AChecker: Statically Detecting Smart Contract Access Control Vulnerabilities


Asem Ghaleb, Karthik Pattabiraman, Julia Rubin

Date of Publication


As most smart contracts have a financial nature and handle valuable assets, smart contract developers use access control to protect assets managed by smart contracts from being misused by malicious or unauthorized people. Unfortunately, programming languages used for writing smart contracts, such as Solidity, were not designed with a permission-based security model in mind. Therefore, smart contract developers implement access control checks based on their judgment and in an ad-hoc manner, which results in several vulnerabilities in smart contracts, called access control vulnerabilities. Further, the inconsistency in implementing access control makes it difficult to reason about whether a contract meets access control needs and is free of access control vulnerabilities. In this work, we propose AChecker – an approach for detecting access control vulnerabilities. Unlike prior work, AChecker does not rely on pre-defined patterns or contract transactions history. Instead, it infers access control implemented in smart contracts via static data-flow analysis. Moreover, the approach performs further symbolic-based analysis to distinguish cases when unauthorized people can obtain control of the contract as intended functionality.

We evaluated AChecker on three public datasets of real-world smart contracts, including one which consists of contracts with assigned access control CVEs, and compared its effectiveness with eight analysis tools. The evaluation results showed that AChecker outperforms these tools in terms of both precision and recall. In addition, AChecker flagged vulnerabilities in 21 frequently-used contracts on Ethereum blockchain with 90% precision.

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First Nations land acknowledegement

We acknowledge that the UBC Point Grey campus is situated on the traditional, ancestral, and unceded territory of the xʷməθkʷəy̓əm.

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