TwentyOne
First Flight #29
Beginner FriendlyGameFiFoundrySolidity
100 EXP
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Submission Details
Severity: low
Invalid

Excess player bets can get stuck

0xlasadie

Summary

If a player transfer more than 1 ether during startGame(), the excess ether can get stuck in the contract because when the player wins, they only receive back 2 ether.

Vulnerability Details

In startGame(), this allows the user to transfer more than 1 ether even when the bet is 1 ether. And in endGame(), the player receives 2 ether when he wins.

function startGame() public payable returns (uint256) {
address player = msg.sender;
require(msg.value >= 1 ether, "not enough ether sent");
initializeDeck(player);
uint256 card1 = drawCard(player);
uint256 card2 = drawCard(player);
addCardForPlayer(player, card1);
addCardForPlayer(player, card2);
return playersHand(player);
}
​
function endGame(address player, bool playerWon) internal {
delete playersDeck[player].playersCards; // Clear the player's cards
delete dealersDeck[player].dealersCards; // Clear the dealer's cards
delete availableCards[player]; // Reset the deck
if (playerWon) {
payable(player).transfer(2 ether); // Transfer the prize to the player
emit FeeWithdrawn(player, 2 ether); // Emit the prize withdrawal event
}
}
​

Impact

In the scenario where the player transfers 3 ether to startGame() and won the game, he would only receive 2 ether back. And have 1 ether stuck in the contract.

Tools Used

Foundry

Recommendations

  1. Implement a system to track how much player has transferred over and return the excess ether when a player wins or loses.

  2. Check if msg.value == 1 ether instead

function startGame() public payable returns (uint256) {
address player = msg.sender;
- require(msg.value >= 1 ether, "not enough ether sent");
+ require(msg.value == 1 ether, "not enough ether sent");
initializeDeck(player);
uint256 card1 = drawCard(player);
uint256 card2 = drawCard(player);
addCardForPlayer(player, card1);
addCardForPlayer(player, card2);
return playersHand(player);
}
Updates

Lead Judging Commences

inallhonesty Lead Judge 11 months ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity
Assigned finding tags:

[INVALID] User mistake, too much ETH sent

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