Zaros Part 1

Summary

This report details the absence of a __gap variable in the TradingAccountBranchTestnet contract, which is crucial for maintaining storage compatibility during upgrades. The lack of this variable poses risks to the integrity and functionality of the contract, especially in scenarios involving future upgrades or modifications.

Vulnerability Details

Description

The TradingAccountBranchTestnet contract, an upgradeable smart contract, lacks a __gap variable. This variable serves as a placeholder for future state variables, ensuring that adding new state variables does not disrupt the storage layout compatibility with existing deployments. Without this variable, any addition of new state variables could lead to a shift in the storage layout, rendering the contract incompatible with its upgraded versions.

Technical Analysis

In Solidity, the order and layout of state variables within a contract are significant due to how Ethereum stores contract data on the blockchain. When a contract inherits from another, the storage layout of the parent contract dictates the layout of the child contract. Adding new state variables can alter this layout, causing issues with contract interactions and potentially leading to bugs or vulnerabilities.

The __gap variable acts as a buffer zone, allowing for the addition of new state variables without affecting the overall storage layout. Its presence ensures that the total storage cost remains constant across upgrades, preventing layout shifts that could break contract functionality.

Impact

The absence of a __gap variable in the TradingAccountBranchTestnet contract:

• Breaks Storage Compatibility: Future upgrades or modifications to the contract could inadvertently change the storage layout, leading to compatibility issues between different versions of the contract.

• Increases Risk of Bugs: Changes in the storage layout can introduce subtle bugs or vulnerabilities, such as unexpected behavior in functions or incorrect data handling.

• Limits Contract Flexibility: Without the ability to safely add new state variables, the contract becomes less flexible and harder to maintain over time.

Tools Used

• Manual review

Recommendations

• Implement a __gap Variable: Add a __gap variable at the end of the contract to reserve space for future state variables. This will ensure that adding new state variables in the future does not compromise storage compatibility.