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Category:   Application (File Transfer/Sharing)  >   FTP (Generic) Vendors:   IBM
IBM AIX ftpd Discloses Passwords to Certain Local Users and Lets Remote Users Deny Service
SecurityTracker Alert ID:  1017480
SecurityTracker URL:  http://securitytracker.com/id/1017480
CVE Reference:   CVE-2006-6914, CVE-2006-6915   (Links to External Site)
Updated:  May 20 2008
Original Entry Date:  Jan 9 2007
Impact:   Denial of service via network, Disclosure of authentication information, Disclosure of system information
Fix Available:  Yes  Vendor Confirmed:  Yes  

Description:   Two vulnerabilities were reported in ftpd on IBM AIX. A remote user can cause denial of service conditions. A local user can obtain passwords in certain cases.

A local user can obtain passwords in certain cases. A local user may be able to obtain passwords for password protected anonymous users and groups ('puseronly' and 'pgrouponly' users listed in the '/etc/ftpaccess.ctl' file).

If the '/etc/ftpaccess.ctl' file does not exist or if both the 'puseronly' and 'pgrouponly' lines do not exist in the file, the system is not affected.

A remote user can send specially crafted data to cause the target service to consume all available ephemeral ports.

Impact:   A remote user can cause denial of service conditions.

A local user can obtain passwords in certain cases.

Solution:   The vendor has issued the following fixes:

APAR number for AIX 5.2.0: IY91787 (available approx. 01/24/07)
APAR number for AIX 5.3.0: IY89168 (available)

The vendor has also issued an interim fix, available at:

ftp://aix.software.ibm.com/aix/efixes/security/ftpd2_ifix.tar.Z

Vendor URL:  www.ibm.com/ (Links to External Site)
Cause:   Access control error
Underlying OS:  UNIX (AIX)
Underlying OS Comments:  5.2 - 5.2.0.98, 5.3 - 5.3.0.53

Message History:   None.


 Source Message Contents

Subject:  Technical Support Bulletin - UNIX

 
Subscription service for UNIX servers
 
 


AIX 5.2 : Security advisories (2007.01.08)
Multiple vulnerabilities in ftpd

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

IBM SECURITY ADVISORY


First Issued: Mon Jan  8 11:00:00 CST 2007
==========================================================================
                           VULNERABILITY SUMMARY

VULNERABILITY:      Multiple vulnerabilities in ftpd

PLATFORMS:          AIX 5.2 and 5.3.

SOLUTION:           Apply the APAR, interim fix or workaround as 
		    described below.

THREAT:             Password disclosure and denial of service
                    vulnerabilities in ftpd.

CERT VU Number:     n/a
CVE Number:         n/a
==========================================================================
                           DETAILED INFORMATION


I.  Description
===============

Two vulnerabilities were discovered in ftpd. First, a password disclosure
vulnerability exists in ftpd. Affected user accounts will be listed in
/etc/ftpaccess.ctl on the "puseronly" or "pgrouponly" lines. "puseronly"
and "pgrouponly" are used to designate password protected anonymous users
and password protected anonymous groups respectively. If /etc/ftpaccess.ctl
does not exist or if both the "puseronly" and "pgrouponly" lines do not
exist, ftpd is not affected by this vulnerability. An authorized local user
may be able to gain access to passwords for "puseronly" and "pgrouponly"
users. This issue affects AIX 5300-03 and later releases.

The following table shows the vulnerable versions of bos.net.tcp.client
which are affected by the password disclosure vulnerability:

AIX Release          Lower         Upper
                     Level         Level
===========================================
AIX 5.2              n/a           n/a
AIX 5.3              5.3.0.30      5.3.0.53

Second, a denial of service vulnerability has been found in ftpd which
allows a remote user to cause a denial of service by exhausting available
ephemeral ports.

The following table shows the vulnerable versions of bos.net.tcp.client
which are affected by the denial of service vulnerability:

AIX Release          Lower         Upper
                     Level         Level
===========================================
AIX 5.2              5.2.0.0       5.2.0.98
AIX 5.3              5.3.0.0       5.3.0.53


II. Impact
==========

A password disclosure vulnerability in ftpd may allow a local authorized
user to gain access to passwords for password protected anonymous users and
groups.

A vulnerability in ftpd may allow a remote authorized user to cause a
denial of service.

