31460 - [SC - Insight] supportsInterface does not return typeIERCRecei...

Submitted on May 19th 2024 at 21:40:50 UTC by @OxRizwan for Boost | Alchemix

Report ID: #31460

Report type: Smart Contract

Report severity: Insight

Target: https://immunefi.com

Impacts:

• Contract fails to deliver promised returns, but doesn't lose value

Description

Brief/Intro

supportsInterface() does not return type(IERC721Receiver).interfaceId

Vulnerability Details

AlchemixGovernor.sol contract has inherited L2Governor abstract as base contract. This base contract has supportsInterface() function which returns the supported interface id by Alchemix Governor contract. It should be noted that Alchemix governor contract supports both IERC721Receiver interface id and IERC1155Receiver interface id, however, the implementation of supportsInterface has only returned IERC1155Receiver and does not return the IERC721Receiver interface id and this can be seen as below:

    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC165) returns (bool) {
        // In addition to the current interfaceId, also support previous version of the interfaceId that did not
        // include the castVoteWithReasonAndParams() function as standard
        return
            interfaceId ==
            (type(IGovernor).interfaceId ^
                this.castVoteWithReasonAndParams.selector ^
                this.castVoteWithReasonAndParamsBySig.selector ^
                this.getVotesWithParams.selector) ||
            interfaceId == type(IGovernor).interfaceId ||
            interfaceId == type(IERC1155Receiver).interfaceId ||
            super.supportsInterface(interfaceId);
    }

Impact Details

supportsInterface() does not explicitely return the interfaceId == type(IERC721Receiver).interfaceId while calling it. The Alchemix governor supports the ERC721Receiver but the interface id does not return it so its a low severity issue

References

https://github.com/alchemix-finance/alchemix-v2-dao/blob/f1007439ad3a32e412468c4c42f62f676822dc1f/src/governance/L2Governor.sol#L130-L142

Recommendation to fix

    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC165) returns (bool) {
        // In addition to the current interfaceId, also support previous version of the interfaceId that did not
        // include the castVoteWithReasonAndParams() function as standard
        return
            interfaceId ==
            (type(IGovernor).interfaceId ^
                this.castVoteWithReasonAndParams.selector ^
                this.castVoteWithReasonAndParamsBySig.selector ^
                this.getVotesWithParams.selector) ||
            interfaceId == type(IGovernor).interfaceId ||
+          interfaceId == type(IERC721Receiver).interfaceId ||
            interfaceId == type(IERC1155Receiver).interfaceId ||
            super.supportsInterface(interfaceId);
    }

Proof of Concept

The issue is simple to understand and very straight forward. It explains the interfaceId function unable to return the promised return i.e interfaceId == type(IERC721Receiver).interfaceId as true.

The issue is not complex so i believe it can be easily understood with above description and recommendation.

Thank you for your understanding.