try_sasl (CamelPOP3Store *store,
          const gchar *mechanism,
          GCancellable *cancellable,
          GError **error)
{
	CamelPOP3Engine *pop3_engine;
	CamelPOP3Stream *pop3_stream;
	CamelNetworkSettings *network_settings;
	CamelAuthenticationResult result;
	CamelSettings *settings;
	CamelService *service;
	guchar *line, *resp;
	CamelSasl *sasl = NULL;
	gchar *string;
	gchar *host;
	guint len;
	gint ret;

	service = CAMEL_SERVICE (store);

	settings = camel_service_ref_settings (service);

	network_settings = CAMEL_NETWORK_SETTINGS (settings);
	host = camel_network_settings_dup_host (network_settings);

	g_object_unref (settings);

	pop3_engine = camel_pop3_store_ref_engine (store);
	if (!pop3_engine) {
		g_set_error_literal (
			error, CAMEL_SERVICE_ERROR,
			CAMEL_SERVICE_ERROR_UNAVAILABLE,
			_("You must be working online to complete this operation"));
		result = CAMEL_AUTHENTICATION_ERROR;
		goto exit;
	}

	pop3_stream = pop3_engine->stream;

	sasl = camel_sasl_new ("pop", mechanism, service);
	if (sasl == NULL) {
		g_set_error (
			error, CAMEL_SERVICE_ERROR,
			CAMEL_SERVICE_ERROR_URL_INVALID,
			_("No support for %s authentication"), mechanism);
		result = CAMEL_AUTHENTICATION_ERROR;
		goto exit;
	}

	string = g_strdup_printf ("AUTH %s\r\n", camel_sasl_is_xoauth2_alias (mechanism) ? "XOAUTH2" : mechanism);
	ret = camel_stream_write_string (
		CAMEL_STREAM (pop3_stream), string, cancellable, error);
	g_free (string);

	if (ret == -1)
		goto ioerror;

	while (1) {
		GError *local_error = NULL;

		if (camel_pop3_stream_line (pop3_stream, &line, &len, cancellable, error) == -1)
			goto ioerror;

		if (strncmp ((gchar *) line, "+OK", 3) == 0) {
			result = CAMEL_AUTHENTICATION_ACCEPTED;
			break;
		}

		if (strncmp ((gchar *) line, "-ERR", 4) == 0) {
			result = CAMEL_AUTHENTICATION_REJECTED;
			break;
		}

		/* If we dont get continuation, or the sasl object's run out
		 * of work, or we dont get a challenge, its a protocol error,
		 * so fail, and try reset the server. */
		if (strncmp ((gchar *) line, "+ ", 2) != 0
		    || camel_sasl_get_authenticated (sasl)
		    || (resp = (guchar *) camel_sasl_challenge_base64_sync (sasl, (const gchar *) line + 2, cancellable, &local_error)) == NULL) {
			if (camel_stream_write_string (CAMEL_STREAM (pop3_stream), "*\r\n", cancellable, NULL)) {
				/* coverity[unchecked_value] */
				if (!camel_pop3_stream_line (pop3_stream, &line, &len, cancellable, NULL)) {
					;
				}
			}

			if (local_error) {
				g_propagate_error (error, local_error);
				local_error = NULL;
				goto ioerror;
			}

			g_set_error (
				error, CAMEL_SERVICE_ERROR,
				CAMEL_SERVICE_ERROR_CANT_AUTHENTICATE,
				_("Cannot login to POP server %s: "
				"SASL Protocol error"), host);
			result = CAMEL_AUTHENTICATION_ERROR;
			goto exit;
		}

		string = g_strdup_printf ("%s\r\n", resp);
		ret = camel_stream_write_string (
			CAMEL_STREAM (pop3_stream), string, cancellable, error);
		g_free (string);

		g_free (resp);

		if (ret == -1)
			goto ioerror;

	}

	goto exit;

ioerror:
	g_prefix_error (
		error, _("Failed to authenticate on POP server %s: "), host);
	result = CAMEL_AUTHENTICATION_ERROR;

exit:
	if (sasl != NULL)
		g_object_unref (sasl);

	g_free (host);

	g_clear_object (&pop3_engine);

	return result;
}