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JSP spring boot / cloud 使用filter防止XSS
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JSP spring boot / cloud 使用filter防止XSS

一.前言

XSS(跨站脚本攻击)

跨站脚本攻击(Cross Site Scripting)，为不和层叠样式表(Cascading Style Sheets, CSS)的缩写混淆，故将跨站脚本攻击缩写为XSS。恶意攻击者往Web页面里插入恶意Script代码，当用户浏览该页之时，嵌入其中Web里面的Script代码会被执行，从而达到恶意攻击用户的目的。

二.思路

基于filter拦截,将特殊字符替换为html转意字符 (如: "<" 转意为 "&lt;") , 需要拦截的点如下:

  • 请求头 requestHeader
  • 请求体 requestBody
  • 请求参数 requestParameter

三.实现

1.创建XssHttpServletRequestWrapper类

在获取请求头,请求参数的这些地方,将目标值使用HtmlUtils.htmlEscape方法转意为html字符,而避免恶意代码参与到后续的流程中

/**
 * XssHttpServletRequestWrapper.java
 * Created at 2016-09-19
 * Created by wangkang
 * Copyright (C) 2016 egridcloud.com, All rights reserved.
 */
package com.egridcloud.udf.core.xss;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import org.springframework.web.util.HtmlUtils;

/**
 * 描述 : 跨站请求防范
 *
 * @author wangkang
 *
 */
public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper {

 /**
  * 描述 : 构造函数
  *
  * @param request 请求对象
  */
 public XssHttpServletRequestWrapper(HttpServletRequest request) {
  super(request);
 }

 @Override
 public String getHeader(String name) {
  String value = super.getHeader(name);
  return HtmlUtils.htmlEscape(value);
 }

 @Override
 public String getParameter(String name) {
  String value = super.getParameter(name);
  return HtmlUtils.htmlEscape(value);
 }

 @Override
 public String[] getParameterValues(String name) {
  String[] values = super.getParameterValues(name);
  if (values != null) {
   int length = values.length;
   String[] escapseValues = new String[length];
   for (int i = 0; i < length; i++) {
    escapseValues[i] = HtmlUtils.htmlEscape(values[i]);
   }
   return escapseValues;
  }
  return super.getParameterValues(name);
 }

}

2.创建XssStringJsonSerializer类

其次是涉及到json转换的地方,也一样需要进行转意,比如,rerquestBody,responseBody

/**
 * XssStringJsonSerializer.java
 * Created at 2016-09-19
 * Created by wangkang
 * Copyright (C) 2016 egridcloud.com, All rights reserved.
 */
package com.egridcloud.udf.core.xss;

import java.io.IOException;

import org.springframework.web.util.HtmlUtils;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

/**
 * 描述 : 基于xss的JsonSerializer
 *
 * @author wangkang
 *
 */
public class XssStringJsonSerializer extends JsonSerializer<String> {

 @Override
 public Class<String> handledType() {
  return String.class;
 }

 @Override
 public void serialize(String value, JsonGenerator jsonGenerator,
   SerializerProvider serializerProvider) throws IOException {
  if (value != null) {
   String encodedValue = HtmlUtils.htmlEscape(value);
   jsonGenerator.writeString(encodedValue);
  }
 }

}

3.创建Bean

在启动类中,创建XssObjectMapper的bean,替换spring boot原有的实例,用于整个系统的json转换.

 /**
  * 描述 : xssObjectMapper
  *
  * @param builder builder
  * @return xssObjectMapper
  */
 @Bean
 @Primary
 public ObjectMapper xssObjectMapper(Jackson2ObjectMapperBuilder builder) {
  //解析器
  ObjectMapper objectMapper = builder.createXmlMapper(false).build();
  //注册xss解析器
  SimpleModule xssModule = new SimpleModule("XssStringJsonSerializer");
  xssModule.addSerializer(new XssStringJsonSerializer());
  objectMapper.registerModule(xssModule);
  //返回
  return objectMapper;
 }

4.创建XssFilter

首先是拦截所有的请求,然后在doFilter方法中,将HttpServletRequest强制类型转换成XssHttpServletRequestWrapper

然后传递下去.

/**
 * XssFilter.java
 * Created at 2016-09-19
 * Created by wangkang
 * Copyright (C) 2016 egridcloud.com, All rights reserved.
 */
package com.egridcloud.udf.core.xss;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 描述 : 跨站请求防范
 *
 * @author wangkang
 *
 */
@WebFilter(filterName = "xssFilter", urlPatterns = "/*", asyncSupported = true)
public class XssFilter implements Filter {

 /**
  * 描述 : 日志
  */
 private static final Logger LOGGER = LoggerFactory.getLogger(XssFilter.class);

 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
  LOGGER.debug("(XssFilter) initialize");
 }

 @Override
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
   throws IOException, ServletException {
  XssHttpServletRequestWrapper xssRequest =
    new XssHttpServletRequestWrapper((HttpServletRequest) request);
  chain.doFilter(xssRequest, response);
 }

 @Override
 public void destroy() {
  LOGGER.debug("(XssFilter) destroy");
 }

}

四.结束

本文虽基于spring boot实现主题,但是思路是一致的,不限于任何框架.

 感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！

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