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S-97-10.asc

S-97-10.asc
Posted Jan 10, 2000

Subject SGI IRIX startmidi/stopmidi vulnerability Date 12-Feb-97

systems | irix
MD5 | 90d4d1aafc7ab6a8d07253269541d0ca

S-97-10.asc

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===============================================================================
>> 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 to CERT-NL information contained in this advisory are therefore outdated.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.
===============================================================================

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