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

## [M-3] Incorrect `totalAmountCollected` When Players Have Refunded

sulex25

Root + Impact

Description

  • The selectWinner() function calculates prize pool based on players.length * entranceFee

  • When players refund, the array length stays the same but the actual ETH balance is reduced

  • This causes the function to attempt sending more ETH than the contract holds

@> uint256 totalAmountCollected = players.length * entranceFee; // Counts ALL slots including refunded
uint256 prizePool = (totalAmountCollected * 80) / 100;
// ...
(bool success,) = winner.call{value: prizePool}(""); // May exceed actual balance

Risk

Likelihood:

  • Occurs when at least one player has refunded before selectWinner() is called

  • Common scenario in any raffle where refunds are allowed

Impact:

  • selectWinner() will revert due to insufficient balance

  • Raffle becomes stuck and cannot complete

  • Remaining players' funds are locked

Proof of Concept

function test_InsufficientBalanceAfterRefunds() public {
// 4 players enter (4 ETH total)
address[] memory players = new address[](4);
players[0] = address(1);
players[1] = address(2);
players[2] = address(3);
players[3] = address(4);
puppyRaffle.enterRaffle{value: 4 ether}(players);
​
// 2 players refund (contract now has 2 ETH)
vm.prank(address(1));
puppyRaffle.refund(0);
vm.prank(address(2));
puppyRaffle.refund(1);
​
// Contract balance: 2 ETH
// But totalAmountCollected = 4 * 1 ETH = 4 ETH
// prizePool = 4 * 80% = 3.2 ETH (more than balance!)
​
vm.warp(block.timestamp + duration + 1);
​
// This will revert - trying to send 3.2 ETH when only 2 ETH available
vm.expectRevert();
puppyRaffle.selectWinner();
}

Recommended Mitigation

function selectWinner() external {
require(block.timestamp >= raffleStartTime + raffleDuration, "PuppyRaffle: Raffle not over");
require(players.length >= 4, "PuppyRaffle: Need at least 4 players");
​
- uint256 totalAmountCollected = players.length * entranceFee;
+ // Count only active (non-refunded) players
+ uint256 activePlayerCount = 0;
+ for (uint256 i = 0; i < players.length; i++) {
+ if (players[i] != address(0)) activePlayerCount++;
+ }
+ uint256 totalAmountCollected = activePlayerCount * entranceFee;
​
uint256 prizePool = (totalAmountCollected * 80) / 100;
// ...
}
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 17 days ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-04] `PuppyRaffle::refund` replaces an index with address(0) which can cause the function `PuppyRaffle::selectWinner` to always revert

## Description `PuppyRaffle::refund` is supposed to refund a player and remove him from the current players. But instead, it replaces his index value with address(0) which is considered a valid value by solidity. This can cause a lot issues because the players array length is unchanged and address(0) is now considered a player. ## Vulnerability Details ```javascript players[playerIndex] = address(0); @> uint256 totalAmountCollected = players.length * entranceFee; (bool success,) = winner.call{value: prizePool}(""); require(success, "PuppyRaffle: Failed to send prize pool to winner"); _safeMint(winner, tokenId); ``` If a player refunds his position, the function `PuppyRaffle::selectWinner` will always revert. Because more than likely the following call will not work because the `prizePool` is based on a amount calculated by considering that that no player has refunded his position and exit the lottery. And it will try to send more tokens that what the contract has : ```javascript uint256 totalAmountCollected = players.length * entranceFee; uint256 prizePool = (totalAmountCollected * 80) / 100; (bool success,) = winner.call{value: prizePool}(""); require(success, "PuppyRaffle: Failed to send prize pool to winner"); ``` However, even if this calls passes for some reason (maby there are more native tokens that what the players have sent or because of the 80% ...). The call will thankfully still fail because of the following line is minting to the zero address is not allowed. ```javascript _safeMint(winner, tokenId); ``` ## Impact The lottery is stoped, any call to the function `PuppyRaffle::selectWinner`will revert. There is no actual loss of funds for users as they can always refund and get their tokens back. However, the protocol is shut down and will lose all it's customers. A core functionality is exposed. Impact is high ### Proof of concept To execute this test : forge test --mt testWinnerSelectionRevertsAfterExit -vvvv ```javascript function testWinnerSelectionRevertsAfterExit() public playersEntered { vm.warp(block.timestamp + duration + 1); vm.roll(block.number + 1); // There are four winners. Winner is last slot vm.prank(playerFour); puppyRaffle.refund(3); // reverts because out of Funds vm.expectRevert(); puppyRaffle.selectWinner(); vm.deal(address(puppyRaffle), 10 ether); vm.expectRevert("ERC721: mint to the zero address"); puppyRaffle.selectWinner(); } ``` ## Recommendations Delete the player index that has refunded. ```diff - players[playerIndex] = address(0); + players[playerIndex] = players[players.length - 1]; + players.pop() ```

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