M-03.md

Reth poolPrice calculation may overflow

Impact

The Reth derivative contract implements the poolPrice function to get the spot price of the derivative asset using a Uniswap V3 pool. The function queries the pool to fetch the sqrtPriceX96 and does the following calculation:

https://github.com/code-423n4/2023-03-asymmetry/blob/main/contracts/SafEth/derivatives/Reth.sol#L228-L242

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);
}

The main issue here is that the multiplications in the expression sqrtPriceX96 * (uint(sqrtPriceX96)) * (1e18) may eventually overflow. This case is taken into consideration by the implementation of the OracleLibrary.getQuoteAtTick function which is part of the Uniswap V3 periphery set of contracts.

https://github.com/Uniswap/v3-periphery/blob/main/contracts/libraries/OracleLibrary.sol#L49-L69

49:     function getQuoteAtTick(
50:         int24 tick,
51:         uint128 baseAmount,
52:         address baseToken,
53:         address quoteToken
54:     ) internal pure returns (uint256 quoteAmount) {
55:         uint160 sqrtRatioX96 = TickMath.getSqrtRatioAtTick(tick);
56: 
57:         // Calculate quoteAmount with better precision if it doesn't overflow when multiplied by itself
58:         if (sqrtRatioX96 <= type(uint128).max) {
59:             uint256 ratioX192 = uint256(sqrtRatioX96) * sqrtRatioX96;
60:             quoteAmount = baseToken < quoteToken
61:                 ? FullMath.mulDiv(ratioX192, baseAmount, 1 << 192)
62:                 : FullMath.mulDiv(1 << 192, baseAmount, ratioX192);
63:         } else {
64:             uint256 ratioX128 = FullMath.mulDiv(sqrtRatioX96, sqrtRatioX96, 1 << 64);
65:             quoteAmount = baseToken < quoteToken
66:                 ? FullMath.mulDiv(ratioX128, baseAmount, 1 << 128)
67:                 : FullMath.mulDiv(1 << 128, baseAmount, ratioX128);
68:         }
69:     }

Note that this implementation guards against different numerical issues. In particular, the if in line 58 checks for a potential overflow of sqrtRatioX96 and switches the implementation to avoid the issue.

Recommendation

The poolPrice function can delegate the calculation directly to the OracleLibrary.getQuoteAtTick function of the v3-periphery package:

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)
    );
    (, int24 tick, , , , , ) = pool.slot0();
    return OracleLibrary.getQuoteAtTick(tick, 1e18, rocketTokenRETHAddress, W_ETH_ADDRESS);
}