Vulnerabilities in OpenSSH affect AIX

IBM SECURITY ADVISORY

First Issued: Tue May 3 10:03:39 CDT 2016
|Updated: Fri May 13 09:51:05 CDT 2016
|Update: New iFixes now available.

The most recent version of this document is available here:

http://aix.software.ibm.com/aix/efixes/security/openssh_advisory8.asc
https://aix.software.ibm.com/aix/efixes/security/openssh_advisory8.asc
ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory8.asc

Security Bulletin: Vulnerabilities in OpenSSH affect AIX (CVE-2016-3115 and
CVE-2016-1908)

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

SUMMARY:

Vulnerabilities in OpenSSH affect AIX 

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

VULNERABILITY DETAILS:

CVEID: CVE-2016-3115
DESCRIPTION: OpenSSH could allow a remote authenticated attacker to
    execute arbitrary commands on the system, caused by improper
    validation of user-supplied X11 authentication credentials by the sshd
    server. By sending specially crafted X11 credential data, an attacker
    could exploit this vulnerability to inject xauth commands and execute
    arbitrary commands on the system with the privileges of the victim. 
CVSS Base Score: 8.8 
CVSS Temporal Score: See
    https://exchange.xforce.ibmcloud.com/vulnerabilities/111431 for the 
    current score.
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

CVEID: CVE-2016-1908
DESCRIPTION: OpenSSH could allow a remote authenticated attacker to bypass
    security restrictions, caused by the improper handling of errors when
    generating authentication cookies for untrusted X11 forwarding. An
    attacker could exploit this vulnerability to gain access to the target
    local X server. 
CVSS Base Score: 4.3 
CVSS Temporal Score: See
    https://exchange.xforce.ibmcloud.com/vulnerabilities/110030 for the
    current score.
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N) 

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    6.0.0.6201     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 | 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_fix8.tar
        http://aix.software.ibm.com/aix/efixes/security/openssh_fix8.tar
        https://aix.software.ibm.com/aix/efixes/security/openssh_fix8.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 OpenSSH fixes are cumulative, so installing the latest fixes
        will cover previously released AIX security bulletins for
        OpenSSH. 

    AIX Level           Interim Fix (*.Z)        Fileset Name(prereq for installation) KEY
    --------------------------------------------------------------------------------------------

| 5.3, 6.1, 7.1, 7.2 IV84698m9b.160513.epkg.Z openssh.base(6.0.0.6110 version) key_w_fix
| 5.3, 6.1, 7.1, 7.2 IV84698m9a.160513.epkg.Z openssh.base(6.0.0.6201 version) key_w_fix

    VIOS Level     Interim Fix (*.Z)	     Fileset Name(prereq for installation) KEY
    ----------------------------------------------------------------------------------------

| 2.2.* IV84698m9b.160513.epkg.Z openssh.base(6.0.0.6110 version) key_w_fix
| 2.2.* IV84698m9a.160513.epkg.Z openssh.base(6.0.0.6201 version) key_w_fix

| The above fixes are cumulative and contain fixes for all
| previously announced OpenSSH security vulnerabilities on
| AIX.

| The ssh connection hang is specifically seen in scenarios
| when ssh is used with pseudo tty. The login will succeed
| but later connections get hanged.

        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.
        
        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

        OpenSSH 6.0.0.6201 version is also part of AIX Service pack: 
        6100-09-06-1543, that was released in Dec. 2015.
        
        To extract the fix from the tar file:

        tar xvf openssh_fix8.tar
        cd openssh_fix8

        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
    -----------------------------------------------------------------------------------------------------

| 933ac42222856c63beae729fce8ea3f94a428904a622e5395e6df4dc2b8d41b2 IV84698m9b.160513.epkg.Z key_w_csum
| 974370174695d0be3f65baa87be7bca6238d7d980531c21c50348c6f8ee25121 IV84698m9a.160513.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_advisory8.asc.sig
    https://aix.software.ibm.com/aix/efixes/security/openssh_advisory8.asc.sig
    ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory8.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:

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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/111431
X-Force Vulnerability Database:
    https://exchange.xforce.ibmcloud.com/vulnerabilities/110030
CVE-2016-3115:
    https://vulners.com/cve/CVE-2016-3115
CVE-2016-1908:
    https://vulners.com/cve/CVE-2016-1908

ACKNOWLEDGEMENTS:

None

CHANGE HISTORY:

First Issued: Tue May  3 10:03:39 CDT 2016 
Updated: Tue May 10 11:23:23 CDT 2016
Update: Temporarily removing fixes due to a potential hanging issue
    introduced by the fixes.  Updated fixes will be live within 24 hours.
Updated: Thu May 12 10:42:22 CDT 2016
Update: Temporarily removing fixes due to a potential hanging issue
    introduced by the fixes.  Updated fixes will be live on May 13.

| Updated: Fri May 13 09:51:05 CDT 2016
| Update: New iFixes now available.

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

*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.