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---
-- A library that implements the basics of the STUN protocol (Session
-- Traversal Utilities for NAT) per RFC3489 and RFC5389. A protocol
-- overview is available at http://en.wikipedia.org/wiki/STUN.
--
-- @args stun.mode Mode container to use. Supported containers: "modern"
-- (default) or "classic"
--
-- @author Patrik Karlsson <patrik@cqure.net>
--
local bin = require "bin"
local ipOps = require "ipOps"
local match = require "match"
local math = require "math"
local nmap = require "nmap"
local stdnse = require "stdnse"
local string = require "string"
local table = require "table"
_ENV = stdnse.module("stun", stdnse.seeall)
-- The supported request types
MessageType = {
BINDING_REQUEST = 0x0001,
BINDING_RESPONSE = 0x0101,
}
-- The header used in both request and responses
Header = {
-- the header size in bytes
size = 20,
--- creates a new instance of Header
-- @param type number the request/response type
-- @param trans_id string the 128-bit transaction id
-- @param length number the packet length
-- @return new instance of Header
-- @name Header.new
new = function(self, type, trans_id, length)
local o = { type = type, trans_id = trans_id, length = length or 0 }
setmetatable(o, self)
self.__index = self
return o
end,
--- parses an opaque string and creates a new Header instance
-- @param data opaque string
-- @return new instance of Header
-- @name Header.parse
parse = function(data)
local header = Header:new()
local pos
pos, header.type, header.length, header.trans_id = bin.unpack(">SSA16", data)
return header
end,
-- converts the header to an opaque string
-- @return string containing the header instance
__tostring = function(self)
return bin.pack(">SSA", self.type, self.length, self.trans_id)
end,
}
Request = {
-- The binding request
Bind = {
--- Creates a new Bind request
-- @param trans_id string containing the 128 bit transaction ID
-- @return new instance of the Bind request
-- @name Request.Bind.new
new = function(self, trans_id)
local o = {
header = Header:new(MessageType.BINDING_REQUEST, trans_id),
attributes = {}
}
setmetatable(o, self)
self.__index = self
return o
end,
-- converts the instance to an opaque string
-- @return string containing the Bind request as string
__tostring = function(self)
local data = ""
for _, attrib in ipairs(self.attributes) do
data = data .. tostring(attrib)
end
self.header.length = #data
return tostring(self.header) .. data
end,
}
}
-- The attribute class
Attribute = {
MAPPED_ADDRESS = 0x0001,
RESPONSE_ADDRESS = 0x0002,
CHANGE_REQUEST = 0x0003,
SOURCE_ADDRESS = 0x0004,
CHANGED_ADDRESS = 0x0005,
USERNAME = 0x0006,
PASSWORD = 0x0007,
MESSAGE_INTEGRITY = 0x0008,
ERROR_CODE = 0x0009,
UNKNOWN_ATTRIBUTES = 0x000a,
REFLECTED_FROM = 0x000b,
SERVER = 0x8022,
--- creates a new attribute instance
-- @param type number containing the attribute type
-- @param data string containing the attribute value
-- @return instance of attribute
-- @name Attribute.new
new = function(self, type, data)
local o = {
type = type,
length = (data and #data or 0),
data = data,
}
setmetatable(o, self)
self.__index = self
return o
end,
--- parses a string and creates an Attribute instance
-- @param data string containing the raw attribute
-- @return new attribute instance
-- @name Attribute.parse
parse = function(data)
local attr = Attribute:new()
local pos = 1
pos, attr.type, attr.length = bin.unpack(">SS", data, pos)
local function parseAddress(data, pos)
local _, addr = nil, {}
pos, _, addr.family, addr.port, addr.ip = bin.unpack("<CCSI", data, pos)
if ( addr.ip ) then
addr.ip = ipOps.fromdword(addr.ip)
end
return addr
end
if ( ( attr.type == Attribute.MAPPED_ADDRESS ) or
( attr.type == Attribute.RESPONSE_ADDRESS ) or
( attr.type == Attribute.SOURCE_ADDRESS ) or
( attr.type == Attribute.CHANGED_ADDRESS ) ) then
if ( attr.length ~= 8 ) then
stdnse.debug2("Incorrect attribute length")
end
attr.addr = parseAddress(data, pos)
elseif( attr.type == Attribute.SERVER ) then
pos, attr.server = bin.unpack("A" .. attr.length-1, data, pos)
end
return attr
end,
-- converts an attribute to string
-- @return string containing the serialized attribute
__tostring = function(self)
return bin.pack(">SSA", self.type, self.length, self.data or "")
end,
}
-- Response class container
Response = {
-- Bind response class
Bind = {
--- creates a new instance of the Bind response
-- @param trans_id string containing the 128 bit transaction id
-- @return new Bind instance
-- @name Response.Bind.new
new = function(self, trans_id)
local o = { header = Header:new(MessageType.BINDING_RESPONSE, trans_id) }
setmetatable(o, self)
self.__index = self
return o
end,
--- parses a raw string and creates a new Bind instance
-- @param data string containing the raw data
-- @return a new Bind instance
-- @name Response.Bind.parse
parse = function(data)
local resp = Response.Bind:new()
local pos = Header.size
resp.header = Header.parse(data)
resp.attributes = {}
while( pos < #data ) do
local attr = Attribute.parse(data:sub(pos))
table.insert(resp.attributes, attr)
pos = pos + attr.length + 4
end
return resp
end
}
}
-- The communication class
Comm = {
--- creates a new Comm instance
-- @param host table
-- @param port table
-- @param options table, currently supporting:
-- <code>timeout</code> - socket timeout in ms.
