【漏洞三】跨站点脚本(XSS)攻击

【漏洞】

跨站点脚本(XSS)攻击

【原因】

跨站点脚本(也称为xss)是一个漏洞，攻击者可以发送恶意代码(通常在(Javascript的形式)给另一个用户。因为浏览器无法知道脚本是否值得信任，所以它将在用户上下文中执行脚本，从而允许攻击者访问任何cookie。

【解决】增加敏感脚本过滤器（转一篇整理较好的实现方案： https://blog.csdn.net/yucaifu1989/article/details/61616870）

使用filter过滤xss攻击,filter实现脚注入攻击过滤源码。先说一下实现思路：

1. 使用正则表达式的方式实现脚本过滤，这个方法准确率较高，但是可能根据不能的要求会变动；

2. 为了保证配置灵活（包括正则表达式灵活），使用xml配置文件的方式记录配置信息，配置信息包含是否开启校验、是否记录日志、是否中断请求、是否替换脚本字符等；

3. 为保证xml与正则表达式的特殊字符不冲突，使用<![CDATA[]]>标签存放正则表达式，但是在类中需要特殊处理；

4. 通过继承HttpRequestWrapper的方式实现request中header和parameter信息过滤；

5. xml解析使用dom4j，稍后会对这个工具的使用写一篇文章，暂时辛苦大家去网站查找资料

6. 使用XSSSecurityManager类实现配置信息加载和处理，XSSSecurityConfig记录匹配信息，XSSSecurityCon标识程序所需常量；

一共改了 7 个文件，如下：

1、XSSHttpRequestWrapper

package com.sg.security;

import java.io.IOException;

import java.util.Enumeration;

import java.util.Map;

import java.util.Set;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletRequestWrapper;

import javax.servlet.http.HttpServletResponse;

/**

* @author winnie

* @date

* @describe request信息封装类，用于判断、处理request请求中特殊字符

public class XSSHttpRequestWrapper extends HttpServletRequestWrapper {

/**

* 封装http请求

* @param request

public XSSHttpRequestWrapper(HttpServletRequest request) {

super(request);

}

@Override

public String getHeader(String name) {

String value = super.getHeader(name);

// 若开启特殊字符替换，对特殊字符进行替换

if(XSSSecurityConfig.REPLACE){

XSSSecurityManager.securityReplace(name);

}

return value;

}

@Override

public String getParameter(String name) {

String value = super.getParameter(name);

// 若开启特殊字符替换，对特殊字符进行替换

if(XSSSecurityConfig.REPLACE){

XSSSecurityManager.securityReplace(name);

}

return value;

}

/**

* 没有违规的数据，就返回false;

* @return

@SuppressWarnings("unchecked")

private boolean checkHeader(){

Enumeration<String> headerParams = this.getHeaderNames();

while(headerParams.hasMoreElements()){

String headerName = headerParams.nextElement();

String headerValue = this.getHeader(headerName);

if(XSSSecurityManager.matches(headerValue)){

return true;

}

return false;

}

/**

* 没有违规的数据，就返回false;

* @return

@SuppressWarnings("unchecked")

private boolean checkParameter(){

Map<String,Object> submitParams = this.getParameterMap();

Set<String> submitNames = submitParams.keySet();

for(String submitName : submitNames){

Object submitValues = submitParams.get(submitName);

if(submitValues instanceof String){

if(XSSSecurityManager.matches((String)submitValues)){

return true;

}

}else if(submitValues instanceof String[]){

for(String submitValue : (String[])submitValues){

if(XSSSecurityManager.matches((String)submitValue)){

return true;

}

return false;

}

/**

* 没有违规的数据，就返回false;

* 若存在违规数据，根据配置信息判断是否跳转到错误页面

* @param response

* @return

* @throws IOException

* @throws ServletException

public boolean validateParameter(HttpServletResponse response) throws ServletException, IOException{

// 开始header校验，对header信息进行校验

if(XSSSecurityConfig.IS_CHECK_HEADER){

if(this.checkHeader()){

return true;

}

// 开始parameter校验，对parameter信息进行校验

if(XSSSecurityConfig.IS_CHECK_PARAMETER){

if(this.checkParameter()){

return true;

}

return false;

}

2、XSSSecurityFilter

package com.sg.security;

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 javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

/**

* @author winnie

* @date

* @describe 安全信息审核类

public class XSSSecurityFilter implements Filter{

private static Logger logger = Logger.getLogger(XSSSecurityFilter.class);

/**

* 销毁操作

public void destroy() {

logger.info("XSSSecurityFilter destroy() begin");

XSSSecurityManager.destroy();

logger.info("XSSSecurityFilter destroy() end");

