code: def process_auth(self):
          
          r = self._reader
          w = self._writer
          pdu_size = r.get_smallint()
          if not self.authentication:
              raise tds_base.Error('Got unexpected token')
          packet = self.authentication.handle_next(readall(r, pdu_size))
          if packet:
              w.write(packet)
              w.flush()
docs: Reads and processes SSPI stream.
  
          Stream info: http://msdn.microsoft.com/en-us/library/dd302844.aspx