Last Man Standing
First Flight #45
Beginner FriendlyFoundrySolidity
100 EXP
View results
Previous Next
Submission Details
Impact: low
Likelihood: high
Invalid

nonReentrant modifier should always be the first modifier in the function declaration

anuragshingare2005

nonReentrant modifier should always be the first modifier in the function declaration, but in Game::claimThrone function it is declared as second modifier

Description

  • In Game::claimThrone function nonReentrant modifier is used after another modifier gameNotEnded which just checks for game end state

  • Current implementation is accidentally safe because gameNotEnded doesn't make any external calls, but the pattern is wrong

@> 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.");
​
uint256 sentAmount = msg.value;
uint256 previousKingPayout = 0;
uint256 currentPlatformFee = 0;
uint256 amountToPot = 0;
​
// Calculate platform fee
currentPlatformFee = (sentAmount * platformFeePercentage) / 100;
​
// Defensive check to ensure platformFee doesn't exceed available amount after previousKingPayout
if (currentPlatformFee > (sentAmount - previousKingPayout)) {
currentPlatformFee = sentAmount - previousKingPayout;
}
platformFeesBalance = platformFeesBalance + currentPlatformFee;
​
// Remaining amount goes to the pot
amountToPot = sentAmount - currentPlatformFee;
pot = pot + amountToPot;
​
// Update game state
currentKing = msg.sender;
lastClaimTime = block.timestamp;
playerClaimCount[msg.sender] = playerClaimCount[msg.sender] + 1;
totalClaims = totalClaims + 1;
​
// Increase the claim fee for the next player
claimFee = claimFee + (claimFee * feeIncreasePercentage) / 100;
​
emit ThroneClaimed(
msg.sender,
sentAmount,
claimFee,
pot,
block.timestamp
);
}

Risk

Likelihood: medium

  • With the current order, whenever user calls claimThrone function, gameNotEnded modifier will check the gameEnd state with no Reentrancy protection yet. An attacker could reenter during the check as _locked=false

Impact: low

  • In current implementation, gameNotEnded modifier doesn't do any external call and no state change. The function is accidentally safe


Recommended Mitigation

  • Add the nonReentrant modifier before the gameNotEnded modifier

- function claimThrone() external payable gameNotEnded nonReentrant {
+ function claimThrone() external payable nonReentrant gameNotEnded {
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.");
uint256 sentAmount = msg.value;
uint256 previousKingPayout = 0;
uint256 currentPlatformFee = 0;
uint256 amountToPot = 0;
​
// Calculate platform fee
currentPlatformFee = (sentAmount * platformFeePercentage) / 100;
​
// Defensive check to ensure platformFee doesn't exceed available amount after previousKingPayout
if (currentPlatformFee > (sentAmount - previousKingPayout)) {
currentPlatformFee = sentAmount - previousKingPayout;
}
platformFeesBalance = platformFeesBalance + currentPlatformFee;
​
// Remaining amount goes to the pot
amountToPot = sentAmount - currentPlatformFee;
pot = pot + amountToPot;
​
// Update game state
currentKing = msg.sender;
lastClaimTime = block.timestamp;
playerClaimCount[msg.sender] = playerClaimCount[msg.sender] + 1;
totalClaims = totalClaims + 1;
​
// Increase the claim fee for the next player
claimFee = claimFee + (claimFee * feeIncreasePercentage) / 100;
​
emit ThroneClaimed(
msg.sender,
sentAmount,
claimFee,
pot,
block.timestamp
);
}
Updates

Appeal created

inallhonesty Lead Judge about 2 months ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity

Support

FAQs

Can't find an answer? Chat with us on Discord, Twitter or Linkedin.