Summary

The current implementation of randomness in the SpookySwap contract uses a pseudo-random number generator based on keccak256 and block.timestamp, which is vulnerable to miner manipulation. This allows for the possibility of unfair outcomes in the trick-or-treat process

Vulnerability Details

In the trickOrTreat function, randomness is generated using the following code:

uint256 random = uint256(keccak256(abi.encodePacked(block.timestamp, msg.sender, nextTokenId, block.prevrandao))) % 1000 + 1;

This method of generating randomness is not secure. Miners can manipulate the block timestamp or choose whether or not to include certain transactions based on favorable outcomes, especially given the 1/1000 chance for the "trick" (double price) and "treat" (half price).

Impact

The manipulation of randomness could lead to the following:

• Users obtaining an unfair advantage in the minting process, receiving a treat (half-price mint) more frequently.

• Exploiting the "trick" scenario by intentionally delaying transactions or controlling the outcome, resulting in financial losses for other users and unfair pricing.

• This could erode trust in the platform's fairness, particularly if malicious actors exploit these vulnerabilities.

Tools Used

• Manual Code Review: A thorough review of the smart contract identified the use of insecure pseudo-randomness.

  • Solidity Security Best Practices: Cross-checked against industry standards for secure randomness.

Recommendations

To securely generate randomness and prevent manipulation, it is recommended to integrate Chainlink VRF. This provides a cryptographically secure and provable source of randomness.
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