# Stem Docs

## stem.response.authchallenge

# Source code for stem.response.authchallenge

    # Copyright 2012-2019, Damian Johnson and The Tor Project
    # See LICENSE for licensing information

    import binascii

    import stem.response
    import stem.socket
    import stem.util.str_tools
    import stem.util.tor_tools

    class AuthChallengeResponse(stem.response.ControlMessage):
      """
      AUTHCHALLENGE query response.

      :var str server_hash: server hash provided by tor
      :var str server_nonce: server nonce provided by tor
      """

      def _parse_message(self):
        # Example:
        #   250 AUTHCHALLENGE SERVERHASH=680A73C9836C4F557314EA1C4EDE54C285DB9DC89C83627401AEF9D7D27A95D5 SERVERNONCE=F8EA4B1F2C8B40EF1AF68860171605B910E3BBCABADF6FC3DB1FA064F4690E85

        self.server_hash = None
        self.server_nonce = None

        if not self.is_ok():
          raise stem.ProtocolError("AUTHCHALLENGE response didn't have an OK status:\n%s" % self)
        elif len(self) > 1:
          raise stem.ProtocolError('Received multiline AUTHCHALLENGE response:\n%s' % self)

        line = self[0]

        # sanity check that we're a AUTHCHALLENGE response
        if not line.pop() == 'AUTHCHALLENGE':
          raise stem.ProtocolError('Message is not an AUTHCHALLENGE response (%s)' % self)

        if line.is_next_mapping('SERVERHASH'):
          value = line.pop_mapping()[1]

          if not stem.util.tor_tools.is_hex_digits(value, 64):
            raise stem.ProtocolError('SERVERHASH has an invalid value: %s' % value)

          self.server_hash = binascii.unhexlify(stem.util.str_tools._to_bytes(value))
        else:
          raise stem.ProtocolError('Missing SERVERHASH mapping: %s' % line)

        if line.is_next_mapping('SERVERNONCE'):
          value = line.pop_mapping()[1]

          if not stem.util.tor_tools.is_hex_digits(value, 64):
            raise stem.ProtocolError('SERVERNONCE has an invalid value: %s' % value)

          self.server_nonce = binascii.unhexlify(stem.util.str_tools._to_bytes(value))
        else:
          raise stem.ProtocolError('Missing SERVERNONCE mapping: %s' % line)