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

Manager cut is sent to the ContestManager contract, which has no token egress, permanently trapping all manager fees

nahmstay

Root + Impact

Description

  • When a Pot is closed, the 10% manager cut should be paid to the human manager who operates the protocol.

  • Pot inherits Ownable(msg.sender) and every Pot is deployed by ContestManager.createContest via new Pot(...), so the Pot's owner is the ContestManager contract. closePot is onlyOwner and is only reachable through ContestManager.closeContest, so msg.sender inside closePot is the ContestManager address. i_token.transfer(msg.sender, managerCut) therefore credits the cut to ContestManager, which exposes no function to move ERC20 tokens out, so every manager fee is permanently frozen.

// src/Pot.sol
@> contract Pot is Ownable(msg.sender) { // owner = the deployer = the ContestManager contract
...
function closePot() external onlyOwner {
...
uint256 managerCut = remainingRewards / managerCutPercent;
@> i_token.transfer(msg.sender, managerCut); // msg.sender == ContestManager, which cannot withdraw
}
}
​
// src/ContestManager.sol
function createContest(...) public onlyOwner returns (address) {
@> Pot pot = new Pot(players, rewards, token, totalRewards); // ContestManager becomes Pot.owner()
...
}
// ContestManager has no withdraw / transfer / sweep function

Risk

Likelihood:

  • When any contest is closed with a non-zero leftover — the standard end state — the managerCut transfer executes and lands in ContestManager.

  • When the protocol operates as designed; no misconfiguration or malicious action is required.

Impact:

  • The 10% commission from every partially-claimed contest is permanently trapped in the ContestManager contract and is unrecoverable.

  • The protocol's entire fee revenue stream is silently destroyed.

Proof of Concept

function testManagerCutTrappedInContestManager() public {
// Create + fund a 2-player pot; manager (user) ends with 0 tokens.
vm.startPrank(user);
contest = ContestManager(conMan).createContest(players, rewards, IERC20(weth), totalRewards);
ContestManager(conMan).fundContest(0);
vm.stopPrank();
​
// player1 claims 50; 50 remains unclaimed.
vm.prank(player1);
Pot(contest).claimCut();
​
// Manager closes after 90 days. managerCut = 50/10 = 5.
uint256 managerBalBefore = weth.balanceOf(user);
vm.warp(block.timestamp + 91 days);
vm.prank(user);
ContestManager(conMan).closeContest(contest);
​
// Buggy code: the 5-token cut goes to ContestManager, not the human manager.
assertEq(weth.balanceOf(user), managerBalBefore + 5, "manager should receive their cut");
assertEq(weth.balanceOf(conMan), 0, "no fees should be trapped in ContestManager");
}

Recommended Mitigation

Record the real manager at Pot construction and pay the cut there (note: owner() in closePot is also the ContestManager, so it is not a valid target — the recipient must be passed in):

// src/ContestManager.sol
- Pot pot = new Pot(players, rewards, token, totalRewards);
+ Pot pot = new Pot(players, rewards, token, totalRewards, owner());
// src/Pot.sol
+ address private immutable i_manager;
​
- constructor(address[] memory players, uint256[] memory rewards, IERC20 token, uint256 totalRewards) {
+ constructor(address[] memory players, uint256[] memory rewards, IERC20 token, uint256 totalRewards, address manager) {
+ i_manager = manager;
...
- i_token.transfer(msg.sender, managerCut);
+ i_token.transfer(i_manager, managerCut);
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 6 hours 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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