code: private AuthenticatedUser updateAuthenticatedUser(AuthenticatedUser authenticatedUser,
              Credentials credentials) throws GuacamoleException {
  
          // Get original AuthenticationProvider
          AuthenticationProvider authProvider = authenticatedUser.getAuthenticationProvider();
  
          // Re-authenticate the AuthenticatedUser against the original AuthenticationProvider only
          authenticatedUser = authProvider.updateAuthenticatedUser(authenticatedUser, credentials);
          if (authenticatedUser == null)
              throw new GuacamoleSecurityException("User re-authentication failed.");
  
          return authenticatedUser;
  
      }
docs: Re-authenticates the given AuthenticatedUser against the
  AuthenticationProvider that originally created it, using the given
  Credentials.
  
  @param authenticatedUser
  The AuthenticatedUser to re-authenticate.
  
  @param credentials
  The Credentials to use to re-authenticate the user.
  
  @return
  A AuthenticatedUser which may have been updated due to re-
  authentication.
  
  @throws GuacamoleException
  If an error prevents the user from being re-authenticated.