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UPC Sentinel: An Accurate Approach for Detecting Upgradeability Proxy Contracts in Ethereum

Amir M. Ebrahimi, Bram Adams, Gustavo A. Oliva, Ahmed E. Hassan

TL;DR

UPC Sentinel provides a robust three-layer framework for detecting upgradeability proxy contracts (UPCs) on Ethereum directly from contract bytecode, combining dynamic proxy detection with static/dynamic upgradeability analyses and pattern-level classification. Evaluated on two ground-truth datasets, it achieves near-perfect recall and precision (GE ≈99% recall; GB with perfect precision and ≈99.3% recall), outperforming the USCHUNT baseline in multiple settings. The approach derives three bytecode-level Upgradeability Reference Designs (SMUP, ESUP, DUP) to cover major UPC patterns, and offers fine-grained classification into specific proxy patterns, enabling precise auditing and research into DApp maintenance practices. The work highlights the value of bytecode-centric UPC detection for open- and closed-source contracts and discusses practical considerations, limitations, and avenues for extending the method to inactive UPCs and broader data sources.

Abstract

Software applications that run on a blockchain platform are known as DApps. DApps are built using smart contracts, which are immutable after deployment. Just like any real-world software system, DApps need to receive new features and bug fixes over time in order to remain useful and secure. However, Ethereum lacks native solutions for post-deployment smart contract maintenance, requiring developers to devise their own methods. A popular method is known as the upgradeability proxy contract (UPC), which involves implementing the proxy design pattern (as defined by the Gang of Four). In this method, client calls first hit a proxy contract, which then delegates calls to a certain implementation contract. Most importantly, the proxy contract can be reconfigured during runtime to delegate calls to another implementation contract, effectively enabling application upgrades. For researchers, the accurate detection of UPCs is a strong requirement in the understanding of how exactly real-world DApps are maintained over time. For practitioners, the accurate detection of UPCs is crucial for providing application behavior transparency and enabling auditing. In this paper, we introduce UPC Sentinel, a novel three-layer algorithm that utilizes both static and dynamic analysis of smart contract bytecode to accurately detect active UPCs. We evaluated UPC Sentinel using two distinct ground truth datasets. In the first dataset, our method demonstrated a near-perfect accuracy of 99%. The evaluation on the second dataset further established our method's efficacy, showing a perfect precision rate of 100% and a near-perfect recall of 99.3%, outperforming the state of the art. Finally, we discuss the potential value of UPC Sentinel in advancing future research efforts.

UPC Sentinel: An Accurate Approach for Detecting Upgradeability Proxy Contracts in Ethereum

TL;DR

UPC Sentinel provides a robust three-layer framework for detecting upgradeability proxy contracts (UPCs) on Ethereum directly from contract bytecode, combining dynamic proxy detection with static/dynamic upgradeability analyses and pattern-level classification. Evaluated on two ground-truth datasets, it achieves near-perfect recall and precision (GE ≈99% recall; GB with perfect precision and ≈99.3% recall), outperforming the USCHUNT baseline in multiple settings. The approach derives three bytecode-level Upgradeability Reference Designs (SMUP, ESUP, DUP) to cover major UPC patterns, and offers fine-grained classification into specific proxy patterns, enabling precise auditing and research into DApp maintenance practices. The work highlights the value of bytecode-centric UPC detection for open- and closed-source contracts and discusses practical considerations, limitations, and avenues for extending the method to inactive UPCs and broader data sources.

Abstract

Software applications that run on a blockchain platform are known as DApps. DApps are built using smart contracts, which are immutable after deployment. Just like any real-world software system, DApps need to receive new features and bug fixes over time in order to remain useful and secure. However, Ethereum lacks native solutions for post-deployment smart contract maintenance, requiring developers to devise their own methods. A popular method is known as the upgradeability proxy contract (UPC), which involves implementing the proxy design pattern (as defined by the Gang of Four). In this method, client calls first hit a proxy contract, which then delegates calls to a certain implementation contract. Most importantly, the proxy contract can be reconfigured during runtime to delegate calls to another implementation contract, effectively enabling application upgrades. For researchers, the accurate detection of UPCs is a strong requirement in the understanding of how exactly real-world DApps are maintained over time. For practitioners, the accurate detection of UPCs is crucial for providing application behavior transparency and enabling auditing. In this paper, we introduce UPC Sentinel, a novel three-layer algorithm that utilizes both static and dynamic analysis of smart contract bytecode to accurately detect active UPCs. We evaluated UPC Sentinel using two distinct ground truth datasets. In the first dataset, our method demonstrated a near-perfect accuracy of 99%. The evaluation on the second dataset further established our method's efficacy, showing a perfect precision rate of 100% and a near-perfect recall of 99.3%, outperforming the state of the art. Finally, we discuss the potential value of UPC Sentinel in advancing future research efforts.
Paper Structure (74 sections, 27 figures, 9 tables)

This paper contains 74 sections, 27 figures, 9 tables.

Table of Contents

  1. Introduction
  2. Background
  3. The Anatomy of Proxy Contracts
  4. Fallback Function
  5. UPC Sentinel Approach
  6. Technical Requirements
  7. Three-layered Design of UPC Sentinel
  8. Proxy Detector Layer
  9. Upgradeability Detector Layer
  10. Deriving Upgradeability Reference Designs (URDs)
  11. URD #1: Self-managed Upgradeability Proxy (SMUP).
  12. URD #2: Externally Supervised Upgradeability Proxy (ESUP).
  13. URD #3: Delegated Upgradeability Proxy (DUP).
  14. Major Components of UPC Sentinel
  15. A: SMUP Detector.
  16. ...and 59 more sections

Figures (27)

  • Figure 1: The basic proxy contract design.
  • Figure 2: UPC Sentinel architecture.
  • Figure 3: An illustrative example demonstrating how a proxy is identified based on its two inherent properties.
  • Figure 4: The structure of the three URDs and their variants. Note that all the used identifiers (e.g., function names or variable names) are examples, and in practice, one can use any arbitrary identifiers.
  • Figure 5: The detailed design of the "A: SMUP Detector" module.
  • ...and 22 more figures