Bunshin: Compositing Security Mechanisms through Diversification (with Appendix)
This addresses the challenge of improving security for programs in unsafe languages by enabling the use of multiple mechanisms without the typical performance penalties, though it is incremental in its approach to existing diversification techniques.
The paper tackles the problem of combining multiple security mechanisms for programs written in unsafe languages, which often leads to prohibitive slowdowns and conflicts, by presenting Bunshin, an N-version-based system that reduces execution slowdown through parallel execution and eliminates conflicts between security checks.
A number of security mechanisms have been proposed to harden programs written in unsafe languages, each of which mitigates a specific type of memory error. Intuitively, enforcing multiple security mechanisms on a target program will improve its overall security. However, this is not yet a viable approach in practice because the execution slowdown caused by various security mechanisms is often non-linearly accumulated, making the combined protection prohibitively expensive; further, most security mechanisms are designed for independent or isolated uses and thus are often in conflict with each other, making it impossible to fuse them in a straightforward way. In this paper, we present Bunshin, an N-version-based system that enables different and even conflicting security mechanisms to be combined to secure a program while at the same time reducing the execution slowdown. In particular, we propose an automated mechanism to distribute runtime security checks in multiple program variants in such a way that conflicts between security checks are inherently eliminated and execution slowdown is minimized with parallel execution. We also present an N-version execution engine to seamlessly synchronize these variants so that all distributed security checks work together to guarantee the security of a target program.