Zaros Part 1

Summary

The ChainlinkUtil library has sequencerUptimeFeed checks in place to assert if the sequencer on an L2 is running but these checks are not implemented correctly. The chainlink docs say that sequencerUptimeFeed can return a 0 value for startedAt if it is called during an "invalid round".

https://discord.com/channels/592041321326182401/605768708266131456/1213847312141525002

Please note that an "invalid round" is described to mean there was a problem updating the sequencer's status, possibly due to network issues or problems with data from oracles, and is shown by a startedAt time of 0 and answer is 0. Further explanation can be seen as given by an official chainlink engineer as seen here in the chainlink public discord

Vulnerability Details

This makes the implemented check below in the ChainlinUtil::getPrice to be useless if it’s called in an invalid round.

as startedAt will be 0, the arithmetic operation block.timestamp - startedAt will result in a value greater than SEQUENCER_GRACE_PERIOD_TIME (which is hardcoded to be 3600) i.e block.timestamp = 1719739032, so 1719739032 - 0 = 1719739032 which is bigger than 3600. The code won't revert.

Imagine a case where a round starts, at the beginning startedAt is recorded to be 0, and answer, the initial status is set to be 0. Note that docs say that if answer = 0, sequencer is up, if equals to 1, sequencer is down. But in this case here, answer and startedAt can be 0 initially, till after all data is gotten from oracles and update is confirmed then the values are reset to the correct values that show the correct status of the sequencer.

From these explanations and information, it can be seen that startedAt value is a second value that should be used in the check for if a sequencer is down/up or correctly updated. The checks in ChainlinUtil::getPrice will allow for successful calls in an invalid round because reverts don’t happen if answer == 0 and startedAt == 0 thus defeating the purpose of having a sequencerFeed check to assert the status of the sequencerFeed on L2 i.e if it is up/down/active or if its status is actually confirmed to be either.

Impact

inadequate checks to confirm the correct status of the sequecncer/sequecncerUptimeFeed in ChainlinUtil::getPrice contract will cause getPrice() to not revert even when the sequcncer uptime feed is not updated or is called in an invalid round. This will eventually allow traders to use Zaros when sequencer experience an invalid round.

For reference, here is the exact same issue reported - https://github.com/code-423n4/2024-06-size-findings/issues/209

Tools Used

Manual Review

Recommendations

Add a check that reverts if startedAt is returned as 0.