First Flight #2: Puppy Raffle

Summary

The storage variable PuppyRaffle#totalFees can overflow if fees are not withdrawn after a certain period and start accumulating.

Vulnerability Details

Using a uint64 for the storage variable PuppyRaffle#totalFees and not handling overflow manually due to the fact the solidity version you are using is ^0.7.6 can cause an overflow after PuppyRaffle#totalFees reach type(uint64).max, a value of 18.446.744.073.709.551.616 (~18 ether).

Impact

The overflow of PuppyRaffle#totalFees cause a loss of funds for the owner because all the fees collected for every round will go to 0.

Tools Used

Manual review.

Recommendations

You have tree options to handle this:

• Use a bigger uint size, for example uint256 to have enough space for the total fees collected

• Use the OpenZeppelin library SafeMath and handle the possible overflow in the PuppyRaffle#selectWinner() function

• Use a Solidity version >=0.8 that will throw an error for arithmetic overflow or underflow