MyCut

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

Reward Redistribution Uses Total Player Count Instead of Claimant Count

Root + Impact

Protocol Accounting is incorrect, leaving undistributed tokens in the pot.

Description

Whilst closing the pot in the https://github.com/CodeHawks-Contests/ai-mycut/blob/819134663950999ca5ab29a91eeceddb80274743/src/Pot.sol#L49 function, the remaining rewards are redistributed among users who successfully claimed during the claim period.
However, the redistribution amount is calculated using the total number of registered players instead of the number of actual claimants.
https://github.com/CodeHawks-Contests/ai-mycut/blob/819134663950999ca5ab29a91eeceddb80274743/src/Pot.sol#L57
Later only claimants receive this amount.
https://github.com/CodeHawks-Contests/ai-mycut/blob/819134663950999ca5ab29a91eeceddb80274743/src/Pot.sol#L58
https://github.com/CodeHawks-Contests/ai-mycut/blob/819134663950999ca5ab29a91eeceddb80274743/src/Pot.sol#L59
If fewer users claim than the total number of registered players, each claimant receives significantly less than intended. The undistributed tokens permanently remain inside the Pot contract.
Protocol accounting becomes incorrect.
// Root cause in the codebase with @> marks to highlight the relevant section

Risk

Likelihood:

Highly likely.

Impact:

It impacts on protocol Accounting.

Proof of Concept

Suppose:
players.length = 10
claimants.length = 2
remainingRewards = 800
Manager receives:
800 / 10 = 80
Remaining:
720
Current code:
720 / 10 = 72
Distributed:
each player gets 72
meaning total distributed = 72 * 2 = 144
576 tokens Locked forever:
tokens
/**params
uint256[] rewards = [100, 100, 100, 100, 100, 100, 100, 100, 100, 100];
uint256 totalRewards = 1000;
address[] players = [player1,player2,player3, player4,player5, player6,player7, player8,player9,player10];
*/
function test_LostClaims() public {
address contests;
uint256 assumedBal = 576;
vm.startPrank(owner);
contests = _contestManager.createContest(players, rewards, IERC20(ERC20Mock(weth)), 1000);
_contestManager.fundContest(0);
vm.stopPrank();
vm.warp(100 days);
//player 1 claims 100
vm.startPrank(player1);
Pot(contests).claimCut();
vm.stopPrank();
//player 2 claims 100
vm.startPrank(player2);
Pot(contests).claimCut();
vm.stopPrank();
// Pots close reward distributed
vm.startPrank(owner);
_contestManager.closeContest(contests);
vm.stopPrank();
uint256 player1Bal = weth.balanceOf(player1);
uint256 player2Bal = weth.balanceOf(player2);
uint256 contestBalRemaing = weth.balanceOf(address(contests));
console.log("Player 1 Balance After closing:", player1Bal);
console.log("Player 2 Balance After closing:", player2Bal);
console.log("Contest contract After closing:", contestBalRemaing);
assertEq(contestBalRemaing, assumedBal);
}
forge test --match-test test_LostClaims -vvvv
Results
console::log("Player 1 Balance After closing:", 172) [staticcall]
│ └─ ← [Stop]
├─ [0] console::log("Player 2 Balance After closing:", 172) [staticcall]
│ └─ ← [Stop]
├─ [0] console::log("Contest contract After closing:", 576) [staticcall]
│ └─ ← [Stop]
└─ ← [Stop]
Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 23.75ms (4.90ms CPU time)

Recommended Mitigation

This causes permanent loss of funds.
claimantCut = 720 / 2 = 360
Entire redistribution would be distributed as intended (minus rounding dust).
Use the claimant count.
uint256 claimantCut = (remainingRewards - managerCut) / i_players.length;- remove this code
uint256 claimantCut = (remainingRewards - managerCut) / claimants.length; + add this code
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 1 day 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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