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AUSCERT External Security Bulletin Redistribution
ESB-2008.0856 -- [AIX]
AIX swcons file ownership/permission vulnerability.
18 September 2008
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: swcons
Publisher: IBM
Operating System: AIX
Impact: Root Compromise
Access: Existing Account
CVE Names: CVE-2008-4018
Ref: ESB-2007.0852
Original Bulletin:
http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd?mode=18&ID=4356
Revision History: September 18 2008: Added CVE Reference
September 4 2008: Initial Release
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IBM SECURITY ADVISORY
First Issued: Wed Sep 3 09:53:43 CDT 2008
===============================================================================
VULNERABILITY SUMMARY
VULNERABILITY: AIX swcons file ownership/permission vulnerability.
PLATFORMS: AIX 5.2, 5.3, 6.1
SOLUTION: Apply the fix or workaround as described below.
THREAT: An local attacker in the system group may create
files owned by root with arbitrary contents.
CERT VU Number: n/a
CVE Number: n/a
Reboot required? NO
Workarounds? YES
Protected by FPM? YES (high, medium, or low)
Protected by SED? NO
NOTE: This issue was initially fixed in October 2007. We have found
security issues in the original fix, so a new set of APARs and interim
fixes is being released.
===============================================================================
DETAILED INFORMATION
I. OVERVIEW
The AIX Console command 'swcons' is a utility for redirecting,
temporarily, the system console output to a specified device or
file. This command contains a vulnerability that allows a local
attacker to create files owned by root that have insecure
permissions allowing for arbitrary content creation within the
file.
II. DESCRIPTION
A file permission/ownership vulnerability exists in the
'bos.rte.console' fileset command listed below whereby a local
attacker may create arbitrary contents within a file owned by root
using the 'swcons' command. The local attacker must be a member
of the 'system' group (gid=0) to execute this command.
The following commands are vulnerable:
/usr/sbin/swcons
III. IMPACT
The successful exploitation of this vulnerability allows a user in
the system group to execute code with root privileges.
IV. PLATFORM VULNERABILITY ASSESSMENT
To determine if your system is vulnerable, execute the following
command:
lslpp -L bos.rte.console
The following fileset levels are vulnerable:
AIX Fileset Lower Level Upper Level
---------------------------------------------------
bos.rte.console 5.2.0.0 5.2.0.107
bos.rte.console 5.3.0.0 5.3.0.51
bos.rte.console 5.3.0.60 5.3.0.62
bos.rte.console 5.3.7.0 5.3.7.0
bos.rte.console 5.3.8.0 5.3.8.0
bos.rte.console 6.1.0.0 6.1.0.0
bos.rte.console 6.1.1.0 6.1.1.0
V. SOLUTIONS
A. APARS
IBM has assigned the following APARs to this problem:
AIX Level APAR number Availability
----------------------------------------------------
5.2.0 IZ18335 Now
5.3.0 IZ18339 10/29/2008
5.3.7 IZ18338 10/29/2008
5.3.8 IZ18334 10/29/2008
6.1.0 IZ18341 11/19/2008
6.1.1 IZ28943 11/19/2008
Subscribe to the APARs here:
http://www.ibm.com/support/docview.wss?uid=isg1IZ18335
http://www.ibm.com/support/docview.wss?uid=isg1IZ18339
http://www.ibm.com/support/docview.wss?uid=isg1IZ18338
http://www.ibm.com/support/docview.wss?uid=isg1IZ18334
http://www.ibm.com/support/docview.wss?uid=isg1IZ18341
http://www.ibm.com/support/docview.wss?uid=isg1IZ28943
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 available. The fixes can be downloaded from:
http://aix.software.ibm.com/aix/efixes/security/swcons_fix.tar
ftp://aix.software.ibm.com/aix/efixes/security/swcons_fix.tar
The links above are to a tar file containing this signed
advisory, fix packages, and PGP signatures for each package.
The fixes below include prerequisite checking. This will
enforce the correct mapping between the fixes and AIX
Technology Levels.
