@Override
    public AuthenticatedUser authenticateUser(Credentials credentials)
            throws GuacamoleException {
        return null;
    }
{@inheritDoc}

<p>This implementation performs no authentication whatsoever, ignoring
the provided {@code credentials} and simply returning {@code null}. Any
authentication attempt will thus fall through to other
{@link AuthenticationProvider} implementations, perhaps within other
installed extensions, with this {@code AuthenticationProvider} making no
claim regarding the user's identity nor whether the user should be
allowed or disallowed from accessing Guacamole. Implementations that wish
to authenticate users should override this function.
guacamole-ext/src/main/java/org/apache/guacamole/net/auth/AbstractAuthenticationProvider.java