-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN SGI IRIX startmidi/stopmidi Vulnerability February 13, 1997 00:00 GMT Number H-28 ______________________________________________________________________________ PROBLEM: A vulnerability exists in the startmidi(1)/stopmidi(1) program. PLATFORM: All SGI systems running IRIX 5.2, 5.3, 6.0, 6.0.1, and 6.1 with an IRIS Digital Media Execution Environment. DAMAGE: This vulnerability may allow local users to gain root privileges or perform a denial of service attack. 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-97.05 AUSCERT Advisory SGI IRIX startmidi/stopmidi Vulnerability 11 February 1997 Last Revised: -- - ---------------------------------------------------------------------------- AUSCERT has received information that a vulnerability exists in the startmidi(1)/stopmidi(1) program which is part of the SGI IRIS Digital Media Execution Environment. This vulnerability may allow local users to gain root privileges or perform a denial of service attack. Exploit information 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 SGI IRIS Digital Media Execution Environment contains the basic system components necessary to support audio, MIDI (Musical Instrument Digital Interface), and video applications on an IRIS workstation. One part of this product is the MIDI Execution Environment, which among other things, contains the startmidi/stopmidi program. stopmidi is a symbolic link to the startmidi program. Before any MIDI applications can be run, it is usually necessary to configure the serial ports for use with MIDI. startmidi initializes the serial ports and links them to the MIDI streams driver. stopmidi disables MIDI on the specified device. During the execution of startmidi, files are created in an insecure manner with insecure permissions. As this program executes with root privileges, it is possible for local users to create or truncate arbitrary files on the system. It also possible to alter the contents of these temporary files, which may allow users to perform a denial of service attack. Exploit information has been made publicly available. The default location for startmidi/stopmidi is /usr/sbin/. At this stage, IRIX 5.2, 5.3, 6.0, 6.0.1, and 6.1 are known to contain this vulnerability. Sites can determine the version of the operating system with the command: % /sbin/uname -a 2. Impact Local users may be able to create or truncate arbitrary files on the system, which may be leveraged to gain root access. They may also be able to change the contents of temporary files, allowing a denial of service attack. 3. Workarounds/Solution AUSCERT recommends that sites prevent the exploitation of this vulnerability in startmidi/stopmidi by immediately applying the workaround given in Section 3.1. If the MIDI Execution Environment is not required, it is recommended that sites remove it from their systems (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 startmidi. To do this, the following command should be run as root: # /bin/chmod 400 /usr/sbin/startmidi # /bin/ls -l /usr/sbin/startmidi -r-------- 1 root sys 18608 Nov 22 1994 /usr/sbin/startmidi Note that this will remove the ability for any user to run the startmidi or stopmidi program. If only the setuid permissions are removed, it is still possible for users to gain privileges when startmidi is executed by the root user. 3.2 Remove the MIDI Execution Environment If the MIDI Execution Environment is no longer needed, sites are encouraged to remove it completely from their systems. This can be done by running, as root, the GUI software management tool, swmgr, or the command: # /usr/sbin/versions remove dmedia_eoe.sw.midi Sites can check that the package has been removed with the command: # /usr/sbin/versions dmedia_eoe.sw.midi 4. 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 / \( -perm -4000 -o -perm -2000 \) -exec ls -ld {} \; 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 startmidi/stopmidi program is not needed by most 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 and Silicon Graphics 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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LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC) H-18: Denial-of-Service Attack via ping H-19: HP Software Installation Programs Vulnerability H-20: Vulnerability in IRIX csetup H-21: HP Security Vulnerabilities (newgrp, authentication, passwor H-22: talkd Buffer Overrun Vulnerability H-23: Sendmail MIME Conversion Buffer Overrun Vulnerability H-24: IBM AIX(r) "gethostbyname()" Buffer Overrun Vulnerability H-25: Vulnerability in rlogin/term H-26: FreeBSD setlocale() Vulnerability H-27: HP-UX vgdisplay Buffer Overrun Vulnerability RECENT CIAC NOTES ISSUED (Previous Notes available from CIAC) Notes 07 - 3/29/95 A comprehensive review of SATAN Notes 08 - 4/4/95 A Courtney update Notes 09 - 4/24/95 More on the "Good Times" virus urban legend Notes 10 - 6/16/95 PKZ300B Trojan, Logdaemon/FreeBSD, vulnerability in S/Key, EBOLA Virus Hoax, and Caibua Virus Notes 11 - 7/31/95 Virus Update, Hats Off to Administrators, America On-Line Virus Scare, SPI 3.2.2 Released, The Die_Hard Virus Notes 12 - 9/12/95 Securely configuring Public Telnet Services, X Windows, beta release of Merlin, Microsoft Word Macro Viruses, Allegations of Inappropriate Data Collection in Win95 Notes 96-01 - 3/18/96 Java and JavaScript Vulnerabilities, FIRST Conference Announcement, Security and Web Search Engines, Microsoft Word Macro Virus Update -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMxtc3LnzJzdsy3QZAQHnugQA0ldUaY6qHvoT4/ekthiA50b+/DOUOnJq Q8XdWy72dKaa0AZASKo/AFtklLbp4wY5LXAzvC7ErBmXma0YIXOTHwRByB5hVSYh cWqMm4KBUkhoB0Euflb1Am4jqUtpeKEYF0tntVxvobBoCsrWIauq5nwIg6ntdNc8 9jDYendNdGU= =+Xd2 -----END PGP SIGNATURE-----