Puppy Raffle
AI First Flight #1
Beginner FriendlyFoundrySolidityNFT
EXP
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Submission Details
Severity: high
Valid

Integer overflow of `PuppyRaffle::totalFees` loses the fees of contract

wisesky825

[H] Integer overflow of PuppyRaffle::totalFees loses the fees of contract

Description: In Solidity versions befor 0.8.0, integers were subject to integer overflows.

uint64 myVar = type(uint64).max;
// myVar will be 18446744073709551615
myVar = myVar + 1;
// myVar will be 0

Impact: In PuppyRaffle::selectWinner, totalFees are accumulated for the feeAddress to collect later in withdrawFees. However, if the totalFees variable overflows, the feeAddress may not collect the correct amount of fees

Proof of Concept:

  1. We first conclude a raffle of 4 players to collect some fees.

  2. We then have 89 additional players enter a new raffle, and we conclude that raffle

  3. totalFees will be:

totalFees = totalFees + uint64(fee);
// substituted
totalFees = 800000000000000000 + 17800000000000000000;
// due to overflow, the following is now the case
totalFees = 153255926290448384;

  1. You will now not be able to withdraw, due to this line in PuppyRaffle::withdrawFees:

require(address(this).balance == uint256(totalFees), "PuppyRaffle: There are currently players active!");
Proof Of Code put this into the `PuppyRaffleTest.t.sol` file.
function testTotalFeesOverflow() public playersEntered {
vm.warp(block.timestamp + duration + 1);
vm.roll(block.number + 1);
puppyRaffle.selectWinner();
uint256 startingTotalFees = puppyRaffle.totalFees();
/
uint256 playersNum = 89;
address[] memory players = new address[](playersNum);
for (uint256 i = 0; i < playersNum; i++) {
players[i] = address(i);
}
puppyRaffle.enterRaffle{value: entranceFee * playersNum}(players);
vm.warp(block.timestamp + duration + 1);
vm.roll(block.number + 1);
​
puppyRaffle.selectWinner();
​
uint256 endingTotalFees = puppyRaffle.totalFees();
console.log("ending total fees", endingTotalFees);
assert(endingTotalFees < startingTotalFees);
​
vm.prank(puppyRaffle.feeAddress());
vm.expectRevert("PuppyRaffle: There are currently players active!");
puppyRaffle.withdrawFees();
}

Recommended Mitigation:.

  1. Use a newer version of Solidity

- pragma solidity ^0.7.6;
+ pragma solidity ^0.8.18;

  1. use a library like OpenZeppelin's SafeMath

Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 2 hours ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-05] Typecasting from uint256 to uint64 in PuppyRaffle.selectWinner() May Lead to Overflow and Incorrect Fee Calculation

## Description ## Vulnerability Details The type conversion from uint256 to uint64 in the expression 'totalFees = totalFees + uint64(fee)' may potentially cause overflow problems if the 'fee' exceeds the maximum value that a uint64 can accommodate (2^64 - 1). ```javascript totalFees = totalFees + uint64(fee); ``` ## POC <details> <summary>Code</summary> ```javascript function testOverflow() public { uint256 initialBalance = address(puppyRaffle).balance; // This value is greater than the maximum value a uint64 can hold uint256 fee = 2**64; // Send ether to the contract (bool success, ) = address(puppyRaffle).call{value: fee}(""); assertTrue(success); uint256 finalBalance = address(puppyRaffle).balance; // Check if the contract's balance increased by the expected amount assertEq(finalBalance, initialBalance + fee); } ``` </details> In this test, assertTrue(success) checks if the ether was successfully sent to the contract, and assertEq(finalBalance, initialBalance + fee) checks if the contract's balance increased by the expected amount. If the balance didn't increase as expected, it could indicate an overflow. ## Impact This could consequently lead to inaccuracies in the computation of 'totalFees'. ## Recommendations To resolve this issue, you should change the data type of `totalFees` from `uint64` to `uint256`. This will prevent any potential overflow issues, as `uint256` can accommodate much larger numbers than `uint64`. Here's how you can do it: Change the declaration of `totalFees` from: ```javascript uint64 public totalFees = 0; ``` to: ```jasvascript uint256 public totalFees = 0; ``` And update the line where `totalFees` is updated from: ```diff - totalFees = totalFees + uint64(fee); + totalFees = totalFees + fee; ``` This way, you ensure that the data types are consistent and can handle the range of values that your contract may encounter.

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