First Flight #2: Puppy Raffle

Summary

Detection of the reentrancy bug. Do not report reentrancies that involve Ether (see reentrancy-eth).

Vulnerability Details

Location:

Reentrancy in PuppyRaffle.refund(uint256) (src/PuppyRaffle.sol#96-105):
External calls:

• address(msg.sender).sendValue(entranceFee) (src/PuppyRaffle.sol#101)
  State variables written after the call(s):

• players[playerIndex] = address(0) (src/PuppyRaffle.sol#103)
  PuppyRaffle.players (src/PuppyRaffle.sol#23) can be used in cross function reentrancies:

• PuppyRaffle.enterRaffle(address[]) (src/PuppyRaffle.sol#79-92)

• PuppyRaffle.getActivePlayerIndex(address) (src/PuppyRaffle.sol#110-117)

• PuppyRaffle.players (src/PuppyRaffle.sol#23)

• PuppyRaffle.refund(uint256) (src/PuppyRaffle.sol#96-105)

• PuppyRaffle.selectWinner() (src/PuppyRaffle.sol#125-154)

Impact

If the participant's address is a contract, and it has a fallback function that reverts or consumes more than 2300 gas, the refund will fail.

Tools Used

Audit Wizard (Slither)

Recommendations

Apply the check-effects-interactions pattern.