Summary

The contract does not emit events for critical actions such as when a president is elected or when votes are cast. Events are essential in smart contracts for off-chain applications to track and respond to on-chain activities efficiently. The absence of events makes it difficult for users, interfaces, or monitoring services to detect and respond to important state changes within the contract.

Vulnerability Details

• Affected Functions:

  • selectPresident

  • _rankCandidates

• Issue Explanation:

  • No Events on President Selection: When a new president is selected, the contract updates s_currentPresident but does not emit an event to notify off-chain listeners.

  • No Events on Voting: When a voter casts or updates their vote using _rankCandidates, there is no event emitted to signal that a vote has been cast.

  • Impact on Users and DApps:

    • Lack of Transparency: Users cannot easily track when important actions occur.

    • Inefficient Monitoring: Off-chain services have to poll the contract state continuously to detect changes, leading to increased resource usage.

Impact

Severity: Low

• Usability Concerns: The absence of events affects the user experience and the ability of external applications to interact seamlessly with the contract.

• Ecosystem Integration: DApps, explorers, and monitoring tools rely on events to provide real-time updates to users.

• No Direct Security Risk: While this issue does not pose a direct threat to the contract's security or integrity, it hampers effective communication with off-chain systems.

Tools Used

• Manual Code Review: Examined the contract code to identify the absence of event emissions after key state changes.

Recommendations

• Define Events for Key Actions:

  • Event for President Selection:

    event PresidentElected(address indexed president, uint256 voteNumber);

  • Event for Vote Casting:

    event VoteCast(address indexed voter, uint256 voteNumber);

• Emit Events in Functions:

  • In selectPresident Function:

    s_currentPresident = winnerList[0];

    emit PresidentElected(s_currentPresident, s_voteNumber);

  • In _rankCandidates Function:

    s_rankings[voter][s_voteNumber] = orderedCandidates;

    emit VoteCast(voter, s_voteNumber);

• Benefits of Implementing Events:

  • Improved Transparency: Users and applications can listen to events to get immediate notifications of important actions.

  • Easier Debugging and Monitoring: Developers can track contract interactions more efficiently.

  • Integration with Off-Chain Systems: Facilitates integration with wallets, DApps, and analytics tools.

• Follow Solidity Best Practices:

  • Emit events for all state-changing public functions, especially those that are critical to the contract's functionality.