MyCut

AI First Flight #8
Beginner FriendlyFoundry
EXP
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Submission Details
Severity: high
Valid

Funds Stuck in Contract Due to Incorrect Claimant Calculation

Description

  • When the pot is closed after 90 days, any unclaimed rewards are redistributed: the manager receives a cut, and the remainder is divided among claimants who actually claimed their rewards.

  • The code divides the remaining funds by i_players.length (the total number of original players), but distributes the calculated cut only to claimants.length addresses (players who actually claimed). Since not all players necessarily claim their rewards, claimants.length <= i_players.length, causing a portion of funds to remain permanently locked in the contract.

function closePot() external onlyOwner {
if (remainingRewards > 0) {
uint256 managerCut = remainingRewards / managerCutPercent;
i_token.transfer(msg.sender, managerCut);
// @> Divides by i_players.length but only distributes to claimants.length
uint256 claimantCut = (remainingRewards - managerCut) /
i_players.length;
for (uint256 i = 0; i < claimants.length; i++) {
_transferReward(claimants[i], claimantCut);
}
}
}

Risk

Likelihood:

  • This occurs whenever the pot is closed and not all players have claimed their rewards.

  • Players may fail to claim due to forgotten credentials, address changes, contract interaction issues, or deliberate choice not to participate.

Impact:

  • Funds are permanently lost and become inaccessible to all parties, including the contract owner.

  • The amount lost scales with the number of unclaimed rewards; if 2 out of 5 players don't claim, 40% of the remainder is locked forever.

  • Users who did claim may not receive their expected share of the unclaimed pool due to reduced distribution.

Proof of Concept

// Setup: 5 players with 100 tokens each = 500 total
address[] memory players = new address[](5);
uint256[] memory rewards = new uint256[](5);
for (uint i = 0; i < 5; i++) {
players[i] = createAddress(i);
rewards[i] = 100e18;
}
Pot pot = new Pot(players, rewards, token, 500e18);
// Only 3 players claim their rewards
vm.prank(players[0]);
pot.claimCut(); // claims 100
vm.prank(players[1]);
pot.claimCut(); // claims 100
vm.prank(players[2]);
pot.claimCut(); // claims 100
// After 90 days, owner closes the pot
// Remaining: 200 tokens
// Manager cut (10%): 200 / 10 = 20 tokens
// Claimant cut calculation: (200 - 20) / 5 = 36 tokens per player
// Distributed to 3 claimants: 36 * 3 = 108 tokens
// Stuck in contract: 72 tokens (lost forever!)

Recommended Mitigation

function closePot() external onlyOwner {
if (block.timestamp - i_deployedAt < 90 days) {
revert Pot__StillOpenForClaim();
}
if (remainingRewards > 0) {
uint256 managerCut = (remainingRewards * managerCutPercent) / 100;
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);
}
}
}
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 11 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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