Existing designs for fine-grained, dynamic information-flow control assume that it is acceptable to terminate the entire system when an incorrect flow is detected-i.e, they give up availability for the sake of confidentiality and integrity. This is an unrealistic limitation for systems such as long-running servers.We identify public labels and delayed exceptions as crucial ingredients for making information-flow errors recoverable in a sound and usable language, and we propose two new errorhandling mechanisms that make all errors recoverable. The first mechanism builds directly on these basic ingredients, using not-a-values (NaVs) and data flow to propagate errors. The second mechanism adapts the standard exception model to satisfy the extra constraints arising from information flow control, converting thrown exceptions to delayed ones at certain points. We prove that both mechanisms enjoy the fundamental soundness property of non-interference. Finally, we describe a prototype implementation of a full-scale language with NaVs and report on our experience building robust software components in this setting.

Developers of large-scale software systems may use third-party modules to reduce costs and accelerate release cycles, at some risk to safety and security. BREAKAPP exploits module boundaries to automate compartmentalization of systems and enforce security policies, enhancing reliability and security. BREAKAPP transparently spawns modules in protected compartments while preserving their original behavior. Optional high-level policies decouple security assumptions made during development from requirements imposed for module composition and use. These policies allow fine-tuning trade-offs such as security and performance based on changing threat models or load patterns. Evaluation of BREAKAPP with a prototype implementation for JavaScript demonstrates feasibility by enabling simplified security hardening of existing systems with low performance overhead.

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Safe is a clean-slate design for a secure host architecture. It integrates advances in programming languages, operating systems, and hardware and incorporates formal methods at every step. Though the project is still at an early stage, we have assembled a set of basic architectural choices that we believe will yield a high-assurance system. We sketch the current state of the design and discuss several of these choices.

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