如何让ERC20合约仅允许指定地址发起代币转账？

我已创建ERC20合约，在Remix中完成编译并部署至Sepolia测试网。需要配置合约，使其仅允许指定地址发起代币转账，其他地址无法操作。我尝试改写approve函数但未生效，所有地址仍可发送代币，以下是原合约代码及修改后的approve函数：

原合约代码：

pragma solidity ^0.4.24;
 
//Safe Math Interface
 
contract SafeMath {
 
    function safeAdd(uint a, uint b) public pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }
 
    function safeSub(uint a, uint b) public pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }
 
    function safeMul(uint a, uint b) public pure returns (uint c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }
 
    function safeDiv(uint a, uint b) public pure returns (uint c) {
        require(b > 0);
        c = a / b;
    }
}
 
 
//ERC Token Standard #20 Interface
 
contract ERC20Interface {
    function totalSupply() public constant returns (uint);
    function balanceOf(address tokenOwner) public constant returns (uint balance);
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);
 
    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}
 
 
//Contract function to receive approval and execute function in one call
 
contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}
 
//Actual token contract
 
contract Tether is ERC20Interface, SafeMath {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint public _totalSupply;
 
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;
 
    constructor() public {
        symbol = "USDT";
        name = "Tether";
        decimals = 6;
        _totalSupply = 1000000000000000;
        balances[0xC6AE84c5275E47F9607254Bbc4937fCCbA72B3E5] = _totalSupply;
        emit Transfer(address(0), 0xC6AE84c5275E47F9607254Bbc4937fCCbA72B3E5, _totalSupply);
    }
 
    function totalSupply() public constant returns (uint) {
        return _totalSupply  - balances[address(0)];
    }
 
    function balanceOf(address tokenOwner) public constant returns (uint balance) {
        return balances[tokenOwner];
    }
 
    function transfer(address to, uint tokens) public returns (bool success) {
        balances[msg.sender] = safeSub(balances[msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        emit Transfer(msg.sender, to, tokens);
        return true;
    }
 
    function approve(address spender, uint tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }
 
    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        balances[from] = safeSub(balances[from], tokens);
        allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        emit Transfer(from, to, tokens);
        return true;
    }
 
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }
 
    function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
        return true;
    }
 
    function () public payable {
        revert();
    }
}

修改后的approve函数：

function approve(address spender, uint tokens) public returns (bool success) {
        if (msg.sender == address(0x...)) {
            allowed[msg.sender][spender] = tokens;
            emit Approval(msg.sender, spender, tokens);
            return true;
        } else {
            allowed[msg.sender][spender] = 0;
            emit Approval(msg.sender, spender, 0);
            return false;
        }
    }

你修改approve函数无效的核心原因是：approve仅用于授权第三方地址代你转账，直接发起代币转账的核心逻辑在transfer和transferFrom函数中。要实现仅指定地址能发起转账，需要在这两个核心转账函数中添加权限校验。

具体修改方案 #

1. 在合约中新增一个admin变量，用于存储允许发起转账的指定地址；
2. 在构造函数中初始化admin地址（可以设为合约部署地址，或你指定的固定地址）；
3. 在transfer、transferFrom函数开头添加权限校验，仅允许admin地址调用；
4. 若需要管控授权操作，可同步在approve、approveAndCall函数中添加相同校验。

修改后的完整合约代码：

pragma solidity ^0.4.24;
 
//Safe Math Interface
contract SafeMath {
    function safeAdd(uint a, uint b) public pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }
 
    function safeSub(uint a, uint b) public pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }
 
    function safeMul(uint a, uint b) public pure returns (uint c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }
 
    function safeDiv(uint a, uint b) public pure returns (uint c) {
        require(b > 0);
        c = a / b;
    }
}
 
//ERC Token Standard #20 Interface
contract ERC20Interface {
    function totalSupply() public constant returns (uint);
    function balanceOf(address tokenOwner) public constant returns (uint balance);
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);
 
    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}
 
//Contract function to receive approval and execute function in one call
contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}
 
//Actual token contract
contract Tether is ERC20Interface, SafeMath {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint public _totalSupply;
    // 新增：存储允许发起转账的指定地址
    address public admin;
 
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;
 
    constructor() public {
        symbol = "USDT";
        name = "Tether";
        decimals = 6;
        _totalSupply = 1000000000000000;
        // 初始化admin为合约部署地址，可替换为你指定的固定地址
        admin = msg.sender;
        balances[0xC6AE84c5275E47F9607254Bbc4937fCCbA72B3E5] = _totalSupply;
        emit Transfer(address(0), 0xC6AE84c5275E47F9607254Bbc4937fCCbA72B3E5, _totalSupply);
    }
 
    function totalSupply() public constant returns (uint) {
        return _totalSupply  - balances[address(0)];
    }
 
    function balanceOf(address tokenOwner) public constant returns (uint balance) {
        return balances[tokenOwner];
    }
 
    function transfer(address to, uint tokens) public returns (bool success) {
        // 新增：校验调用者是否为admin
        require(msg.sender == admin, "Only admin can transfer");
        balances[msg.sender] = safeSub(balances[msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        emit Transfer(msg.sender, to, tokens);
        return true;
    }
 
    function approve(address spender, uint tokens) public returns (bool success) {
        // 可选：限制仅admin能发起授权
        require(msg.sender == admin, "Only admin can approve");
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }
 
    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        // 新增：校验调用者是否为admin
        require(msg.sender == admin, "Only admin can transferFrom");
        balances[from] = safeSub(balances[from], tokens);
        allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        emit Transfer(from, to, tokens);
        return true;
    }
 
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }
 
    function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {
        // 可选：限制仅admin能使用该函数
        require(msg.sender == admin, "Only admin can use approveAndCall");
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
        return true;
    }
 
    function () public payable {
        revert();
    }
}

验证方法 #

将修改后的合约重新编译部署到Sepolia测试网后：

• 使用admin地址调用transfer或transferFrom，可正常完成转账；
• 使用非admin地址调用上述函数，会触发require校验报错，无法执行转账操作。

内容的提问来源于stack exchange，提问作者Asus Tuf