A storage gateway is employed as part of a security enhancing protocol in a data processing system which includes at least one metadata controller node and at least one application node which is granted a time limited access to files in a shared storage system. The gateway is provided with information as to data blocks to which access is to be allowed and also with information concerning the duration of special access granted to a requesting application node. This insures that metadata cannot be improperly used, changed or corrupted by users operating on an application node.