In recent years, fuzz testing has benefited from increased computational
power and important algorithmic advances, leading to systems that have
discovered many critical bugs and vulnerabilities in production software.
Despite these successes, not all applications can be fuzzed efficiently. In
particular, stateful applications such as network protocol implementations are
constrained by their low fuzzing throughput and the need to develop fuzzing
harnesses that reset their state and isolate their side effects. In this paper,
we present SnapFuzz, a novel fuzzing framework for network applications.
SnapFuzz offers a robust architecture that transforms slow asynchronous network
communication into fast synchronous communication based on UNIX domain sockets,
speeds up all file operations by redirecting them to an in-memory filesystem,
and removes the need for many fragile modifications, such as configuring time
delays or writing cleanup scripts, together with several other improvements.
Using SnapFuzz, we fuzzed five popular networking applications: LightFTP,
Dnsmasq, LIVE555, TinyDTLS and Dcmqrscp. We report impressive performance
speedups of 72.4x, 49.7x, 24.8x, 23.9x, and 8.5x, respectively, with
significantly simpler fuzzing harnesses in all cases. Through its performance
advantage, SnapFuzz has also found 12 previously-unknown crashes in these