HP security bulletin #00053, 13 February 1997, "Security Vulnerability in the ppl executable", do not correct this problem. Currently there are no vendor patches available that address this vulnerability. AUSCERT recommends that sites take the steps outlined in section 3 as soon as possible. This advisory will be updated as more information becomes available. - ---------------------------------------------------------------------------- 1. Description AUSCERT has received information that a vulnerability exists in the HP-UX ppl(1) program used to perform point-to-point serial networking using SLIP or CSLIP. ppl is a setuid root program. While ppl is executing with root privileges, it is possible for local users to force ppl to core dump. As users have the ability to manipulate the location of the core, this vulnerability may be used to create or overwrite any file on the system. This vulnerability is known to exist in HP-UX 9.x and 10.x. The patches listed in HP security bulletin #00053, 13 February 1997, "Security Vulnerability in the ppl executable", do not correct this problem. They address other security vulnerabilities. Exploit information involving this vulnerability has been made publicly available. The default location for ppl under HP-UX 9.x and 10.x is /usr/bin. 2. Impact Local users may be able to create or overwrite arbitrary files on the system. This can be leveraged to gain root privileges. 3. Workarounds/Solution AUSCERT recommends that sites prevent the exploitation of the vulnerability in ppl by immediately applying the workaround given in Section 3.1. If the ppl functionality is required for non privileged users, AUSCERT recommends that access be restricted to a trusted set of users as given in Section 3.2. Currently there are no vendor patches available that address this vulnerability. AUSCERT recommends that official vendor patches be installed when they are made available. 3.1 Remove setuid and execute permissions Until official vendor patches are made available, sites should remove the setuid root and execute permissions from ppl. To do this, the following command should be run as root: # chmod 400 /usr/bin/ppl # ls -l /usr/bin/ppl -r-------- 1 root bin 98304 Jan 24 08:13 /usr/bin/ppl Note that this will remove the ability for any user to run this program. 3.2 Restrict ppl access If the ppl functionality is required by a small set of trusted users, sites may wish to restrict the execution of ppl to that group of users. For example, if the Unix group "trusted" exists and contains only those users allowed to use the ppl functionality, the following commands will restrict its use: # chgrp trusted /usr/bin/ppl # chmod 4550 /usr/bin/ppl # ls -l /usr/bin/ppl -r-sr-x--- 1 root trusted 98304 Jan 24 08:13 /usr/bin/ppl Note access to any account in the "trusted" group will allow the ppl package to be exploited. 4. Previous patches During the installation of HP-UX patches, copies of files being replaced are saved in case the patches need to be backed out of. The original versions of patched files are stored in the following locations: HP-UX 9.x: /system//orig/ HP-UX 10.x: /var/adm/sw/patch// If patches for vulnerable programs have been previously installed, copies of the vulnerable programs may be available in the above locations. Sites should ensure the directories have permissions which restrict access to the patch areas. 5. Additional measures Most Unix systems ship with numerous programs which have setuid or setgid privileges. Often the functionality supplied by these privileged programs is not required by many sites. The large number of privileged programs that are shipped by default are to cater for all possible uses of the system. AUSCERT encourages sites to examine all the setuid/setgid programs and determine the necessity of each program. If a program does not absolutely require the setuid/setgid privileges to operate (for example, it is only run by the root user), the setuid/setgid privileges should be removed. Furthermore, if a program is not required at your site, then all execute permissions should be removed. A sample command to find all setuid/setgid programs is (run as root): # find / \( -perm -4000 -o -perm -2000 \) -type f -exec ls -l {} \; It is AUSCERT's experience that many vulnerability are being discovered in setuid/setgid programs which are not necessary for the correct operation of most systems. Sites can increase their security by removing unnecessary setuid/setgid programs. For example, the functionality provided by the ppl program is not needed by many sites. If sites had previously disabled this program, they would not have been susceptible to this latest vulnerability. - ---------------------------------------------------------------------------- [ End AUSCERT Advisory ] _____________________________________________________________________________ CIAC wishes to acknowledge the contributions of AUSCERT & Hewlett-Packard 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. 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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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