XSS扫描器成长记
2020-02-25 10:00:52 Author: www.freebuf.com(查看原文) 阅读量:207 收藏

为了实现自动刷SRC的目标,过年前就开始对w13scan的xss扫描功能进行优化,灵感注入xray所引起的基于语义的扫描技术。

xss扫描之前是w3afxss payload,通常在以下几个部分。

1.png

后面我认真的学习了一下XsstrikeXrayAwvs中的检测技巧以及检测参数,想将它们的优点和为一体。

XSStrike

先说说Xsstrike,里面带有xss扫描和fuzz,但感觉xss扫描的效果也不是太理想。不过它的一些特性还是可以学习的。

DOM XSS

Xsstrike的dom扫描,是通过正则来分析敏感函数

sources = r'''document\.(URL|documentURI|URLUnencoded|baseURI|cookie|referrer)|location\.(href|search|hash|pathname)|window\.name|history\.(pushState|replaceState)(local|session)Storage'''
    sinks = r'''eval|evaluate|execCommand|assign|navigate|getResponseHeaderopen|showModalDialog|Function|set(Timeout|Interval|Immediate)|execScript|crypto.generateCRMFRequest|ScriptElement\.(src|text|textContent|innerText)|.*?\.onEventName|document\.(write|writeln)|.*?\.innerHTML|Range\.createContextualFragment|(document|window)\.location'''
    scripts = re.findall(r'(?i)(?s)<script[^>]*>(.*?)</script>', response)

通过将script脚本内的内容提取出来,通过一些正则来获取,最后输出。但这种方式准确度很低,只能用于辅助,不太适合自动化扫描。

内置参数

它里面有内置一些参数,在检测时转化这些参数也一起发送

blindParams = [  # common paramtere names to be bruteforced for parameter discovery
    'redirect', 'redir', 'url', 'link', 'goto', 'debug', '_debug', 'test', 'get', 'index', 'src', 'source', 'file',
    'frame', 'config', 'new', 'old', 'var', 'rurl', 'return_to', '_return', 'returl', 'last', 'text', 'load', 'email',
    'mail', 'user', 'username', 'password', 'pass', 'passwd', 'first_name', 'last_name', 'back', 'href', 'ref', 'data', 'input',
    'out', 'net', 'host', 'address', 'code', 'auth', 'userid', 'auth_token', 'token', 'error', 'keyword', 'key', 'q', 'query', 'aid',
    'bid', 'cid', 'did', 'eid', 'fid', 'gid', 'hid', 'iid', 'jid', 'kid', 'lid', 'mid', 'nid', 'oid', 'pid', 'qid', 'rid', 'sid',
    'tid', 'uid', 'vid', 'wid', 'xid', 'yid', 'zid', 'cal', 'country', 'x', 'y', 'topic', 'title', 'head', 'higher', 'lower', 'width',
    'height', 'add', 'result', 'log', 'demo', 'example', 'message']

很好的思路,后面我的扫描器中也使用了这一点,从乌云镜像XSS分类中提取出了top10参数,在扫描时也会将这些参数加上。

HTML解析和分析反射

如果参数可以回显,那么通过html解析就可以获得参数位置,分析回显的环境(是否在html标签内,是否在html属性内,是否在注释中,是否在js中)等等,否则来确定检测的payload。

后面我的扫描器的检测流程也是这样,非常准确和效率,不过Xsstrike分析html是自己写的分析函数,刚开始我也想直接用它的来着,但是这个函数内容过多,调试困难,代码也很难理解。

其实如果把html解析理解为html的语义分析,用python3自带的html提取函数很容易就能完成这一点。

Xray

XSStrike让我学习到了新一代xss扫描器应该如何编写,但新一代xss扫描器的payload是在Xray上学到的。

由于Xray没有开源,所以就通过分析日志的方式来看它的工作原理。

准备工作

<html>
<body>
<a href="?q=1&w=2&e=3&r=4&t=5" />
<script>
<php
foreach($_GET as $key => $value){
    // $_GET[$key] = htmlspecialchars($value);
}
$q = $_GET["q"];
$w = $_GET["w"];
$e = $_GET["e"];
$r = $_GET["r"];
$t = $_GET["t"];
if(stripos($q,"prompt") > 0){
    die("error");
}
$var = 'var a = "'.$q.'";';
echo $var;
>
</script>
<div>
<textarea><?php echo $w;?></textarea>
</div>
<input style="color:<?php echo $e;?>" value="<?php echo $r;?>"/>
    <!--
        this is comment
        <?php echo $t;?>
        -->
</body>
</html>

