jfyuen / tgc

TCP Gender Changer

TCP Gender Changer

TCP Gender Changer is a small utility to connect/connect on a local service to a remote server using a listen/listen setup. More information on wikipedia.

This is heavily inspired by http://tgcd.sourceforge.net

Installation

$ go get -u github.com/jfyuen/tgc

Usage

On the node on which to access a server on a LAN, run the connect/connect setup:

$ tgc -C -s ${LOCAL_ADDRESS} -c ${REMOTE_ADDRESS}

On the remote node on which you can connect to, run the listen/listen setup:

$ tgc -L -q ${EXTERNAL_PORT} -p ${LOCAL_PORT}

The remote node now has access to the local server on the LAN via ${LOCAL_PORT}. A connection is initiated to the local server only when data are received from the remote server, unless the -r flag is specified to automatically (re)connect to the local server.

Additionally, a secure connection can be established between the Connect/Connect node and the Listen/Listen node by using the following options for both modes:

• ca: CA of the connecting party, on the server side, provide the client CA; on the client side, provide the server CA. They can be the same CA
• crt: x509 cert file signed by the CA provided to the remote node
• key: key file

Example

Forward local port 8080 to a remote server (${REMOTE}) on port 8000 via port 80. On the local server:

$ tgc -C -s 127.0.0.1:8080 -c ${REMOTE}:80

On the remote server:

$ tgc -L -q ${REMOTE}:80 -p 127.0.0.1:8000

Secure connection between nodes

A script generate_certificates.sh helps create a basic CA, server and client certificate. Give the CN (Common Name) as parameter:

$ ./generate_certificates.sh ${REMOTE}

Forward local port 8080 to a remote server on port 8000 via port 80. On the local server:

$ tgc -C -s 127.0.0.1:8080 -c ${REMOTE}:80 -ca ca.crt -crt client.crt -key client.key

On the remote server:

$ tgc -L -q ${REMOTE}:80 -p 127.0.0.1:8000  -ca ca.crt -crt server.crt -key server.key