A Security Vulnerability in samba(7) Domain logons may allow execution of Arbitrary code with Root privileges

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A Security Vulnerability in samba(7) Domain logons may allow execution of Arbitrary code with Root privileges

1. Impact

A stack-based buffer overflow security vulnerability exists in the send_mailslot function in nmbd(8) in Samba 3.0.0 through 3.0.27a when the "domain logons" option is enabled. This vulnerability may allow a remote unprivileged user the ability to execute arbitrary code as "root" user via a GETDC mailslot request composed of a long GETDC string following an offset username in a SAMLOGON logon request.

More info on this issue can be found in the following document:


2. Contributing Factors

This issue can occur in the following releases:

SPARC Platform

• Solaris 9 without patch 114684-11
  
• Solaris 10 without patch 119757-10

x86 Platform

• Solaris 9 without patch 114685-11
  
• Solaris 10 without patch 119758-10

with the following versions of Samba software:

• Samba 3.0.0 through 3.0.27a

Note: Solaris 8 does not include the Samba software and is therefore not affected by this issue.

To determine the version of Samba installed on a system, the following command can be run:

% /usr/sfw/sbin/smbd -V
Version  3.0.4

This issue only affects systems configured as Samba servers that have enabled the netlogon service for Windows 9X network logons.

To determine if a system is configured as a Samba server, the following command can be run to check for processes related to Samba:

% ps -ef | grep mbd
root   317     1   0   May 26 ?           0:01 /usr/sfw/sbin/smbd -D
root   325   317   0   May 26 ?           0:00 /usr/sfw/sbin/smbd -D
root   314     1   0   May 26 ?           0:27 /usr/sfw/sbin/nmbd -D
root 28369 17382   0 23:17:46 pts/2       0:00 grep mbd

If the output shows "smbd" or "nmbd" running as a daemon (with the -D parameter), the system is configured as a Samba server.

To determine if the Samba server has enabled the netlogon service for Windows 9X network logons, the following steps may be employed:

1. Verify that the process "/usr/sfw/sbin/nmbd -D" is running. This may be done using the ps(1) command as shown above.

2. Verify that the "domain logons" configuration parameter is set to "yes" to provide the netlogon service for Windows 9X network logons. This may be verified looking into the /etc/sfw/smb.conf file.

For more details, please see the Samba documentation at:

http://us1.samba.org/samba/docs/man/manpages-3/smb.conf.5.html#DOMAINLOGONS

3. Symptoms

There are no predictable symptoms that would indicate the described vulnerability has been exploited to run arbitrary code.

4. Workaround

To work around the described issue, the netlogon service for Windows 9X network logons may be stopped. This can be achieved by modifying the "domain logons" entry in the /etc/sfw/smb.conf file to "no". The Samba server must be restarted after making this modification for the changes to take effect. This may be done using the following command (as 'root' user):

On Solaris 9:

# /etc/init.d/samba stop
# /etc/init.d/samba start

On Solaris 10:

# svcadm disable wins
# svcadm enable wins

5. Resolution

This issue is addressed in the following releases:

SPARC Platform

• Solaris 9 with patch 114684-11 or later
  
• Solaris 10 with patch 119757-10 or later

x86 Platform

• Solaris 9 with patch 114685-11 or later
  
• Solaris 10 with patch 119758-10 or later

For more information on Security Sun Alerts, see Technical Instruction ID 213557.

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Modification History

11-Jun-2008: Updated Contributing Factors and Resolution sections; RESOLVED

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