public String getClientSecret() throws GuacamoleException {
        return environment.getRequiredProperty(DUO_CLIENT_SECRET);
    }
Returns the client secret received from Duo for verifying Guacamole users,
as defined in guacamole.properties by the "duo-client-secret" property.
This value MUST be exactly 20 characters.

@return
    The client secret received from Duo for verifying Guacamole users.

@throws GuacamoleException
    If the associated property within guacamole.properties is missing.
extensions/guacamole-auth-duo/src/main/java/org/apache/guacamole/auth/duo/conf/ConfigurationService.java