【修复代码】常见漏洞修复代码

public class UserDao {        private static final String USERNAME = "username";    private static final String PASSWORD = "password";    private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/myDB";

    public List<User> getUsers(String userName, String password) {        List<User> users = new ArrayList<>();

        String sql = "SELECT * FROM users WHERE username = ? AND password = ?"; 

        // 使用 try-with-resources 语句自动关闭资源        try (Connection conn = this.createConnection();             PreparedStatement pstmt = conn.prepareStatement(sql)) {

            //设置参数值，参数索引从1开始            pstmt.setString(1, userName);            pstmt.setString(2, password);

            //执行查询            ResultSet rs = pstmt.executeQuery();

            while (rs.next()) {                 User user = new User();                // 设置 user 的值 ...                users.add(user);            }

        } catch (SQLException e) {            // Log error        }

        return users;    }

    private Connection createConnection() {        try {            Class.forName("com.mysql.jdbc.Driver");            return DriverManager.getConnection(DATABASE_URL, USERNAME, PASSWORD);        } catch (Exception e) {            // Log error            return null;        }    }}

import org.apache.commons.text.StringEscapeUtils;

public class XSSPrevention {    public String secureOutput(String unsafeInput){        if(unsafeInput == null || unsafeInput.length() == 0) {            // 如果为空，就不需要编码            return unsafeInput;        }

        String safeOutput = StringEscapeUtils.escapeHtml4(unsafeInput);        return safeOutput;    }}

import org.springframework.web.multipart.MultipartFile;

import javax.imageio.ImageIO;import java.awt.image.BufferedImage;import java.io.IOException;import java.nio.file.Files;import java.nio.file.Path;import java.util.Arrays;import java.util.HashSet;import java.util.Set;import java.util.UUID;

public class FileUploadHandler {

    private static final long MAX_FILE_SIZE = 10 * 1024 * 1024; // 可配置的文件大小限制    private static final String UPLOAD_DIRECTORY = "/path/to/uploads"; // 可配置的上传目录    private static final Set<String> ALLOWED_EXTENSIONS = new HashSet<>(Arrays.asList(".jpg", ".png"));

    public void handleFileUpload(MultipartFile file) {        if (validateFile(file)) {            // 生成文件名            String extension = getFileExtension(file);            String filename = UUID.randomUUID().toString() + extension;

            // 存储路径            Path filePath = Paths.get(UPLOAD_DIRECTORY, filename);

            // 上传文件            try {                file.transferTo(filePath);            } catch (IOException e) {                throw new RuntimeException("文件读写异常", e);            }        }    }

    public boolean validateFile(MultipartFile file) {        try {            // 检查文件是否为空            if (file.isEmpty()) {                throw new IllegalArgumentException("文件不能为空");            }

            // 检查文件的大小            if (file.getSize() > MAX_FILE_SIZE) {                throw new IllegalArgumentException("文件过大");            }

            // 检查文件的扩展名            String extension = getFileExtension(file);            if (!ALLOWED_EXTENSIONS.contains(extension)) {                throw new IllegalArgumentException("不支持的文件扩展名");            }

            // 检查文件的MIME类型            String mimeType = file.getContentType();            if (!mimeType.startsWith("image/")) {                throw new IllegalArgumentException("文件必须是图像");            }

            // 检查文件的内容, 确认其实际为一个图像            BufferedImage image = ImageIO.read(file.getInputStream());            if (image == null) {                throw new IllegalArgumentException("文件内容不符合图像格式");            }            return true;

        } catch (IOException e) {            throw new RuntimeException("无法验证文件", e);        }    }

    public String getFileExtension(MultipartFile file) {        String name = file.getOriginalFilename();        return name.substring(name.lastIndexOf("."));    }}

import java.net.URL;import java.util.HashSet;import java.util.Set;import java.util.function.Function;import java.util.function.Predicate;import java.util.logging.Level;import java.util.logging.Logger;

public class UrlValidator {    private final Predicate<String> hostFilter; // 允许访问的主机列表    private final Predicate<String> pathFilter; // 允许的URL路径列表    private static final Set<String> ALLOWED_PROTOCOLS = new HashSet<>(Arrays.asList("http", "https")); // 允许的协议    private static final Logger LOG = Logger.getLogger(UrlValidator.class.getName());

    public UrlValidator(Predicate<String> hostFilter, Predicate<String> pathFilter) {        this.hostFilter = hostFilter;        this.pathFilter = pathFilter;    }

    public boolean isSafe(String urlString) {        try {            // 验证URL格式            URL url = new URL(urlString);

            // 验证协议            if (!ALLOWED_PROTOCOLS.contains(url.getProtocol())) {                LOG.log(Level.WARNING, "无效的协议: " + url.getProtocol());                return false;            }

            // 验证主机名            if (!hostFilter.test(url.getHost())) {                LOG.log(Level.WARNING, "主机名不在白名单: " + url.getHost());                return false;            }

            // 验证路径            if (!pathFilter.test(url.getPath())) {                LOG.log(Level.WARNING, "路径不在白名单: " + url.getPath());                return false;            }

            return true;        } catch (Exception e) {            LOG.log(Level.WARNING, "无法解析URL: " + urlString, e);            return false;        }    }}

// 使用举例public class UrlHandler {    private final UrlValidator urlValidator; // 注入UrlValidator

    public UrlHandler(UrlValidator urlValidator){        this.urlValidator = urlValidator;    }

    public void processUrl(String urlString){        if (urlValidator.isSafe(urlString)) {            // 发送请求        } else {            throw new IllegalArgumentException("非法的URL: " + urlString);        }    }}

import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;

public class BankAccount {    private volatile double balance; // 账户余额    private final Lock lock = new ReentrantLock();

    public BankAccount(double balance) {        this.balance = balance;    }

    // 提现功能    public void withdraw(double amount) {        lock.lock(); // 获得锁        try {            if (balance < amount) {                System.out.println("余额不足，无法提现！");                return;            }            balance -= amount;            System.out.println("提现成功，提现金额：" + amount + "，剩余余额：" + balance);        } finally {            lock.unlock(); // 释放锁        }    }

    // 获取余额    public double getBalance() {        return balance;    }}