Backd contest - wuwe1's results

Lines of code

https://github.com/code-423n4/2022-04-backd/blob/main/backd/contracts/pool/EthPool.sol#L30

Vulnerability details

Proof of Concept

1. transfer has hard coded gas budget and can fail when the user is a smart contract. This way any programmatical usage of EthPool is at risk.
2. https://github.com/code-423n4/2022-04-backd/blob/main/backd/contracts/pool/EthPool.sol#L30

    function _doTransferOut(address payable to, uint256 amount) internal override {
        to.transfer(amount);
    }

3. User can not redeem due to this gas budget

https://github.com/code-423n4/2022-04-backd/blob/main/backd/contracts/pool/LiquidityPool.sol#L567

References

https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/

Recommended Mitigation Steps

Using low-level call.value(amount) with the corresponding result check or using the OpenZeppelin Address.sendValue is advised:

https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Address.sol#L60

Lines of code

https://github.com/code-423n4/2022-04-backd/blob/main/backd/contracts/pool/LiquidityPool.sol#L523

Vulnerability details

Proof of Concept

This exploit requires that the _underlying token transfers control to the msg.sender.

depositFor can be reentered and by pass cap check.

https://github.com/code-423n4/2022-04-backd/blob/main/backd/contracts/pool/LiquidityPool.sol#L523

    function depositFor(
        address account,
        uint256 depositAmount,
        uint256 minTokenAmount
    ) public payable override notPaused returns (uint256) {
        uint256 rate = exchangeRate();

        if (isCapped()) {
            uint256 lpBalance = lpToken.balanceOf(account);
            uint256 stakedAndLockedBalance = staker.stakedAndActionLockedBalanceOf(account);
            uint256 currentUnderlyingBalance = (lpBalance + stakedAndLockedBalance).scaledMul(rate);
            require(
                currentUnderlyingBalance + depositAmount <= depositCap,
                Error.EXCEEDS_DEPOSIT_CAP
            );
        }

        _doTransferIn(msg.sender, depositAmount);

Recommended Mitigation Steps

Move

        _doTransferIn(msg.sender, depositAmount);

    if (isCapped()) {

before