简单写了一个脚本,用来分别测试xss在script,style内,html标签内,注释这几种情况下xray的发包过程。

发包探索

1.对于在script的脚本内的回显内容,对于以下case

<script>
   $var = 'var a = "'.$_GET['q'].'";';
   echo $var;
   </script>

X射线顺序发送了以下payloadpdrjzsqc"-pdrjzsqc-"</sCrIpT><ojyrqvrzar>

最后会给出payload,但这个包并没有发送。后面把prompt作为关键词屏蔽,发现最后还是给出这个payload。

还有一种情况,在script中的注释中输出

 <html>
    <body>
      <script>
        var a = 11;
        // inline <?php echo $_GET["a"];?>
        /* <?php echo $_GET["b"];?> */
      </script>
    </body>
    </html>
xray会发送`\n;chxdsdkm;//`来判定,最后给出payload `\n;prompt(1);//`

2.对于在标签内的内容,针对以下case

<textarea><?php echo $_GET["w"];?></textarea>

xray顺序发送了以下payload:spzzmsntfzikatuchsvu,</tExTaReA><lixoorqfwj>,当确定尖括号没有被过滤时,会继续发送以下payload:</TeXtArEa>sCrIpTjhymehqbkrScRiPt,</TeXtArEa>iMgSrCoNeRrOrjhymehqbkr>,</TeXtArEa>SvGoNlOaDjhymehqbkr>,</TeXtArEa>IfRaMeSrCjAvAsCrIpTjhymehqbkr>,</TeXtArEa>aHrEfJaVaScRiPtjhymehqbkrClIcKa,</TeXtArEa>iNpUtAuToFoCuSoNfOcUsjhymehqbkr>,进行关键词的试探,最后给出payload为</TeXtArEa><img src=1>

3.对于在style里内容,以下case

   <input style="color:<?php echo

xray顺序发送了以下payload:kmbrocvz,expression(a(kmbrocvz))

4.对于在html标签内的内容,以下case

   <input style="color:3" value="<?php echo $_GET["r"];?>"/>

xray顺序发送了以下payload:spzzmsntfzikatuchsvu,"ljxxrwom=",'ljxxrwom=',ljxxrwom=,当确认引号没有被过滤时,会继续发送以下payload:"><vkvjfzrtgi>,">ScRiPtvkvjfzrtgiScRiPt,">ImGsRcOnErRoRvkvjfzrtgi>,">SvGoNlOaDvkvjfzrtgi>,">iFrAmEsRcJaVaScRiPtvkvjfzrtgi>,">aHrEfJaVaScRiPtvkvjfzrtgicLiCkA,">InPuTaUtOfOcUsOnFoCuSvkvjfzrtgi>," OnMoUsEoVeR=xviinqws,最后可以确定payload为"><img src=1>,"OnMoUsEoVeR=prompt(1)//

如果针对此类case:

 <img src=1 onerror="a<?php echo htmlspecialchars($_GET["a"]);?>" />

xray返回payload为prompt(1),说明xray会把onerror后面的内容当作JavaScript脚本来执行,如果把onerror改为onerror1,同样会返回prompt。在awvs规则中也看到过类似的规则

