protected User getCurrentUser() {
    final Object principal = getSubject().getPrincipal();
    final User user = userService.load(principal.toString());

    if (user == null) {
      LOG.error(
          "Loading the current user failed, this should not happen. Did you call this method in an unauthenticated REST resource?");
    }

    return user;
  }
  @Override
  protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken token)
      throws AuthenticationException {
    SessionIdToken sessionIdToken = (SessionIdToken) token;
    final Subject subject =
        new Subject.Builder().sessionId(sessionIdToken.getSessionId()).buildSubject();
    final Session session = subject.getSession(false);
    if (session == null) {
      LOG.debug(
          "Invalid session {}. Either it has expired or did not exist.",
          sessionIdToken.getSessionId());
      return null;
    }

    final Object username = subject.getPrincipal();
    final User user = userService.load(String.valueOf(username));
    if (user == null) {
      LOG.debug("No user named {} found for session {}", username, sessionIdToken.getSessionId());
      return null;
    }
    if (user.isExternalUser() && !ldapAuthenticator.isEnabled()) {
      throw new LockedAccountException("LDAP authentication is currently disabled.");
    }

    if (LOG.isDebugEnabled()) {
      LOG.debug("Found session {} for user name {}", session.getId(), username);
    }

    @SuppressWarnings("unchecked")
    final MultivaluedMap<String, String> requestHeaders =
        (MultivaluedMap<String, String>) ThreadContext.get("REQUEST_HEADERS");
    // extend session unless the relevant header was passed.
    if (requestHeaders == null
        || !"true".equalsIgnoreCase(requestHeaders.getFirst("X-Graylog-No-Session-Extension"))) {
      session.touch();
    } else {
      LOG.debug("Not extending session because the request indicated not to.");
    }
    ThreadContext.bind(subject);

    return new SimpleAccount(user.getName(), null, "session authenticator");
  }