SignatureChecker.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/cryptography/SignatureChecker.sol)

pragma solidity ^0.8.0;

import "./ECDSA.sol";
import "../Address.sol";
import "../../interfaces/IERC1271.sol";

/**
 * @dev Signature verification helper that can be used instead of `ECDSA.recover` to seamlessly support both ECDSA
 * signatures from externally owned accounts (EOAs) as well as ERC1271 signatures from smart contract wallets like
 * Argent and Gnosis Safe.
 *
 * _Available since v4.1._
 */
library SignatureChecker {
    /**
     * @dev Checks if a signature is valid for a given signer and data hash. If the signer is a smart contract, the
     * signature is validated against that smart contract using ERC1271, otherwise it's validated using `ECDSA.recover`.
     *
     * NOTE: Unlike ECDSA signatures, contract signatures are revocable, and the outcome of this function can thus
     * change through time. It could return true at block N and false at block N+1 (or the opposite).
     */
    function isValidSignatureNow(
        address signer,
        bytes32 hash,
        bytes memory signature
    ) internal view returns (bool) {
        (address recovered, ECDSA.RecoverError error) = ECDSA.tryRecover(hash, signature);
        if (error == ECDSA.RecoverError.NoError && recovered == signer) {
            return true;
        }

        (bool success, bytes memory result) = signer.staticcall(
            abi.encodeWithSelector(IERC1271.isValidSignature.selector, hash, signature)
        );
        return (success &&
            result.length == 32 &&
            abi.decode(result, (bytes32)) == bytes32(IERC1271.isValidSignature.selector));
    }
}