A large-scale exploratory study on the proxy pattern in Ethereum

The proxy pattern is a well-known design pattern with numerous use cases in several sectors of the software industry (e.g., network applications, microservices, and IoT). As such, the use of the proxy pattern is also a common approach in the development of complex decentralized applications (DApps) on the Ethereum blockchain. A contract that implements the proxy pattern (proxy contract) acts as a layer between the clients and the target contract, enabling greater flexibility (e.g., data validation checks) and upgradeability (e.g., online smart contract replacement with zero downtime) in DApp development. Despite the importance of proxy contracts, little is known about (i) how their prevalence changed over time, (ii) the ways in which developers integrate proxies in the design of DApps, and (iii) what proxy types are being most commonly leveraged by developers. In this paper, we present a large-scale exploratory study on the use of the proxy pattern in Ethereum. We analyze a dataset of all Ethereum smart contracts as of Sep. 2022 containing 50M smart contracts and 1.6B transactions, and apply both quantitative and qualitative methods in order to (i) determine the prevalence of proxy contracts, (ii) understand the ways they are deployed and integrated into applications, and (iii) uncover the prevalence of different types of proxy contracts. Our findings reveal that 14.2% of all deployed smart contracts are proxy contracts. We show that proxy contracts are being more actively used than non-proxy contracts. Also, the usage of proxy contracts in various contexts, transactions involving proxy contracts, and adoption of proxy contracts by users have shown an upward trend over time, peaking at the end of our study period. They are either deployed through off-chain scripts or on-chain factory contracts, with the former and latter being employed in 39.1% and 60.9% of identified usage contexts in turn. We found that while the majority (67.8%) of proxies act as an interceptor, 32.2% enables upgradeability. Proxy contracts are typically (79%) implemented based on known reference implementations with 29.4% being of type ERC-1167, a class of proxies that aims to cheaply reuse and clone contracts' functionality. Our evaluation shows that our proposed behavioral proxy detection method has a precision and recall of 100% in detecting active proxies. Finally, we derive a set of practical recommendations for developers and introduce open research questions to guide future research on the topic.