The interface com.openexchange.file.storage.File is enhanced by the following method:

/**
* Gets the object permissions in case they are defined.
*
* @return A list holding additional object permissions, or <code>null</code> if not defined or not supported by the storage
*/
List<FileStorageObjectPermission> getObjectPermissions();

If object permissions are not supported by the file storage backend, it's safe to always return null here. If supported, the capability should be signalled by the file storage via implementing the marker interface com.openexchange.file.storage.ObjectPermissionAwar e.