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Security Vulnerability in CIFS/9000 Server #2
HPSBUX0107-157
Published: 2001-07-03 00:00:00
Updated: 2001-07-03 00:00:00

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    HEWLETT-PACKARD COMPANY SECURITY ADVISORY: #0157, 3 July '01
------------------------------------------------------------------------

The information in the following Security Advisory should be acted upon
as soon as possible.  Hewlett-Packard Company will not be liable for any
consequences to any customer resulting from customer's failure to fully
implement instructions in this Security Advisory as soon as possible.

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PROBLEM:  CIFS/9000 Server (Samba) - use of certain configuration
          options may compromise system security.

PLATFORM: HP 9000 servers running CIFS/9000 Server version A.01.07 or
          lower; HP 3000 servers running Samba/iX

DAMAGE:   Data may be appended to arbitrary files and devices

SOLUTION: Remove offending configuration options to avoid vulnerability

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A. Background

   The NetBIOS name of remote clients is substituted into the "%m"  macro
   wherever it occurs in the configuration file smb.conf.  The use of
   contrived NetBIOS names may result in Samba using a file path
   outside of the intended Samba directories.  This can be used to cause
   Samba to append data to important system files, which in turn can be
   used to compromise security on the server.

B. Fixing the problem

   An immediate fix is to edit your smb.conf configuration file and
   remove all occurances of the macro "%m".  Depending on the
   requirements of each site, other smb.conf macros may be suitable
   replacements.

C. Workarounds

   The "log file" option is the most vulnerable to this redefinition
   problem.  The sample configuration file supplied with CIFS/9000
   Server contains the path "/var/opt/samba/log.%m" for this option.
   Using this default path does NOT create a vulnerability unless
   there happens to exist a subdirectory in /var/opt/samba which
   starts with the prefix "log.".

   Sites that chooose to maintain the use of the "%m" macro in the
   "log file" option should use the default value:
      /var/opt/samba/log.%m

D. To subscribe to automatically receive future NEW HP Security
   Bulletins from the HP IT Resource Center via electronic mail,
   do the following:

   Use your browser to get to the HP IT Resource Center page at:

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   Under the Maintenance and Support Menu:
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   Use the 'Login' tab at the left side of the screen to login
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   On the "Support Information Digest Main" page:
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E. To report new security vulnerabilities, send email to

   security-alert@hp.com

   Please encrypt any exploit information using the security-alert
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