Operating System:

[AIX]

Published:

14 March 2008

Protect yourself against future threats.

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             AUSCERT External Security Bulletin Redistribution

                          ESB-2008.0265 -- [AIX]
                        AIX reboot buffer overflow
                               14 March 2008

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:              AIX 5.2
                      AIX 5.3
Publisher:            IBM
Operating System:     AIX
Impact:               Execute Arbitrary Code/Commands
Access:               Existing Account

Original Bulletin:    
http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd?mode=18&ID=4164

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IBM SECURITY ADVISORY

First Issued: Tue Mar 11 10:01:36 CDT 2008
===============================================================================
                           VULNERABILITY SUMMARY

VULNERABILITY:      AIX reboot buffer overflow

PLATFORMS:          AIX 5.2, 5.3

SOLUTION:           Apply the fix or workaround as described below.

THREAT:             A local attacker in the shutdown group may execute
                    arbitrary code.

CVE Number:         n/a

Reboot required?    NO
Workarounds?        YES
Protected by FPM?   YES (high, medium, or low)
Protected by SED?   YES
===============================================================================
                           DETAILED INFORMATION

I. DESCRIPTION

    The reboot command contains a stack based buffer overflow.  A
    local attacker in the shutdown group may exploit this overflow to
    execute arbitrary code with root privileges because the command is
    setuid root.

    The following files are vulnerable:

    /usr/sbin/reboot

II. PLATFORM VULNERABILITY ASSESSMENT

    To determine if your system is vulnerable, execute the following
    command:

    lslpp -L bos.rte.control

    The following fileset levels are vulnerable:

    AIX Fileset      Lower Level    Upper Level
    -----------------------------------------------------------
    bos.rte.control  5.2.0.85       5.2.0.86
    bos.rte.control  5.2.0.95       5.2.0.96
    bos.rte.control  5.2.0.105      5.2.0.107
    bos.rte.control  5.3.0.50       5.3.0.51
    bos.rte.control  5.3.0.60       5.3.0.65

III. SOLUTIONS

    A. APARS

        IBM has assigned the following APARs to this problem:

        AIX Level           APAR number        Availability
        ---------------------------------------------------
        5.2.0               IZ15479            Now
        5.3.0               IZ15480            3/17/2008

        Subscribe to the APARs here:

        http://www.ibm.com/support/docview.wss?uid=isg1IZ15479
        http://www.ibm.com/support/docview.wss?uid=isg1IZ15480

        By subscribing, you will receive periodic email alerting you
        to the status of the APAR, and a link to download the fix once
        it becomes available.

    B. FIXES

        Fixes are available.  The fixes can be downloaded via ftp
        from:

        ftp://aix.software.ibm.com/aix/efixes/security/reboot_fix.tar

        The link above is to a tar file containing this signed
        advisory, fix packages, and PGP signatures for each package.
        The fixes below include prerequisite checking. This will
        enforce the correct mapping between the fixes and AIX
        Technology Levels.

        AIX Level          Fix (*.U) and Interim Fix (*.Z)
        -------------------------------------------------------------------
        5.2.0 TL8          IZ15479_08.080304.epkg.Z
        5.2.0 TL9          IZ15479_09.080304.epkg.Z
        5.2.0 TL10         bos.rte.control.5.2.0.108.U
        5.3.0 TL5          IZ15480_05.080304.epkg.Z
        5.3.0 TL6          IZ15480_06.080304.epkg.Z

        To extract the fixes from the tar file:

        tar xvf reboot_fix.tar
        cd reboot_fix

        Verify you have retrieved the fixes intact:

        The checksums below were generated using the "sum", "cksum",
        "csum -h MD5" (md5sum), and "csum -h SHA1" (sha1sum) commands
        and are as follows:

        sum         filename
        ---------------------------------------
        26129  1230 bos.rte.control.5.2.0.108.U
        17518     9 IZ15479_08.080304.epkg.Z
        06763     9 IZ15479_09.080304.epkg.Z
        07673     9 IZ15480_05.080304.epkg.Z
        45139     9 IZ15480_06.080304.epkg.Z

        cksum             filename
        ---------------------------------------------
        808140130 1259520 bos.rte.control.5.2.0.108.U
        2710419270 8725 IZ15479_08.080304.epkg.Z
        1948359668 8712 IZ15479_09.080304.epkg.Z
        1891405268 8631 IZ15480_05.080304.epkg.Z
        2577625393 8800 IZ15480_06.080304.epkg.Z

