`getSequencerStatus` don't check the grace period

[rotcivegaf]

Affected smart contract

• https://github.com/LodestarFinance/lodestar-protocol/blob/cfca1ae275d023a02198798bbcb24b2a1f646776/contracts/Oracle/PriceOracleProxyETH.sol#L165-L174

Description

The function getSequencerStatus on contract PriceOracleProxyETH don't check the grace period

Attack scenario

If the latestRoundData returns 0 the round is invalid

Look in Chainlink DOC

"startedAt: This timestamp indicates when the sequencer changed status. This timestamp returns 0 if a round is invalid. When the sequencer comes back up after an outage, wait for the GRACE_PERIOD_TIME to pass before accepting answers from the price data feed. Subtract startedAt from block.timestamp and revert the request if the result is less than the GRACE_PERIOD_TIME."

Recommendation

Check the startedAt returned of getSequencerStatus:

@@ -18,6 +18,8 @@ contract PriceOracleProxyETH is Exponential {

     bool public constant isPriceOracle = true;

+    uint256 private constant GRACE_PERIOD_TIME = 3600;
+
     /// @notice ChainLink aggregator base, currently support USD and ETH
     enum AggregatorBase {
         USD,
@@ -164,8 +166,9 @@ contract PriceOracleProxyETH is Exponential {
      */
     function getSequencerStatus(address sequencer) internal view returns (bool) {
         bool status;
-        (, int256 answer, , , ) = AggregatorV3Interface(sequencer).latestRoundData();
-        if (answer == 0) {
+        (, int256 answer, uint256 startedAt, , ) = AggregatorV3Interface(sequencer).latestRoundData();
+
+        if (answer == 0 && block.timestamp - startedAt > GRACE_PERIOD_TIME) {
             status = true;
         } else if (answer == 1) {
             status = false;