AIX OpenSSH Vulnerability

IBM SECURITY ADVISORY

First Issued: Thu Sep 8 14:36:37 CDT 2016

The most recent version of this document is available here:

http://aix.software.ibm.com/aix/efixes/security/openssh_advisory9.asc
https://aix.software.ibm.com/aix/efixes/security/openssh_advisory9.asc
ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory9.asc

Security Bulletin: Vulnerabilities in OpenSSH affect AIX (CVE-2015-8325,
CVE-2016-6210 and CVE-2016-6515)

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

SUMMARY:

Vulnerabilities in OpenSSH affect AIX

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

VULNERABILITY DETAILS:

CVEID: CVE-2015-8325
DESCRIPTION: When the UseLogin feature is enabled and PAM is configured to 
    read .pam_environment files in user home directories, allows local users 
    to gain privileges by triggering a crafted environment for the /bin/login 
    program, as demonstrated by an LD_PRELOAD environment variable.
CVSS Base Score: 7.4
CVSS Temporal Score: See
    https://exchange.xforce.ibmcloud.com/vulnerabilities/114628 for the 
    current score.
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

CVEID: CVE-2016-6210
DESCRIPTION: An attacker can measure timing differences in password 
authentication that could be used to discern valid from invalid account 
names when long passwords were sent and particular password hashing
   algorithms are in use on the server 
CVSS Base Score: 4.3
CVSS Temporal Score: See
    https://exchange.xforce.ibmcloud.com/vulnerabilities/115128 for the 
    current score.
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)

CVEID: CVE-2016-6515
DESCRIPTION: sshd does not limit password lengths for password authentication, 
    which allows remote attackers to cause a denial of service 
    (crypt CPU consumption) via a long string.  
CVSS Base Score: 7.5 
CVSS Temporal Score: See
    https://exchange.xforce.ibmcloud.com/vulnerabilities/115911 for the 
    current score.
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)


AFFECTED PRODUCTS AND VERSION:

    AIX 5.3, 6.1, 7.1, 7.2
    VIOS 2.2.x
    
    The following fileset levels are vulnerable:
    
    key_fileset = osrcaix
    
    Fileset                 Lower Level   Upper Level    KEY
    -------------------------------------------------------------
    openssh.base.client     4.0.0.5200    6.0.0.6202     key_w_fs
    openssh.base.server     4.0.0.5200    6.0.0.6202     key_w_fs

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

        lslpp -L | grep -i openssh.base.client
        lslpp -L | grep -i 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_fix9.tar
        http://aix.software.ibm.com/aix/efixes/security/openssh_fix9.tar
        https://aix.software.ibm.com/aix/efixes/security/openssh_fix9.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) KEY
    --------------------------------------------------------------------------------------------
    5.3, 6.1, 7.1, 7.2  6202_ifix.160830.epkg.Z openssh.base(6.0.0.6202 version)      key_w_fix

    VIOS Level     Interim Fix (*.Z)         Fileset Name(prereq for installation) KEY
    ----------------------------------------------------------------------------------------
    2.2.*          6202_ifix.160830.epkg.Z  openssh.base(6.0.0.6202 version)      key_w_fix


        Latest level of OpenSSH fileset is available from the web download site:
        https://www14.software.ibm.com/webapp/iwm/web/reg/download.do?source=aixbp&lang=en_US&S_PKG=openssh&cp=UTF-8

       
        To extract the fix from the tar file:

        tar xvf openssh_fix9.tar
        cd openssh_fix9

        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                 KEY
    -----------------------------------------------------------------------------------------------------
    d7d9c1dd5cfb8687a641daab19254f24e6ab4f2677f263acd21742e42ff02a50  6202_ifix.160830.epkg.Z key_w_csum

        
        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_advisory9.asc.sig
    https://aix.software.ibm.com/aix/efixes/security/openssh_advisory9.asc.sig
    ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory9.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

    After applying fix, IBM recommends that you regenerate your SSH keys as
    a precaution. 

    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 v3 Guide:  http://www.first.org/cvss/user-guide
On-line Calculator v3:
    http://www.first.org/cvss/calculator/3.0

X-Force Vulnerability Database: https://exchange.xforce.ibmcloud.com/vulnerabilities/114628
X-Force Vulnerability Database: https://exchange.xforce.ibmcloud.com/vulnerabilities/115128
X-Force Vulnerability Database: https://exchange.xforce.ibmcloud.com/vulnerabilities/115911
CVE-2015-8325 : https://vulners.com/cve/CVE-2015-8325
CVE-2016-6210 : https://vulners.com/cve/CVE-2016-6210
CVE-2016-6515 : https://vulners.com/cve/CVE-2016-6515

ACKNOWLEDGEMENTS:

None

CHANGE HISTORY:

First Issued: Thu Sep  8 14:36:37 CDT 2016

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

*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.