First Flight #2: Puppy Raffle

Summary

Utilizing division for both awards and expenses, but calculation errors may cause the sum to be incorrect when added together.

Vulnerability Details

The formula is as follows
uint256 prizePool = (totalAmountCollected * 80) / 100;
uint256 fee = (totalAmountCollected * 20) / 100;
These are expected to add up to totalAmountCollected, but may not actually do so due to rounding errors. This may prevent withdrawFees() from passing require(address(this).balance == uint256(totalFees)).

Impact

Failure to extract expenses

Tools Used

Manual

Recommendations

Recommend the following
uint256 prizePool = (totalAmountCollected * 80) / 100;
uint256 fee = totalAmountCollected - prizePool