natpmp.lua

---
-- This library implements the basics of NAT-PMP as described in the
-- NAT Port Mapping Protocol (NAT-PMP) draft:
--   o https://tools.ietf.org/html/draft-cheshire-nat-pmp-03
--
--
-- @author Patrik Karlsson <patrik@cqure.net>
--
local datetime = require "datetime"
local ipOps = require "ipOps"
local nmap = require "nmap"
local stdnse = require "stdnse"
local string = require "string"
_ENV = stdnse.module("natpmp", stdnse.seeall)

local ResultCode = {
  SUCCESS = 0,
  UNSUPPORTED_VERSION = 1,
  NOT_AUTHORIZED = 2,
  NETWORK_FAILURE = 3,
  OUT_OF_RESOURCES = 4,
  UNSUPPORTED_OPCODE = 5,
}

local ErrorMessage = {
  [ResultCode.UNSUPPORTED_VERSION] = "The device did not support the protocol version",
  [ResultCode.NOT_AUTHORIZED] = "The operation was not authorized",
  [ResultCode.NETWORK_FAILURE] = "Network failure",
  [ResultCode.OUT_OF_RESOURCES] = "The device is out of resources",
  [ResultCode.UNSUPPORTED_OPCODE] = "The requested operation was not supported",
}


Request = {

  GetWANIP = {

    new = function(self)
      local o = { version = 0, op = 0 }
      setmetatable(o, self)
      self.__index = self
      return o
    end,

    __tostring = function(self)
      return string.pack(">BB", self.version, self.op)
    end,

  },

  MapPort = {

    new = function(self, pubport, privport, proto, lifetime)
      assert(proto == "udp" or proto == "tcp", "Unsupported protocol")
      local o = {
        version = 0,
        pubport = pubport,
        privport = privport,
        proto = proto,
        lifetime = lifetime or 3600
      }
      setmetatable(o, self)
      self.__index = self
      return o
    end,

    __tostring = function(self)
      return string.pack(">BBI2I2I2I4",
        self.version,
        (self.proto=="udp" and 1 or 2),
        0, -- reserved
        self.privport, self.pubport,
        self.lifetime)
    end,

  }

}

Response = {

  GetWANIP = {

    new = function(self, data)
      local o = { data = data }
      setmetatable(o, self)
      self.__index = self
      if ( o:parse() ) then
        return o
      end
    end,

    parse = function(self)
      if ( #self.data ~= 12 ) then
        return
      end

      local pos
      self.version, self.op, self.rescode, pos = string.unpack(">BBI2", self.data)

      if ( self.rescode ~= ResultCode.SUCCESS or self.op ~= 128 ) then
        return
      end

      self.time, self.ip, pos = string.unpack(">I4I4", self.data, pos)
      self.ip = ipOps.fromdword(self.ip)
      self.time = datetime.format_timestamp(self.time)
      return true
    end,

  },

  MapPort = {

    new = function(self, data)
      local o = { data = data }
      setmetatable(o, self)
      self.__index = self
      if ( o:parse() ) then
        return o
      end
    end,

    parse = function(self)
      if ( #self.data ~= 16 ) then
        return
      end

      local pos
      self.version, self.op, self.rescode, pos = string.unpack(">BBI2", self.data)

      if ( self.rescode ~= ResultCode.SUCCESS ) then
        return
      end

      self.time, self.privport, self.pubport, self.lifetime, pos = string.unpack(">I4I2I2I4", self.data, pos)
      return true
    end,
  }


}





Helper = {

  new = function(self, host, port)
    local o = { host = host, port = port }
    setmetatable(o, self)
    self.__index = self
    return o
  end,

  exchPacket = function(self, data)
    local socket = nmap.new_socket("udp")
    socket:set_timeout(5000)

    local status = socket:sendto(self.host, self.port, data)
    if ( not(status) ) then
      socket:close()
      return false, "Failed to send request to device"
    end

    local response
    status, response = socket:receive()
    socket:close()
    if ( not(status) ) then
      return false, "Failed to receive response from router"
    end
    return true, response
  end,

  --- Gets the WAN ip of the router
  getWANIP = function(self)
    local packet = Request.GetWANIP:new()
    local status, response = self:exchPacket(tostring(packet))
    if ( not(status) ) then
      return status, response
    end

    response = Response.GetWANIP:new(response)
    if ( not(response) ) then
      return false, "Failed to parse response from router"
    end

    return true, response
  end,

  --- Maps a public port to a private port
  -- @param pubport number containing the public external port to map
  -- @param privport number containing the private internal port to map
  -- @param protocol string containing the protocol to map (udp|tcp)
  -- @param lifetime [optional] number containing the lifetime in seconds
  mapPort = function(self, pubport, privport, protocol, lifetime)
    local packet = Request.MapPort:new(pubport, privport, protocol, lifetime)
    local status, response = self:exchPacket(tostring(packet))
    if ( not(status) ) then
      return status, response
    end

    response = Response.MapPort:new(response)
    if ( not(response) ) then
      return false, "Failed to parse response from router"
    end

    return true, response
  end,

  unmapPort = function(self, pubport, privport)
    return self:mapPort(pubport, privport, 0)
  end,

  unmapAllPorts = function(self)
    return self.mapPort(0, 0, 0)
  end,

}

return _ENV;