LENT-SSE: Leveraging Executed and Near Transactions for Speculative Symbolic Execution of Smart Contracts

Symbolic execution has proven effective for code analytics in smart contracts. However, for smart contracts, existing symbolic tools use multiple-transaction symbolic execution, which differs from traditional symbolic tools and also exacerbates the path explosion problem. In this paper, we first quantitatively analyze the bottleneck of symbolic execution in multiple transactions (TXs), finding the redundancy of the paths of TXs. Based on this finding, we propose LENT-SSE as a new speculation heuristic for Speculative Symbolic Execution of smart contracts, which leverages the executed and near TXs for skipping and recalling the SMT solving of paths. LENT-SSE uses an executed-transaction-based skipping algorithm to reduce the time required for SMT solving by leveraging the redundancy between executed and executing paths. Moreover, LENT-SSE uses a near-transaction-based recalling algorithm to reduce false skipping of the solving paths. Experimental results on the SmartBugs dataset show that LENT-SSE can reduce the total time by 37.4% and the solving time of paths by 65.2% on average without reducing the reported bugs. On the other dataset of 1000 realistic contracts, the total time and solving time are reduced by 38.1% and 54.7%.