Re: Fw: Remote bufferoverflow exploit for ftpd from AIX 4.3.2 running on an RS6000. (power)

[troy () AUSTIN IBM COM (Troy A. Bollinger)]

Quoting W.H.J.Pinckaers (W.H.J.Pinckaers () CPEDU RUG NL):
> sq01 () Yorku Ca <sq01 () Yorku Ca> Wrote
>
> > > Short of disabling ftpd completely, is there a work-around that will not
> > > affect our users ?

We released an advisory this morning but I haven't seen it on bugtraq
yet.  I've attached it below in case it got lost.  It includes
instructions on where to download the workaround.

> You can check this by running something like:
> perl -e 'print "A" x 5000' | nc -v -v aix 21
> (effectivly sending a long string to the aix ftpd)
> if this returns immediatly (ftpd dies) you are vulnerable if it returns a
> lot of 500 AAAAAAA... unknown command or something like that
> errors you are NOT vulnerable.

Be careful.  Sometimes ftpd prints an error message but still core
dumps.  All unpatched 4.3.x machines are vulnerable.

--
Troy Bollinger                            troy () austin ibm com
AIX Security Development        security-alert () austin ibm com
PGP keyid: 1024/0xB7783129 Troy's opinions are not IBM policy


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                           EMERGENCY RESPONSE SERVICE
                          SECURITY VULNERABILITY ALERT

29 September 1999 11:30 GMT                      Number: ERS-SVA-E01-1999:004.1
===============================================================================
                           VULNERABILITY SUMMARY

VULNERABILITY:    Remote buffer overflow in ftpd daemon.

PLATFORMS:        IBM AIX(r) 4.3.x

SOLUTION:         Apply the fixes listed below.

THREAT:           Remote users can become root.

==============================================================================
                           DETAILED INFORMATION

I.  Description

A buffer overflow vulnerability has been found in the AIX 4.3.x ftpd
daemon that allows remote attackers to gain root access.  Example
exploit code has been publically released.

II.  Solutions

  A.  How to alleviate the problem

      A temporary fix is available via anonymous ftp from:

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

      Filename     sum                md5
      =================================================================
      ftpd         02584   147        4577818c9c95b47ffc915ab750f36bd3

      This temporary fix has not been fully regression tested.  Use the
      following steps (as root) to install the temporary fix:

      1. Uncompress and extract the fix.

         # uncompress < ftpd.tar.Z | tar xf -
         # cd ftpd

      2. Replace the vulnerable ftpd.

         # mv /usr/sbin/ftpd /usr/sbin/ftpd.before_security_fix
         # chown root.system /usr/sbin/ftpd.before_security_fix
         # chmod 0 /usr/sbin/ftpd.before_security_fix
         # cp ./ftpd /usr/sbin/ftpd
         # chown root.system /usr/sbin/ftpd
         # chmod 4554 /usr/sbin/ftpd

  B.  Official fix

      IBM is working on the following fixes which will be available soon.

         AIX 4.2.x and earlier:  not vulnerable
         AIX 4.3.x:  IY04477

III. Obtaining Fixes

IBM AIX APARs may be ordered using Electronic Fix Distribution (via the
FixDist program), or from the IBM Support Center.  For more information
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   http://techsupport.services.ibm.com/support/rs6000.support/downloads

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