Several recent operating systems provide system calls that allow an application to explicitly manage the privileges of modules with which the application interacts. Such privilege-aware operating systems allow a programmer to a write a program that satisfies a strong security policy, even when it interacts with untrusted modules. However, it is often non-trivial to rewrite a program to correctly use the system calls to satisfy a high-level security policy. This paper concerns the policy-weaving problem, which is to take as input a program, a desired high-level policy for the program, and a description of how system calls affect privilege, and automatically rewrite the program to invoke the system calls so that it satisfies the policy. We present an algorithm that solves the policy-weaving problem by reducing it to finding a winning modular strategy to a visibly pushdown safety game, and applies a novel game-solving algorithm to the resulting game. Our experiments demonstrate that our algorithm can efficiently rewrite practical programs for a practical privilege-aware system.

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