Summary

The selectPresident function aggregates all candidates from voters' submissions, potentially leading to an extremely large s_candidateList. If voters submit ballots with numerous unique candidates, it could cause the function to exceed the block gas limit, resulting in a Denial of Service (DoS) where the election cannot be completed.

Vulnerability Details

• Affected Function: selectPresident

• Issue Explanation:

  • Unbounded Loop: The function iterates over VOTERS and their orderedCandidates, adding new candidates to s_candidateList without limits.

  • Gas Limit Exceeded: With enough unique candidates, the gas required to execute the function could surpass the block gas limit.

  • DoS Scenario: If the function cannot complete due to gas constraints, the election process halts.

Impact

Severity: High

• Election Halt: The president cannot be selected, effectively stopping the election process.

• System Vulnerability: Malicious actors can intentionally cause this condition to disrupt governance.

• Resource Exhaustion: Excessive gas consumption leads to increased costs for users and potential network strain.

Tools Used

• Manual Code Review: Identified loops with potential for unbounded iteration.

Recommendations

• Limit Candidate Entries:

  • Max Candidates Per Voter: Enforce a maximum number of candidates each voter can submit.

    uint256 private constant MAX_CANDIDATES_PER_VOTER = 10;
    require(orderedCandidates.length <= MAX_CANDIDATES_PER_VOTER, "Too many candidates");

• Track Unique Candidates Efficiently:

  • Use Mappings: Replace array searches with mappings to efficiently check for existing candidates.

    mapping(address => bool) private candidateExists;

  • Avoid Nested Loops: Refactor the code to eliminate or minimize nested looping structures.

• Process Candidates Off-Chain:

  • Perform candidate aggregation off-chain and submit a compressed list to the contract.

• Implement Batching:

  • If the list is too large, process candidates in batches over multiple transactions.

• Set Gas Limits:

  • Include checks to ensure the function does not proceed if gas consumption is approaching limits.