parName == "ONAFTERPRINT" || 
                               parName == "ONBEFOREPRINT" || 
                               parName == "ONBEFOREONLOAD" || 
                               parName == "ONBLUR" || 
                               parName == "ONERROR" || 
                               parName == "ONFOCUS" || 
                               parName == "ONHASCHANGE" || 
                               parName == "ONLOAD" || 
                               parName == "ONMESSAGE" || 
                               parName == "ONOFFLINE" || 
                               parName == "ONONLINE" || 
                               parName == "ONPAGEHIDE" || 
                               parName == "ONPAGESHOW" || 
                               parName == "ONPOPSTATE" || 
                               parName == "ONREDO" || 
                               parName == "ONRESIZE" || 
                               parName == "ONSTORAGE" || 
                               parName == "ONUNDO" || 
                               parName == "ONUNLOAD" || 
                               parName == "ONBLUR" || 
                               parName == "ONCHANGE" || 
                               parName == "ONCONTEXTMENU" || 
                               parName == "ONFOCUS" || 
                               parName == "ONFORMCHANGE" || 
                               parName == "ONFORMINPUT" || 
                               parName == "ONINPUT" || 
                               parName == "ONINVALID" || 
                               parName == "ONRESET" || 
                               parName == "ONSELECT" || 
                               parName == "ONSUBMIT" || 
                               parName == "ONKEYDOWN" || 
                               parName == "ONKEYPRESS" || 
                               parName == "ONKEYUP" || 
                               parName == "ONCLICK" || 
                               parName == "ONDBLCLICK" || 
                               parName == "ONDRAG" || 
                               parName == "ONDRAGEND" || 
                               parName == "ONDRAGENTER" || 
                               parName == "ONDRAGLEAVE" || 
                               parName == "ONDRAGOVER" || 
                               parName == "ONDRAGSTART" || 
                               parName == "ONDROP" || 
                               parName == "ONMOUSEDOWN" || 
                               parName == "ONMOUSEMOVE" || 
                               parName == "ONMOUSEOUT" || 
                               parName == "ONMOUSEOVER" || 
                               parName == "ONMOUSEUP" || 
                               parName == "ONMOUSEWHEEL" || 
                               parName == "ONSCROLL" || 
                               parName == "ONABORT" || 
                               parName == "ONCANPLAY" || 
                               parName == "ONCANPLAYTHROUGH" || 
                               parName == "ONDURATIONCHANGE" || 
                               parName == "ONEMPTIED" || 
                               parName == "ONENDED" || 
                               parName == "ONERROR" || 
                               parName == "ONLOADEDDATA" || 
                               parName == "ONLOADEDMETADATA" || 
                               parName == "ONLOADSTART" || 
                               parName == "ONPAUSE" || 
                               parName == "ONPLAY" || 
                               parName == "ONPLAYING" || 
                               parName == "ONPROGRESS" || 
                               parName == "ONRATECHANGE" || 
                               parName == "ONREADYSTATECHANGE" || 
                               parName == "ONSEEKED" || 
                               parName == "ONSEEKING" || 
                               parName == "ONSTALLED" || 
                               parName == "ONSUSPEND" || 
                               parName == "ONTIMEUPDATE" || 
                               parName == "ONVOLUMECHANGE" || 
                               parName == "ONWAITING" || 
                            parName == "ONTOUCHSTART" || 
                            parName == "ONTOUCHMOVE" || 
                            parName == "ONTOUCHEND" || 
                            parName == "ONTOUCHENTER" || 
                            parName == "ONTOUCHLEAVE" || 
                            parName == "ONTOUCHCANCEL" ||           
                            parName == "ONGESTURESTART" || 
                            parName == "ONGESTURECHANGE" || 
                            parName == "ONGESTUREEND" || 
                            parName == "ONPOINTERDOWN" || 
                            parName == "ONPOINTERUP" || 
                            parName == "ONPOINTERCANCEL" || 
                            parName == "ONPOINTERMOVE" || 
                            parName == "ONPOINTEROVER" || 
                            parName == "ONPOINTEROUT" || 
                            parName == "ONPOINTERENTER" || 
                            parName == "ONPOINTERLEAVE" || 
                            parName == "ONGOTPOINTERCAPTURE" || 
                            parName == "ONLOSTPOINTERCAPTURE" || 
                            parName == "ONCUT" || 
                            parName == "ONCOPY" || 
                            parName == "ONPASTE" || 
                            parName == "ONBEFORECUT" || 
                            parName == "ONBEFORECOPY" || 
                            parName == "ONBEFOREPASTE" || 
                            parName == "ONAFTERUPDATE" || 
                            parName == "ONBEFOREUPDATE" || 
                            parName == "ONCELLCHANGE" || 
                            parName == "ONDATAAVAILABLE" || 
                            parName == "ONDATASETCHANGED" || 
                            parName == "ONDATASETCOMPLETE" || 
                            parName == "ONERRORUPDATE" || 
                            parName == "ONROWENTER" || 
                            parName == "ONROWEXIT" || 
                            parName == "ONROWSDELETE" || 
                            parName == "ONROWINSERTED" || 
                            parName == "ONCONTEXTMENU" || 
                            parName == "ONDRAG" || 
                            parName == "ONDRAGSTART" || 
                            parName == "ONDRAGENTER" || 
                            parName == "ONDRAGOVER" || 
                            parName == "ONDRAGLEAVE" || 
                            parName == "ONDRAGEND" || 
                            parName == "ONDROP" || 
                            parName == "ONSELECTSTART" || 
                            parName == "ONHELP" || 
                            parName == "ONBEFOREUNLOAD" || 
                            parName == "ONSTOP" || 
                            parName == "ONBEFOREEDITFOCUS" || 
                            parName == "ONSTART" || 
                            parName == "ONFINISH" || 
                            parName == "ONBOUNCE" || 
                            parName == "ONBEFOREPRINT" || 
                            parName == "ONAFTERPRINT" || 
                            parName == "ONPROPERTYCHANGE" || 
                            parName == "ONFILTERCHANGE" || 
                            parName == "ONREADYSTATECHANGE" || 
                            parName == "ONLOSECAPTURE" || 
                            parName == "ONDRAGDROP" || 
                            parName == "ONDRAGENTER" || 
                            parName == "ONDRAGEXIT" || 
                            parName == "ONDRAGGESTURE" || 
                            parName == "ONDRAGOVER" || 
                            parName == "ONCLOSE" || 
                            parName == "ONCOMMAND" || 
                            parName == "ONINPUT" || 
                            parName == "ONCONTEXTMENU" || 
                            parName == "ONOVERFLOW" || 
                            parName == "ONOVERFLOWCHANGED" || 
                            parName == "ONUNDERFLOW" || 
                            parName == "ONPOPUPHIDDEN" || 
                            parName == "ONPOPUPHIDING" || 
                            parName == "ONPOPUPSHOWING" || 
                            parName == "ONPOPUPSHOWN" || 
                            parName == "ONBROADCAST" || 
                            parName == "ONCOMMANDUPDATE" || 
                               parName == "STYLE"

