Beedle - Oracle free perpetual lending

Summary

Despite the solidity version having safe-math in-built it is still a good practice to divide before you multiply in your business logic to avoid potential integer overflow/underflow bugs in the interest rate calculations.

Vulnerability Details

This funtion has potential overflow/underflow vulnerabilities

function _calculateInterest(
    Loan memory l
) internal view returns (uint256 interest, uint256 fees) {
    uint256 timeElapsed = block.timestamp - l.startTimestamp;
    interest = (l.interestRate * l.debt * timeElapsed) / 10000 / 365 days;
    fees = (lenderFee * interest) / 10000;
    interest -= fees;
}

Impact

Loss of funds and unexpected behavior

Tools Used

Manual review

Recommendations

Always divide before you multiply in your business logic.