MyCut
AI First Flight #8
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Submission Details
Severity: high
Valid

closePot distributes leftover rewards to claimants using wrong divisor, permanently locking funds in Pot

diegotrigueros

Root + Impact

Description

  • When a contest closes after 90 days, closePot() is meant to distribute unclaimed leftover rewards as a bonus among players who did claim (claimants) plus a 10% manager cut.

  • The function divides the leftover by i_players.length (total players) but only iterates over claimants.length (players who claimed). The portion meant for non-claimants is never distributed and is permanently locked in the contract with no recovery mechanism.

function closePot() external onlyOwner {
if (block.timestamp - i_deployedAt < 90 days) {
revert Pot__StillOpenForClaim();
}
if (remainingRewards > 0) {
uint256 managerCut = remainingRewards / managerCutPercent;
i_token.transfer(msg.sender, managerCut);
​
@> uint256 claimantCut = (remainingRewards - managerCut) / i_players.length; // divides by ALL players
@> for (uint256 i = 0; i < claimants.length; i++) { // but only iterates CLAIMANTS
_transferReward(claimants[i], claimantCut);
}
}
}
​

Risk

Likelihood:

  • Every time closePot() is called on a contest where at least one player did NOT claim, tokens are permanently locked. This is the normal expected scenario since the 90-day window exists precisely because some players are expected not to claim.

  • The more players who fail to claim, the larger the portion of tokens locked forever.

Impact:

  • Tokens proportional to (i_players.length - claimants.length) * claimantCut are permanently stuck in the Pot contract with no withdrawal or rescue function.

  • For a contest with 10 players where only 5 claimed and 100 tokens remain: managerCut = 10, claimantCut = 90/10 = 9 per player, distributed = 5*9 = 45, locked forever = 45 tokens (45% of remaining).

  • The contract owner (ContestManager) has no way to recover these funds.

Proof of Concept

The following Foundry test demonstrates that after closePot() executes on a contest where only half the players claimed, a significant amount of tokens remain permanently stuck in the Pot contract with no way to retrieve them.

function testLockedFundsInClosePot() public {
// Setup: 10 players, each with 10 token reward, totalRewards = 100
address[] memory players = new address[](10);
uint256[] memory rewards = new uint256[](10);
for (uint i = 0; i < 10; i++) {
players[i] = address(uint160(i + 1));
rewards[i] = 10 ether;
}
​
// Create and fund contest
Pot pot = new Pot(players, rewards, token, 100 ether);
token.transfer(address(pot), 100 ether);
​
// Only 5 players claim their rewards
for (uint i = 0; i < 5; i++) {
vm.prank(players[i]);
pot.claimCut();
}
// remainingRewards = 50 ether (5 unclaimed * 10 each)
​
// Warp past 90 days and close
vm.warp(block.timestamp + 91 days);
pot.closePot();
​
// Manager gets: 50 / 10 = 5 ether
// claimantCut = (50 - 5) / 10 = 4.5 -> truncated to 4 ether each
// Distributed to 5 claimants: 5 * 4 = 20 ether
// Total out: 5 + 20 = 25 ether
// LOCKED FOREVER: 25 ether stuck in Pot contract
uint256 stuck = token.balanceOf(address(pot));
assertGt(stuck, 0); // 25 ether permanently locked
}

Recommended Mitigation

Change the divisor from i_players.length to claimants.length so the leftover bonus is split only among players who actually claimed. Also set remainingRewards = 0 after distribution to keep accounting consistent and prevent stale state.

function closePot() external onlyOwner {
if (block.timestamp - i_deployedAt < 90 days) {
revert Pot__StillOpenForClaim();
}
if (remainingRewards > 0) {
uint256 managerCut = remainingRewards / managerCutPercent;
i_token.transfer(msg.sender, managerCut);
​
- uint256 claimantCut = (remainingRewards - managerCut) / i_players.length;
+ uint256 claimantCut = (remainingRewards - managerCut) / claimants.length;
for (uint256 i = 0; i < claimants.length; i++) {
_transferReward(claimants[i], claimantCut);
}
+ remainingRewards = 0;
}
}
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 2 days ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-02] Incorrect logic in `Pot::closePot` leads to unfair distribution to `claimants`, potentially locking the funds with no way to take that out

