AUSCERT External Security Bulletin Redistribution

                      ESB-2001.272 -- HPSBMP0107-012
               Security Vulnerability in CIFS/9000 Server #2
                                4 July 2001


        AusCERT Security Bulletin Summary

Product:                CIFS/3000 Server (Samba/iX)
Vendor:                 Hewlett-Packard
Operating System:       HP-UX
Platform:               HP3000 MPE/iX
Impact:                 Modify Arbitrary Files
Access Required:        Remote

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Document ID:  HPSBMP0107-012
Date Loaded:  20010702
      Title:  Security Vulnerability in CIFS/9000 Server #2

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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/3000 Server (Samba) - use of certain configuration
          options may compromise system security

PLATFORM: All HP3000 MPE/iX 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

C. Workarounds

   The "log file" option is the most vulnerable to this redefinition
   problem.  The sample configuration file supplied with CIFS/3000
   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:

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


   Under the Maintenance and Support Menu:
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   Under the "Notifications" section (near the bottom of
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   To -subscribe- to future HP Security Bulletins or other
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   For information on the HP-UX Security Patch Check tool, see:

   The security patch matrix is also available via anonymous ftp:


   On the "Support Information Digest Main" page:
   click on the "HP Security Bulletin Archive".

E. To report new security vulnerabilities, send email to


    Please encrypt any exploit information using the security-alert
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    Permission is granted for copying and circulating this Advisory
    to Hewlett-Packard (HP) customers (or the Internet community) for
    the purpose of alerting them to problems, if and only if, the
    Advisory is not edited or changed in any way, is attributed to
    HP, and provided such reproduction and/or distribution is
    performed for non-commercial purposes.

    Any other use of this information is prohibited. HP is not liable
    for any misuse of this information by any third party.
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