Park: accelerating smart contract vulnerability detection via parallel-fork symbolic execution

Symbolic detection has been widely used to detect vulnerabilities in smart contracts. Unfortunately, as reported, existing symbolic tools cost too much time, since they need to execute all paths to detect vulnerabilities. Thus, their accuracy is limited by time. To tackle this problem, in this paper, we propose Park, the first general framework of parallel-fork symbolic execution for smart contracts. The main idea is to use multiple processes during symbolic execution, leveraging multiple CPU cores to enhance efficiency. Firstly, we propose a fork-operation based dynamic forking algorithm to achieve parallel symbolic contract execution. Secondly, to address the SMT performance loss problem in parallelization, we propose an adaptive processes restriction and adjustment algorithm. Thirdly, we design a shared-memory based global variable reconstruction method to collect and rebuild the global variables from different processes. We implement Park as a plug-in and apply it to two popular symbolic execution tools for smart contracts: Oyente and Mythril. The experimental results with third-party datasets show that Park-Oyente and Park-Mythril can provide up to 6.84x and 7.06x speedup compared to original tools, respectively.