III.  Solutions
===============

A. APARs

IBM provides the following fixes:

      APAR number for AIX 5.2.0: IY91787 (available approx. 01/24/07) 
      APAR number for AIX 5.3.0: IY89168 (available)

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

B. Interim Fix

Interim fixes are available. The interim fixes can be downloaded via ftp
from:

    ftp://aix.software.ibm.com/aix/efixes/security/ftpd2_ifix.tar.Z

This is a compressed tarball containing this advisory, interim fix packages
and cleartext PGP signatures for each package.


Verify you have retrieved the fixes intact:
+------------------------------------------
The checksums below were generated using the "sum" and "md5sum" commands
and are as follows:


Filename                   sum           md5
=========================================================================
IY91787_07.061115.epkg.Z   46904   104   c5133ce9a80b9c5b828933b57620f6f7
IY91787_08.061115.epkg.Z   41655   107   ca7cdd5ac6e455f41f4eb61cc1dbc8bd
IY91787_09.061211.epkg.Z   45473   106   19c4e727c283d352391dac4cd8f76d32
IY89168_03.061115.epkg.Z   55003   109   84a52fe979a0516f47827989cbb55fd2
IY89168_04.061115.epkg.Z   45154   112   7af2a4496287f74d7a8aef4bd8ab4ddb

See the table below to determine which AIX Technology Level a given interim
fix maps to.

These sums should match exactly. The PGP signatures in the compressed
tarball and on this advisory can also be used to verify the integrity of
the various files they correspond to. If the sums or signatures cannot be
confirmed, double check the command results and the download site address.
If those are OK, contact IBM AIX Security at security-alert@austin.ibm.com
and describe the discrepancy.

The interim fixes include prerequisite checking. This will ensure the
correct mapping between the interim fixes and AIX Technology Levels. The
following table shows the prerequisite fileset levels required for the
fixes above. The fileset levels listed are for bos.rte.methods.

Interim                    Fileset Level     Fileset Level   AIX
Fix                        (lower limit)     (upper limit)   Level
=====================================================================
IY91787_07.061115.epkg.Z   5.2.0.77           5.2.0.77       5200-07
IY91787_08.061115.epkg.Z   5.2.0.85           5.2.0.88       5200-08
IY91787_09.061211.epkg.Z   5.2.0.95           5.2.0.98       5200-09
IY89168_03.061115.epkg.Z   5.3.0.30           5.3.0.32       5300-03
IY89168_04.061115.epkg.Z   5.3.0.40           5.3.0.44       5300-04

IMPORTANT: If possible, it is recommended that a mksysb backup of the
system is created. Verify it is both bootable, and readable before
proceeding.

Customers may contact IBM support if any issues arise with these interim
fixes.


Interim Installation Instructions:
+---------------------------------
These packages use the new Interim Fix Management Solution to install and
manage interim fixes. More information can be found at:

     http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html

To preview an epkg interim fix installation execute the following command:

# emgr -e ipkg_name -p       # where ipkg_name is the name of the
                             # interim fix package being previewed.

To install an epkg interim fix package, execute the following command:

# emgr -e ipkg_name -X       # where ipkg_name is the name of the
                             # interim fix package being installed.

The "X" flag will expand any filesystems if required.

C. Workaround

The password disclosure vulnerability can be mitigated by ensuring that
only trusted users have access to messages generated by syslogd for ftpd.

The denial of service vulnerability can be mitigated by setting the
nofiles_hard resource limit for users. This will limit the number of
ephemeral ports a given user can have open at a given time. This
vulnerability can also be mitigated by using the "no" (network options)
command to manage relevant network tuning parameters. The relevant
parameters are sockthresh, tcp_ephemeral_high and tcp_ephemeral_low. The
sockthresh parameter specifies the maximum amount of network memory that
can be allocated for sockets. By lowering this value, system administrators
can limit the number of sockets the system will create. The
tcp_ephemeral_high and tcp_ephemeral_low parameters can be used together to
limit to number of ephemeral ports the system will use at a given time. 


IV. Obtaining Fixes
===================

AIX Version 5 APARs can be downloaded from:

     http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html

Security related Interim Fixes can be downloaded from:

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


V.  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 send email to security-alert@austin.ibm.com
with a subject of "get key". The key can also be downloaded from a PGP
Public Key Server. The key id is 0x1B14F299.

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.
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Version: GnuPG v1.4.3 (GNU/Linux)

iD8DBQFFomUCofN/JhsU8pkRAkhNAJ4zEmbiJ4Um2waS09UZwBu53QEC7ACfZR0R
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