President Elector
First Flight #24
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Submission Details
Severity: low
Invalid

In `RankedChoice::_rankCandidates` function there is no check for if a voter has voted in the election making it possible to vote multiple times in the same election

phylax

Description

There is no check in the RankedChoice::_rankCandidates function for if a voter has already voted in the election. This makes it possible for voters to vote multiple times and manipulate the election result.

Impact

When a voter can vote multiple times in the same election there is a critical issue with governance because it makes it possible to manipulate the election result undermining the integrity of the election.

Proof of Concept

In the code below the same voter votes two times in the same election.

Add this code to the test suit:

function testVoteMultipleTimes() public {
orderedCandidates = [candidates[0], candidates[1], candidates[2]];
vm.prank(voters[0]);
rankedChoice.rankCandidates(orderedCandidates);
vm.prank(voters[0]);
rankedChoice.rankCandidates(orderedCandidates);
​
vm.warp(block.timestamp + rankedChoice.getDuration());
​
rankedChoice.selectPresident();
}

Tools used

Manual code review

Recommendation

This could be mitigated by adding a check to the RankedChoice::_rankCandidates function:

+ error RankedChoice__AlreadyVoted();
​
+ mapping(address => mapping(uint256 => bool)) private hasVoted;
​
function _rankCandidates(address[] memory orderedCandidates, address voter) internal {
+ if (hasVoted[msg.sender][s_voteNumber]) {
+ revert RankedChoice__AlreadyVoted();
+ }
+ hasVoted[msg.sender][s_voteNumber] = true;
// Checks
if (orderedCandidates.length > MAX_CANDIDATES) {
revert RankedChoice__InvalidInput();
}
// @audit - An storage array is handled as a memory array
if (!_isInArray(VOTERS, voter)) {
revert RankedChoice__InvalidVoter();
}
​
// Internal Effects
s_rankings[voter][s_voteNumber] = orderedCandidates;
}
Updates

Lead Judging Commences

inallhonesty Lead Judge
9 months ago
inallhonesty Lead Judge 9 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
Assigned finding tags:

[Invalid] Same vote can vote multiple times

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