问题

我已经创建了ERC20合同，将其编译在Remix中，并部署到Sepolia测试网。如何使该合同只能从适当的地址发送代币，不允许其他地址发送？在此先行致谢。

以下是合同代码：

pragma solidity ^0.4.24;

// 安全数学接口

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;
    }
}

// ERC20代币标准接口

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);
}

// 接收批准并执行函数的合同功能

contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}

// 实际代币合同

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();
    }
}

你尝试重写approve函数，但并没有达到你的预期目标。代币仍然可以从任何地址发送。如果你想要限制只有特定地址可以发送代币，你需要在transfer和transferFrom函数中添加适当的权限检查。你可以在这两个函数的开头加入条件来验证msg.sender是否是允许的地址。如果不是允许的地址，你可以选择拒绝转账或采取其他适当的措施。

英文:

I've created the ERC20 contract, compiled it in Remix and deployed to Sepolia testnet.
How can I make this contract to send tokens from an appropriate addresses only. Other addresses should not be allowed to send. Thanks in advance.

Here's the contract code:

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 &gt;= a);
}
function safeSub(uint a, uint b) public pure returns (uint c) {
require(b &lt;= 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 &gt; 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 =&gt; uint) balances;
mapping(address =&gt; mapping(address =&gt; uint)) allowed;
constructor() public {
symbol = &quot;USDT&quot;;
name = &quot;Tether&quot;;
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();
}
}

I tried to rewrite the approve function like this but it didn't work out. Tokens still can sent from any address.

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;
}
}

答案1

得分: 1

如果您希望仅对特定地址启用转账，那么您应该将 if-else 逻辑添加到 `transfer` 而不是 `approve` 中。

因此，您的代码应该类似于以下内容。

```js
function transfer(address to, uint tokens) public returns (bool success) {
   if (msg.sender == "specific-address") {
      balances[msg.sender] = safeSub(balances[msg.sender], tokens);
      balances[to] = safeAdd(balances[to], tokens);
      emit Transfer(msg.sender, to, tokens);
      return true;
   }

   return false;
}

这样，如果其他地址尝试转移代币，则将无法通过 transfer 进行转移。


<details>
<summary>英文:</summary>
If you like to enable the transfer only for certain addresses, then you should instead add the if-else logic not in `approve`, but instead in `transfer`.
So your code should look something like this.
```js
function transfer(address to, uint tokens) public returns (bool success) {
if (msg.sender == &quot;specific-address&quot;) {
balances[msg.sender] = safeSub(balances[msg.sender], tokens);
balances[to] = safeAdd(balances[to], tokens);
emit Transfer(msg.sender, to, tokens);
return true;
}
return false;
}

This way if other addresses try to transfer the token then it will fail to do so using transfer.

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