Axelar Bridge Adapter - Moonwell

1. Introduction

Moonwell engaged Halborn to conduct a security assessment on their AxelarBridgeAdapter.sol smart contract beginning on April 8th and ending on April 10th. The security assessment was scoped to the smart contract provided in the moonwell-fi/moonwell-contracts-v2 GitHub repository. Commit hash and further details can be found in the Scope section of this report.

2. Assessment Summary

Halborn was provided 2 days for the engagement and assigned 1 full-time security engineer to review the security of the smart contract in scope. The engineer is a blockchain and smart contract security expert with advanced penetration testing and smart contract hacking skills, and deep knowledge of multiple blockchain protocols.

The purpose of the assessment is to:

• Identify potential security issues within the smart contract AxelarBridgeAdapter.sol.

• Ensure that smart contract functionality operates as intended.

In summary, Halborn has not identified any security risk inherent to the contract under analysis, given the engagement scope.

3. Test Approach and Methodology

Halborn performed a combination of manual and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of this assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation; automated testing techniques help enhance coverage of the code and can quickly identify items that do not follow the security best practices. The following phases and associated tools were used during the assessment:

• Research into architecture and purpose.

• Smart contract manual code review and walkthrough.

• Graphing out functionality and contract logic/connectivity/functions (solgraph).

• Manual assessment of use and safety for the critical Solidity variables and functions in scope to identify any arithmetic-related vulnerability classes.

• Manual testing by custom scripts.

• Static Analysis of security for scoped contract, and imported functions (slither).

• Testnet deployment (Foundry).

4. Manual Testing

The contract in scope was thoroughly and manually analyzed for potential vulnerabilities and bugs, as well as known optimizations and best practices when developing Smart Contracts in Solidity.

While no major vulnerabilities were found within the scope and time frame provided, it's always important to highlight good practices that were identified during the assessment, which contribute positively to the security maturity of the contracts in-scope, such as:

- Thorough documentation using NatSpec.

- The use of unchecked blocks in for loops extends gas optimization.

- The usage of Ownable2Step pattern is considered a good security practice and mitigates this risk by introducing a two-step process for ownership transfer. The current owner initiates the transfer by proposing a new owner, but the transfer only completes when the proposed new owner accepts it.

- Contract calls are validated in the execute function through the call to gateway.validateContractCall, this helps preventing unallowed actions passing through the execution mechanism.

These security practices are applied industry-wide and should be preserved in future implementations and developments.