Last Man Standing
First Flight #45
Beginner FriendlyFoundrySolidity
100 EXP
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Submission Details
Severity: medium
Valid

[H-2] The `Game::claimThrone` function will always revert if called by a player who is not the current king, leading to a loss of control over the game.

thecil

Root + Impact

[H-2] The Game::claimThrone function will always revert if called by a player who is not the current king, leading to a loss of control over the game.

Description

The Game::claimThrone function checks if the caller is the current king using the Game::currentKing variable. If not, it will revert with a message indicating that the player is not the current king. This ensures that only the current king can claim the throne.

function claimThrone() external payable gameNotEnded nonReentrant {
require(msg.value >= claimFee, "Game: Insufficient ETH sent to claim the throne.");
@> require(msg.sender == currentKing, "Game: You are already the king. No need to re-claim.");
​

Risk

Likelihood: High

  • Reason 1 : A player wants to enter the game by calling claimThrone function and pay the claimFee.

Impact: High

  • Impact 1: No one can enter the game, since the Game::currentKing variable starts at address(0).

Proof of Concept

(Proof of code)

The following unit test will demonstrate how the function reverts when called by a player who is not the Game::currentKing and Game::currentKing value is address(0):

function test_claimThrone() public {
address _currentKing = game.currentKing();
console2.log("Current King: ", _currentKing);
// Check that the current king is zero before claiming
assertEq(
_currentKing,
address(0),
"Current King should be zero before claiming"
);
vm.startPrank(player1);
vm.expectRevert("Game: You are already the king. No need to re-claim.");
game.claimThrone{value: INITIAL_CLAIM_FEE}();
vm.stopPrank();
}

Recommended Mitigation

Replace the strict equality with a more robust comparison, such as:

- require(msg.sender == currentKing, "Game: You are already the king. No need to re-claim.");
+ require(msg.sender != currentKing, "Game: You are already the king. No need to re-claim.");
Updates

Appeal created

inallhonesty Lead Judge 11 days ago
Submission Judgement Published
Validated
Assigned finding tags:

Game::claimThrone `msg.sender == currentKing` check is busted

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