Design and Implementation of NFS for a Multilevel Secure System

Popular software for high assurance systems is not readily available. Developers do not want to develop or port applications for secure systems because of the perception that high assurance development is too time consuming, in some cases impossible, and that performance is inadequate. This trend must be stopped by showing that if an intelligent approach to porting software is used, then the development costs will be acceptable. The network file system (NFS) service, which is a rather complex module that provides widely used functionality for file sharing, has been ported to the XTS-400 to show that a port can be completed in a timely manner and to assess the challenges of development for a multilevel system. Porting starts by analyzing the major requirements of the software and of the target system, and then proceeds to developing an approach for tackling the port. The hardest part of porting is the learning curve required to understand the target system and the software to be ported. Once this is accomplished, then porting becomes straightforward. Tests demonstrated that remote clients were able to access shared files on the NFS server. The XTS-400 now has the capability to share files through the popular NFS protocol.