Lines of code

https://github.com/Cyfrin/2024-07-biconomy/blob/9590f25cd63f7ad2c54feb618036984774f3879d/contracts/Nexus.sol#L1-L552

Impact

The absence of ERC-165 implementation means that other contracts and off-chain services cannot programmatically verify that the Nexus contract supports the required interfaces. This can lead to interoperability issues and hinder the integration of the Nexus contract with other systems that rely on interface detection.

Proof of Concept

The Nexus contract is designed to handle modular smart accounts compliant with ERC-7579 and ERC-4337 standards. However, it currently lacks the implementation of the ERC-165 standard, which is a requirement for ERC-7579 compliance. ERC-165 provides a standard method to publish and detect what interfaces a smart contract implements.

Example:

1. A user or another contract attempts to verify if the Nexus contract supports a specific interface using the supportsInterface method.

2. Since the Nexus contract does not implement supportsInterface, the call fails, returning false or reverting.

3. This failure prevents the user or contract from confirming the Nexus contract's capabilities, leading to potential integration failures.

Recommended Mitigation Steps

Implement the supportsInterface method as specified in ERC-165. This method should return true for the interface IDs of all interfaces that the Nexus contract supports, including ERC-165 itself.