First Flight #2: Puppy Raffle

Vulnerability Details

The selectWinner function is designed to randomly select a winner among the participants. However, being a public function, it is susceptible to front-running attacks. The function uses the following code to select a winner:

Impact

• Manipulation of Results: A malicious actor, especially one with the ability to influence transaction order (like a miner), could exploit this vulnerability to increase their chances of winning. They can do this by ensuring their transaction is the last to be included in a block or by placing their address in a favorable position within the players array.

• Loss of Fairness: If participants can influence the outcome of the raffle, it undermines the fairness and integrity of the game, leading to a loss of trust among users.

• Economic Impact: The potential to manipulate results could lead to financial losses for honest participants and unjust gains for the attacker.

Recommendations

• Implement Commit-Reveal Scheme: A commit-reveal scheme could mitigate front-running. In this scheme, players submit a hash of their choice (commit) in one transaction and reveal their actual choice in a subsequent transaction, making it difficult to predict or manipulate outcomes.

• Time-Lock Mechanism: Implementing a time-lock mechanism that prevents any changes to the players array shortly before the winner selection could reduce the risk of last-minute manipulations.

• Randomness Improvement: Utilize external oracles or other secure sources of randomness to select winners. Services like Chainlink VRF (Verifiable Random Function) provide verifiable randomness that is difficult to manipulate.