RCMarket.sol - Gas optimization in claimCard

[code423n4]

Handle

PierrickGT

Vulnerability details

Impact

We can avoid one sload by storing card[_card].longestOwner in a private variable.

Proof of Concept

https://github.com/code-423n4/2021-08-realitycards/blob/514a6157fb7bd0df1d27a4affece131ba5056818/contracts/RCMarket.sol#L550-L551

Tools Used

Manual analysis

Recommended Mitigation Steps

Store card[_card].longestOwner in a private variable to avoid one sload.

address _cardLongestOwner = card[_card].longestOwner;

if (_user == _cardLongestOwner) {
    _transferCard(ownerOf(_card), _cardLongestOwner, _card);
} else {
    leaderboard.claimNFT(_user, _card);
    factory.mintCopyOfNFT(_user, _card);
}

[Splidge]

Duplicate of #6

[0xean]

Not a duplicate, same optimization, different location in the code.