Robustly Safe Compilation, an Efficient Form of Secure Compilation

Security-preserving compilers generate compiled code that withstands target-level attacks such as alteration of control flow, data leaks or memory corruption. Many existing security-preserving compilers are proven to be fully abstract, meaning that they reflect and preserve observational equivalence. Fully abstract compilation is strong and useful but, in certain cases, comes at the cost of requiring expensive runtime constructs in compiled code. These constructs may have no relevance for security, but are needed to accommodate differences between the source and target languages that fully abstract compilation necessarily needs. As an alternative to fully abstract compilation, this paper explores a different criterion for secure compilation called robustly safe compilation or RSC. Briefly, this criterion means that the compiled code preserves relevant safety properties of the source program against all adversarial contexts interacting with the compiled program. We show that RSC can be proved more easily than fully abstract compilation and also often results in more efficient code. We also present two different proof techniques for establishing that a compiler attains RSC and, to illustrate them, develop three illustrative robustly-safe compilers that rely on different target-level protection mechanisms. We then proceed to turn one of our compilers into a fully abstract one and through this example argue that proving RSC can be simpler than proving fully abstraction.