Omniscia Xcaliswap Audit

VotingEscrow Manual Review Findings

VotingEscrow Manual Review Findings

VEW-01M: Inexistent Validation of ERC721 Conformity

TypeSeverityLocation
Standard ConformityVotingEscrow.sol:L374

Description:

The IERC721Receiver hook invoked is meant to yield the IERC721Receiver.onERC721Received.selector as the bytes4 result to ensure compliance with the EIP-721 standard, however, no such validation occurs.

Impact:

The contract is now non-compliant with the EIP-721 standard and could hinder integrations with other protocols.

Example:

contracts/periphery/VotingEscrow.sol
364function safeTransferFrom(
365    address _from,
366    address _to,
367    uint _tokenId,
368    bytes memory _data
369) public {
370    _transferFrom(_from, _to, _tokenId, msg.sender);
371

372    if (_isContract(_to)) {
373        // Throws if transfer destination is a contract which does not implement 'onERC721Received'
374        try IERC721Receiver(_to).onERC721Received(msg.sender, _from, _tokenId, _data) returns (bytes4) {} catch (
375            bytes memory reason
376        ) {
377            if (reason.length == 0) {
378                revert('ERC721: transfer to non ERC721Receiver implementer');
379            } else {
380                assembly {
381                    revert(add(32, reason), mload(reason))
382                }
383            }
384        }
385    }
386}

Recommendation:

We advise the yielded bytes4 value to be validated as equal to the onERC721Received selector as otherwise interactions with non-EIP-721 compliant tokens will be permitted.

Alleviation:

The Xcaliswap team has fixed this issue by validating that the returned bytes4 value is equal to the onERC721Received selector.

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