Renzo - btk's results

Lines of code

https://github.com/code-423n4/2024-04-renzo/blob/main/contracts/Withdraw/WithdrawQueue.sol#L206

Vulnerability details

Impact

Users will loss assets due to the absence of slippage control.

Proof of Concept

The WithdrawQueue lacks a mechanism for usersto express their minimum acceptable output.

It is reasonable that as the users deposit(sends input tokens) to the contract, he/she should receive the rightful amount of tokens on that moment. Also, when the users withdraw his/her tokens he/she should receive the rightful amount of usdc on that moment.

If the token amount to be received is less than what he/she expects, the transaction should revert. This deficiency exposes them to potential losses of their assets due to price fluctuations.

Here is the withdraw() function that contains 0 slippage protection:

    function withdraw(uint256 _amount, address _assetOut) external nonReentrant {
        // code

        // calculate totalTVL
        (, , uint256 totalTVL) = restakeManager.calculateTVLs();

        // Calculate amount to Redeem in ETH
        uint256 amountToRedeem = renzoOracle.calculateRedeemAmount(
            _amount,
            ezETH.totalSupply(),
            totalTVL
        );

        // update amount in claim asset, if claim asset is not ETH
        if (_assetOut != IS_NATIVE) {
            // Get ERC20 asset equivalent amount
            amountToRedeem = renzoOracle.lookupTokenAmountFromValue(
                IERC20(_assetOut),
                amountToRedeem
            );
        }

        // code

        // add redeem amount to claimReserve of claim asset
        claimReserve[_assetOut] += amountToRedeem;
    }

The WithdrawQueue uses lookupTokenAmountFromValue which uses chainlink.latestRoundData to retrieve the last price:

    function lookupTokenAmountFromValue(
        IERC20 _token,
        uint256 _value
    ) external view returns (uint256) {
        AggregatorV3Interface oracle = tokenOracleLookup[_token];
        if (address(oracle) == address(0x0)) revert OracleNotFound();

        (, int256 price, , uint256 timestamp, ) = oracle.latestRoundData();
        if (timestamp < block.timestamp - MAX_TIME_WINDOW) revert OraclePriceExpired();
        if (price <= 0) revert InvalidOraclePrice();

        // Price is times 10**18 ensure token amount is scaled
        return (_value * SCALE_FACTOR) / uint256(price);
    }

For instance, if an users attempts to withdraw his assets from the contract and their transaction is delayed due to low gas or network congestion, any price change would result in the trade occurring at a sub-optimal price, harming the investor.

Tools Used

Manual review

Recommended Mitigation Steps

Allow users to specify a minOut & deadline inputs to protect against slippage.

Assessed type

Other