        csum -h MD5 (md5sum)              filename
        -------------------------------------------------------------
        b348db57f81460c46e1aba3412d571fb  bos.rte.control.5.2.0.108.U
        903fa4c1129660394d1e453682a2a9dc  IZ15479_08.080304.epkg.Z
        9905edf82c0061cfb51d20c5fb4dfee6  IZ15479_09.080304.epkg.Z
        0910faf81462969185015a2da8823ffc  IZ15480_05.080304.epkg.Z
        56e059b6448468a36c07c4e69ca7931c  IZ15480_06.080304.epkg.Z

        csum -h SHA1 (sha1sum)                    filename
        ---------------------------------------------------------------------
        92552078a7f489820a6df3ff1431d8a2394e41e8  bos.rte.control.5.2.0.108.U
        7bfd16ef7b581acc9c6e2c5b0eb8b1517bc7a8fe  IZ15479_08.080304.epkg.Z
        b3284aae31fa850e057118af7ba508f046e89964  IZ15479_09.080304.epkg.Z
        01ae1a25fbd69a40ff07247ab24647c0fbb8ea3a  IZ15480_05.080304.epkg.Z
        1dc7ec97ff0df146775da4785860d6b1cd744fc9  IZ15480_06.080304.epkg.Z

        To verify the sums, use the text of this advisory as input to
        csum, md5sum, or sha1sum. For example:

        csum -h SHA1 -i Advisory.asc
        md5sum -c Advisory.asc
        sha1sum -c Advisory.asc

        These sums should match exactly. The PGP signatures in the tar
        file and on this advisory can also be used to verify the
        integrity of the fixes.  If the sums or signatures cannot be
        confirmed, contact IBM AIX Security at
        security-alert@austin.ibm.com and describe the discrepancy.

     C. FIX AND INTERIM FIX INSTALLATION

        IMPORTANT: If possible, it is recommended that a mksysb backup
        of the system be created.  Verify it is both bootable and
        readable before proceeding.

        To preview a fix installation:

        installp -a -d fix_name -p all  # where fix_name is the name of the
                                        # fix package being previewed.
        To install a fix package:

        installp -a -d fix_name -X all  # where fix_name is the name of the  
                                        # fix package being installed.

        Interim fixes have had limited functional and regression
        testing but not the full regression testing that takes place
        for Service Packs; thus, IBM does not warrant the fully
        correct functionality of an interim fix.

        Interim fix management documentation can be found at:

        http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html

        To preview an interim fix installation:

        emgr -e ipkg_name -p         # where ipkg_name is the name of the  
                                     # interim fix package being previewed.

        To install an interim fix package:

        emgr -e ipkg_name -X         # where ipkg_name is the name of the  
                                     # interim fix package being installed.

IV. WORKAROUNDS

    There are two workarounds available.

    A. OPTION 1

        Change the permissions of these commands to remove the setuid
        bit using the following commands:

        chmod 500 /usr/sbin/reboot

        NOTE: chmod will disable functionality of these commands for
        all users except root.

    B. OPTION 2 (AIX 6.1, AIX 5.3 TL6 and TL7)

        Use the File Permissions Manager (fpm) command to manage
        setuid and setgid programs.

        fpm documentation can be found in the AIX 6 Security Redbook
        at:

        http://www.redbooks.ibm.com/abstracts/sg247430.html

        An fpm level of high, medium, or low will remove the setuid
        bit from the affected commands.  For example:

        fpm -l high -p    # to preview changes
        fpm -l high       # to execute changes

        NOTE: Please review the documentation before execution.  fpm
        will disable functionality of multiple commands for all users
        except root.


V. OBTAINING FIXES

    AIX security fixes can be downloaded from:

        ftp://aix.software.ibm.com/aix/efixes/security

    AIX fixes can be downloaded from:

        http://www.ibm.com/eserver/support/fixes/fixcentral/main/pseries/aix

    NOTE: Affected customers are urged to upgrade to the latest
    applicable Technology Level and Service Pack.

VI. CONTACT INFORMATION

    If you would like to receive AIX Security Advisories via email,
    please visit:

        http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd
 
    Comments regarding the content of this announcement can be
    directed to:

        security-alert@austin.ibm.com

    To request the PGP public key that can be used to communicate
    securely with the AIX Security Team you can either:

        A. Send an email with "get key" in the subject line to:

            security-alert@austin.ibm.com

        B. Download the key from a PGP Public Key Server. The key ID is:

            0xA6A36CCC

    Please contact your local IBM AIX support center for any
    assistance.

    eServer is a trademark of International Business Machines
    Corporation.  IBM, AIX and pSeries are registered trademarks of
    International Business Machines Corporation.  All other trademarks
    are property of their respective holders.

VII. ACKNOWLEDGMENTS

    IBM discovered and fixed this vulnerability as part of its
    commitment to secure the AIX operating system.

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