code: def onAuthenticate(self, signature, extra):
          
          log.msg("onAuthenticate: {} {}".format(signature, extra))
  
          ## if there is a pending auth, and the signature provided by client matches ..
          if self._pending_auth:
  
              if signature == self._pending_auth.signature:
  
                  ## accept the client
                  return types.Accept(authid = self._pending_auth.uid,
                      authrole = self._pending_auth.authrole,
                      authmethod = self._pending_auth.authmethod,
                      authprovider = self._pending_auth.authprovider)
              else:
  
                  ## deny client
                  return types.Deny(message = u"signature is invalid")
          else:
  
              ## deny client
              return types.Deny(message = u"no pending authentication")
docs: Callback fired when a client responds to an authentication challenge.