Submission Details
Severity:
[H-1] endgame :: TwentyOne allows for reentrancy
Summary
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
}
}
the if statement requires playerWonto be true before transfer of ether. After the transfer the value was not set to false. Thereby allowing a malicious attacker to be able reenter the function and exhaust the contract funds
Vulnerability Details
Impact
The contract losses other players fund to the malicious attacker
Tools Used
Manual analysis
Recommendations
if (playerWon) {
payable(player).transfer(2 ether); // Transfer the prize to the player
+ playerWon = false
emit FeeWithdrawn(player, 2 ether); // Emit the prize withdrawal event
}
Rewards breakdown
nSLOC
147This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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