XSS抵御脚本攻击

XSS攻击的基本概念主要是: 
    恶意用户在网页的可输入的地方输入可执行的脚本(如javascript)代码,从而使网页解析执行该脚本代码来达到攻击的效果, 比如在网站上写一篇文章时包含这段代码: ,如果该字符串在后台没有进行XSS攻击防范,就会导致导致其他人访问该文章时网页执行上面的脚本从而alert(1).

防止XSS攻击最主要方式 : 
      把特殊标签符号转码,比如把”<”, “>”, “&”等这些特殊字符转码即可防止XSS攻击.

要考虑代码的维护问题,我们不能把太多的XSS防攻击代码侵入到业务代码中, 我们可以使用过滤器的方式来转换编码.在过滤器中获取每一个参数进行转换编码:

做法: 
1. 在web.xml中加入filter如下:

 </filter-mapping>    
  <!-- XSS抵御脚本攻击 -->
  <filter>
    <filter-name>XSSFilter</filter-name>
    <filter-class>com.pupeiyuan.system.core.filter.XSSFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>XSSFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

XSSFilter.java

package com.pupeiyuan.system.core.filter;
import java.io.IOException;
import java.util.LinkedHashMap;
import java.util.Map;
 
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.http.HttpServletRequest;
 
public class XSSFilter implements Filter {
 
    // XSS处理Map
    private static Map<String,String> xssMap = new LinkedHashMap<String,String>();
     
    public void init(FilterConfig filterConfig) throws ServletException {
        // 含有脚本： script
        xssMap.put("[s|S][c|C][r|R][i|C][p|P][t|T]", "");
        // 含有脚本 javascript
        xssMap.put("[\\\"\\\'][\\s]*[j|J][a|A][v|V][a|A][s|S][c|C][r|R][i|I][p|P][t|T]:(.*)[\\\"\\\']", "\"\"");
        // 含有函数： eval
        xssMap.put("[e|E][v|V][a|A][l|L]\\((.*)\\)", "");
        // 含有符号 <
        xssMap.put("<", "&lt;");
        // 含有符号 >
        xssMap.put(">", "&gt;");
        // 含有符号 (
        xssMap.put("\\(", "(");
        // 含有符号 )
        xssMap.put("\\)", ")");
        // 含有符号 '
        xssMap.put("'", "'");
        // 含有符号 "
        xssMap.put("\"", "");
    }
     
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        // 强制类型转换 HttpServletRequest
        HttpServletRequest httpReq = (HttpServletRequest)request;
        // 构造HttpRequestWrapper对象处理XSS
        HttpRequestWrapper httpReqWarp = new HttpRequestWrapper(httpReq,xssMap);
        // 
        chain.doFilter(httpReqWarp, response);
 
    }
 
    public void destroy() {
         
    }
}

HttpRequestWrapper.java

package com.pupeiyuan.system.core.filter;

import java.util.Map;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
 
public final class HttpRequestWrapper extends HttpServletRequestWrapper {
 
    private Map<String, String> xssMap;
     
    public HttpRequestWrapper(HttpServletRequest request) {
        super(request);
    }
 
    public HttpRequestWrapper(HttpServletRequest request,
            Map<String, String> xssMap) {
        super(request);
        this.xssMap = xssMap;
    }
 
    @Override
    public String[] getParameterValues(String parameter) {
        String[] values = super.getParameterValues(parameter);
        if (values == null) {
            return null;
        }
        int count = values.length;
        // 遍历每一个参数，检查是否含有
        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 null;
        }
        return cleanXSS(value);
    }
 
    public String getHeader(String name) {
        String value = super.getHeader(name);
        if (value == null)
            return null;
        return cleanXSS(value);
 
    }
 
    /**
     * 清除恶意的XSS脚本
     * 
     * @param value
     * @return
     */
    private String cleanXSS(String value) {
        Set<String> keySet = xssMap.keySet();
        for(String key : keySet){
            String v = xssMap.get(key);
            value = value.replaceAll(key,v);
        }
        return value;
    }
}