hash - Can start draw will return incorrectly

[sherlock-admin3]

hash

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Can start draw will return incorrectly

Summary

Can start draw will return incorrectly

Vulnerability Detail

The auction duration is checked with the drawClosesAt instead of the closing time of the previous auction. Also it is not checked if the block number one is querying is the same as the block number of the last draw auction. This causes the bots to not call the function even when it is callable and hence causes the draw to not be awarded

link

  function canStartDraw() public view returns (bool) {
    uint24 drawId = prizePool.getDrawIdToAward();
    uint48 drawClosesAt = prizePool.drawClosesAt(drawId);
    StartDrawAuction memory lastStartDrawAuction = getLastStartDrawAuction();
    return (
      (
        // if we're on a new draw
        drawId != lastStartDrawAuction.drawId ||
        // OR we're on the same draw, but the request has failed and we haven't retried too many times
        (rng.isRequestFailed(lastStartDrawAuction.rngRequestId) && _startDrawAuctions.length <= maxRetries)
      ) && // we haven't started it, or we have and the request has failed
      block.timestamp >= drawClosesAt && // the draw has closed
=>    _computeElapsedTime(drawClosesAt, block.timestamp) <= auctionDuration // the draw hasn't expired
    );

Impact

Bots relying on canStartDraw might not start the draw even when it is actually startable

Code Snippet

Tool used

Manual Review

Recommendation

Use the close time of the previous auction instead of the close time of the draw

Duplicate of #129