XSS漏洞解决方案之一：过滤器

一：web.xml文件

  <!-- 解决xss漏洞 -->
  <filter>
    <filter-name>xssFilter</filter-name>
     <filter-class>com.baidu.rigel.sandbox.core.filter.XSSFilter</filter-class>
  </filter>

  <!-- 解决xss漏洞 -->
  <filter-mapping>
    <filter-name>xssFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

二：过滤器:XSSFilter.java

package com.rigel.sandbox.core.filter;

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.http.HttpServletRequest;

import com.rigel.sandbox.core.util.XssHttpServletRequestWrapper;

public class XSSFilter implements Filter {

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
	}

	@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() {
	}

}

三：包装器：XssHttpServletRequestWrapper.java

package com.rigel.sandbox.core.util;

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

public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper {
	HttpServletRequest orgRequest = null;

	public XssHttpServletRequestWrapper(HttpServletRequest request) {
		super(request);
		orgRequest = request;
	}

	/**
	 * 覆盖getParameter方法，将参数名和参数值都做xss过滤。<br/>
	 * 如果需要获得原始的值，则通过super.getParameterValues(name)来获取<br/>
	 * getParameterNames,getParameterValues和getParameterMap也可能需要覆盖
	 */
	@Override
	public String getParameter(String name) {
		String value = super.getParameter(xssEncode(name));
		if (value != null) {
			value = xssEncode(value);
		}
		return value;
	}

	/**
	 * 覆盖getHeader方法，将参数名和参数值都做xss过滤。<br/>
	 * 如果需要获得原始的值，则通过super.getHeaders(name)来获取<br/>
	 * getHeaderNames 也可能需要覆盖
	 */
	@Override
	public String getHeader(String name) {

		String value = super.getHeader(xssEncode(name));
		if (value != null) {
			value = xssEncode(value);
		}
		return value;
	}

	/**
	 * 将容易引起xss漏洞的半角字符直接替换成全角字符
	 *
	 * @param s
	 * @return
	 */
	private static String xssEncode(String s) {
		if (s == null || s.isEmpty()) {
			return s;
		}
		StringBuilder sb = new StringBuilder(s.length() + 16);
		for (int i = 0; i < s.length(); i++) {
			char c = s.charAt(i);
			switch (c) {
			case '>':
				sb.append(">");// 转义大于号
				break;
			case '<':
				sb.append("<");// 转义小于号
				break;
			case '\'':
				sb.append("'");// 转义单引号
				break;
			case '\"':
				sb.append(""");// 转义双引号
				break;
			case '&':
				sb.append("&");// 转义&
				break;
			default:
				sb.append(c);
				break;
			}
		}
		return sb.toString();
	}

	/**
	 * 获取最原始的request
	 *
	 * @return
	 */
	public HttpServletRequest getOrgRequest() {
		return orgRequest;
	}

	/**
	 * 获取最原始的request的静态方法
	 *
	 * @return
	 */
	public static HttpServletRequest getOrgRequest(HttpServletRequest req) {
		if (req instanceof XssHttpServletRequestWrapper) {
			return ((XssHttpServletRequestWrapper) req).getOrgRequest();
		}

		return req;
	}
}