一、什么是XSS攻击
XSS是一种经常出现在web应用中的计算机安全漏洞,它允许恶意web用户将代码植入到提供给其它用户使用的页面中。比如这些代码包括HTML代码和客户端脚本。攻击者利用XSS漏洞旁路掉访问控制——例如同源策略(same origin policy)。这种类型的漏洞由于被黑客用来编写危害性更大的网络钓鱼(Phishing)攻击而变得广为人知。对于跨站脚本攻击,黑客界共识是:跨站脚本攻击是新型的“缓冲区溢出攻击“,而JavaScript是新型的“ShellCode”。
二、XSS漏洞的危害
(1)网络钓鱼,包括盗取各类用户账号;
(2)窃取用户cookies资料,从而获取用户隐私信息,或利用用户身份进一步对网站执行操作;
(3)劫持用户(浏览器)会话,从而执行任意操作,例如进行非法转账、强制发表日志、发送电子邮件等;
(4)强制弹出广告页面、刷流量等;
(5)网页挂马;
(6)进行恶意操作,例如任意篡改页面信息、删除文章等;
(7)进行大量的客户端攻击,如DDoS攻击;
(8)获取客户端信息,例如用户的浏览历史、真实IP、开放端口等;
(9)控制受害者机器向其他网站发起攻击;
(10)结合其他漏洞,如CSRF漏洞,实施进一步作恶;
(11)提升用户权限,包括进一步渗透网站;
(12)传播跨站脚本蠕虫等;
……
三、如何编写代码来避免
如下代码可以避免XSS注入,但是作者因知识面有限,故不能保证100%能完全将XSS攻击者拒之门外,还需大家根据实际情况进行优化和改进。
既然我们通过代码来解决问题,就尽可能的不涉及开发人员的对原有代码修改,所以我们增加过滤器来拦截处理,本文原有框架使用springmvc。
1、IllegalCharacterFilter.java
package com.lenovo.common.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;/** * 非法字符过滤器,用来处理request.getParamater中的非法字符。如<script>alert('123');</script> * * @author 单红宇(365384722) * @myblog http://blog.csdn.net/catoop/ * @create 2015年9月18日 */public class IllegalCharacterFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest)req; request = new MHttpServletRequest(request); chain.doFilter(request, res); } @Override public void destroy() { }}
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2、MHttpServletRequest.java
package com.lenovo.common.filter;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletRequestWrapper;import com.lenovo.common.utils.XssShieldUtil;/** * 参数特殊字符过滤 * * @author 单红宇(365384722) * @myblog http://blog.csdn.net/catoop/ * @create 2015年9月18日 */public class MHttpServletRequest extends HttpServletRequestWrapper { public MHttpServletRequest(HttpServletRequest request) { super(request); } @Override public String getParameter(String name) { return XssShieldUtil.stripXss(super.getParameter(XssShieldUtil.stripXss(name))); } @Override public String[] getParameterValues(String name) { String[] values = super.getParameterValues(XssShieldUtil.stripXss(name)); if(values != null){ for (int i = 0; i < values.length; i++) { values[i] = XssShieldUtil.stripXss(values[i]); } } return values; }}
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3、XssShieldUtil.java
package com.lenovo.common.utils;import java.util.ArrayList;import java.util.List;import java.util.regex.Matcher;import java.util.regex.Pattern;import org.apache.commons.lang.StringUtils;public class XssShieldUtil { private static List<Pattern> patterns = null; private static List<Object[]> getXssPatternList() { List<Object[]> ret = new ArrayList<Object[]>(); ret.add(new Object[]{"<(no)?script[^>]*>.*?</(no)?script>", Pattern.CASE_INSENSITIVE}); ret.add(new Object[]{"eval\\((.*?)\\)", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL}); ret.add(new Object[]{"expression\\((.*?)\\)", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL}); ret.add(new Object[]{"(javascript:|vbscript:|view-source:)*", Pattern.CASE_INSENSITIVE}); ret.add(new Object[]{"<(\"[^\"]*\"|\'[^\']*\'|[^\'\">])*>", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL}); ret.add(new Object[]{"(window\\.location|window\\.|\\.location|document\\.cookie|document\\.|alert\\(.*?