Abstract-Randomization is used in computer security as a tool to introduce unpredictability into the software infrastructure. In this paper, we study the use of randomization to achieve the secrecy and integrity guarantees for local memory.We follow the approach set out by Abadi and Plotkin (2010). We consider the execution of an idealized language in two environments. In the strict environment, opponents cannot access local variables of the user program. In the lax environment, opponents may attempt to guess allocated memory locations and thus, with small probability, gain access the local memory of the user program. We model these environments using two novel calculi: λµhashref and λµproberef.Our contribution to the Abadi-Plotkin program is to enrich the programming language with dynamic memory allocation, first class and higher order references and call/cc-style control. On the one hand, these enhancements allow us to directly model a larger class of system hardening principles. On the other hand, the class of opponents is also enhanced since our enriched language permits natural and direct encoding of attacks that alter the control flow of programs.Our main technical result is a fully abstract translation (upto probability) of λµhashref into λµproberef. Thus, in the presence of randomized layouts, the opponent gains no new power from being able to guess local references of the user program. Our numerical bounds are similar to those of Abadi and Plotkin; thus, the extra programming language features do not cause a concomitant increase in the resources required for protection via randomization.
We propose an extension of the asynchronous π -calculus in which a variety of security properties may be captured using types. These are an extension of the input/output types for the π-calculus in which I/O capabilities are assigned specific security levels. The main innovation is a uniform typing system that, by varying slightly the allowed set of types, captures different notions of security.We first define a typing system that ensures that processes running at security level σ cannot access resources with a security level higher than σ . The notion of access control guaranteed by this system is formalized in terms of a Type Safety Theorem.We then show that, by restricting the allowed types, our system prohibits implicit information flow from high-level to low-level processes. We prove that low-level behavior can not be influenced by changes to high-level behavior. This is formalized as a noninterference theorem with respect to may testing.• 567 Additional
Abstract. This is the first paper to propose a pure event structures model of relaxed memory. We propose confusion-free event structures over an alphabet with a justification relation as a model. Executions are modeled by justified configurations, where every read event has a justifying write event. Justification alone is too weak a criterion, since it allows cycles of the kind that result in so-called thin-air reads. Acyclic justification forbids such cycles, but also invalidates event reorderings that result from compiler optimizations and dynamic instruction scheduling. We propose a notion well-justification, based on a game-like model, which strikes a middle ground.We show that well-justified configurations satisfy the DRF theorem: in any data-race free program, all well-justified configurations are sequentially consistent. We also show that rely-guarantee reasoning is sound for well-justified configurations, but not for justified configurations. For example, well-justified configurations are type-safe.Well-justification allows many, but not all reorderings performed by relaxed memory. In particular, it fails to validate the commutation of independent reads. We discuss variations that may address these shortcomings.
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