#!/usr/bin/ruby
=begin
**
** xmitm.rb
** 26/DEC/2007
** ETD-Software
**  - Daniel Martin Gomez <etd[-at-]nomejortu.com>
**
** Desc:
**  Man in the Middle ASCII based TCP communications
**
** Version:
**  v1.0 [26/Dec/2007]: first released
**
**  This program is free software: you can redistribute it and/or modify
**  it under the terms of the GNU General Public License as published by
**  the Free Software Foundation, either version 2 of the License, or
**  (at your option) any later version.
**
**  This program is distributed in the hope that it will be useful,
**  but WITHOUT ANY WARRANTY; without even the implied warranty of
**  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
**  GNU General Public License for more details.
**
**  You should have received a copy of the GNU General Public License
**  along with this program.  If not, see <http://www.gnu.org/licenses/>.

=end

require 'socket'
require 'net/http'

# ------------------------------------------------------------ config
# local end point, the client will connect here
$local_host = 'localhost'
$local_port = 1234

# remote end point, the client wishes to connect here
$remote_host = 'www.nomejortu.com'
$remote_port = 1234

# external proxy tool
$proxy_host = 'localhost'
$proxy_port = 8080

# external dummy http server
$dummyhttp_host = 'localhost'
$dummyhttp_port = 2000

# end of message: client and server end their messages with a NULL byte
$eom = '' << 0
# ------------------------------------------------------------ /config


# create a server that accepts connections from the client
server = TCPServer.new($local_host, $local_port)

while(local = server.accept ) do
  # everytime we accept a connection for the client, we open a connection
  # with the server to stablish the dialog.
  remote = TCPSocket.new($remote_host, $remote_port)

  # if one of the ends of the communication closes the socket, we
  # toggle this flag
  alive = true
    
  while alive do
    result = select([local, remote], nil, nil)
  
    if result != nil then
      for socket in result[0]

        # detect if one end of the connection is closed and
        # close the other end
        if (socket.eof?)
          local.close
          remote.close
          alive = false
          break
        end

        # read the information that one peer wants to send to the other        
        data = socket.gets($eom)

        # encapsulate the data into an HTTP proxy request
        res = Net::HTTP.new($proxy_host, $proxy_port).start do |http| 
          req = Net::HTTP::Post.new("http://#{$dummyhttp_host}:#{$dummyhttp_port}/")
          req.body= data
          http.request(req)
        end

        modified_data = res.body.chomp

        # send the modified data to the other end of the connection
        if (socket == local)
          remote.puts(modified_data)
        else
          local.puts(modified_data)
        end
        socket.flush
      end
    end
  end
end