-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= CERT(sm) Advisory CA-96.17 Original issue date: August 6, 1996 Last revised: August 30, 1996 Removed references to the advisory README file. A complete revision history is at the end of this file. Topic: Vulnerability in Solaris vold - ----------------------------------------------------------------------------- The text of this advisory was originally released on August 2, 1996, as AUSCERT Advisory AL-96.04, developed by the Australian Computer Emergency Response Team. We are reprinting the AUSCERT advisory here with their permission. Only the contact information at the end has changed: AUSCERT contact information has been replaced with CERT/CC contact information. We will update this advisory as we receive additional information. Please check advisory files regularly for updates that relate to your site. ============================================================================= AUSCERT has received a report of a vulnerability in the Sun Microsystems Solaris 2.x distribution involving the Volume Management daemon, vold(1M). This program is used to help manage CDROM and floppy devices. This vulnerability may allow a local user to gain root privileges. Exploit details involving this vulnerability have been made publicly available. At this stage, AUSCERT is not aware of any official patches. AUSCERT recommends that sites take the actions suggested in Section 3 until official patches are available. - ----------------------------------------------------------------------------- 1. Description The Volume Management daemon, vold(1M), manages the CDROM and floppy devices. For example, it provides the ability to automatically detect, and then mount, removable media such as CDROMs and floppy devices. vold is part of the Solaris 2.x Volume Management package (SUNWvolu). It is executed as a background daemon on system startup and runs as root. When vold detects that a CDROM or floppy has been inserted into a drive, it is configured to automatically mount the media, making it available to users. Part of this process includes the creation of temporary files, which are used to allow the Openwindows File Manager, filemgr(1), to determine that new media has been mounted. These files are created by the action_filemgr.so shared object which is called indirectly by vold through rmmount(1M). The handling of these files is not performed in a secure manner. As vold is configured to access these temporary files with root privileges, it may be possible to manipulate vold into creating or over-writing arbitrary files on the system. This vulnerability requires that vold be running and media managed by vold, such as a CDROM or floppy, be physically loaded into a drive. Note that a local user need not have physical access to the media drive to exploit this vulnerability. It is enough to wait until somebody else loads the drive, exploiting the vulnerability at that time. This vulnerability is known to be present in Solaris 2.4 and Solaris 2.5. Solaris distributions prior to Solaris 2.4 are also expected to be vulnerable. 2. Impact Local users may be able to create or over-write arbitrary files on the system. This can be leveraged to gain root privileges. 3. Workaround AUSCERT believes the workarounds given in Sections 3.1 or 3.2 will address this vulnerability. Vendor patches may also address this vulnerability in the future (Section 3.3). 3.1 Edit /etc/rmmount.conf The temporary files which are susceptible to attack are created by the /usr/lib/rmmount/action_filemgr.so.1 shared object which is called indirectly by vold through rmmount(1M). rmmount(1M) can be configured so that it does not create the temporary files, thereby removing this vulnerability. To our knowledge, configuring rmmount(1M) in this fashion will not affect the functionality of vold. It will, however, remove the ability of the Openwindows File Manager, filemgr(1), to automatically detect newly mounted media. To prevent rmmount(1M) creating temporary files, sites must edit the /etc/rmmount.conf file and comment out (or remove) any entry which references action_filemgr.so. The standard /etc/rmmount.conf contains the following entries which must be commented out (or deleted) to remove this vulnerability: action cdrom action_filemgr.so action floppy action_filemgr.so After applying this workaround, an example of /etc/rmmount.conf may look like: # @(#)rmmount.conf 1.2 92/09/23 SMI # # Removable Media Mounter configuration file. # # File system identification ident hsfs ident_hsfs.so cdrom ident ufs ident_ufs.so cdrom floppy pcmem ident pcfs ident_pcfs.so floppy pcmem # Actions # # Following two lines commented out to remove vold vulnerability # # action cdrom action_filemgr.so # action floppy action_filemgr.so Note that vold does not have to be restarted for these changes to take effect. 3.2 Remove the Volume Management system Sites who do not require the vold functionality should remove the complete set of Volume Management packages. These are SUNWvolg, SUNWvolu and SUNWvolr. These packages can be removed using pkgrm(1M). 3.3 Install vendor patches Currently, AUSCERT is not aware of any official patches which address this vulnerability. When official patches are made available, AUSCERT suggests that they be installed. - ----------------------------------------------------------------------------- AUSCERT wishes to thanks to Leif Hedstrom, Mark McPherson(QTAC), Marek Krawus(UQ), DFN-CERT and CERT/CC for their assistance in this matter. - ----------------------------------------------------------------------------- If you believe that your system has been compromised, contact the CERT Coordination Center or your representative in the Forum of Incident Response and Security Teams (FIRST). We strongly urge you to encrypt any sensitive information you send by email. The CERT Coordination Center can support a shared DES key and PGP. Contact the CERT staff for more information. Location of CERT PGP key ftp://info.cert.org/pub/CERT_PGP.key CERT Contact Information - ------------------------ Email cert@cert.org Phone +1 412-268-7090 (24-hour hotline) CERT personnel answer 8:30-5:00 p.m. EST (GMT-5)/EDT(GMT-4), and are on call for emergencies during other hours. Fax +1 412-268-6989 Postal address CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh PA 15213-3890 USA CERT publications, information about FIRST representatives, and other security-related information are available for anonymous FTP from http://www.cert.org/ ftp://info.cert.org/pub/ CERT advisories and bulletins are also posted on the USENET newsgroup comp.security.announce To be added to our mailing list for CERT advisories and bulletins, send your email address to cert-advisory-request@cert.org CERT is a service mark of Carnegie Mellon University. This file: ftp://info.cert.org/pub/cert_advisories/CA-96.17.Solaris_vold_vul http://www.cert.org click on "CERT Advisories" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Revision history Aug. 30, 1996 Removed references to CA-96.17.README. Beginning of the advisory - removed AUSCERT advisory header to avoid confusion. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMiTFq3VP+x0t4w7BAQG5VwP/fwY/1z1OKfXRAhNynR6fLuqR4KYqBIKe 2OhwlHxfdNhCVb7gYqWW0Dq1KMgMx8uBAqMqQtQ9BmZ9jjExk7x/hAOQKjVIPcKE dbgNhPtSZHN5mZMTP/HPj07jYkd5oI92yvJD8ci9Tjh2s3OHdGxRe+L1T7u1MF2q Cql9+g5MsC4= =O/qX -----END PGP SIGNATURE-----