sigh.rb

require 'rubygems'
require 'eventmachine'

module ProxyConnection
  def initialize(client, request)
    @client, @request = client, request
  end

  def post_init
    EM::enable_proxy(self, @client)
  end

  def connection_completed
    send_data @request
  end

  def proxy_target_unbound
    close_connection
  end

  def unbind
    @client.close_connection_after_writing
  end
end

module ProxyServer
  
  def receive_data(data)
    (@buf ||= "") << data
    
    return  if @buf.size < 9
    null_index = @buf[8..-1].index("\0")
    return if null_index.nil?

    header_request = @buf.slice! 0, 9 + null_index
    version, cmd, port, host = header_request.unpack("CCnA4")

    if version != 4 || cmd != 1
      resp = [0, 0x5b, 0, 0, 0, 0, 0, 0].pack("C8")
      send_data resp
      close_connection_after_writing
    else
      host = host.unpack("C*").join(".")
      EM.connect host, port, ProxyConnection, self, data
      send_data [0, 0x5a, 0, 0, 0, 0, 0, 0].pack("C8")
    end
  end
end

EventMachine::run {
  EventMachine::start_server "127.0.0.1", 1080, ProxyServer
  puts "running proxy"
}