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ESB-2007.0567 -- [AIX] -- AIX ftp client gets() Buffer Overflow Vulnerabilities

Date: 27 July 2007

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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                          ESB-2007.0567 -- [AIX]
           AIX ftp client gets() Buffer Overflow Vulnerabilities
                               27 July 2007

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

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

Product:              ftp(2)
Publisher:            IBM
Operating System:     AIX 5.2, 5.3
Impact:               Root Compromise
Access:               Existing Account
CVE Names:            CVE-2007-4004

Original Bulletin:    
  http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=571

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IBM SECURITY ADVISORY

First Issued: Tue Jul 24 10:03:54 CDT 2007
===============================================================================
                           VULNERABILITY SUMMARY

VULNERABILITY:   AIX ftp gets() Buffer Overflow Vulnerabilities

PLATFORMS:       AIX 5.2, 5.3

SOLUTION:        Apply the APAR, interim fix or workaround as described
                 below.

THREAT:          An attacker may run arbitrary code as root privileges.

CERT VU Number:  n/a
CVE Number:      n/a
===============================================================================
                           DETAILED INFORMATION

I. OVERVIEW

    The ftp command uses the File Transfer Protocol (FTP) to transfer files
    between the local host and a remote host or between two remote hosts.  The
    program is installed by default and is setuid.

II. DESCRIPTION

    A local vulnerability exists in the client part of the ftp application
    whereby a user may execute arbitrary code with root privileges.  This is
    due to calls to the deprecated routine 'gets()'.

III. IMPACT

    The successful exploitation of this vulnerability allows a non-privileged
    user to execute code with root privileges.

IV. PLATFORM VULNERABILITY ASSESSMENT

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

    # lslpp -l | grep bos.net.tcp.client

    The following filesets are vulnerable:

    AIX Level           Lower Level       Upper Level
    -------------------------------------------------
    5.2.0               5.2.0.85          5.2.0.107
    5.3.0               5.3.0.40          5.3.0.62

V. SOLUTIONS

    A. APARS

        IBM provides the following fixes:

        AIX Level           APAR number       Availability
        --------------------------------------------------------------------
        5.2.0               IZ01812           10/31/2007 (subject to change)
        5.3.0               IZ01813           11/27/2007 (subject to change)

        AIX Version 5 APARs can be downloaded from:

        http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html

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

    B. INTERIM FIXES

        Interim fixes are available.  The interim fix can be downloaded via
        ftp from:

        ftp://aix.software.ibm.com/aix/efixes/security/ftpgets_ifix.tar.Z

        This is a compressed tarball containing this advisory, interim fix
        packages and PGP signatures for each package.  The interim fixes below
        include prerequisite checking. This will enforce the correct mapping
        between the fixes and AIX Technology Levels.

        AIX Release & Technology Level         Interim fix
        ---------------------------------------------------------------
        5200-08                                IZ01812_08.070723.epkg.Z
        5200-09                                IZ01812_09.070723.epkg.Z
        5200-10                                IZ01812_10.070723.epkg.Z
        5300-04                                IZ01813_04.070723.epkg.Z
        5300-05                                IZ01813_05.070723.epkg.Z
        5300-06                                IZ01813_06.070723.epkg.Z

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

        These interim fixes have not been fully regression tested; thus, IBM
        does not warrant the fully correct functionality of the interim fix.
        Customers install the interim fix and operate the modified version of
        AIX at their own risk.

        Verify you have retrieved the fixes intact:

        The interim fixes below are named by using the technology level
        corresponding to the release that the fix applies to. The checksums
        below were generated using the "sum" and "md5sum" commands and are as
        follows:

        Filename                   sum        md5sum
        ----------------------------------------------------------------------
        IZ01812_08.070723.epkg.Z   64692 123  a2f21e469e0b64a99455bd3ef0b86484
        IZ01812_09.070723.epkg.Z   18190 123  6a1e448cf3211bc5a323064d45bfb8eb
        IZ01812_10.070723.epkg.Z   45986 126  babccdd3a10113a3611995af8e49062c
        IZ01813_04.070723.epkg.Z   00288 126  bc0e7084191fd4672475bf4da9dfc494
        IZ01813_05.070723.epkg.Z   58925 126  dc83cce43dcb7654ab9d4f82b7b588f8
        IZ01813_06.070723.epkg.Z   36147 129  e0ee8317805a5120a64e72ae49522657

        These sums should match exactly. The PGP signatures in the
        compressed tarball and on this advisory can also be used to verify
        the integrity of the various files they correspond to.  If the sums
        or signatures cannot be confirmed, double check the command results
        and the download site address.  If those are OK, contact IBM AIX
        Security at security-alert@austin.ibm.com and describe the
        discrepancy.

    C. INTERIM FIX INSTALLATION

        These packages use the new Interim Fix Management Solution to install
        and manage interim fixes.  More information can be found at:

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

        To preview an epkg interim fix installation execute the following
        command:

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

        To install an epkg interim fix package, execute the following command:

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

        The "X" flag will expand any filesystems if required.

VI. WORKAROUNDS

    Due to the nature of ftp there are not many workarounds.  If the program is
    not necessary, the following options are available.

    A. OPTION 1

        Install openssl and openssh and take advantage of the secure copy 'scp'
        command to transfer files between systems.

    B. OPTION 2

        Remove the setuid bit with the following command:

        # chmod 555 /usr/bin/ftp

        NOTE: This will effectively remove functionality from all users except
        root.

VII. OBTAINING FIXES

    AIX Version 5 APARs can be downloaded from:

        http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html

    Security related Interim Fixes can be downloaded from:

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

VII. 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 send email to
    security-alert@austin.ibm.com with a subject of "get key". The key
    can also be downloaded from a PGP Public Key Server. The key id is
    0x4265D862.

    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.

VIII. ACKNOWLEDGMENTS

    iDefense (http://labs.idefense.com/) credits an anonymous contributer.

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===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
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===========================================================================

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