## Description in `closePot` function while calclulating the shares for claimaint cut, `i_players.length` is used, instead of `claimants.length`, causing low amount being distributed to claimants. ## Vulnerability Details [2024-08-MyCut/src/Pot.sol at main · Cyfrin/2024-08-MyCut (github.com)](https://github.com/Cyfrin/2024-08-MyCut/blob/main/src/Pot.sol#L57) `Pot::closePot` function is meant to be called once contest passed 90 days, it sends the owner cut to owner and rest is splitted among the users who claimed b/w 90 days period. However, current implementation is wrong.&#x20; It uses total users (i_players.length) instead of the users (claimants.length) who claimed during the duration. This creates an unfair distribution to the participants and some of the funds could be locked in the contract. In worst case scenerio, it could be 90% if nobody has claimed from the protocol during the 90 days duration. ## POC In existing test suite, add following test: ```solidity function testUnfairDistributionInClosePot() public mintAndApproveTokens { // Setup address[] memory testPlayers = new address[](3); testPlayers[0] = makeAddr("player1"); testPlayers[1] = makeAddr("player2"); testPlayers[2] = makeAddr("player3"); uint256[] memory testRewards = new uint256[](3); testRewards[0] = 400; testRewards[1] = 300; testRewards[2] = 300; uint256 testTotalRewards = 1000; // Create and fund the contest vm.startPrank(user); address testContest = ContestManager(conMan).createContest( testPlayers, testRewards, IERC20(ERC20Mock(weth)), testTotalRewards ); ContestManager(conMan).fundContest(0); vm.stopPrank(); // Only player1 claims their reward vm.prank(testPlayers[0]); Pot(testContest).claimCut(); // Fast forward 91 days vm.warp(block.timestamp + 91 days); // Record balances before closing the pot uint256 player1BalanceBefore = ERC20Mock(weth).balanceOf( testPlayers[0] ); // Close the contest vm.prank(user); ContestManager(conMan).closeContest(testContest); // Check balances after closing the pot uint256 player1BalanceAfter = ERC20Mock(weth).balanceOf(testPlayers[0]); // Calculate expected distributions uint256 remainingRewards = 600; // 300 + 300 unclaimed rewards uint256 ownerCut = remainingRewards / 10; // 10% of remaining rewards uint256 distributionPerPlayer = (remainingRewards - ownerCut) / 1; // as only 1 user claimed uint256 fundStucked = ERC20Mock(weth).balanceOf(address(testContest)); // actual results console.log("expected reward:", distributionPerPlayer); console.log( "actual reward:", player1BalanceAfter - player1BalanceBefore ); console.log("Fund stucked:", fundStucked); } ``` then run `forge test --mt testUnfairDistributionInClosePot -vv` in the terminal and it will show following output: ```js [⠊] Compiling... [⠒] Compiling 1 files with Solc 0.8.20 [⠘] Solc 0.8.20 finished in 1.63s Compiler run successful! Ran 1 test for test/TestMyCut.t.sol:TestMyCut [PASS] testUnfairDistributionInClosePot() (gas: 905951) Logs: User Address: 0x6CA6d1e2D5347Bfab1d91e883F1915560e09129D Contest Manager Address 1: 0x7BD1119CEC127eeCDBa5DCA7d1Bd59986f6d7353 Minting tokens to: 0x6CA6d1e2D5347Bfab1d91e883F1915560e09129D Approved tokens to: 0x7BD1119CEC127eeCDBa5DCA7d1Bd59986f6d7353 expected reward: 540 actual reward: 180 Fund stucked: 360 Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 1.58ms (506.33µs CPU time) ``` ## Impact Loss of funds, Unfair distribution b/w users ## Recommendations Fix the functions as shown below: ```diff function closePot() external onlyOwner { if (block.timestamp - i_deployedAt < 90 days) { revert Pot__StillOpenForClaim(); } if (remainingRewards > 0) { uint256 managerCut = remainingRewards / managerCutPercent; i_token.transfer(msg.sender, managerCut); - uint256 claimantCut = (remainingRewards - managerCut) / i_players.length; + uint256 totalClaimants = claimants.length; + if(totalClaimant == 0){ + _transferReward(msg.sender, remainingRewards - managerCut); + } else { + uint256 claimantCut = (remainingRewards - managerCut) / claimants.length; for (uint256 i = 0; i < claimants.length; i++) { _transferReward(claimants[i], claimantCut); } } + } } ```

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