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IBM SECURITY ADVISORY

First Issued: Tue Sep 29 12:42:51 CDT 2009

The most recent version of this document is available here:

http://aix.software.ibm.com/aix/efixes/security/nfs4_advisory.asc
or
ftp://aix.software.ibm.com/aix/efixes/security/nfs4_advisory.asc

VULNERABILITY SUMMARY

VULNERABILITY: AIX NFSv4 nfs_portmon and Kerberos vulnerabilities.

PLATFORMS: AIX 5.3, 6.1

SOLUTION: Apply the fix as described below.

THREAT: A local user can gain unauthorized access to
Kerberized AIX NFSv4 shares. A remote user can gain
unauthorized network access to AIX NFSv4 shares
protected by the nfs_portmon tunable.

CERT VU Number: n/a
CVE Number: n/a

Reboot required? YES*
Workarounds? NO
Protected by FPM? NO
Protected by SED? NO

* For the nfs_portmon fix, the machine must be rebooted to reload the
NFS kernel extensions. For the Kerberos fix, the gssd daemon must
be restarted.

DETAILED INFORMATION

I. DESCRIPTION

There are two security vulnerabilities in the AIX NFSv4 (Network
File System version 4) implementation.

The first vulnerability is an error in the handling of the NFSv4
Kerberos credential cache. The successful exploitation of this
vulnerability allows a local user to access Kerberized network
shares without authorization.

The second vulnerability is that the nfs_portmon tunable is not
utilized correctly in NFSv4. The successful exploitation of this
vulnerability allows a remote user to access network shares
protected by nfs_portmon without authorization.

The following commands are vulnerable:

/usr/sbin/gssd
/usr/lib/drivers/nfs.ext

II. PLATFORM VULNERABILITY ASSESSMENT

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

lslpp -L bos.net.nfs.client

The following fileset levels are vulnerable:

AIX Fileset Lower Level Upper Level
---------------------------------------------------
bos.net.nfs.client all earlier versions of 5.3
bos.net.nfs.client 5.3.7.0 5.3.7.8
bos.net.nfs.client 5.3.8.0 5.3.8.6
bos.net.nfs.client 5.3.9.0 5.3.9.2
bos.net.nfs.client 6.1.0.0 6.1.0.8
bos.net.nfs.client 6.1.1.0 6.1.1.4
bos.net.nfs.client 6.1.2.0 6.1.2.3

III. SOLUTIONS

A. APARS

IBM has assigned the following APARs to this problem:

AIX Level APAR number Availability
----------------------------------------------------
5.3.7 IZ50496 Now (SP9)
5.3.8 IZ50444 Now (SP7)
5.3.9 IZ50399 Now (SP4)
6.1.0 IZ49278 Now (SP9)
6.1.1 IZ49096 Now (SP5)
6.1.2 IZ49024 Now (SP4)

Subscribe to the APARs here:

http://www.ibm.com/support/docview.wss?uid=isg1IZ50496
http://www.ibm.com/support/docview.wss?uid=isg1IZ50444
http://www.ibm.com/support/docview.wss?uid=isg1IZ50399
http://www.ibm.com/support/docview.wss?uid=isg1IZ49278
http://www.ibm.com/support/docview.wss?uid=isg1IZ49096
http://www.ibm.com/support/docview.wss?uid=isg1IZ49024

By subscribing, you will receive periodic email alerting you
to the status of the APAR, and a link to download the fix once
it becomes available.

B. FIXES

Fixes are now available. The fixes can be downloaded from:

http://aix.software.ibm.com/aix/efixes/security/nfs4_fix.tar
ftp://aix.software.ibm.com/aix/efixes/security/nfs4_fix.tar

The links above are to a tar file containing this signed
advisory, fix packages, and PGP signatures for each package.

AIX Level Fix
----------------------------------------------------
5.3.7 bos.net.nfs.client.5.3.7.9.U
5.3.8 bos.net.nfs.client.5.3.8.7.U
5.3.9 bos.net.nfs.client.5.3.9.3.U
6.1.0 bos.net.nfs.client.6.1.0.9.U
6.1.1 bos.net.nfs.client.6.1.1.5.U
6.1.2 bos.net.nfs.client.6.1.2.4.U

To extract the fixes from the tar file:

tar xvf nfs4_fix.tar
cd nfs4_fix

Verify you have retrieved the fixes intact:

The checksums below were generated using the "csum -h SHA1"
(sha1sum) commands and are as follows:

csum -h SHA1 (sha1sum) filename
----------------------------------------------------------------------
6498591e2a75f5081f30487220ef205649be34a3 bos.net.nfs.client.5.3.7.9.U
55ff5576fccb052c05d0432250619ef9e3bd1fe1 bos.net.nfs.client.5.3.8.7.U
c98585939e0bf02c5b88adbb0bbc48c52d261e07 bos.net.nfs.client.5.3.9.3.U
d0d3f99ea11fcae97bacd782b904363f60191351 bos.net.nfs.client.6.1.0.9.U
5c73c73eca95fa782f82ade9c5b56f64217113ab bos.net.nfs.client.6.1.1.5.U
a3251008ee0e4e4a67b7e9beff5a0d9550407fcf bos.net.nfs.client.6.1.2.4.U

To verify the sums, use the text of this advisory as input to
csum or sha1sum. For example:

csum -h SHA1 -i Advisory.asc
sha1sum -c Advisory.asc

These sums should match exactly. The PGP 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 and describe the
discrepancy at the following address:

security-alert@austin.ibm.com

C. 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.

IV. WORKAROUNDS

There are no workarounds.

V. OBTAINING FIXES

AIX security fixes can be downloaded from:

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

AIX fixes can be downloaded from:

http://www.ibm.com/eserver/support/fixes/fixcentral/main/pseries/aix

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

VI. CONTACT INFORMATION

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

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

and click on the "My notifications" link.

To view previously issued advisories, 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 obtain the PGP public key that can be used to communicate
securely with the AIX Security Team you can either:

A. Download the key from our web page:

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

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

0xADA6EB4D

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.

VII. ACKNOWLEDGMENTS

The vulnerabilties were reported by Anton Lundin.

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