Simple Operator Filter for ERC721 & ERC721A

README.md

What

This is a quick implementation of the OpenSea OperatorFilter with a way to activate / deactivate it over time

Usage

ERC721A

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

import {WithOperatorFilter} from './WithOperatorFilter.sol';
import {ERC721A} from "erc721a/contracts/ERC721A.sol";
import {ERC2981} from '@openzeppelin/contracts/token/common/ERC2981.sol';

contract MyToken is ERC721A, WithOperatorFilter, Ownable {

    constructor() ERC721A('Token', 'TOKEN') {}
    
    /// @inheritdoc ERC721A
    function supportsInterface(bytes4 interfaceId)
        public
        view
        virtual
        override(ERC721A, ERC2981)
        returns (bool)
    {
        return ERC721A.supportsInterface(interfaceId) || ERC2981.supportsInterface(interfaceId);
    }
    
    /// @inheritdoc ERC2981
    function royaltyInfo(uint256 tokenId, uint256 amount) public view override returns (address recipient, uint256 amount) {
      return (owner(), amount * 1000 / 10000);
    }

    /////////////////////////////////////////////////////////
    // Interactions                                        //
    /////////////////////////////////////////////////////////

    /// @inheritdoc ERC721A
    /// @dev overrode to add the FilterOperator
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public payable override onlyAllowedOperator(from) {
        super.transferFrom(from, to, tokenId);
    }

    /// @inheritdoc ERC721A
    /// @dev overrode to add the FilterOperator
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public payable override onlyAllowedOperator(from) {
        super.safeTransferFrom(from, to, tokenId);
    }

    /// @inheritdoc ERC721A
    /// @dev overrode to add the FilterOperator
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory data
    ) public payable override onlyAllowedOperator(from) {
        super.safeTransferFrom(from, to, tokenId, data);
    }

    /// @inheritdoc ERC721A
    /// @dev overrode to add the FilterOperator
    function setApprovalForAll(address operator, bool _approved)
        public
        override
        onlyAllowedOperatorForApproval(operator, _approved)
    {
        super.setApprovalForAll(operator, _approved);
    }
    
    
    /////////////////////////////////////////////////////////
    // Gated Owner                                         //
    /////////////////////////////////////////////////////////
    
    /// @notice Allows owner to switch on/off the OperatorFilter
    /// @param newIsEnabled the new state
    function setIsOperatorFilterEnabled(bool newIsEnabled) public onlyOwner {
        isOperatorFilterEnabled = newIsEnabled;
    }
}

ERC721

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

import {WithOperatorFilter} from './WithOperatorFilter.sol';
import {ERC721} from "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import {ERC2981} from '@openzeppelin/contracts/token/common/ERC2981.sol';

contract MyToken is ERC721, WithOperatorFilter, Ownable {

    constructor() ERC721('Token', 'TOKEN') {}
    
    /// @inheritdoc ERC721
    function supportsInterface(bytes4 interfaceId)
        public
        view
        virtual
        override(ERC721, ERC2981)
        returns (bool)
    {
        return ERC721.supportsInterface(interfaceId) || ERC2981.supportsInterface(interfaceId);
    }
    
    /// @inheritdoc ERC2981
    function royaltyInfo(uint256 tokenId, uint256 amount) public view override returns (address, uint256) {
      return (owner(), amount * 1000 / 10000);
    }
    
    /////////////////////////////////////////////////////////
    // Interactions                                        //
    /////////////////////////////////////////////////////////

    /// @inheritdoc ERC721
    /// @dev overrode to add the FilterOperator
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public override onlyAllowedOperator(from) {
        super.transferFrom(from, to, tokenId);
    }

    /// @inheritdoc ERC721
    /// @dev overrode to add the FilterOperator
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public override onlyAllowedOperator(from) {
        super.safeTransferFrom(from, to, tokenId);
    }

    /// @inheritdoc ERC721
    /// @dev overrode to add the FilterOperator
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory data
    ) public override onlyAllowedOperator(from) {
        super.safeTransferFrom(from, to, tokenId, data);
    }

    /// @inheritdoc ERC721
    /// @dev overrode to add the FilterOperator
    function setApprovalForAll(address operator, bool _approved)
        public
        override
        onlyAllowedOperatorForApproval(operator, _approved)
    {
        super.setApprovalForAll(operator, _approved);
    }
    
    
    /////////////////////////////////////////////////////////
    // Gated Owner                                         //
    /////////////////////////////////////////////////////////
    