AIX Level Fix
----------------------------------------------------
5.2.0 TL10 IZ18335_10.080826.epkg.Z
5.3.0 TL5 IZ18339_05.080826.epkg.Z
5.3.0 TL6 IZ18339_06.080826.epkg.Z
5.3.7 IZ18338_07.080826.epkg.Z
5.3.8 IZ18334_08.080826.epkg.Z
6.1.0 IZ18341_00.080826.epkg.Z
6.1.1 IZ28943_01.080826.epkg.Z
To extract the fixes from the tar file:
tar xvf swcons_fix.tar
cd swcons_fix
Verify you have retrieved the fixes intact:
The checksums below were generated using the "sum", "cksum",
"csum -h MD5" (md5sum), and "csum -h SHA1" (sha1sum) commands
and are as follows:
sum filename
------------------------------------
50004 32 IZ18334_08.080826.epkg.Z
50164 32 IZ18335_10.080826.epkg.Z
33545 32 IZ18338_07.080826.epkg.Z
30874 32 IZ18339_05.080826.epkg.Z
60994 33 IZ18339_06.080826.epkg.Z
44187 36 IZ18341_00.080826.epkg.Z
64728 36 IZ28943_01.080826.epkg.Z
cksum filename
-----------------------------------------
724913179 32705 IZ18334_08.080826.epkg.Z
2252439840 32703 IZ18335_10.080826.epkg.Z
378004369 32728 IZ18338_07.080826.epkg.Z
3098309145 32542 IZ18339_05.080826.epkg.Z
1158533085 33005 IZ18339_06.080826.epkg.Z
184154673 36594 IZ18341_00.080826.epkg.Z
4029788068 36647 IZ28943_01.080826.epkg.Z
csum -h MD5 (md5sum) filename
----------------------------------------------------------
58360a3cb7ec971016b77b7342d663c8 IZ18334_08.080826.epkg.Z
e4323c48eae84a4d76a220a5d214fe83 IZ18335_10.080826.epkg.Z
def0fa6de3b0ddbad3ea1d7a2fc84c3a IZ18338_07.080826.epkg.Z
c03949a68447daf0e19585316ee48242 IZ18339_05.080826.epkg.Z
fb5441c3bacfd77b10164d34293c2987 IZ18339_06.080826.epkg.Z
ecc856d9c901b706923875c720adf9cb IZ18341_00.080826.epkg.Z
80bbf4dc5546ff085041fbc14b7809b6 IZ28943_01.080826.epkg.Z
csum -h SHA1 (sha1sum) filename
------------------------------------------------------------------
a831f59acf084bc129337cc83f904eead10da617 IZ18334_08.080826.epkg.Z
efa693f507b14c5dd43f6335d2eb094cf2509d8a IZ18335_10.080826.epkg.Z
e780b1acaa471247aa9c6f8d9b1b771ac380b240 IZ18338_07.080826.epkg.Z
9701fcd688c00c336037fa8006fc195d4bfb87b4 IZ18339_05.080826.epkg.Z
147ba9de1ca5df271f623fb03f859244b635c443 IZ18339_06.080826.epkg.Z
aef122bb24ab98cc3c23827c6e265cf4b3fdf232 IZ18341_00.080826.epkg.Z
f6954fc2ef564efc0fa5e58d0e14e68d2d26dafe IZ28943_01.080826.epkg.Z
To verify the sums, use the text of this advisory as input to
csum, md5sum, or sha1sum. For example:
csum -h SHA1 -i Advisory.asc
md5sum -c 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. 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.
Interim fixes have had limited functional and regression
testing but not the full regression testing that takes place
for Service Packs; thus, IBM does not warrant the fully
correct functionality of an interim fix.
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.
VI. WORKAROUNDS
There are two workarounds available.
A. OPTION 1
Change the permissions of these commands to remove the setuid
bit using the following commands:
chmod 500 /usr/sbin/swcons
NOTE: chmod will disable functionality of these commands for
all users except root.
B. OPTION 2 (AIX 6.1, AIX 5.3 TL6 and TL7)
Use the File Permissions Manager (fpm) command to manage
setuid and setgid programs.
fpm documentation can be found in the AIX 6 Security Redbook
at:
http://www.redbooks.ibm.com/abstracts/sg247430.html
An fpm level of high, medium, or low will remove the setuid
bit from the affected commands. For example:
fpm -l high -p # to preview changes
fpm -l high # to execute changes
NOTE: Please review the documentation before execution. fpm
will disable functionality of multiple commands for all users
except root.
VII. OBTAINING FIXES
AIX security fixes can be downloaded from:
http://aix.software.ibm.com/aix/efixes/security
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.
VIII. CONTACT INFORMATION
If you would like to receive AIX Security Advisories via email,
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 request the PGP public key that can be used to communicate
securely with the AIX Security Team you can either:
A. Send an email with "get key" in the subject line to:
security-alert@austin.ibm.com
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.
IX. ACKNOWLEDGMENTS
This vulnerability was reported by iDefense Labs.
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