}

/**

* 安全审核

* 读取配置信息

public void doFilter(ServletRequest request, ServletResponse response,

FilterChain chain) throws IOException, ServletException {

// 判断是否使用HTTP

checkRequestResponse(request, response);

// 转型

HttpServletRequest httpRequest = (HttpServletRequest) request;

HttpServletResponse httpResponse = (HttpServletResponse) response;

// http信息封装类

XSSHttpRequestWrapper xssRequest = new XSSHttpRequestWrapper(httpRequest);

// 对request信息进行封装并进行校验工作，若校验失败（含非法字符），根据配置信息进行日志记录和请求中断处理

if(xssRequest.validateParameter(httpResponse)){

if(XSSSecurityConfig.IS_LOG){

// 记录攻击访问日志

// 可使用数据库、日志、文件等方式

}

if(XSSSecurityConfig.IS_CHAIN){

httpRequest.getRequestDispatcher(XSSSecurityCon.FILTER_ERROR_PAGE).forward( httpRequest, httpResponse);

return;

}

chain.doFilter(xssRequest, response);

}

/**

* 初始化操作

public void init(FilterConfig filterConfig) throws ServletException {

XSSSecurityManager.init(filterConfig);

}

/**

* 判断Request ,Response 类型

* @param request

* ServletRequest

* @param response

* ServletResponse

* @throws ServletException

private void checkRequestResponse(ServletRequest request,

ServletResponse response) throws ServletException {

if (!(request instanceof HttpServletRequest)) {

throw new ServletException("Can only process HttpServletRequest");

}

if (!(response instanceof HttpServletResponse)) {

throw new ServletException("Can only process HttpServletResponse");

}

3、XSSSecurityManager

package com.sg.security;

import java.util.Iterator;

import java.util.regex.Pattern;

import javax.servlet.FilterConfig;

import org.apache.log4j.Logger;

import org.dom4j.DocumentException;

import org.dom4j.Element;

import org.dom4j.io.SAXReader;

/**

* @author winnie

* @date

* @describe 安全过滤配置管理类，由XSSSecurityManger修改

public class XSSSecurityManager {

private static Logger logger = Logger.getLogger(XSSSecurityManager.class);

/**

* REGEX：校验正则表达式

public static String REGEX;

/**

* 特殊字符匹配

private static Pattern XSS_PATTERN ;

private XSSSecurityManager(){

//不可被实例化

}

public static void init(FilterConfig config){

logger.info("XSSSecurityManager init(FilterConfig config) begin");

//初始化过滤配置文件

String xssPath = config.getServletContext().getRealPath("/")

+ config.getInitParameter("securityconfig");

// 初始化安全过滤配置

try {

if(initConfig(xssPath)){

// 生成匹配器

XSS_PATTERN = Pattern.compile(REGEX);

}

} catch (DocumentException e) {

logger.error("安全过滤配置文件xss_security_config.xml加载异常",e);

}

logger.info("XSSSecurityManager init(FilterConfig config) end");

}

/**

* 读取安全审核配置文件xss_security_config.xml

* 设置XSSSecurityConfig配置信息

* @param path 配置文件地址 eg C:/apache-tomcat-6.0.33/webapps/security_filter/WebRoot/config/xss/xss_security_config.xml

* @return

* @throws DocumentException

@SuppressWarnings("unchecked")

public static boolean initConfig(String path) throws DocumentException {

logger.info("XSSSecurityManager.initConfig(String path) begin");

Element superElement = new SAXReader().read(path).getRootElement();

XSSSecurityConfig.IS_CHECK_HEADER = new Boolean(getEleValue(superElement,XSSSecurityCon.IS_CHECK_HEADER));

XSSSecurityConfig.IS_CHECK_PARAMETER = new Boolean(getEleValue(superElement,XSSSecurityCon.IS_CHECK_PARAMETER));

XSSSecurityConfig.IS_LOG = new Boolean(getEleValue(superElement,XSSSecurityCon.IS_LOG));

XSSSecurityConfig.IS_CHAIN = new Boolean(getEleValue(superElement,XSSSecurityCon.IS_CHAIN));

XSSSecurityConfig.REPLACE = new Boolean(getEleValue(superElement,XSSSecurityCon.REPLACE));

Element regexEle = superElement.element(XSSSecurityCon.REGEX_LIST);

if(regexEle != null){

Iterator<Element> regexIt = regexEle.elementIterator();

StringBuffer tempStr = new StringBuffer("^");

//xml的cdata标签传输数据时，会默认在前加，需要将\替换为

while(regexIt.hasNext()){

Element regex = (Element)regexIt.next();

String tmp = regex.getText();

tmp = tmp.replaceAll("\\\\", "\\");

tempStr.append(tmp);

tempStr.append("|");

