All sub sequent _deposit() function calls DOS if the ``_scaledPrice `` price goes less than 1ETH

[c4-bot-5]

Lines of code

https://github.com/code-423n4/2024-04-renzo/blob/519e518f2d8dec9acf6482b84a181e403070d22d/contracts/Bridge/L2/Oracle/RenzoOracleL2.sol#L55 https://github.com/code-423n4/2024-04-renzo/blob/519e518f2d8dec9acf6482b84a181e403070d22d/contracts/Bridge/L2/xRenzoDeposit.sol#L245 https://github.com/code-423n4/2024-04-renzo/blob/519e518f2d8dec9acf6482b84a181e403070d22d/contracts/Bridge/L2/xRenzoDeposit.sol#L293

Vulnerability details

Impact

All subsequent _deposit() function calls reverts. Even can't use the lastPrice, lastPriceTimestamp as per current implementations.

Proof of Concept

FILE: 2024-04-renzo/contracts/Bridge/L2/Oracle/RenzoOracleL2.sol

function getMintRate() public view returns (uint256, uint256) {
        (, int256 price, , uint256 timestamp, ) = oracle.latestRoundData();
        if (timestamp < block.timestamp - MAX_TIME_WINDOW) revert OraclePriceExpired();
        // scale the price to have 18 decimals
        uint256 _scaledPrice = (uint256(price)) * 10 ** (18 - oracle.decimals());
        if (_scaledPrice < 1 ether) revert InvalidOraclePrice();
        return (_scaledPrice, timestamp);
    }

FILE: 2024-04-renzo/contracts/Bridge/L2/xRenzoDeposit.sol

// Fetch price and timestamp of ezETH from the configured price feed
(uint256 _lastPrice, uint256 _lastPriceTimestamp) = getMintRate();

 /**
     * @notice Fetch the price of ezETH from configured price feeds
     */
    function getMintRate() public view returns (uint256, uint256) {
        // revert if PriceFeedNotAvailable
        if (receiver == address(0) && address(oracle) == address(0)) revert PriceFeedNotAvailable();
        if (address(oracle) != address(0)) {
            (uint256 oraclePrice, uint256 oracleTimestamp) = oracle.getMintRate();
            return
                oracleTimestamp > lastPriceTimestamp
                    ? (oraclePrice, oracleTimestamp)
                    : (lastPrice, lastPriceTimestamp);
        } else {
            return (lastPrice, lastPriceTimestamp);
        }
    }

Possible situations oracle price down

• Disruptions or failures in data feeds and APIs can lead to incorrect lower prices
• Economic downturns or macroeconomic shifts can reduce asset values
• Assets with low trading volume can experience sharp price drops
• Sudden changes in market conditions can lead to rapid price decreases

POC

• _deposit() function initiates a call to the getMintRate() function to fetch the current price of ezETH.

• Inside getMintRate(), the function checks if the oracle address is set and then calls the external oracle’s getMintRate() to obtain the latest price data.

• The price fetched from the oracle is scaled to have 18 decimals.

• The getMintRate() function checks if the scaled price is below 1 ETH (_scaledPrice < 1 ether) so this function reverts.

• Due to the reversion, any ongoing transactions or operations relying on this function for price data are immediately stopped.

• If the oracle continues to report ezETH prices below 1 ETH, the smart contract operations requiring price data remain inoperative.

This creates a potential Denial of Service (DoS) all subsequent _deposit() calls become DOS. Yes its possible to access lastPrice, lastPriceTimestamp for alternative but this is only possible situations where,

• the oracle address is 0
• or oracleTimestamp < lastPriceTimestamp

If oracle is set always price fetched from oracle itself.

Tools Used

Manual Audit

Recommended Mitigation Steps

Change the code to following way.This will solve the issue

FILE: 2024-04-renzo/contracts/Bridge/L2/Oracle/RenzoOracleL2.sol

function getMintRate() public view returns (uint256, uint256) {
        (, int256 price, , uint256 timestamp, ) = oracle.latestRoundData();
        if (timestamp < block.timestamp - MAX_TIME_WINDOW) revert OraclePriceExpired();
        // scale the price to have 18 decimals
        uint256 _scaledPrice = (uint256(price)) * 10 ** (18 - oracle.decimals());
-        if (_scaledPrice < 1 ether) revert InvalidOraclePrice();
        return (_scaledPrice, timestamp);
    }

FILE: 2024-04-renzo/contracts/Bridge/L2/xRenzoDeposit.sol

function getMintRate() public view returns (uint256, uint256) {
    // Revert if no valid data source is available
    if (receiver == address(0) && address(oracle) == address(0)) {
        revert PriceFeedNotAvailable();
    }

    if (address(oracle) != address(0)) {
        // Fetch current price and timestamp from the oracle
        (uint256 oraclePrice, uint256 oracleTimestamp) = oracle.getMintRate();

-        // Check if the current price is valid
-        if (oraclePrice < 1 ether) {
-            // If the oracle price is below 1 ETH, return the last known good price and timestamp
-           return (lastPrice, lastPriceTimestamp);
-       }

        // Return the most recent valid data, comparing by timestamp
        return oracleTimestamp > lastPriceTimestamp ? (oraclePrice, oracleTimestamp) : (lastPrice, lastPriceTimestamp);
    } else {
        // Fallback to the last known price if the oracle is unavailable
        return (lastPrice, lastPriceTimestamp);
    }
}

Assessed type

Oracle

[0xJuancito]

Invalid.

From the sponsor comment on Discord:

3. The revert condition in RenzoOracleL2 if (_scaledPrice < 1 ether) revert InvalidOraclePrice();

As, ezETH is a yieldBearing Token which means exchangeRate of ezETH >= 1 ETH. The revert condition is placed to provide a protection of protocol collateral against any wrong oracle feed and restricts user to deposit and mint more ezETH then they are supposed to.

[0xJuancito]

@howlbot reject