  Ethereum smart contracts are an innovation built on top of the blockchain
technology, which provides a platform for automatically executing contracts in
an anonymous, distributed, and trusted way. The problem is magnified by the
fact that smart contracts, unlike ordinary programs, cannot be patched easily
once deployed. It is important for smart contracts to be checked against
potential vulnerabilities. In this work, we propose an alternative approach to
automatically identify critical program paths (with multiple function calls
including inter-contract function calls) in a smart contract, rank the paths
according to their criticalness, discard them if they are infeasible or
otherwise present them with user friendly warnings for user inspection. We
identify paths which involve monetary transaction as critical paths, and
prioritize those which potentially violate important properties. For
scalability, symbolic execution techniques are only applied to top ranked
critical paths. Our approach has been implemented in a tool called sCompile,
which has been applied to 36,099 smart contracts. The experiment results show
that sCompile is efficient, i.e., 5 seconds on average for one smart contract.
Furthermore, we show that many known vulnerabilities can be captured if user
inspects as few as 10 program paths generated by sCompile. Lastly, sCompile
discovered 224 unknown vulnerabilities with a false positive rate of 15.4%
before user inspection.
