First Flight #20: The Predicter
First Flight #20
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Submission Details
Severity: high
Valid

Player with 1 paid prediction is not eligible for reward

soupy

Summary

Player with at least 1 paid prediction shall be eligible for reward. However, in ScoreBoard::isEligibleForReward, the function was found wrongly implemented the condition that disabled player with 1 paid prediction from getting his reward.

Vulnerability Details

According to the rules specified, player can receive an amount from the prize fund only if their total number of points is a positive number and if they had paid at least one prediction fee. However, function ScoreBoard::isEligibleForReward implemented condition that requires player to have more than 1 paid prediction for reward eligibility.

Proof of Concept:
Add the following test to test/ThePredicter.test.sol :

​
function testPlayerWithOnePaidPredictionIsEligibleForReward() public {
address player = makeAddr("Player");
vm.deal(player, 1 ether);
​
vm.prank(player);
thePredicter.register{value: 0.04 ether}();
​
vm.prank(organizer);
thePredicter.approvePlayer(player);
​
// player makes 1 paid prediction
vm.prank(player);
thePredicter.makePrediction{value: 0.0001 ether}(0, ScoreBoard.Result.Second);
​
vm.startPrank(organizer);
for (uint256 i; i < 9; i++) {
scoreBoard.setResult(i, ScoreBoard.Result.Second);
}
vm.stopPrank();
​
vm.prank(player);
bool eligible = scoreBoard.isEligibleForReward(player);
​
assert(eligible == true);
​
}

The test above will fail indicating that scoreBoard.isEligibleForReward has wrong implementation. However, if the condition imposed rectified as in the recommendation section below, a rerun of the same test will pass.

Impact

Player with one paid prediction is not eligible for reward redemption

Tools Used

Manual review

Recommendations

Make correction on the condition as below:

function isEligibleForReward(address player) public view returns (bool) {
return
results[NUM_MATCHES - 1] != Result.Pending &&
- playersPredictions[player].predictionsCount > 1;
+ playersPredictions[player].predictionsCount > 0;
}
​
Updates

Lead Judging Commences

NightHawK Lead Judge about 1 year ago
Submission Judgement Published
Validated
Assigned finding tags:

The eligibility criteria is wrong

Players with only one prediction cannot withdraw.

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