First Flight #6: Voting Booth
First Flight #6
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Submission Details
Severity: low
Valid

One wei left in the contract after distribution when `MIN_FUNDING` is an odd number

wafflemakr

Summary

One wei left in the contract after distribution when MIN_FUNDING is an odd number

Vulnerability Details

Assume the reward calculation bug is fixed and now we are distributing among totalVotesFor amount of voters.

Now, when contract is deployed with an odd number for the MIN_FUNDING, when quorum passes and totalVotesFor is also an odd number, rounding down the rewardPerVoter in VotingBooth.sol#L192 will leave 1 wei left to distribute. Although VotingBooth.sol#L206 tries to account for this, it rounds up and the distribution will end up leaving 1 wei in the contract.

Poc

function testPocOneWeiLeft() public {
vm.prank(address(0x1));
booth.vote(true);
​
vm.prank(address(0x2));
booth.vote(false);
​
vm.prank(address(0x3));
booth.vote(false);
​
vm.prank(address(0x4));
booth.vote(true);
​
vm.prank(address(0x5));
booth.vote(true);
​
assertTrue(!booth.isActive());
​
assertEq(address(booth).balance, 1, "VotingBooth balance");
}

Poc Result

forge test --mt testPocOneWeiLeft -vvv
[⠒] Compiling...
No files changed, compilation skipped
​
Running 1 test for test/VotingBoothTest.t.sol:VotingBoothTest
[PASS] testPocOneWeiLeft() (gas: 356049)
Logs:
ETH left 10000000000000000001
Voter 0x0000000000000000000000000000000000000001 reward 3333333333333333333
ETH left 6666666666666666668
Voter 0x0000000000000000000000000000000000000004 reward 3333333333333333333
ETH left 3333333333333333335
Voter 0x0000000000000000000000000000000000000005 reward 3333333333333333334
​
Test result: ok. 1 passed; 0 failed; 0 skipped; finished in 5.34ms
Ran 1 test suites: 1 tests passed, 0 failed, 0 skipped (1 total tests)

Impact

Medium impact, is not a significant lost, but if this contract is used to do multiple different votings, then the funds lost will grow. Besides, this breaks the invariant that the contract should not have any balance after voting is over.

Tools Used

  • Manual Review

  • Foundry Fuzzing

Recommendations

Updates

Lead Judging Commences

0xnevi Lead Judge almost 2 years ago
Submission Judgement Published
Validated
Assigned finding tags:

VotingBooth._distributeRewards(): Dust amount can still remain in contract

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