--- -- A minimalistic Asterisk IAX2 (Inter-Asterisk eXchange v2) VoIP protocol implementation. -- The library implements the minimum needed to perform brute force password guessing. -- -- @author Patrik Karlsson -- local math = require "math" local nmap = require "nmap" local os = require "os" local stdnse = require "stdnse" local string = require "string" local openssl = stdnse.silent_require "openssl" local table = require "table" _ENV = stdnse.module("iax2", stdnse.seeall) IAX2 = { FrameType = { IAX = 6, }, SubClass = { ACK = 0x04, REGACK = 0x0f, REGREJ = 0x10, REGREL = 0x11, CALLTOKEN = 0x28, }, InfoElement = { USERNAME = 0x06, CHALLENGE = 0x0f, MD5_RESULT = 0x10, CALLTOKEN = 0x36, }, PacketType = { FULL = 1, }, -- The IAX2 Header Header = { -- Creates a new Header instance -- @param src_call number containing the source call -- @param dst_call number containing the dest call -- @param timestamp number containing a timestamp -- @param oseqno number containing the seqno of outgoing packets -- @param iseqno number containing the seqno of incoming packets -- @param frametype number containing the frame type -- @param subclass number containing the subclass type new = function(self, src_call, dst_call, timestamp, oseqno, iseqno, frametype, subclass) local o = { type = IAX2.PacketType.FULL, retrans = false, src_call = src_call, dst_call = dst_call, timestamp = timestamp, oseqno = oseqno, iseqno = iseqno, frametype = frametype, subclass = subclass, } setmetatable(o, self) self.__index = self return o end, -- Parses data, a byte string, and creates a new Header instance -- @return header instance of Header parse = function(data) local header = IAX2.Header:new() local frame_type, pos = string.unpack("B", data) if ( (frame_type & 0x80) == 0 ) then stdnse.debug2("Frametype %x not supported", frame_type) return end header.type = IAX2.PacketType.FULL header.src_call, pos = string.unpack(">I2", data) header.src_call = (header.src_call & 0x7FFF) local retrans = string.unpack("B", data, pos) if ( (retrans & 0x80) == 8 ) then header.retrans = true end header.dst_call, pos = string.unpack(">I2", data, pos) header.dst_call = (header.dst_call & 0x7FFF) header.timestamp, header.oseqno, header.iseqno, header.frametype, header.subclass, pos = string.unpack(">I4BBBB", data, pos) return header end, -- Converts the instance to a string -- @return str containing the instance __tostring = function(self) assert(self.src_call < 32767, "Source call exceeds 32767") assert(self.dst_call < 32767, "Dest call exceeds 32767") local src_call = self.src_call local dst_call = self.dst_call if ( self.type == IAX2.PacketType.FULL ) then src_call = src_call + 32768 end if ( self.retrans ) then dst_call = dst_call + 32768 end return string.pack(">I2I2 I4BBBB", src_call, dst_call, self.timestamp, self.oseqno, self.iseqno, self.frametype, self.subclass) end, }, -- The IAX2 Request class Request = { -- Creates a new instance -- @param header instance of Header new = function(self, header) local o = { header = header, ies = {} } setmetatable(o, self) self.__index = self return o end, -- Sets an Info Element or adds one, in case it's missing -- @param key the key value of the IE to add -- @param value string containing the value to set or add setIE = function(self, key, value) for _, ie in ipairs(self.ies or {}) do if ( key == ie.type ) then ie.value = value end end table.insert(self.ies, { type = key, value = value } ) end, -- Gets an information element -- @param key number containing the element number to retrieve -- @return ie table containing the info element if it exists getIE = function(self, key) for _, ie in ipairs(self.ies or {}) do if ( key == ie.type ) then return ie end end end, -- Converts the instance to a string -- @return str containing the instance __tostring = function(self) local data = {} for _, ie in ipairs(self.ies) do data[#data+1] = string.pack("Bs1", ie.type, ie.value ) end return tostring(self.header) .. table.concat(data) end, }, -- The IAX2 Response Response = { -- Creates a new instance new = function(self) local o = { ies = {} } setmetatable(o, self) self.