@Override
    public Map<String, GuacamoleConfiguration>
            getAuthorizedConfigurations(Credentials credentials)
            throws GuacamoleException {

        // Abort authorization if no user mapping exists
        UserMapping userMapping = getUserMapping();
        if (userMapping == null)
            return null;

        // Validate and return info for given user and pass
        Authorization auth = userMapping.getAuthorization(credentials.getUsername());
        if (auth != null && auth.validate(credentials.getUsername(), credentials.getPassword()))
            return auth.getConfigurations();

        // Unauthorized
        return null;

    }
Returns a UserMapping containing all authorization data given within
GUACAMOLE_HOME/user-mapping.xml. If the XML file has been modified or has
not yet been read, this function may reread the file.

@return
    A UserMapping containing all authorization data within the user
    mapping XML file, or null if the file cannot be found/parsed.
guacamole/src/main/java/org/apache/guacamole/auth/file/FileAuthenticationProvider.java