-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =============================================================================== >> CERT-NL, 01-Mar-2000 << >> All CERT-NL information has been moved to http://cert.surfnet.nl. Links << >> to CERT-NL information contained in this advisory are therefore outdated. << >> << >> CERT-NL also has stopped the CERT-CC-Mirror service. Due to this the << >> links to the CERT-CC mirror are obsolete. Visit the CERT-CC site for the << >> complete CERT-CC advisory texts: http://www.cert.org << =============================================================================== =============================================================================== Security Advisory CERT-NL =============================================================================== Author/Source : Olav ten Bosch Index : S-97-10 Distribution : World Page : 1 Classification: External Version: 1 Subject : SGI IRIX startmidi/stopmidi vulnerability Date : 12-Feb-97 =============================================================================== By courtesy of AUSCERT we received the following information: 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. - - --------------------------------------------------------------------------- AUSCERT thanks Silicon Graphics Inc. for their technical assistance in this matter. ============================================================================== CERT-NL is the Computer Emergency Response Team for SURFnet customers. SURFnet is the Dutch network for educational, research and related institutes. CERT-NL is a member of the Forum of Incident Response and Security Teams (FIRST). All CERT-NL material is available under: http://cert.surfnet.nl/ In case of computer or network security problems please contact your local CERT/security-team or CERT-NL (if your institute is NOT a SURFnet customer please address the appropriate (local) CERT/security-team). CERT-NL is one/two hour(s) ahead of UTC (GMT) in winter/summer, i.e. UTC+0100 in winter and UTC+0200 in summer (DST). Email: cert-nl@surfnet.nl ATTENDED REGULARLY ALL DAYS Phone: +31 302 305 305 BUSINESS HOURS ONLY Fax: +31 302 305 329 BUSINESS HOURS ONLY Snailmail: SURFnet bv Attn. CERT-NL P.O. Box 19035 NL - 3501 DA UTRECHT The Netherlands NOODGEVALLEN: 06 22 92 35 64 ALTIJD BEREIKBAAR EMERGENCIES : +31 6 22 92 35 64 ATTENDED AT ALL TIMES CERT-NL'S EMERGENCY PHONENUMBER IS ONLY TO BE USED IN CASE OF EMERGENCIES: THE SURFNET HELPDESK OPERATING THE EMERGENCY NUMBER HAS A *FIXED* PROCEDURE FOR DEALING WITH YOUR ALERT AND WILL IN REGULAR CASES RELAY IT TO CERT-NL IN AN APPROPRIATE MANNER. CERT-NL WILL THEN CONTACT YOU. =============================================================================== -----BEGIN PGP SIGNATURE----- Version: PGP 6.5.1i iQA/AwUBOL6ITDSYjBqwfc9jEQKcngCgssMrgm5YSJ/JOGdd4QZjnDMsbE0An0Jh hBI7Ntwd/fAzeLaWhQ/0Odwe =UOhh -----END PGP SIGNATURE-----