The protocol is designed such that if none of the players have a positive score, all of them are allowed to withdraw the entrance fee. The problem arises in a scenario where almost all players have a negative score, and at least one player has a score of 0. In this case, in the function for withdrawing funds ThePredicter::withdraw, the variable totalPositivePoints used to set the variable totalRewards will be 0. Additionally, the variable maxScore will also be set to 0. In the part of the code where the reward is calculated (variable reward):
and in the given scenario, it will divide by totalShares which has a value of 0, causing a revert.
This will prevent users who are entitled to withdraw certain funds from actually withdrawing those funds.
function test_rewardDistributionWithNoPositiveScoreIfThereIsAtLeastOneZeroScore() public {
address stranger2 = makeAddr("stranger2");
address stranger3 = makeAddr("stranger3");
vm.startPrank(stranger);
vm.deal(stranger, 1 ether);
thePredicter.register{value: 0.04 ether}();
vm.stopPrank();
vm.startPrank(stranger2);
vm.deal(stranger2, 1 ether);
thePredicter.register{value: 0.04 ether}();
vm.stopPrank();
vm.startPrank(stranger3);
vm.deal(stranger3, 1 ether);
thePredicter.register{value: 0.04 ether}();
vm.stopPrank();
vm.startPrank(organizer);
thePredicter.approvePlayer(stranger);
thePredicter.approvePlayer(stranger2);
thePredicter.approvePlayer(stranger3);
vm.stopPrank();
vm.startPrank(stranger);
thePredicter.makePrediction{value: 0.0001 ether}(
1,
ScoreBoard.Result.Draw
);
thePredicter.makePrediction{value: 0.0001 ether}(
2,
ScoreBoard.Result.Draw
);
thePredicter.makePrediction{value: 0.0001 ether}(
3,
ScoreBoard.Result.Draw
);
vm.stopPrank();
vm.startPrank(stranger2);
thePredicter.makePrediction{value: 0.0001 ether}(
1,
ScoreBoard.Result.Draw
);
thePredicter.makePrediction{value: 0.0001 ether}(
2,
ScoreBoard.Result.Draw
);
thePredicter.makePrediction{value: 0.0001 ether}(
3,
ScoreBoard.Result.Draw
);
vm.stopPrank();
vm.startPrank(stranger3);
thePredicter.makePrediction{value: 0.0001 ether}(
1,
ScoreBoard.Result.Draw
);
thePredicter.makePrediction{value: 0.0001 ether}(
2,
ScoreBoard.Result.Draw
);
thePredicter.makePrediction{value: 0.0001 ether}(
3,
ScoreBoard.Result.First
);
vm.stopPrank();
vm.startPrank(organizer);
scoreBoard.setResult(0, ScoreBoard.Result.First);
scoreBoard.setResult(1, ScoreBoard.Result.First);
scoreBoard.setResult(2, ScoreBoard.Result.First);
scoreBoard.setResult(3, ScoreBoard.Result.First);
scoreBoard.setResult(4, ScoreBoard.Result.First);
scoreBoard.setResult(5, ScoreBoard.Result.First);
scoreBoard.setResult(6, ScoreBoard.Result.First);
scoreBoard.setResult(7, ScoreBoard.Result.First);
scoreBoard.setResult(8, ScoreBoard.Result.First);
vm.stopPrank();
vm.startPrank(organizer);
thePredicter.withdrawPredictionFees();
vm.stopPrank();
vm.startPrank(stranger);
thePredicter.withdraw();
vm.stopPrank();
assertEq(stranger.balance, 0.9997 ether);
vm.startPrank(stranger2);
thePredicter.withdraw();
vm.stopPrank();
assertEq(stranger2.balance, 0.9997 ether);
vm.startPrank(stranger3);
thePredicter.withdraw();
vm.stopPrank();
assertEq(stranger3.balance, 0.9997 ether);
assertEq(address(thePredicter).balance, 0 ether);
}
and thereby avoid the possibility of division by zero.
