Submission Details
Severity:
Case of Draw in game is Not managed by the Contract
Summary
The usual backjack game can result in a draw if the player's hand value = dealer's hand value. but `TwentyOne.sol::call()` does not have the case handling of the issue, rather if the player's hand's value= dealer's hand value it would make the dealer winner because of no case of Draw making it unfair to player
Vulnerability Details
Impact
Can make the contract BIAS towards the dealer
Tools Used
Recommendations
adding a case if the dealer' value = player's value that can handle the case and changing the TwentyOne.sol::call()
function call() public {
require(
playersDeck[msg.sender].playersCards.length > 0,
"Game not started"
);
uint256 playerHand = playersHand(msg.sender);
// Calculate the dealer's threshold for stopping (between 17 and 21)
uint256 standThreshold = (uint256(
keccak256(
abi.encodePacked(block.timestamp, msg.sender, block.prevrandao)
)
) % 5) + 17;
// Dealer draws cards until their hand reaches or exceeds the threshold
while (dealersHand(msg.sender) < standThreshold) {
uint256 newCard = drawCard(msg.sender);
addCardForDealer(msg.sender, newCard);
}
uint256 dealerHand = dealersHand(msg.sender);
// Determine the winner
if (dealerHand > 21) {
emit PlayerWonTheGame(
"Dealer went bust, players winning hand: ",
playerHand
);
endGame(msg.sender, true);
} else if (playerHand > dealerHand) {
emit PlayerWonTheGame(
"Dealer's hand is lower, players winning hand: ",
playerHand
);
endGame(msg.sender, true);
}
else if (playerHand == dealerHand) {
emit PlayerLostTheGame(
"It's a tie, dealer's hand: ",
dealerHand
)else {
emit PlayerLostTheGame(
"Dealer's hand is higher, dealers winning hand: ",
dealerHand
);
endGame(msg.sender, false);
}
}
Rewards breakdown
nSLOC
147This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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