Protocol Updates - July 2024 - Moonwell

1. Introduction

Moonwell engaged Halborn to conduct a security assessment on their smart contracts beginning on July 15th and ending on July 17th. The security assessment was scoped to the smart contracts 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 contracts in-scope:

  • xWELLRouter.sol

  • MultichainGovernor.sol

  • MultichainVoteCollection.sol

  • WormholeBridgeAdapter.sol

  • mip-m00.sol

  
  

• Ensure that smart contract functionality operates as intended, considering the modifications performed.

• Review the modifications to the contracts to ensure no vulnerabilities or security hot-spots are added.

  
  

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 contracts in scope were thoroughly and manually analyzed for potential vulnerabilities and bugs, as well as known optimizations and best practices when developing Smart Contracts in Solidity programming language. The review notes of the assessment are the following:

• The MultichainGovernor.sol contract now has a receive() external payable function, and handles correctly the excess amount sent to propose function.

• The MultichainVoteCollection.sol contract now refunds the excess amount sent to emitVotes function.

• The refactored initialize function in the WormholeBridgeAdapter contract has the correct implementation, taking an array of trusted Wormhole chain id's and Trusted senders, and applies verification against array length mismatch, which is recommended.The call to _addTrustedSender takes the correct parameters to the function call.

• In the xWELLRouter.sol contract, hard-coded values for chainId are removed, being now the destination chaindId a parameter to be passed in function calls to bridgeToSender and bridgeToRecipient functions. The allow-list mechanism used by the protocol applies the correct mitigation against permanent loss of funds, even if user provides a wrong chainId.

• All the contracts in-scope are employing thorough and organized NatSpec documentation, what enhances readability.

• Best practices in terms of gas-saving are also being applied.

• The scripts provided within the commit hash in scope are adherent to the modifications.