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

✅ Interger overflow of `PuppyRaffle::totalFees` loses fees

defiak

Root + Impact: Interger overflow of PuppyRaffle::totalFees loses fees

Description

In solidity version prior to `0.8.0` integers were subject to integer overflows.
​
run the following command on chisel
​
```javascript
uint64 myVar = type(uint64).max
//18446744073709551615
myVar = myVar + 1
// 0
​
```

Impact:

  • In `PuppyRaffle::selectWinner`, `totalFees` are accumulated for the `feeAddress` to collect later in `PuppyRaffle::withdrawFees`. However, if the `totalFees` variable overflows, the `feeAddress` may not collect the correct amount of fees, leaving fees permanently stuck in the contract.

Proof of Concept

​
1. We conclude a raffle of 4 players
2. We then have 89 players enter a new raffle, and conclude the reffle
3. `totalFees` will be:
```javascript
totalFees = 800000000000000000 + 17800000000000000000
// and this will overflow!
totalFees = 153255926290448384
```
4. You will not be able to withdraw due to the line in `PuppyRaffle::withFees`:
​
```javascript
require(address(this).balance == uint256(totalFees), "PuppyRaffle: There are currently players active!");
```
​
Although you could use `selfdestruct` to send ETH to this contract in order for the values to match and withdraw the fees, this is clearly not the intended designe= of the protocol. At some point there will be too much `balance` in the contract that the above `require` will be imposible to hit.
​
​
<details>
<summary>Code</summary>
​
```javascript
function testTotalFeesOverflow() public playersEntered {
// We finish a raffle of 4 to collect some fees
vm.warp(block.timestamp + duration + 1);
vm.roll(block.number + 1);
puppyRaffle.selectWinner();
uint256 startingTotalFees = puppyRaffle.totalFees();
// startingTotalFees = 800000000000000000
​
// We then have 89 players enter a new raffle
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);
// We end the raffle
vm.warp(block.timestamp + duration + 1);
vm.roll(block.number + 1);
​
// And here is where the issue occurs
// We will now have fewer fees even though we just finished a second raffle
puppyRaffle.selectWinner();
​
uint256 endingTotalFees = puppyRaffle.totalFees();
console.log("ending total fees", endingTotalFees);
assert(endingTotalFees < startingTotalFees);
​
// We are also unable to withdraw any fees because of the require check
vm.expectRevert("PuppyRaffle: There are currently players active!");
puppyRaffle.withdrawFees();
}
```
</details>

Recommended Mitigation

There are a few possible mitigations.
1. Use a newer version of solidity, and a `uint256` instead of `uint64` for `PuppyRaffle::totalFees`
2. You could also use the `safeMath` library of Openzepplin for version 0.7.6 of solidity, however you would still have a hard time with the `uint64` type if too many fees are collected
3. Remove the balance check from `PuppyRaffle::withdrawFees`
​
```diif
- require(address(this).balance == uint256(totalFees), "PuppyRaffle: There are currently players active!");
```
​
There are more attack vectors with that final require, so we recommend removing it regardless.
code
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 3 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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