Michael.W基于Foundry精读Openzeppelin第35期——Ownable.sol

0. 版本

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

0.1 Ownable.sol

Github: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.8.3/contracts/access/Ownable.sol

Ownable库提供了一种基本的访问控制机制——设置一个owner具有对某些函数特殊的访问权限。通常owner就是本合约的deployer。合约部署后可通过函数transferOwnership()进行owner的修改。本库还提供了modifier onlyOwner，用于为函数限定访问权限。

1. 目标合约

继承Ownable成为一个可调用合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/src/access/MockOwnable.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

import "openzeppelin-contracts/contracts/access/Ownable.sol";

contract MockOwnable is Ownable {
    uint public i;

    function checkOwner() external view {
        _checkOwner();
    }

    function transferOwnershipInternal(address newOwner) external {
        _transferOwnership(newOwner);
    }

    function setI(uint value) external onlyOwner {
        i = value;
    }
}

全部foundry测试合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/test/access/Ownable.t.sol

2. 代码精读

2.1 _checkOwner() && owner() && modifier onlyOwner()

• _checkOwner()：检查当前_msgSender()是否为合约的owner；
• owner()：返回当前合约的owner地址；
• modifier onlyOwner()：用于对外函数访问权限限制的modifier。访问权限：只有当前合约的owner才具有访问权限。

    // 当前合约的owner地址
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    // 合约部署时，默认将deployer设置为本合约的owner
    constructor() {
        _transferOwnership(_msgSender());
    }

    modifier onlyOwner() {
        // 检查当前_msgSender()是否为合约owner，如果不是直接revert
        _checkOwner();
        _;
    }

    function owner() public view virtual returns (address) {
        // 直接返回状态变量_owner
        return _owner;
    }

    function _checkOwner() internal view virtual {
        // 检查当前_msgSender()是否为合约的owner，如果不是直接revert
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

foundry代码验证

contract OwnableTest is Test {
    MockOwnable private _testing;

    function setUp() external {
        _testing = new MockOwnable();
    }

    function test_CheckOwnerAndOnlyOwner() external {
        assertEq(address(this), _testing.owner());
        // test for internal function: _checkOwner
        // case 1: pass
        _testing.checkOwner();
        // case 2: revert if the msgSender() is not owner
        vm.prank(address(1024));
        vm.expectRevert("Ownable: caller is not the owner");
        _testing.checkOwner();

        // test for modifier: onlyOwner
        // case 1: pass the check of modifier
        assertEq(0, _testing.i());
        _testing.setI(1024);
        assertEq(1024, _testing.i());
        // case 2: revert if the msgSender() is not owner
        vm.prank(address(1024));
        vm.expectRevert("Ownable: caller is not the owner");
        _testing.setI(1024);
    }
}

2.2 _transferOwnership(address newOwner) && transferOwnership(address newOwner)

• _transferOwnership(address newOwner)：转移本合约owner身份给一个新的地址。注：该internal函数没有对访问权限的限制；
• transferOwnership(address newOwner)：当前合约owner将owner身份转移给新地址newOwner。

    function transferOwnership(address newOwner) public virtual onlyOwner {
        // modifier onlyOwner对_msgSender()进行检查（必须为当前合约owner）
        // 检查新owner地址不可为0地址，否则revert
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        // 调用_transferOwnership()将newOwner设置为合约的owner
        _transferOwnership(newOwner);
    }

    function _transferOwnership(address newOwner) internal virtual {
        // 合约当前owner地址存储到局部变量oldOwner中
        address oldOwner = _owner;
        // 将_owner状态变量设置为新的owner地址
        _owner = newOwner;
        // 抛出event
        emit OwnershipTransferred(oldOwner, newOwner);
    }

foundry代码验证

contract OwnableTest is Test {
    MockOwnable private _testing;

    function setUp() external {
        _testing = new MockOwnable();
    }

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    function test_TransferOwnership() external {
        // test for public function: transferOwnership
        assertEq(address(this), _testing.owner());
        // case 1: pass
        vm.expectEmit(true, true, false, false, address(_testing));
        emit OwnershipTransferred(address(this), address(1024));
        _testing.transferOwnership(address(1024));
        assertEq(address(1024), _testing.owner());
        // case 2: revert if new owner is 0
        vm.prank(address(1024));
        vm.expectRevert("Ownable: new owner is the zero address");
        _testing.transferOwnership(address(0));

        // test for internal function: _transferOwnership
        // case 1: pass with any address of new owner
        vm.expectEmit(true, true, false, false, address(_testing));
        emit OwnershipTransferred(address(1024), address(2048));
        _testing.transferOwnershipInternal(address(2048));
        assertEq(address(2048), _testing.owner());
        vm.expectEmit(true, true, false, false, address(_testing));
        emit OwnershipTransferred(address(2048), address(0));
        _testing.transferOwnershipInternal(address(0));
        assertEq(address(0), _testing.owner());
    }
}

2.3 renounceOwnership()

当前合约owner在不设置新owner的条件下主动放弃owner身份。

注：当执行该函数后，合约内所有被onlyOwner修饰的函数都将无法被任何人调用。

    function renounceOwnership() public virtual onlyOwner {
        // modifier onlyOwner对_msgSender()进行检查（必须为当前合约owner）
        // 将合约owner身份转移给零地址
        _transferOwnership(address(0));
    }

foundry代码验证

contract OwnableTest is Test {
    MockOwnable private _testing;

    function setUp() external {
        _testing = new MockOwnable();
    }

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    function test_RenounceOwnership() external {
        assertEq(address(this), _testing.owner());
        vm.expectEmit(true, true, false, false, address(_testing));
        emit OwnershipTransferred(address(this), address(0));
        _testing.renounceOwnership();
        assertEq(address(0), _testing.owner());
    }
}

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