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# -*- coding: binary -*-
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##
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#
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# NAT-PMP protocol support
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#
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##
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module Rex
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module Proto
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module NATPMP::Packet
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  # Return a NAT-PMP request to get the external address.
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  def external_address_request
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    [ 0, 0 ].pack('nn')
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  end
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  def get_external_address(udp_sock, host, port, timeout=1)
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    vprint_status("#{host}:#{port} - Probing NAT-PMP for external address")
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    udp_sock.sendto(external_address_request, host, port, 0)
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    external_address = nil
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    while (r = udp_sock.recvfrom(12, timeout) and r[1])
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      (ver, op, result, epoch, external_address) = parse_external_address_response(r[0])
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      if external_address
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        vprint_good("#{host}:#{port} - NAT-PMP external address is #{external_address}")
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        break
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      end
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    end
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    external_address
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  end
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  # Parse a NAT-PMP external address response +resp+.
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  # Returns the decoded parts of the response as an array.
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  def parse_external_address_response(resp)
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    (ver, op, result, epoch, addr) = resp.unpack("CCnNN")
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    [ ver, op, result, epoch, Rex::Socket::addr_itoa(addr) ]
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  end
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  def map_port(udp_sock, host, port, int_port, ext_port, protocol, lifetime, timeout=1)
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    vprint_status("#{host}:#{port} - Sending NAT-PMP mapping request")
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    # build the mapping request
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    req = map_port_request(int_port, ext_port,
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      Rex::Proto::NATPMP.const_get(datastore['PROTOCOL']), datastore['LIFETIME'])
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    # send it
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    udp_sock.sendto(req, host, datastore['RPORT'], 0)
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    # handle the reply
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    while (r = udp_sock.recvfrom(16, timeout) and r[1])
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      (_, _, result, _, _, actual_ext_port, _) = parse_map_port_response(r[0])
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      return (result == 0 ? actual_ext_port : nil)
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    end
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    nil
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  end
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  # Return a NAT-PMP request to map remote port +rport+/+protocol+ to local port +lport+ for +lifetime+ ms
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  def map_port_request(lport, rport, protocol, lifetime)
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    [ Rex::Proto::NATPMP::Version, # version
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      protocol, # opcode, which is now the protocol we are asking to forward
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      0, # reserved
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      lport,
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      rport,
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      lifetime
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    ].pack("CCnnnN")
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  end
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  # Parse a NAT-PMP mapping response +resp+.
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  # Returns the decoded parts as an array.
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  def parse_map_port_response(resp)
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    resp.unpack("CCnNnnN")
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  end
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end
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end
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end
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