openzeppelin-contracts/contracts/metatx/ERC2771Context.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.4) (metatx/ERC2771Context.sol)

pragma solidity ^0.8.9;

import "../utils/Context.sol";

/**
 * @dev Context variant with ERC2771 support.
 *
 * WARNING: The usage of `delegatecall` in this contract is dangerous and may result in context corruption.
 * Any forwarded request to this contract triggering a `delegatecall` to itself will result in an invalid {_msgSender}
 * recovery.
 */
abstract contract ERC2771Context is Context {
    /// @custom:oz-upgrades-unsafe-allow state-variable-immutable
    address private immutable _trustedForwarder;

    /// @custom:oz-upgrades-unsafe-allow constructor
    constructor(address trustedForwarder) {
        _trustedForwarder = trustedForwarder;
    }

    function isTrustedForwarder(address forwarder) public view virtual returns (bool) {
        return forwarder == _trustedForwarder;
    }

    function _msgSender() internal view virtual override returns (address) {
        uint256 calldataLength = msg.data.length;
        uint256 contextSuffixLength = _contextSuffixLength();
        if (isTrustedForwarder(msg.sender) && calldataLength >= contextSuffixLength) {
            return address(bytes20(msg.data[calldataLength - contextSuffixLength:]));
        } else {
            return super._msgSender();
        }
    }

    function _msgData() internal view virtual override returns (bytes calldata) {
        uint256 calldataLength = msg.data.length;
        uint256 contextSuffixLength = _contextSuffixLength();
        if (isTrustedForwarder(msg.sender) && calldataLength >= contextSuffixLength) {
            return msg.data[:calldataLength - contextSuffixLength];
        } else {
            return super._msgData();
        }
    }

    /**
     * @dev ERC-2771 specifies the context as being a single address (20 bytes).
     */
    function _contextSuffixLength() internal view virtual override returns (uint256) {
        return 20;
    }
}