\\)|window\\.open\\()*", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL}); ret.add(new Object[]{"<+\\s*\\w*\\s*(oncontrolselect|oncopy|oncut|ondataavailable|ondatasetchanged|ondatasetcomplete|ondblclick|ondeactivate|ondrag|ondragend|ondragenter|ondragleave|ondragover|ondragstart|ondrop|onerror=|onerroupdate|onfilterchange|onfinish|onfocus|onfocusin|onfocusout|onhelp|onkeydown|onkeypress|onkeyup|onlayoutcomplete|onload|onlosecapture|onmousedown|onmouseenter|onmouseleave|onmousemove|onmousout|onmouseover|onmouseup|onmousewheel|onmove|onmoveend|onmovestart|onabort|onactivate|onafterprint|onafterupdate|onbefore|onbeforeactivate|onbeforecopy|onbeforecut|onbeforedeactivate|onbeforeeditocus|onbeforepaste|onbeforeprint|onbeforeunload|onbeforeupdate|onblur|onbounce|oncellchange|onchange|onclick|oncontextmenu|onpaste|onpropertychange|onreadystatechange|onreset|onresize|onresizend|onresizestart|onrowenter|onrowexit|onrowsdelete|onrowsinserted|onscroll|onselect|onselectionchange|onselectstart|onstart|onstop|onsubmit|onunload)+\\s*=+", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL}); return ret; } private static List<Pattern> getPatterns() { if (patterns == null) { List<Pattern> list = new ArrayList<Pattern>(); String regex = null; Integer flag = null; int arrLength = 0; for(Object[] arr : getXssPatternList()) { arrLength = arr.length; for(int i = 0; i < arrLength; i++) { regex = (String)arr[0]; flag = (Integer)arr[1]; list.add(Pattern.compile(regex, flag)); } } patterns = list; } return patterns; } public static String stripXss(String value) { if(StringUtils.isNotBlank(value)) { Matcher matcher = null; for(Pattern pattern : getPatterns()) { matcher = pattern.matcher(value); if(matcher.find()) { value = matcher.replaceAll(""); } } value = value.replaceAll("<", "<").replaceAll(">", ">"); } return value; } public static void main(String[] args) { String value = null; value = XssShieldUtil.stripXss("<script language=text/javascript>alert(document.cookie);</script>"); System.out.println("type-1: '" + value + "'"); value = XssShieldUtil.stripXss("<script src='' onerror='alert(document.cookie)'></script>"); System.out.println("type-2: '" + value + "'"); value = XssShieldUtil.stripXss("</script>"); System.out.println("type-3: '" + value + "'"); value = XssShieldUtil.stripXss(" eval(abc);"); System.out.println("type-4: '" + value + "'"); value = XssShieldUtil.stripXss(" expression(abc);"); System.out.println("type-5: '" + value + "'"); value = XssShieldUtil.stripXss("<img src='' onerror='alert(document.cookie);'></img>"); System.out.println("type-6: '" + value + "'"); value = XssShieldUtil.stripXss("<img src='' onerror='alert(document.cookie);'/>"); System.out.println("type-7: '" + value + "'"); value = XssShieldUtil.stripXss("<img src='' onerror='alert(document.cookie);'>"); System.out.println("type-8: '" + value + "'"); value = XssShieldUtil.stripXss("<script language=text/javascript>alert(document.cookie);"); System.out.println("type-9: '" + value + "'"); value = XssShieldUtil.stripXss("<script>window.location='url'"); System.out.println("type-10: '" + value + "'"); value = XssShieldUtil.stripXss(" onload='alert(\"abc\");"); System.out.println("type-11: '" + value + "'"); value = XssShieldUtil.stripXss("<img src=x<!--'<\"-->>"); System.out.println("type-12: '" + value + "'"); value = XssShieldUtil.stripXss("<=img onstop="); System.out.println("type-13: '" + value + "'"); }}
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4、web.xml 配置
<filter> <filter-name>IllegalCharacterFilter</filter-name> <filter-class>com.lenovo.common.filter.IllegalCharacterFilter</filter-class> </filter> <filter-mapping> <filter-name>IllegalCharacterFilter</filter-name> <url-pattern>*.do</url-pattern> </filter-mapping>
本文方法针对非Struts2框架,如果在Struts2中解决Xss问题,可以参考:https://yq.aliyun.com/articles/7126