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

The function claimThrone() incorrectly prevents anyone from claiming the throne

retter

Root + Impact

Description

The function claimThrone() in /src/Game.sol incorrectly prevents anyone from claiming the throne - including the first player. This due to a faulty logic check.

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

At deployment, currentKing == address(0). When any user attempts to claim the throne for the first time, this check will always fail, since msg.sender != adress(0). As a result, no one can ever start the game, and the contract becomes unusable.

##Risk: High

Likelihood: 100%

  • This issue will always occur immediatly after deployment, because the currentKing is initialized to address(0) and no one can match that address.

  • It completely blocks the first interaction with the game (first claim), since currentKing is intialized to addrress(0), and no msg.sender can match that.

Impact: total game failure

  • Users cannot participate in the game, because the claimThrone() function always reverts on the first attempt.

  • The contract non-functional and useless, defeating the purpose of the game.

  • Any ETH sent to it is effectively locked.

Proof of Concept

This test simulates a user trying to claim the throne immediately after deployment. Since currentKing == address(0) and msg.sender != address(0), the call reverts. The game cannot be started.

function testCannotClaimThroneInitially() public {
// At deployment, currentKing == address(0)
assertEq(game.currentKing(), address(0));
​
// Any player trying to claim the throne will revert
vm.prank(player1);
vm.expectRevert("Game: You are already the king. No need to re-claim.");
game.claimThrone{value: INITIAL_CLAIM_FEE}();
}

Recommended Mitigation

The intention is to prevent the same player from repeatedly claiming the throne - not to block everyone. Replacing == with != fixes the logic and allows new players to claim, while still preventing reduntant self claims.

- 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 9 days ago
Submission Judgement Published
Validated
Assigned finding tags:

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

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