Off-by-One Timing in Winner Declaration Can Be Exploited with Block Timestamp

Description

• In a time-based logic like declareWinner, correctness depends on precise comparison against the grace period deadline.

• This introduces a 1-second window of ambiguity at the exact moment of expiry. If block.timestamp == lastClaimTime + gracePeriod, the winner cannot be declared, even though the grace period should be considered expired.

• Worse, an attacker could manipulate or mine a block at that exact timestamp, stalling winner declaration for a block.

• The current implementation uses:

Risk

Likelihood:

• Very likely in active networks with small gracePeriod values (e.g., < 1 min).

• Block producers (especially in testnets or low-difficulty chains) can influence block.timestamp.

  
  

Impact:

• Prevents timely winner declaration.

• Can be exploited to delay game resolution, especially if combined with front-running or selfish mining.

Proof of Concept

Recommended Mitigation