MyCut

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

`Pot::closePot` divides the claimant pool by `i_players.length` instead of `claimants.length`, locking funds

Root + Impact

Description

  • After 90 days, closePot should take the manager's 10% and split the remaining pool **equally among the players who actually claimed in time** (`claimants`).

  • The per-claimant share is computed by dividing by `i_players.length` (the **total** number of players) but the payout loop only pays `claimants`. Whenever `claimants.length < i_players.length`, each claimant is underpaid and the undistributed remainder is stranded in the `Pot` with no way to recover it.

/ src/Pot.sol :: closePot
uint256 managerCut = remainingRewards / managerCutPercent;
i_token.transfer(msg.sender, managerCut);
@> uint256 claimantCut = (remainingRewards - managerCut) / i_players.length; // BUG: total players, not claimants
for (uint256 i = 0; i < claimants.length; i++) {
_transferReward(claimants[i], claimantCut); // only claimants are paid
}

Risk

Likelihood:

  • Triggers on any close where at least one player did **not** claim (the normal case — the whole point of the 90-day window and redistribution is that some players don't claim).

  • The larger the gap between total players and claimants, the larger the locked amount (up to ~90% of the pool if nobody claimed).

    **Impact:**

Impact:

  • Claimants receive far less than their entitled equal share.

  • The shortfall is permanently locked in the `Pot`; there is no function to sweep it.

Proof of Concept

function test_H02_wrongDenominator() public mintAndApproveTokens {
address[] memory p = new address[](4);
p[0] = makeAddr("a"); p[1] = makeAddr("b"); p[2] = makeAddr("c"); p[3] = makeAddr("d");
uint256[] memory r = new uint256[](4);
r[0] = 25; r[1] = 25; r[2] = 25; r[3] = 25;
vm.startPrank(user);
contest = ContestManager(conMan).createContest(p, r, IERC20(ERC20Mock(weth)), 100);
ContestManager(conMan).fundContest(0);
vm.stopPrank();
vm.prank(p[0]); Pot(contest).claimCut();
vm.prank(p[1]); Pot(contest).claimCut();
vm.warp(block.timestamp + 91 days);
vm.prank(user);
ContestManager(conMan).closeContest(contest);
assertEq(ERC20Mock(weth).balanceOf(contest), 23); // 23 of 50 locked forever
}

Result: `[PASS]` — 23 tokens stranded in the `Pot`.

Recommended Mitigation

Divide by `claimants.length`, and handle the zero-claimant case (otherwise a division by zero / the same locking issue occurs — see M-01):

uint256 managerCut = remainingRewards / managerCutPercent;
i_token.transfer(msg.sender, managerCut);
- uint256 claimantCut = (remainingRewards - managerCut) / i_players.length;
- for (uint256 i = 0; i < claimants.length; i++) {
- _transferReward(claimants[i], claimantCut);
- }
+ if (claimants.length == 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);
+ }
+ }
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 2 hours 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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