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code-423n4 / 2021-08-realitycards-findings

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Unclear conditional check within bidExists() function #36

Closed code423n4 closed 3 years ago

code423n4 commented 3 years ago

Handle

0xImpostor

Vulnerability details

Impact

It is not clear in the bidExists() function in RCOrderbook.sol why there is a need to check that the user's first bid corresponds to the market and card.

Tools Used

Manual analysis

Recommended Mitigation Steps

Remove https://github.com/code-423n4/2021-08-realitycards/blob/main/contracts/RCOrderbook.sol#L837-L841

Splidge commented 3 years ago

An easy way to find out if the bid exists is to check if the index is non-zero, that's what's done here. However there still exists the possibility that the bid is in the first position of the array, index zero. The bid in index zero could be for any market and any card. We need to check IF the bid in position zero matches the same market AND card, if it does then the bid does exist (it just happens to be in the zero index position and would have been ignored by the earlier check).

0xean commented 3 years ago

Resolving as the check is indeed necessary.