MCI Telecommunications internetMCI Security Group Report Title: iMCI MIIGS Security Alert Report Name: HP-UX vgdisplay overrun Report Number: iMCISE:IMCIAUSCERT:020997:01:P1R1 Report Date: 02/09/97 Report Format: Formal Report Classification: MCI Informational Report Reference: http://www.security.mci.net Report Distribution: iMCI Security, MCI Internal Internet Gateway Security (MIIGS), MCI Emergency Alert LiSt (MEALS) (names on file) -------------------------------------------------------------------------- =========================================================================== AA-97.04 AUSCERT Advisory HP-UX vgdisplay Buffer Overrun Vulnerability 7 February 1997 Last Revised: -- - --------------------------------------------------------------------------- AUSCERT has received information that a vulnerability exists in the vgdisplay(1M) program which is part of the Logical Volume Manager subsystem under HP-UX 10.x. This vulnerability may allow local users to gain root privileges. Exploit information involving this vulnerability has been made publicly available. 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 The HP-UX Logical Volume Manager (LVM) is a subsystem for managing disk space. It comprises a number of auxiliary programs used to create, display and manipulate the LVM information. AUSCERT has received information that a vulnerability exists in the vgdisplay(1M) program used to display information about LVM volume groups. Due to insufficient bounds checking on arguments which are supplied by users, it is possible to overwrite the internal stack space of the vgdisplay program while it is executing. By supplying a carefully designed argument to the vgdisplay program, intruders may be able to force vgdisplay to execute arbitrary commands. As vgdisplay is setuid root, this may allow intruders to run arbitrary commands with root privileges. This vulnerability is known to affect HP-UX 10.x. Note that many of the LVM utility programs are hard links to vgdisplay(1M). This indicates that these utility programs share the same code with vgdisplay, and may also be subject to similar attacks. The following programs are all hard links: lvchange, lvcreate, lvdisplay, lvextend, lvlnboot, lvreduce, lvremove, lvrmboot, pvchange, pvcreate, pvdisplay, pvmove, vgcfgbackup, vgcfgrestore, vgchange, vgcreate, vgdisplay, vgexport, vgextend, vgimport, vgreduce, vgremove, vgscan. By default, dynamically linked versions of the LVM programs are found in /usr/sbin under HP-UX 10.x. Statically linked versions are also available under HP-UX 10.x in /sbin. Exploit information involving this vulnerability has been made publicly available. 2. Impact Local users may gain root privileges. 3. Workarounds/Solution AUSCERT recommends that sites limit the possible exploitation of this vulnerability by immediately removing the setuid permissions as stated in Section 3.1. 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 non-root execute permissions To prevent the exploitation of the vulnerability described in this advisory, AUSCERT recommends that the setuid permissions be removed from the vgdisplay program immediately. Note that permission changes to vgdisplay will also affect those LVM utility programs which are hard links to vgdisplay. As the vgdisplay and related programs will no longer work for non-root users, it is recommended that the execute permissions also be removed. Sites will need to restrict permissions on both the dynamically linked copies in /usr/sbin and the statically linked copies in /sbin. First, restrict permissions on the copies in /usr/sbin. For example: # ls -l /usr/sbin/vgdisplay -r-sr-xr-x 23 root sys 376832 Jun 10 1996 /usr/sbin/vgdisplay # chmod 500 /usr/sbin/vgdisplay # ls -l /usr/sbin/vgdisplay -r-x------ 23 root sys 376832 Jun 10 1996 /usr/sbin/vgdisplay Second, restrict permissions on the copies in /sbin. For example: # ls -l /sbin/vgdisplay -r-sr-xr-x 23 root sys 606208 Jun 10 1996 /sbin/vgdisplay # chmod 500 /sbin/vgdisplay # ls -l /sbin/vgdisplay -r-x------ 23 root sys 606208 Jun 10 1996 /sbin/vgdisplay Note that this will remove the ability for any non-root user to run vgdisplay or any of the LVM utility programs which are hard linked to vgdisplay. 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 often stored in the following location: 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 location. Sites should ensure the directories have permissions which restrict access to the patch areas. 5. Additional measures Most Unix systems ship 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 / \( -perm -4000 -o -perm -2000 \) -exec ls -ld {} \; It is AUSCERT's experience that many vulnerabilities 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. - --------------------------------------------------------------------------- AUSCERT thanks Hewlett-Packard for their continued assistance and technical expertise essential for the production of this advisory. - --------------------------------------------------------------------------- The AUSCERT team have made every effort to ensure that the information contained in this document is accurate. However, the decision to use the information described is the responsibility of each user or organisation. The appropriateness of this document for an organisation or individual system should be considered before application in conjunction with local policies and procedures. AUSCERT takes no responsibility for the consequences of applying the contents of this document. If you believe that your system has been compromised, contact AUSCERT or your representative in FIRST (Forum of Incident Response and Security Teams). AUSCERT is located at The University of Queensland within the Prentice Centre. AUSCERT is a full member of the Forum of Incident Response and Security Teams (FIRST). AUSCERT maintains an anonymous FTP service which is found on: ftp://ftp.auscert.org.au/pub/. This archive contains past SERT and AUSCERT Advisories, and other computer security information. AUSCERT also maintains a World Wide Web service which is found on: http://www.auscert.org.au/. Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 4477 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AUSCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for emergencies. Postal: Australian Computer Emergency Response Team c/- Prentice Centre The University of Queensland Brisbane Qld. 4072. AUSTRALIA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Revision History ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBMvs/jih9+71yA2DNAQGjmQP/b9/TK9adYXZxSEVQqKHrB89kXWBTrFQ4 Rq2L6yivu2PTG7GPCVOhfIIQxvs8RMZK28nvq7lRFJRwKZ3CSOPsH4kVAj5v7OgN hEpAlm3O/KmODIbcHHmN2D24IZMkd5q+tdOod8mXhTc5fYckWuHVdCq6q/+zjffe 8jNGnNpqUbg= =FvhT -----END PGP SIGNATURE-----