Efficient, Verifiable Binary Sandboxing for a CISC Architecture

Abstract

Executing untrusted code while preserving security requiresenforcement of memory and control-flow safety policies:untrusted code must be prevented from modifying memory orexecuting code except as explicitly allowed. Software-basedfault isolation (SFI) or \"sandboxing\" enforces thosepolicies by rewriting the untrusted code at the level ofindividual instructions. However, the original sandboxingtechnique of Wahbe et al. is applicable only to RISCarchitectures, and other previous work is either insecure,or has been not described in enough detail to giveconfidence in its security properties. We present a noveltechnique that allows sandboxing to be easily applied to aCISC architecture like the IA-32. The technique can beverified to have been applied at load time, so that neitherthe rewriting tool nor the compiler needs to be trusted. Wedescribe a prototype implementation which provides a robustsecurity guarantee, is scalable to programs of any size, andhas low runtime overheads. Further, we give amachine-checked proof that any program approved by theverification algorithm is guaranteed to respect the desiredsafety property.