Eggstravaganza

Summary

The searchForEgg function in the smart contract relies on an insecure method of generating randomness using on-chain variables such as block.timestamp, block.prevrandao, msg.sender, and eggCounter. This approach allows attackers to guess the outcome and mint an EggstravaganzaNFT.

Vulnerability Details

The vulnerability arises from the following line in the searchForEgg function:

uint256 random = uint256(keccak256(abi.encodePacked(block.timestamp,block.prevrandao, msg.sender,eggCounter))) % 100;

This method is not truly random because an attacker can estimate block.timestamp, block.prevrandao, and eggCounter values since they are publicly accessible or can be influenced.

Impact

An attacker can manipulate randomness to increase their chances of finding EggstravaganzaNFT unfairly, affecting game integrity.

Tools Used

Manual code review

Recommendations

Consider generating random numbers off-chain, either using services like Chainlink VRF or using your own internal server.