Toward Specifying and Validating Cross-Domain Policies

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Formal security policies are extremely useful for two related reasons. First, they allow a policy to be considered in isolation, separate from programs under the purview of the policy and separate from the implementation of the policy's enforcement. Second, policies can be checked for compliance against higher-level security goals by using automated analyses. By contrast, ad hoc enforcement mechanisms (for which no separate policies are specified) enjoy neither benefit, and non-formal policies enjoy the first but not the second.

We would like to understand how best to define (and enforce) multi-level security policies when information must be shared across domains that have varying levels of trust (the so-called "cross domain" problem). Because we wish to show such policies meet higher-level security goals with high assurance, we are interested in specifying cross domain policies formally, and then reasoning about them using automated tools. In this report, we briefly survey work that presents formal security policies with cross-domain concerns, in particular with respect to the problem of downgrading. We also describe correctness properties for such policies, all based on noninterference. Finally, we briefly discuss recently-developed tools for analyzing formal security policies; though no existing tools focus on the analysis of downgrading-oriented policies, existing research points the way to providing such support.