First Flight #20: The Predicter

Summary

The reward calculation in the withdraw function doesn't check for a zero divisor, which could lead to a division by zero error.

Vulnerability Details

In the withdraw function:

There's no check to ensure totalShares is not zero before performing the division.

Impact

If totalShares is zero (which could happen if all players have zero or negative scores), the function will revert due to a division by zero error.

Tools Used

Manual code review

Recommendations

1. Add a check for zero totalShares:

   require(totalShares > 0, "No positive scores");

2. Handle the case where all scores are zero or negative separately:

   if (totalShares == 0) {

   reward = entranceFee;

   } else {

   reward = (shares * players.length * entranceFee) / totalShares;

   }