-- @return new instance of Comm
-- @name Comm.new
new = function(self, host, port, options)
local o = {
host = host,
port = port,
options = options or { timeout = 10000 },
socket = nmap.new_socket(),
}
setmetatable(o, self)
self.__index = self
return o
end,
--- connects the socket to the server
-- @return status true on success, false on failure
-- @return err string containing an error message, if status is false
-- @name Comm.connect
connect = function(self)
self.socket:set_timeout(self.options.timeout)
return self.socket:connect(self.host, self.port)
end,
--- sends a request to the server
-- @return status true on success, false on failure
-- @return err string containing an error message, if status is false
-- @name Comm.send
send = function(self, data)
return self.socket:send(data)
end,
--- receives a response from the server
-- @return status true on success, false on failure
-- @return response containing a response instance, or
-- err string containing an error message, if status is false
-- @name Comm.recv
recv = function(self)
local status, hdr_data = self.socket:receive_buf(match.numbytes(Header.size), false)
if ( not(status) ) then
return false, "Failed to receive response from server"
end
local header = Header.parse(hdr_data)
if ( not(header) ) then
return false, "Failed to parse response header"
end
local status, data = self.socket:receive_buf(match.numbytes(header.length), false)
if ( header.type == MessageType.BINDING_RESPONSE ) then
local resp = Response.Bind.parse(hdr_data .. data)
return true, resp
end
return false, "Unknown response message received"
end,
--- sends the request instance to the server and receives the response
-- @param req request class instance
-- @return status true on success, false on failure
-- @return response containing a response instance, or
-- err string containing an error message, if status is false
-- @name Comm.exch
exch = function(self, req)
local status, err = self:send(tostring(req))
if ( not(status) ) then
return false, "Failed to send request to server"
end
return self:recv()
end,
--- closes the connection to the server
-- @return status true on success, false on failure
-- @return err string containing an error message, if status is false
-- @name Comm.close
close = function(self)
self.socket:close()
end,
}
-- The Util class
Util = {
--- creates a random string
-- @param len number containing the length of the generated random string
-- @return str containing the random string
-- @name Util.randomString
randomString = function(len)
local str = {}
for i=1, len do str[i] = string.char(math.random(255)) end
return table.concat(str)
end
}
-- The Helper class
Helper = {
--- creates a new Helper instance
-- @param host table
-- @param port table
-- @param options table, currently supporting:
-- <code>timeout</code> - socket timeout in ms.
-- @param mode containing the mode container. Supported containers: "modern"
-- (default) or "classic"
-- @return o new instance of Helper
-- @name Helper.new
new = function(self, host, port, options, mode)
local o = {
mode = mode or stdnse.get_script_args("stun.mode") or "modern",
comm = Comm:new(host, port, options),
}
assert(o.mode == "modern" or o.mode == "classic", "Unsupported mode")
setmetatable(o, self)
self.__index = self
return o
end,
--- connects to the server
-- @return status true on success, false on failure
-- @return err string containing an error message, if status is false
-- @name Helper.connect
connect = function(self)
return self.comm:connect()
end,
--- Gets the external public IP
-- @return status true on success, false on failure
-- @return result containing the IP as string
-- @name Helper.getExternalAddress
getExternalAddress = function(self)
local trans_id
if ( self.mode == "classic" ) then
trans_id = Util.randomString(16)
else
trans_id = bin.pack("HA","2112A442", Util.randomString(12))
end
local req = Request.Bind:new(trans_id)
local status, response = self.comm:exch(req)
if ( not(status) ) then
return false, "Failed to send data to server"
end
local result
for k, attr in pairs(response.attributes) do
if (attr.type == Attribute.MAPPED_ADDRESS ) then
result = ( attr.addr and attr.addr.ip or "<unknown>" )
end
if ( attr.type == Attribute.SERVER ) then
self.cache = self.cache or {}
self.cache.server = attr.server
end
end
if ( not(result) and not(self.cache) ) then
return false, "Server returned no response"
end
return status, result
end,
--- Gets the server version if it was returned by the server
-- @return status true on success, false on failure
-- @return version string containing the server product and version
-- @name Helper.getVersion
getVersion = function(self)
local status, response = false, nil
-- check if the server version was cached
if ( not(self.cache) or not(self.cache.version) ) then
local status, response = self:getExternalAddress()
if ( status ) then
return true, (self.cache and self.cache.server or "")
end
return false, response
end
return true, (self.cache and self.cache.server or "")
end,
--- closes the connection to the server
-- @return status true on success, false on failure
-- @return err string containing an error message, if status is false
-- @name Helper.close
close = function(self)
return self.comm:close()
end,
}
return _ENV;
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