Flask Design and Implementation

This section defines the components of the Flask security architecture and identifies the requirements on each component necessary to meet the goals of the system. The Flask security architecture is described here in the context of its implementation within a microkernel-based multiserver operating system. However, the security architecture only requires that the operating system include a reference monitor [16, Ch. 10]. In particular, the architecture requires the completeness and isolation properties, although verifiability is also ultimately necessary for confidence in any implementation of the architecture.

The Flask prototype was derived from the Fluke microkernel-based operating system [14]. The Fluke microkernel is especially well-suited for implementing the Flask architecture due to its lack of global resources [14] and the atomic properties of its API [13]. However, the original Fluke system was capability-based and was not in itself adequate to meet the requirements of the Flask architecture.

The remainder of this section starts by providing an overview of the Flask architecture. Then, it describes general support mechanisms required for the basic Flask architecture. It discusses the specific changes required for the microkernel. It explains how the complications caused by the need for revocation were overcome. This section ends by describing the prototype security server.