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

Manager cut sent to ContestManager contract with no withdrawal mechanism causes permanent fund lock

aditya41205

[H-2] Manager cut sent to ContestManager contract with no withdrawal mechanism causes permanent fund lock

Description: When closePot() is called via ContestManager.closeContest(), the 10% manager cut is sent to msg.sender, which is the ContestManager contract itself. However, ContestManager has no function to withdraw ERC20 tokens, causing all manager cuts to be permanently locked in the ContestManager contract.

Root cause chain:

  1. ContestManager creates Pot via createContest() -> Pot's owner = ContestManager address

  2. ContestManager calls Pot.closePot() via closeContest()

  3. Pot sends manager cut: i_token.transfer(msg.sender, managerCut) where msg.sender = ContestManager

  4. ContestManager has no withdraw() or rescue() function

  5. Funds permanently locked

// In Pot.sol
function closePot() external onlyOwner {
// ...
uint256 managerCut = remainingRewards / managerCutPercent;
i_token.transfer(msg.sender, managerCut); // WARNING: Sends to ContestManager
// ...
}
​
// In ContestManager.sol - NO WITHDRAWAL FUNCTION
contract ContestManager is Ownable {
// ... no way to extract tokens sent to this contract
}

Impact:

  • CRITICAL severity - Protocol economically broken

  • 10% of remaining rewards permanently locked per contest

  • No recovery mechanism exists

  • Affects ALL contests created by the system

  • Cumulative loss increases with each closed contest

Financial impact example:

Contest 1: 10,000 tokens -> 1,000 locked (10%)
Contest 2: 50,000 tokens -> 5,000 locked (10%)
Contest 3: 100,000 tokens -> 10,000 locked (10%)
Total locked: 16,000 tokens permanently lost

Proof of Concept:

function testManagerCutLockedInContractManager() public {
// Setup and fund contest
vm.startPrank(owner);
address pot = manager.createContest(players, rewards, token, 200e18);
token.approve(address(manager), 200e18);
manager.fundContest(0);
// Warp 90 days and close
vm.warp(block.timestamp + 91 days);
uint256 managerBalanceBefore = token.balanceOf(address(manager));
assertEq(managerBalanceBefore, 0);
manager.closeContest(pot);
// Manager cut (10% of 200 = 20) sent to ContestManager
uint256 managerBalanceAfter = token.balanceOf(address(manager));
assertEq(managerBalanceAfter, 20e18);
// Owner did NOT receive the manager cut
uint256 ownerBalance = token.balanceOf(owner);
assertEq(ownerBalance, 800e18); // Still only has leftover from initial mint
// NO FUNCTION TO WITHDRAW - funds stuck forever
vm.stopPrank();
}

Recommended Mitigation:

Option 1: Send to actual owner (RECOMMENDED)

// In Pot.sol
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);
+ // Get the actual human owner (ContestManager's owner)
+ address actualOwner = Ownable(msg.sender).owner();
+ i_token.transfer(actualOwner, managerCut);
// ... rest of code
}
}

Option 2: Add withdrawal function to ContestManager

// In ContestManager.sol
+ function withdrawTokens(IERC20 token, address recipient, uint256 amount) external onlyOwner {
+ require(token.balanceOf(address(this)) >= amount, "Insufficient balance");
+ token.transfer(recipient, amount);
+ }
+
+ function rescueTokens(IERC20 token) external onlyOwner {
+ uint256 balance = token.balanceOf(address(this));
+ require(balance > 0, "No tokens to rescue");
+ token.transfer(msg.sender, balance);
+ }
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 10 days ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-01] Owner Cut Stuck in `ContestManager`

