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.

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