AIX OpenSSH Vulnerability

IBM SECURITY ADVISORY

First Issued: Wed Oct 21 09:17:40 CDT 2015

The most recent version of this document is available here:

http://aix.software.ibm.com/aix/efixes/security/openssh_advisory6.asc
https://aix.software.ibm.com/aix/efixes/security/openssh_advisory6.asc
ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory6.asc

Security Bulletin: Vulnerabilities in OpenSSH affect AIX (CVE-2015-6563 and
CVE-2015-6564)

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

SUMMARY:

Vulnerabilities in OpenSSH affect AIX

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

VULNERABILITY DETAILS:

CVEID: CVE-2015-6563
DESCRIPTION: The monitor component in sshd accepts extraneous username 
    data in MONITOR_REQ_PAM_INIT_CTX requests, which allows local users to
    conduct impersonation attacks by leveraging any SSH login access in
    conjunction with control of the sshd uid to send a crafted
    MONITOR_REQ_PWNAM request.
CVSS Base Score: 4
CVSS Temporal Score: See
    https://exchange.xforce.ibmcloud.com/vulnerabilities/105881 for the
    current score.
CVSS Environmental Score*: Undefined
CVSS Vector: (AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N)


CVEID: CVE-2015-6564
DESCRIPTION: Use-after-free vulnerability in the mm_answer_pam_free_ctx 
    function in sshd might allow local users to gain privileges by
    leveraging control of the sshd uid to send an unexpectedly early
    MONITOR_REQ_PAM_FREE_CTX request.
CVSS Base Score: 7.4
CVSS Temporal Score: See
    https://exchange.xforce.ibmcloud.com/vulnerabilities/105882 for the
    current score.
CVSS Environmental Score*: Undefined
CVSS Vector: (AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H)


AFFECTED PRODUCTS AND VERSIONS:

    AIX 5.3, 6.1, 7.1
    VIOS 2.2.x

    The following fileset levels are vulnerable:

    AIX Fileset             Lower Level   Upper Level    KEY
    -------------------------------------------------------------
    openssh.base.client     4.0.0.5200    6.0.0.6201     key_w_fs
    openssh.base.server     4.0.0.5200    6.0.0.6201     key_w_fs
    
    Note:  To determine if your system is vulnerable, execute the
    following commands:

        lslpp -L openssh.base.client
        lslpp -L openssh.base.server
        
    

REMEDIATION:

    A. FIXES

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

        ftp://aix.software.ibm.com/aix/efixes/security/openssh_fix6.tar
        http://aix.software.ibm.com/aix/efixes/security/openssh_fix6.tar
        https://aix.software.ibm.com/aix/efixes/security/openssh_fix6.tar

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

        Note that the tar file contains Interim fixes that are based on
        OpenSSH version as given below - 

        You must be on the 'prereq for installation' level before
        applying the interim fix. This may require installing a new
        level(prereq version) first.
        

        AIX Level      Interim Fix (*.Z)         Fileset Name(prereq for installation)
        ---------------------------------------------------------------------------------
        5.3, 6.1, 7.1  6110_ifix.151009.epkg.Z   openssh.base(6.0.0.6110 version)
        5.3, 6.1, 7.1  6201_ifix.151009.epkg.Z   openssh.base(6.0.0.6201 version)

        VIOS Level     Interim Fix (*.Z)	     Fileset Name(prereq for installation)
        ---------------------------------------------------------------------------------
        2.2.*          6110_ifix.151009.epkg.Z   openssh.base(6.0.0.6110 version)
        2.2.*          6201_ifix.151009.epkg.Z   openssh.base(6.0.0.6201 version)


        Note - OpenSSH releases 6.0.0.6110 and 6.0.0.6201 are same
        except that 6.0.0.6201 is compiled with OpenSSL v1.0.1 and
        contains ECDSA key support. Refer to the fileset readme file for
        more details.

        To extract the fix from the tar file:

        tar xvf openssh_fix6.tar
        cd openssh_fix6

        Verify you have retrieved the fix intact:

        The checksums below were generated using the
        "openssl dgst -sha256 file" command is the followng:

        openssl dgst -sha256                                              filename	 
        -----------------------------------------------------------------------------------------
        fa701ce210c496b8692ed339b76a2204f969d156ede171a923125ec313fea3f2  6110_ifix.151009.epkg.Z
        3acd9aba41d2abde519bde08b17b8f2d306ba88392b6788b0fd051a85647a9a2  6201_ifix.151009.epkg.Z

    
        These sums should match exactly. The OpenSSL 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 [email protected] and
        describe the discrepancy.
        
        Published advisory OpenSSL signature file location:

    http://aix.software.ibm.com/aix/efixes/security/openssh_advisory6.asc.sig
    https://aix.software.ibm.com/aix/efixes/security/openssh_advisory6.asc.sig
    ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory6.asc.sig       

    openssl dgst -sha1 -verify <pubkey_file> -signature
        <advisory_file>.sig <advisory_file>

    openssl dgst -sha1 -verify <pubkey_file> -signature
        <ifix_file>.sig <ifix_file>

        
    B. 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; however, IBM does fully support them.

        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.


    WORKAROUNDS AND MITIGATIONS:
    
        None.

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

CONTACT US:

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

    http://www.ibm.com/support/mynotifications

To view previously issued advisories, please visit:

    http://www14.software.ibm.com/webapp/set2/subscriptions/onvdq

Comments regarding the content of this announcement can be
directed to:

    [email protected]

To obtain the OpenSSL public key that can be used to verify the
signed advisories and ifixes:

    Download the key from our web page:

http://www.ibm.com/systems/resources/systems_p_os_aix_security_pubkey.txt

To obtain the PGP public key that can be used to communicate
securely with the AIX Security Team via [email protected] you
can either:

    A. Download the key from our web page:

http://www.ibm.com/systems/resources/systems_p_os_aix_security_pgppubkey.txt

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

        0x28BFAA12

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

REFERENCES:

Note: Keywords labeled as KEY in this document are used for parsing
purposes.

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.

Complete CVSS Guide: http://www.first.org/cvss/v2/guide
On-line Calculator V2: https://nvd.nist.gov/CVSS-v2-Calculator

X-Force Vulnerability Database:
    https://exchange.xforce.ibmcloud.com/vulnerabilities/105881
X-Force Vulnerability Database:
    https://exchange.xforce.ibmcloud.com/vulnerabilities/105882
CVE-2015-6563: https://vulners.com/cve/CVE-2015-6563
CVE-2015-6564: https://vulners.com/cve/CVE-2015-6564

ACKNOWLEDGEMENTS:

None. 

CHANGE HISTORY:

First Issued: Wed Oct 21 09:17:40 CDT 2015 

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

*The CVSS Environment Score is customer environment specific and will
ultimately impact the Overall CVSS Score. Customers can evaluate the
impact of this vulnerability in their environments by accessing the links
in the Reference section of this Flash.

Note: According to the Forum of Incident Response and Security Teams
(FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry
open standard designed to convey vulnerability severity and help to
determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES
"AS IS" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE
RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY
VULNERABILITY.