No check if Arbitrum L2 sequencer is down in Chainlink feeds

Summary

Using Chainlink in L2 chains such as Arbitrum requires to check if the sequencer is down to avoid prices from looking like they are fresh although they are not.

The bug could be leveraged by malicious actors to take advantage of the sequencer downtime.

Vulnerability Detail

The new GLPOracle is used the get the the price of GLP. There is no check that the sequencer is down: https://github.com/sherlock-audit/2023-01-sentiment/blob/main/oracle/src/gmx/GLPOracle.sol#L47

    function getEthPrice() internal view returns (uint) {
        (, int answer,, uint updatedAt,) =
            ethUsdPriceFeed.latestRoundData();

        if (block.timestamp - updatedAt >= 86400)
            revert Errors.StalePrice(address(0), address(ethUsdPriceFeed));

        if (answer <= 0)
            revert Errors.NegativePrice(address(0), address(ethUsdPriceFeed));

        return uint(answer);
    }

Impact

The impact depends on the usage of the GLP. If it is used as part of the collateral for lenders:

Users can get better borrows if the price is above the actual price
Users can avoid liquidations if the price is under the actual price

Code Snippet

Tool used

VS Code

Manual Review

Recommendation

It is recommended to follow the code example of Chainlink: https://docs.chain.link/data-feeds/l2-sequencer-feeds#example-code

sherlock-audit / 2023-01-sentiment-judging

0xdeadbeef - No check if Arbitrum L2 sequencer is down in Chainlink feeds #16