Michael.W基于Foundry精读Openzeppelin第32期——SignatureChecker.sol

0. 版本

[openzeppelin]：v4.8.3，[forge-std]：v1.5.6

0.1 SignatureChecker.sol

Github: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.8.3/contracts/utils/cryptography/SignatureChecker.sol

SignatureChecker库是一个用于链上签名验证的helper库。该库提供的验签函数既支持EOA账户地址的签名验证也支持IERC1271标准合约地址的签名验证。

IERC1271标准往往用于智能合约钱包的签名，例如Argent和Gnosis Safe。

注：关于IERC1271标准的详细解读参见：https://www.learnblockchain.cn/article/6443

1. 目标合约

封装SignatureChecker library成为一个可调用合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/src/utils/cryptography/MockSignatureChecker.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;import "openzeppelin-contracts/contracts/utils/cryptography/SignatureChecker.sol";contract MockSignatureChecker {using SignatureChecker for address;function isValidSignatureNow(address signer,bytes32 hash,bytes memory signature) external view returns (bool){return signer.isValidSignatureNow(hash, signature);}
}

全部foundry测试合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/test/utils/cryptography/SignatureChecker.t.sol

2. 代码精读

2.1 isValidSignatureNow(address signer, bytes32 hash, bytes memory signature)

凭借签名地址、签名内容以及签名本身来验证签名有效性。

需要注意的是：与ECDSA的EOA地址验签不同，基于IERC1271标准的合约地址验签结果是可以改变的。可能在区块高度N和N+1上，IERC1271的验签结果是相反的。

    function isValidSignatureNow(address signer,bytes32 hash,bytes memory signature) internal view returns (bool) {// 将输入的signer当做EOA账户地址，使用ECDSA.tryRecover()以及签名内容和签名还原出signer地址(address recovered, ECDSA.RecoverError error) = ECDSA.tryRecover(hash, signature);if (error == ECDSA.RecoverError.NoError && recovered == signer) {// 如果ECDSA.tryRecover返回的错误类型为ECDSA.RecoverError.NoError且还原出的signer地址与输入signer地址相同，说明signer地址确实为EOA地址，并且通过验签。返回truereturn true;}// 如果没有通过EOA地址验签，那么再假定signer为IERC1271标准的合约地址。使用IERC1271标准的isValidSignature()函数进行验签// 本库使用直接staticcall的方式来调用signer合约的isValidSignature()方法(bool success, bytes memory result) = signer.staticcall(abi.encodeWithSelector(IERC1271.isValidSignature.selector, hash, signature));// 如果staticcall调用成功且返回值只占32字节，同时返回值为IERC1271.isValidSignature的selector，表明通过IERC1271标准的验签——即返回true// 如果不满足以上条件，说明本次既不通过EOA地址验签也不通过IERC1271合约地址验签。可认作是无效的签名，返回falsereturn (success &&result.length == 32 &&abi.decode(result, (bytes32)) == bytes32(IERC1271.isValidSignature.selector));}

foundry代码验证

contract SignatureCheckerTest is Test {using ECDSA for bytes;MockSignatureChecker msc = new MockSignatureChecker();uint eoaSignerPrivateKeyInERC1271 = 1024;MockERC1271 me = new MockERC1271(vm.addr(eoaSignerPrivateKeyInERC1271));uint signerPrivateKey = 2048;address signerAddress = vm.addr(signerPrivateKey);function test_IsValidSignatureNow_AsEOAAddress() external {// case 1: return true with correct eoa signaturebytes32 digestHash = bytes("Michael.W").toEthSignedMessageHash();(uint8 v, bytes32 r, bytes32 s) = vm.sign(signerPrivateKey, digestHash);bytes memory signature = bytes.concat(r, s, bytes1(v));assertTrue(msc.isValidSignatureNow(signerAddress,digestHash,signature));// case 2: return false with incorrect eoa signaturebytes memory incorrectSignature = bytes.concat(r, s, bytes1(v + 1));assertFalse(msc.isValidSignatureNow(signerAddress,digestHash,incorrectSignature));}function test_IsValidSignatureNow_AsIERC1271Address() external {// case 1: return true with valid signature of ERC1271bytes32 digestHash = bytes("Michael.W").toEthSignedMessageHash();(uint8 v, bytes32 r, bytes32 s) = vm.sign(eoaSignerPrivateKeyInERC1271, digestHash);bytes memory signature = bytes.concat(r, s, bytes1(v));assertTrue(msc.isValidSignatureNow(address(me),digestHash,signature));// case 2: return true with invalid signature of ERC1271bytes memory incorrectSignature = bytes.concat(r, s, bytes1(v + 1));assertFalse(msc.isValidSignatureNow(address(me),digestHash,incorrectSignature));// case 3: return false when the signer contract address is not the implementor of IERC1271(v, r, s) = vm.sign(eoaSignerPrivateKeyInERC1271, digestHash);signature = bytes.concat(r, s, bytes1(v));assertFalse(msc.isValidSignatureNow(address(new NotImplementIERC1271()),digestHash,signature));}
}contract MockERC1271 is IERC1271 {using ECDSA for bytes32;address _signerEOA;constructor(address signerEOA){_signerEOA = signerEOA;}function isValidSignature(bytes32 hash, bytes memory signature) external view returns (bytes4 magicValue){return hash.recover(signature) == _signerEOA ? IERC1271.isValidSignature.selector : bytes4(0);}
}contract NotImplementIERC1271 {}

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