Parse the SSH2_MSG_KEXGSS_INIT message (server mode).

        :param `.Message` m: The content of the SSH2_MSG_KEXGSS_INIT message

def _parse_kexgss_init(self, m):
        """
        Parse the SSH2_MSG_KEXGSS_INIT message (server mode).

        :param `.Message` m: The content of the SSH2_MSG_KEXGSS_INIT message
        """
        # server mode
        client_token = m.get_string()
        self.e = m.get_mpint()
        if (self.e < 1) or (self.e > self.P - 1):
            raise SSHException('Client kex "e" is out of range')
        K = pow(self.e, self.x, self.P)
        self.transport.host_key = NullHostKey()
        key = self.transport.host_key.__str__()
        # okay, build up the hash H of
        # (V_C || V_S || I_C || I_S || K_S || e || f || K)
        hm = Message()
        hm.add(
            self.transport.remote_version,
            self.transport.local_version,
            self.transport.remote_kex_init,
            self.transport.local_kex_init,
        )
        hm.add_string(key)
        hm.add_mpint(self.e)
        hm.add_mpint(self.f)
        hm.add_mpint(K)
        H = sha1(hm.asbytes()).digest()
        self.transport._set_K_H(K, H)
        srv_token = self.kexgss.ssh_accept_sec_context(
            self.gss_host, client_token
        )
        m = Message()
        if self.kexgss._gss_srv_ctxt_status:
            mic_token = self.kexgss.ssh_get_mic(
                self.transport.session_id, gss_kex=True
            )
            m.add_byte(c_MSG_KEXGSS_COMPLETE)
            m.add_mpint(self.f)
            m.add_string(mic_token)
            if srv_token is not None:
                m.add_boolean(True)
                m.add_string(srv_token)
            else:
                m.add_boolean(False)
            self.transport._send_message(m)
            self.transport.gss_kex_used = True
            self.transport._activate_outbound()
        else:
            m.add_byte(c_MSG_KEXGSS_CONTINUE)
            m.add_string(srv_token)
            self.transport._send_message(m)
            self.transport._expect_packet(
                MSG_KEXGSS_CONTINUE, MSG_KEXGSS_COMPLETE, MSG_KEXGSS_ERROR
            )