Fuzzing in the 2020s: Novel approaches and solutions

Security remains at risk due to elusive software vulnerabilities, even with extensive fuzzing efforts. Coverage-guided fuzzers, focusing solely on code coverage, often fall short in discovering specific vulnerabilities. The proliferation of diverse fuzzing tools has fragmented the field, making it challenging to combine different fuzzing techniques, assess contributions accurately, and compare tools effectively. To address this, standardized baselines are needed to ensure equitable evaluations. AFL, due to its popularity, is often extended to implement new prototypes despite not being a naive baseline and its monolithic design. On the other hand, custom fuzzers written from scratch tend to reinvent solutions and often lack scalability on multicore systems. This thesis addresses these challenges with several contributions: A new feedback mechanism called InvsCov is introduced, which considers program variable relationships and code coverage. It refines program state approximation for diverse bug detection. Another additional feedback we introduce explores data dependency graphs to enhance fuzzing by rewarding new dataflow edge traversal, effectively finding vulnerabilities missed by standard coverage. We also present a thorough analysis of AFL’s internal mechanisms to shed light on its design choices and their impact on fuzzing performance. Finally, to address fragmentation, LibAFL is introduced as a modular and reusable fuzzing framework. Researchers can extend the core fuzzer pipeline, evaluation of compelling techniques, and combination of orthogonal approaches. An attempt to rewrite AFL++ as a frontend to LibAFL won the SBFT’23 fuzzing competition in the bugfinding track. These contributions advance the field of fuzz testing, addressing the challenges of sensitivity in feedback mechanisms, bug diversity, tool fragmentation, and fuzzers evaluation. They provide a foundation for improving fuzzing techniques, enabling the detection of a broader range of bugs, and fostering collaboration and standardization within the community.