SpecFuzz: Bringing Spectre-type vulnerabilities to the surface.

SpecFuzz is the first tool that enables dynamic testing for speculative execution vulnerabilities (e.g., Spectre). The key is the concept of speculation exposure: The program is instrumented to simulate speculative execution in software by forcefully executing the code paths that could be triggered due to mispredictions, thereby making the speculative memory accesses visible to integrity checkers. Combined with the conventional fuzzing techniques, speculation exposure enables more precise identification of potential vulnerabilities compared to the state-of-the-art static analyzers. Our prototype for detecting Spectre V1 vulnerabilities successfully identifies all known variations of Spectre V1, and dramatically reduces the overheads compared to the deployed Speculative Load Hardening mitigation across the evaluated applications, reducing the amount of necessary instrumentation by 99% in some of them.