Asymmetry contest - fs0c's results

Lines of code

https://github.com/code-423n4/2023-03-asymmetry/blob/main/contracts/SafEth/derivatives/Reth.sol#L173 https://github.com/code-423n4/2023-03-asymmetry/blob/main/contracts/SafEth/derivatives/SfrxEth.sol#L74

Vulnerability details

Impact

A user when staking might actually get less tokens in return from the derivatives and might loose tokens due to sandwich attacks.

POC

In the deposit function in Reth derivative contract, consider the following if condition:

if (!poolCanDeposit(msg.value)) {
            uint rethPerEth = (10 ** 36) / poolPrice(); //@audit sandwich possible?

            uint256 minOut = ((((rethPerEth * msg.value) / 10 ** 18) *
                ((10 ** 18 - maxSlippage))) / 10 ** 18);

            IWETH(W_ETH_ADDRESS).deposit{value: msg.value}();
            uint256 amountSwapped = swapExactInputSingleHop(
                W_ETH_ADDRESS,
                rethAddress(),
                500,
                msg.value,
                minOut
            );

            return amountSwapped;

The poolPrice is calculated as follows:

function poolPrice() private view returns (uint256) {
        address rocketTokenRETHAddress = RocketStorageInterface(
            ROCKET_STORAGE_ADDRESS
        ).getAddress(
                keccak256(
                    abi.encodePacked("contract.address", "rocketTokenRETH")
                )
            );
        IUniswapV3Factory factory = IUniswapV3Factory(UNI_V3_FACTORY);
        IUniswapV3Pool pool = IUniswapV3Pool(
            factory.getPool(rocketTokenRETHAddress, W_ETH_ADDRESS, 500)
        );
        (uint160 sqrtPriceX96, , , , , , ) = pool.slot0();
        return (sqrtPriceX96 * (uint(sqrtPriceX96)) * (1e18)) >> (96 * 2);
    }

Consider the following scenario for a sandwich attack:

1. Legit user starts a transaction to deposit tokens, which if are landed into the following condition if the deposit amount is high enough will swap from WETH to RETH using uniswap pool.
2. When an attacker sees the transaction coming through, they sandwich the transaction and as the minOut depends on the current price, the value of minOut will be decreased in case of the attack, and hence it will have no effect on protecting against slippage.

Tools used.

Manual Analysis

Recommendation

minOut can be taken as an input from user.