}

if(tempStr.charAt(tempStr.length()-1)=='|'){

REGEX= tempStr.substring(0, tempStr.length()-1)+"$";

logger.info("安全匹配规则"+REGEX);

}else{

logger.error("安全过滤配置文件加载失败:正则表达式异常 "+tempStr.toString());

return false;

}

}else{

logger.error("安全过滤配置文件中没有 "+XSSSecurityCon.REGEX_LIST+" 属性");

return false;

}

logger.info("XSSSecurityManager.initConfig(String path) end");

return true;

}

/**

* 从目标element中获取指定标签信息，若找不到该标签，记录错误日志

* @param element 目标节点

* @param tagName 制定标签

* @return

private static String getEleValue(Element element, String tagName){

if (isNullStr(element.elementText(tagName))){

logger.error("安全过滤配置文件中没有 "+XSSSecurityCon.REGEX_LIST+" 属性");

}

return element.elementText(tagName);

}

/**

* 对非法字符进行替换

* @param text

* @return

public static String securityReplace(String text){

if(isNullStr(text)){

return text;

}else{

return text.replaceAll(REGEX, XSSSecurityCon.REPLACEMENT);

}

/**

* 匹配字符是否含特殊字符

* @param text

* @return

public static boolean matches(String text){

if(text==null){

return false;

}

return XSS_PATTERN.matcher(text).matches();

}

/**

* 释放关键信息

public static void destroy(){

logger.info("XSSSecurityManager.destroy() begin");

XSS_PATTERN = null;

REGEX = null;

logger.info("XSSSecurityManager.destroy() end");

}

/**

* 判断是否为空串，建议放到某个工具类中

* @param value

* @return

public static boolean isNullStr(String value){

return value == null || value.trim().equals("");

}

4、 XSSSecurityConfig

package com.sg.security;

/**

* @author winnie

* 安全过滤配置信息类

public class XSSSecurityConfig {

/**

* CHECK_HEADER：是否开启header校验

public static boolean IS_CHECK_HEADER;

/**

* CHECK_PARAMETER：是否开启parameter校验

public static boolean IS_CHECK_PARAMETER;

/**

* IS_LOG：是否记录日志

public static boolean IS_LOG;

/**

* IS_LOG：是否中断操作

public static boolean IS_CHAIN;

/**

* REPLACE：是否开启替换

public static boolean REPLACE;

}

5、XSSSecurityCon

package com.sg.security;

/**

* @author winnie

* @date

* @describe

public class XSSSecurityCon {

/**

* 配置文件标签 isCheckHeader

public static String IS_CHECK_HEADER = "isCheckHeader";

/**

* 配置文件标签 isCheckParameter

public static String IS_CHECK_PARAMETER = "isCheckParameter";

/**

* 配置文件标签 isLog

public static String IS_LOG = "isLog";

/**

* 配置文件标签 isChain

public static String IS_CHAIN = "isChain";

/**

* 配置文件标签 replace

public static String REPLACE = "replace";

/**

* 配置文件标签 regexList

public static String REGEX_LIST = "regexList";

/**

* 替换非法字符的字符串

public static String REPLACEMENT = "";

/**

* FILTER_ERROR_PAGE:过滤后错误页面

public static String FILTER_ERROR_PAGE = "/common/filtererror.jsp";

}

6、xss_security_config.xml

<?xml version="1.0" encoding="UTF-8"?>

<isCheckHeader>false</isCheckHeader>

<isChain>false</isChain>

</regexList>

</XSSConfig>

7、web.xml配置

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5"

xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

<welcome-file-list>

<welcome-file>index.jsp</welcome-file>

</welcome-file-list>

<filter-name>XSSFiler</filter-name>

<filter-class>

com.sg.security.XSSSecurityFilter

</filter-class>

<init-param>

<param-name>securityconfig</param-name>

<param-value>

/WebRoot/config/xss/xss_security_config.xml

</param-value>

</init-param>

</filter>

<filter-mapping>

<filter-name>XSSFiler</filter-name>

<url-pattern>*.jsp</url-pattern>

</filter-mapping>

<filter-mapping>

<filter-name>XSSFiler</filter-name>

<url-pattern>*.do</url-pattern>

</filter-mapping>

</web-app>

Xml代码  

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<filter>
<filter-name>XSSFiler</filter-name>
<filter-class>
com.sg.security.XSSSecurityFilter
</filter-class>
<init-param>
<param-name>securityconfig</param-name>
<param-value>
/WebRoot/config/xss/xss_security_config.xml
</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>XSSFiler</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>XSSFiler</filter-name>
<url-pattern>*.do</url-pattern>
</filter-mapping>
</web-app>

【漏洞三】跨站点脚本(XSS)攻击

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