1 files changed, 340 insertions, 0 deletions
diff --git a/nselib/iax2.lua b/nselib/iax2.lua
new file mode 100644
index 0000000..cb6a9ad
--- /dev/null
+++ b/nselib/iax2.lua
@@ -0,0 +1,340 @@
+---
+-- 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 <patrik@cqure.net>
+--
+
+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
+  --        <code>timeout</code> 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;