一、问题背景

使用 SpringBoot 的项目出现了跨站脚本漏洞（XSS）问题。

二、解决方案

步骤如下：

1、添加maven依赖

在 pom.xml 文件中，增加如下依赖：

		<dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>tomcat-servlet-api</artifactId>
            <version>8.0.36</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>

2、新增 XSSFilter.java

在 config 目录下增加 XSSFilter.java，用于对请求接口进行过滤。
代码如下：

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

@WebFilter(filterName="XSSFilter", urlPatterns="/*")
public class XSSFilter implements Filter {

    FilterConfig filterConfig = null;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        filterChain.doFilter(new XssHttpServletRequestWrapper((HttpServletRequest) servletRequest), servletResponse);
    }

    @Override
    public void destroy() {
        this.filterConfig = null;
    }

}

3、新增 XssHttpServletRequestWrapper.java

在 config 目录下，新增 XssHttpServletRequestWrapper.java，用于对请求参数进行预处理和解析。
代码如下：

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;

public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper {
    public XssHttpServletRequestWrapper(HttpServletRequest request) {
        super(request);
    }

    @Override
    public String[] getParameterValues(String parameter) {
        String[] values = super.getParameterValues(parameter);
        if (values==null)  {
            return null;
        }
        int count = values.length;
        String[] encodedValues = new String[count];
        for (int i = 0; i < count; i++) {
            encodedValues[i] = cleanXSS(values[i]);
        }
        return encodedValues;
    }

    @Override
    public String getParameter(String parameter) {
        String value = super.getParameter(parameter);
        if (value != null) {
            return cleanXSS(value);
        }
        return null;
    }

    /**
     * 对 application/x-www-form-urlencoded 格式的POST请求参数，进行 cleanXSS解析
     * @return cleanXSS解析后的参数
     */
    @Override
    public Map<String, String[]> getParameterMap() {
        Map<String, String[]> values = super.getParameterMap();
        if (values == null) {
            return null;
        }

        Map<String, String[]> result = new HashMap<>();
        for (String key : values.keySet()) {
            String encodedKey = cleanXSS(key);
            int count = values.get(key).length;
            String[] encodedValues = new String[count];
            for (int i = 0; i < count; i++) {
                encodedValues[i] = cleanXSS(values.get(key)[i]);
            }
            result.put(encodedKey, encodedValues);
        }
        return result;
    }

    @Override
    public String getHeader(String name) {
        String value = super.getHeader(name);
        if (value == null)
            return null;
        return cleanXSS(value);
    }

    private static String cleanXSS(String value) {
        value = value.replaceAll("<", "<").replaceAll(">", ">");
        value = value.replaceAll("%3C", "<").replaceAll("%3E", ">");
        value = value.replaceAll("\\(", "(").replaceAll("\\)", ")");
        value = value.replaceAll("%28", "(").replaceAll("%29", ")");
        value = value.replaceAll("'", "'");
        value = value.replaceAll("eval\\((.*)\\)", "");
        value = value.replaceAll("[\\\"\\\'][\\s]*javascript:(.*)[\\\"\\\']", "\"\"");
        value = value.replaceAll("script", "");
        return value;
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream bais = new ByteArrayInputStream(inputHandlers(super.getInputStream ()).getBytes ());

        return new ServletInputStream() {

            @Override
            public int read() throws IOException {
                return bais.read();
            }

            @Override
            public boolean isFinished() {
                return false;
            }

            @Override
            public boolean isReady() {
                return false;
            }

            @Override
            public void setReadListener(ReadListener readListener) { }
        };
    }

    public String inputHandlers(ServletInputStream servletInputStream){
        StringBuilder sb = new StringBuilder();
        BufferedReader reader = null;
        try {
            reader = new BufferedReader(new InputStreamReader(servletInputStream, Charset.forName("UTF-8")));
            String line = "";
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (servletInputStream != null) {
                try {
                    servletInputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return  cleanXSS(sb.toString ());
    }

}

4、添加注解 @ServletComponentScan

在 XXXApplication.java 的类名上方，用于扫描配置类。添加注解如下：

@ServletComponentScan("com.XXX.config")

示例如下：