DatingDapp

Summary

The tokenURI function in the SoulboundProfileNFT smart contract contains a data type mismatch where a uint8 variable (age) is being assigned to a uint256 variable (profileAge). This implicit type conversion results in unnecessary gas consumption due to the increased computational cost of handling a larger data type. While this issue does not impact the contract's core functionality, it introduces inefficiencies that can be optimized for better gas efficiency.

Vulnerability Details

The issue is found in the tokenURI(uint256 tokenId) function, specifically in the following line:

• The age field in the _profiles struct is originally declared as uint8. However, it is being assigned to a uint256 variable, causing an implicit type conversion.

• Since uint256 operations consume more gas than uint8, this conversion leads to unnecessary computational overhead.

• Given that age is stored as uint8, maintaining consistency in its usage would optimize gas costs.

Impact

• Increased Gas Costs: Implicit type conversions result in higher gas consumption, making contract interactions more expensive for users.

• Inefficient Resource Utilization: Using a larger-than-required data type consumes additional computational resources unnecessarily.

• Not a Functional Bug: This issue does not affect the correctness of the contract but leads to avoidable inefficiencies.

Tools Used

• Manual Audit – The issue was identified through a manual review of the smart contract code.

Recommendations

• Modify the variable profileAge to use uint8 instead of uint256 to eliminate unnecessary type conversion and optimize gas efficiency:

  uint8 profileAge = _profiles[tokenId].age;

• Maintain data type consistency throughout the contract to prevent implicit conversions.

• Use Solidity static analysis tools (e.g., Slither, Mythril) to identify similar inefficiencies and improve contract optimization.

By implementing these optimizations, the SoulboundProfileNFT contract can achieve better gas efficiency without altering its core functionality.