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

Critical Logic Flaw in claimThrone(): Throne Cannot Be Claimed Due to Inverted Check

sg_milad

Root + Impact

Description

  • Normally, the claimThrone() function should allow any user who is not the current king to claim the throne by meeting the required conditions (e.g., sending enough ETH, etc.).

  • However, the condition require(msg.sender == currentKing) is incorrectly implemented. This logic only allows the current king to reclaim the throne, defeating the purpose of a game mechanic where others compete to become the new king. The check should instead prevent the current king from reclaiming their own throne.

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

Risk

Likelihood:

  • This will always occur when any user tries to claim the throne and they are not the current king.

  • The contract logic enforces a false precondition that contradicts the intended functionality.

Impact:

  • No new user can ever claim the throne, rendering the core mechanic of the game useless.

  • The contract becomes entirely non-functional in its intended context, potentially locking up funds and making it unusable.

Proof of Concept

The following Foundry test demonstrates that new players are unable to claim the throne due to the incorrect logic in the require statement.

function testClaimThrone_CannotBeUsedByNewPlayers() public {
// Player1 tries to claim the throne but fails because they're not the current king
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

To fix the logic error and restore the correct behavior of the game, update the require condition to reject the current king and allow new players to claim the throne.

- 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 about 1 month ago
Submission Judgement Published
Validated
Assigned finding tags:

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

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