Execution Policies Research and Implementation

摘要

This research studied the application of a software-based ring execution policy, the type of which has previously been implemented via hardware mechanisms, to an open source operating system. Such an execution policy is orthogonal to, and may he used in conjunction with, other mandatory (viz, secrecy, integrity) and discretionary policies. It allows processes running with otherwise similar privileges (such as the root user or secrecy attributes) to be differentiated with respect to priority or privilege regarding system resources and execution. We have found that it is possible to construct a mandatory ring execution policy whose primary function is to restrict subjects from executing certain file system objects, and that this may result in a more coherent and manageable policy than what can be expected from various discretionary (e.g., policy-bypass or privilege-grouping) mechanisms.