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AA-97.12                        AUSCERT Advisory
                 SGI IRIX login LOCKOUT parameter Vulnerability
                                10 April 1997

Last Revised: 16 September 1997

              Added vendor patch and bulletin information to Section 3.

	      A complete revision history is at the end of this file.

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AUSCERT has received information that a vulnerability exists in the login
program when the LOCKOUT parameter in /etc/default/login is set to a number
greater than zero. This vulnerability is known to be present in IRIX 5.3
and 6.2. Other versions of IRIX may also be vulnerable.

This vulnerability may allow users to create arbitrary or corrupt certain
files on the system.

Exploit information involving this vulnerability has been made publicly
available.

Vendor patches have been released addressing 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.

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1.  Description

    Under the IRIX operating system, there is a file /etc/default/login
    which contains default security logging configuration options.  If
    the parameter LOCKOUT is included in this file, and is set to a value
    greater than zero, it causes accounts to be locked after a specified
    number of consecutive unsuccessful login attempts by the same user.

    When LOCKOUT is enabled users may be able to create arbitrary or
    corrupt certain files on the system, due to an inadequate check in
    the login verification process.

    Sites can determine if this functionality is enabled by using the
    command:

	% grep '^LOCKOUT' /etc/default/login
        LOCKOUT=3

    If the number on the same line as LOCKOUT is greater than zero the
    vulnerability may be exploited.

    Information involving this vulnerability has been made publicly
    available.

2.  Impact

    Users may create arbitrary or corrupt certain files on the system.

3.  Workarounds/Solution

    Official vendor patches have been released by Silicon Graphics which
    address this vulnerability (Section 3.2).

    If the patches recommended by Silicon Graphics cannot be applied,
    AUSCERT recommends that sites prevent the exploitation of this
    vulnerability by immediately applying the workaround given in Section
    3.1.

3.1 Disable the LOCKOUT parameter

    To prevent the exploitation of the vulnerability described in this
    advisory, AUSCERT recommends that the functionality provided with the
    LOCKOUT parameter be disabled.

    The LOCKOUT parameter can be disabled by editing /etc/default/login
    and commenting out the line containing the LOCKOUT parameter. The
    comment character for /etc/default/login is "#".

    Note that after applying this workaround, accounts will not be
    automatically locked using the LOCKOUT parameter functionality.

3.2 Install vendor patches

    Silicon Graphics has released security bulletin 19970508-02-PX "IRIX
    LOCKOUT and login/scheme Buffer Overrun" which addresses the
    vulnerability described in this advisory, including patch information.
    AUSCERT recommends that sites apply these patches as soon as possible.

    This SGI security advisory is available from:

        ftp://sgigate.sgi.com/security/19970508-02-PX

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AUSCERT thanks to Alan J Rosenthal from The University of Toronto and
Silicon Graphics Inc. for their assistance in this matter.
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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
Prentice Centre
Brisbane
Qld.  4072.
AUSTRALIA

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Revision History

16 Sep 1997	Silicon Graphics has released a security bulletin,
		addressing the vulnerability described in this advisory.
		Section 3 has been modified to include this information.

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