Rigor Protocol contest - auditor0517's results

Lines of code

https://github.com/code-423n4/2022-08-rigor/blob/5ab7ea84a1516cb726421ef690af5bc41029f88f/contracts/Community.sol#L668-L706

Vulnerability details

Impact

There might be division loss during interest calculation so builders would pay less interest than they should to lenders.

Proof of Concept

During the interest calculation, we calculate the days of the elapsed period.

So if builders repay some amount after 47 hours, the interest will be added for 1 day only.

As a result, builders would pay less interest(almost half if they repay frequently) than they should and lenders might lose their interest.

Tools Used

Manual Review

Recommended Mitigation Steps

Recommend calculating like below with this part.

uint256 _unclaimedInterest = 
        _lentAmount *
        _communities[_communityID].projectDetails[_project].apr *
        (block.timestamp - _communityProject.lastTimestamp) /
        365000 / 86400;