    /// @notice Allows owner to switch on/off the OperatorFilter
    /// @param newIsEnabled the new state
    function setIsOperatorFilterEnabled(bool newIsEnabled) public onlyOwner {
        isOperatorFilterEnabled = newIsEnabled;
    }
}

WithOperatorFilter.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

/// @title WithOperatorFilter
/// @author dev by @dievardump
/// @notice Adds OpenSea's OperatorFilter registry management
abstract contract WithOperatorFilter {
    error OperatorNotAllowed(address operator);

    address constant DEFAULT_SUBSCRIPTION = address(0x3cc6CddA760b79bAfa08dF41ECFA224f810dCeB6);

    IOperatorFilterRegistry public constant OPERATOR_FILTER_REGISTRY =
        IOperatorFilterRegistry(0x000000000000AAeB6D7670E522A718067333cd4E);

    bool public isOperatorFilterEnabled = true;

    constructor() {
        // auto subscribe to the default subscription
        if (address(OPERATOR_FILTER_REGISTRY).code.length > 0) {
            OPERATOR_FILTER_REGISTRY.registerAndSubscribe(address(this), DEFAULT_SUBSCRIPTION);
        }
    }

    /////////////////////////////////////////////////////////
    // modifier                                            //
    /////////////////////////////////////////////////////////

    /// @notice this modifier checks if "msg.sender" is not denied to do transfers
    /// @param from the user we want to transfer the nft from
    modifier onlyAllowedOperator(address from) virtual {
        // if from == msg.sender, always allow
        if (from != msg.sender) {
            // reverts if not allowed
            _checkOperatorFilter(msg.sender);
        }
        _;
    }

    /// @notice this modifier checks if "operator" is not denied to do transfers on the current contract
    /// @dev the check will only be performed when the user is trying to approve the `operator` not unapprove
    /// @param operator the operator to check
    /// @param _approved if we are currently trying to approve the operator
    modifier onlyAllowedOperatorForApproval(address operator, bool _approved) virtual {
        // only check when the user tries to approve an operator, unapprove should always work
        if (_approved) {
            // reverts if not allowed
            _checkOperatorFilter(operator);
        }
        _;
    }

    /////////////////////////////////////////////////////////
    // Internals                                           //
    /////////////////////////////////////////////////////////

    /// @dev Internally checks if the operator filter is enabled and if the current operator is allowed to transfer
    /// @param operator the owner of the item
    function _checkOperatorFilter(address operator) internal view {
        // if the operator filter is on, and the operator registry is
        if (isOperatorFilterEnabled && address(OPERATOR_FILTER_REGISTRY).code.length > 0) {
            // if the operator is not allowed, revert
            if (!OPERATOR_FILTER_REGISTRY.isOperatorAllowed(address(this), operator)) {
                revert OperatorNotAllowed(operator);
            }
        }
    }
}

interface IOperatorFilterRegistry {
    function isOperatorAllowed(address registrant, address operator) external view returns (bool);
    function register(address registrant) external;
    function registerAndSubscribe(address registrant, address subscription) external;
    function registerAndCopyEntries(address registrant, address registrantToCopy) external;
    function updateOperator(address registrant, address operator, bool filtered) external;
    function updateOperators(address registrant, address[] calldata operators, bool filtered) external;
    function updateCodeHash(address registrant, bytes32 codehash, bool filtered) external;
    function updateCodeHashes(address registrant, bytes32[] calldata codeHashes, bool filtered) external;
    function subscribe(address registrant, address registrantToSubscribe) external;
    function unsubscribe(address registrant, bool copyExistingEntries) external;
    function subscriptionOf(address addr) external returns (address registrant);
    function subscribers(address registrant) external returns (address[] memory);
    function subscriberAt(address registrant, uint256 index) external returns (address);
    function copyEntriesOf(address registrant, address registrantToCopy) external;
    function isOperatorFiltered(address registrant, address operator) external returns (bool);
    function isCodeHashOfFiltered(address registrant, address operatorWithCode) external returns (bool);
    function isCodeHashFiltered(address registrant, bytes32 codeHash) external returns (bool);
    function filteredOperators(address addr) external returns (address[] memory);
    function filteredCodeHashes(address addr) external returns (bytes32[] memory);
    function filteredOperatorAt(address registrant, uint256 index) external returns (address);
    function filteredCodeHashAt(address registrant, uint256 index) external returns (bytes32);
    function isRegistered(address addr) external returns (bool);
    function codeHashOf(address addr) external returns (bytes32);
}