deadrxsezzz - Oracle doesn't check if L2 Arbitrum sequencer is down

[sherlock-admin]

deadrxsezzz

medium

Oracle doesn't check if L2 Arbitrum sequencer is down

Summary

Chainlink recommends that all L2 oracles consult the Sequencer Uptime Feed to ensure that the sequencer is live before trusting the data returned by the oracle.

Vulnerability Detail

If the Arbitrum Sequencer goes down, oracle data will not be kept up to date, and thus could become stale. However, users are able to continue to interact with the protocol directly through the L1 optimistic rollup contract. You can review Chainlink docs on L2 Sequencer Uptime Feeds for more details on this.

As a result, users may be able to use the protocol while oracle feeds are stale. This could cause all sorts of problems

Impact

If the Arbitrum sequencer goes down, the protocol will allow users to continue to operate at the previous (stale) rates.

Code Snippet

https://github.com/sherlock-audit/2023-04-jojo/blob/main/smart-contract-EVM/contracts/adaptor/chainlinkAdaptor.sol#L43-#L56

Tool used

Manual Review

Recommendation

add the following lines of code

function isSequencerActive() internal view returns (bool) {
    (, int256 answer, uint256 startedAt,,) = sequencer.latestRoundData();
    if (block.timestamp - startedAt <= GRACE_PERIOD_TIME || answer == 1)
        return false;
    return true;
}

require(isSequencerActive());

Duplicate of #101