Security Bulletin: Vulnerability in OpenSSL affects AIX (CVE-2018-0739)

Summary

There is a vulnerability in OpenSSL used by AIX.

Vulnerability Details

CVEID: CVE-2018-0739 **DESCRIPTION:**Constructed ASN.1 types with a recursive definition (such as can be found in PKCS7) could eventually exceed the stack given malicious input with excessive recursion. This could result in a Denial Of Service attack. **CVSS Base Score: **5.3 **CVSS Temporal Score: **See https://exchange.xforce.ibmcloud.com/vulnerabilities/140847 for the current score *CVSS Environmental Score:**Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H)

Affected Products and Versions

AIX 5.3, 6.1, 7.1, 7.2
VIOS 2.2.x

The following fileset levels are vulnerable:

Fileset Lower Level Upper Level KEY
------------------------------------------------------
openssl.base 1.0.2.500 1.0.2.1300 key_w_fs
openssl.base 20.13.102.1000 20.13.102.1300 key_w_fs

Note:
A. 0.9.8, 1.0.1 OpenSSL versions are out-of-support. Customers are advised to upgrade to currently supported OpenSSL 1.0.2 version.

B. Latest level of OpenSSL 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=openssl&cp=UTF-8

To find out whether the affected filesets are installed on your systems, refer to the lslpp command found in the AIX user’s guide.

Example: lslpp -L | grep -i openssl.base

Remediation/Fixes

A. FIXES

The fixes can be downloaded via ftp or http from:

ftp://aix.software.ibm.com/aix/efixes/security/openssl_fix26.tar
http://aix.software.ibm.com/aix/efixes/security/openssl_fix26.tar
https://aix.software.ibm.com/aix/efixes/security/openssl_fix26.tar

The links above are 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 Technology Levels.

Note that the tar file contains Interim fixes that are based on OpenSSL version, and AIX OpenSSL fixes are cumulative. 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 102ma_ifix.180410.epkg.Z openssl.base(1.0.2.1300) key_w_fix
5.3, 6.1, 7.1, 7.2 fips_102ma.180410.epkg.Z openssl.base(20.13.102.1300) key_w_fix

VIOS Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY
--------------------------------------------------------------------------------------------
2.2.* 102ma_ifix.180410.epkg.Z openssl.base(1.0.2.1300) key_w_fix
2.2.* fips_102ma.180410.epkg.Z openssl.base(20.13.102.1300) key_w_fix

To extract the fixes from the tar file:

tar xvf openssl_fix26.tar
cd openssl_fix26

Verify you have retrieved the fixes intact:

The checksums below were generated using the “openssl dgst -sha256 file” command as the following:

openssl dgst -sha256 filename KEY
------------------------------------------------------------------------------------------------------
bfd40e466a6c7976fcf0cb46474087c550c043dc98b0be57689975388100bfdf 102ma_ifix.180410.epkg.Z key_w_csum
ee752e4a70cd46295141d7441a99e019db0391f6539881c5d185433dd0cd42ae fips_102ma.180410.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 Support at https://ibm.com/support/ and describe the discrepancy.

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

Published advisory OpenSSL signature file location:

http://aix.software.ibm.com/aix/efixes/security/openssl_advisory26.asc.sig
https://aix.software.ibm.com/aix/efixes/security/openssl_advisory26.asc.sig
ftp://aix.software.ibm.com/aix/efixes/security/openssl_advisory26.asc.sig

B. FIX AND INTERIM FIX INSTALLATION

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.