SynFuzz: Leveraging Fuzzing of Netlist to Detect Synthesis Bugs

Abstract: In the evolving landscape of integrated circuit (IC) design, the increasing complexity of modern processors and intellectual property (IP) cores has introduced new challenges in ensuring design correctness and security. The recent advancements in hardware fuzzing techniques have shown their efficacy in detecting hardware bugs and vulnerabilities at the RTL abstraction level of hardware. However, they suffer from several limitations, including an inability to address vulnerabilities introduced during synthesis and gate-level transformations. These methods often fail to detect issues arising from library adversaries, where compromised or malicious library components can introduce backdoors or unintended behaviors into the design. In this paper, we present a novel hardware fuzzer, SynFuzz, designed to overcome the limitations of existing hardware fuzzing frameworks. SynFuzz focuses on fuzzing hardware at the gate-level netlist to identify synthesis bugs and vulnerabilities that arise during the transition from RTL to the gate-level. We analyze the intrinsic hardware behaviors using coverage metrics specifically tailored for the gate-level. Furthermore, SynFuzz implements differential fuzzing to uncover bugs associated with EDA libraries. We evaluated SynFuzz on popular open-source processors and IP designs, successfully identifying 7 new synthesis bugs. Additionally, by exploiting the optimization settings of EDA tools, we performed a compromised library mapping attack (CLiMA), creating a malicious version of hardware designs that remains undetectable by traditional verification methods. We also demonstrate how SynFuzz overcomes the limitations of the industry-standard formal verification tool, Cadence Conformal, providing a more robust and comprehensive approach to hardware verification.