__index = self return o end, -- Sets an Info Element or adds one, in case it's missing -- @param key the key value of the IE to add -- @param value string containing the value to set or add setIE = function(self, key, value) for _, ie in ipairs(self.ies or {}) do if ( key == ie.type ) then ie.value = value end end table.insert(self.ies, { type = key, value = value } ) end, -- Gets an information element -- @param key number containing the element number to retrieve -- @return ie table containing the info element if it exists getIE = function(self, key) for _, ie in ipairs(self.ies or {}) do if ( key == ie.type ) then return ie end end end, -- Parses data, a byte string, and creates a response -- @return resp instance of response parse = function(data) local resp = IAX2.Response:new() if ( not(resp) ) then return end resp.header = IAX2.Header.parse(data) if ( not(resp.header) ) then return end local pos = 13 resp.ies = {} repeat local ie = {} ie.type, ie.value, pos = string.unpack(">Bs1", data, pos) table.insert(resp.ies, ie) until( pos > #data ) return resp end, } } Helper = { -- Creates a new Helper instance -- @param host table as received by the action method -- @param port table as received by the action method -- @param options table containing helper options, currently -- timeout socket timeout in ms -- @return o instance of Helper new = function(self, host, port, options) local o = { host = host, port = port, options = options or {} } setmetatable(o, self) self.__index = self return o end, -- Connects the UDP socket to the server -- @return status true on success, false on failure -- @return err message containing error if status is false connect = function(self) self.socket = nmap.new_socket() self.socket:set_timeout(self.options.timeout or 5000) return self.socket:connect(self.host, self.port) end, -- Sends a request to the server and receives the response -- @param req instance containing the request to send to the server -- @return status true on success, false on failure -- @return resp instance of response on success, -- err containing the error message on failure exch = function(self, req) local status, err = self.socket:send(tostring(req)) if ( not(status) ) then return false, "Failed to send request to server" end local status, data = self.socket:receive() if ( not(status) ) then return false, "Failed to receive response from server" end local resp = IAX2.Response.parse(data) return true, resp end, -- Request a session release -- @param username string containing the extension (username) -- @param password string containing the password regRelease = function(self, username, password) local src_call = math.random(32767) local header = IAX2.Header:new(src_call, 0, os.time(), 0, 0, IAX2.FrameType.IAX, IAX2.SubClass.REGREL) local regrel = IAX2.Request:new(header) regrel:setIE(IAX2.InfoElement.USERNAME, username) regrel:setIE(IAX2.InfoElement.CALLTOKEN, "") local status, resp = self:exch(regrel) if ( not(status) ) then return false, resp end if ( not(resp) or IAX2.SubClass.CALLTOKEN ~= resp.header.subclass ) then return false, "Unexpected response" end local token = resp:getIE(IAX2.InfoElement.CALLTOKEN) if ( not(token) ) then return false, "Failed to get token" end regrel:setIE(IAX2.InfoElement.CALLTOKEN, token.value) status, resp = self:exch(regrel) if ( not(status) ) then return false, resp end local challenge = resp:getIE(IAX2.InfoElement.CHALLENGE) if ( not(challenge) ) then return false, "Failed to retrieve challenge from server" end regrel.header.iseqno = 1 regrel.header.oseqno = 1 regrel.header.dst_call = resp.header.src_call regrel.ies = {} local hash = stdnse.tohex(openssl.md5(challenge.value .. password)) regrel:setIE(IAX2.InfoElement.USERNAME, username) regrel:setIE(IAX2.InfoElement.MD5_RESULT, hash) status, resp = self:exch(regrel) if ( not(status) ) then return false, resp end if ( IAX2.SubClass.ACK == resp.header.subclass ) then local data status, data = self.socket:receive() resp = IAX2.Response.parse(data) end if ( status and IAX2.SubClass.REGACK == resp.header.subclass ) then return true end return false, "Release failed" end, -- Close the connection with the server -- @return true on success, false on failure close = function(self) return self.socket:close() end, } return _ENV;