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Home : Security Tools : Fpipe v2.01 Port Redirector
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FPipe v2.01 - Port redirector.
Copyright 2000 (c) by Foundstone, Inc.
http://www.foundstone.com
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FPipe is a TCP source port forwarder/redirector. It can create a TCP stream
with a source port of your choice. This is useful for getting past firewalls
that allow traffic with source ports of say 23, to connect with internal
servers.
Usually a client has a random, high numbered source port, which the firewall
picks off in its filter. However, the firewall might let Telnet traffic
through. FPipe can force the stream to always use a specific source port, in
this case the Telnet source port. By doing this, the firewall 'sees' the
stream as an allowed service and let's the stream through.
FPipe basically works by indirection. Start FPipe with a listening server
port, a remote destination port (the port you are trying to reach inside
the firewall) and the (optional) local source port number you want. When
FPipe starts it will wait for a client to connect on its listening port.
When a listening connection is made a new connection to the destination
machine and port with the specified local source port will be made - creating
the needed stream. When the full connection has been established, FPipe
forwards all the data received on its inbound connection to the remote
destination port beyond the firewall.
FPipe can run on the local host of the application that you are trying to use
to get inside the firewall, or it can listen on a 3rd server somewhere else.
Say you want to telnet to an internal HTTP server that you just compromised
with MDAC. A netcat shell is waiting on that HTTP server, but you can't
telnet because the firewall blocks it off. Start FPipe with the destination
of the netcat listener, a listening port and a source port that the firewall
will let through. Telnet to FPipe and you will be forwarded to the NetCat
shell. Telnet and FPipe can exist on the same server, or on different servers.
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