## Description When `closeContest` function in the `ContestManager` contract is called, `pot` sends the owner's cut to the `ContestManager` itself, with no mechanism to withdraw these funds. ## Vulnerability Details: Relevant code - [Pot](https://github.com/Cyfrin/2024-08-MyCut/blob/main/src/Pot.sol#L7) [ContestManager](https://github.com/Cyfrin/2024-08-MyCut/blob/main/src/ContestManager.sol#L16-L26) The vulnerability stems from current ownership implementation between the `Pot` and `ContestManager` contracts, leading to funds being irretrievably locked in the `ContestManager` contract. 1. **Ownership Assignment**: When a `Pot` contract is created, it assigns `msg.sender` as its owner: ```solidity contract Pot is Ownable(msg.sender) { ... } ``` 2. **Contract Creation Context**: The `ContestManager` contract creates new `Pot` instances through its `createContest` function: ```solidity function createContest(...) public onlyOwner returns (address) { Pot pot = new Pot(players, rewards, token, totalRewards); ... } ``` In this context, `msg.sender` for the new `Pot` is the `ContestManager` contract itself, not the external owner who called `createContest`. 3. **Unintended Ownership**: As a result, the `ContestManager` becomes the owner of each `Pot` contract it creates, rather than the intended external owner. 4. **Fund Lock-up**: When `closeContest` is called (after the 90-day contest period), it triggers the `closePot` function: ```solidity function closeContest(address contest) public onlyOwner { Pot(contest).closePot(); } ``` The `closePot` function sends the owner's cut to its caller. Since the caller is `ContestManager`, these funds are sent to and locked within the `ContestManager` contract. 5. **Lack of Withdrawal Mechanism**: The `ContestManager` contract does not include any functionality to withdraw or redistribute these locked funds, rendering them permanently inaccessible. This ownership misalignment and the absence of a fund recovery mechanism result in a critical vulnerability where contest rewards become permanently trapped in the `ContestManager` contract. ## POC In existing test suite, add following test ```solidity function testOwnerCutStuckInContestManager() public mintAndApproveTokens { vm.startPrank(user); contest = ContestManager(conMan).createContest( players, rewards, IERC20(ERC20Mock(weth)), 100 ); ContestManager(conMan).fundContest(0); vm.stopPrank(); // Fast forward 91 days vm.warp(block.timestamp + 91 days); uint256 conManBalanceBefore = ERC20Mock(weth).balanceOf(conMan); console.log("contest manager balance before:", conManBalanceBefore); vm.prank(user); ContestManager(conMan).closeContest(contest); uint256 conManBalanceAfter = ERC20Mock(weth).balanceOf(conMan); // Assert that the ContestManager balance has increased (owner cut is stuck) assertGt(conManBalanceAfter, conManBalanceBefore); console.log("contest manager balance after:", conManBalanceAfter); } ``` run `forge test --mt testOwnerCutStuckInContestManager -vv` in the terminal and it will return following output: ```js [⠊] Compiling... [⠑] Compiling 1 files with Solc 0.8.20 [⠘] Solc 0.8.20 finished in 1.66s Compiler run successful! Ran 1 test for test/TestMyCut.t.sol:TestMyCut [PASS] testOwnerCutStuckInContestManager() (gas: 810988) Logs: User Address: 0x6CA6d1e2D5347Bfab1d91e883F1915560e09129D Contest Manager Address 1: 0x7BD1119CEC127eeCDBa5DCA7d1Bd59986f6d7353 Minting tokens to: 0x6CA6d1e2D5347Bfab1d91e883F1915560e09129D Approved tokens to: 0x7BD1119CEC127eeCDBa5DCA7d1Bd59986f6d7353 contest manager balance before: 0 contest manager balance after: 10 Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 10.51ms (1.31ms CPU time) ``` ## Impact Loss of funds for the protocol / owner ## Recommendations Add a claimERC20 function `ContestManager` to solve this issue. ```solidity function claimStuckedERC20(address tkn, address to, uint256 amount) external onlyOwner { // bytes4(keccak256(bytes('transfer(address,uint256)'))); (bool success, bytes memory data) = tkn.call(abi.encodeWithSelector(0xa9059cbb, to, amount)); require( success && (data.length == 0 || abi.decode(data, (bool))), 'ContestManager::safeTransfer: transfer failed' ); ```

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