awvs会比较参数名称来确定。在后面的自动化扫描中,发现这种方式的误报还是很高,最后我将这种情况调整到了awvs的方式,只检测指定的属性key。

从这两处细微的差异可以看到,awvs宁愿漏报也不误报,结果会很准确,xray更多针对白帽子,结果会宽泛一些。

5.对于在html注释内的内容,以下case

<!--
        this is comment
        <?php echo $t;?>
   -->

xray顺序发送了以下payload:spzzmsntfzikatuchsvu,--><husyfmzvuq>,--!><oamtgwmoiz>,和上面类似,当确定-->--!>没有过滤时,会发送

 以 --> 或 --!> 开头,添加如下内容
   <bvwpmjtngz>
   sCrIpTbvwpmjtngzsCrIpT
   ImGsRcOnErRoRbvwpmjtngz>
   sVgOnLoAdbvwpmjtngz>
   iFrAmEsRcJaVaScRiPtbvwpmjtngz>
   aHrEfJaVaScRiPtbvwpmjtngzcLiCkA
   InPuTaUtOfOcUsOnFoCuSbvwpmjtngz>

Avvs

Awvs的扫描规则很多,针对的情况也很多,没有仔细看它的工作方式是怎样的,主要是看它的payload以及检测的情况,和上面两种查漏补缺,最终合成了我的xss扫描器~比如它会对meta标签的content内容进行处理,会对你srcipt,src等tag的属性处理,也有一些对AngularJs等一些流行的框架的XSS探测payload。

我的扫描器

我的XSS扫描器就是综合上面的几种扫描器而来,如果仔细观察,将会发现上面的扫描器的一些不同寻常的细节。

比如xray不会发送xss的payload,都是用一些随机字符来代替,同时也会随机大小写对一些标签名称,属性名称等等。

这些精致的技巧我的扫描器也都一一吸取了,嘿嘿!

扫描流程

我的扫描器扫描流程是这样的

发送随机flag -> 确定参数回显 -> 确定回显位置以及情况(html,js语法解析) -> 根据情况根据不同payload探测 -> 使用html,js语法解析确定是否多出来了标签,属性,js语句等等

使用html语法树检测有很多优势,可以准确判定回显所处的位置,然后通过发送一个随机payload,例如<Asfaa>,再使用语法检测是否有Asfaa这个标签,就能确定payload是否执行成功了。

html语法树用python自带的库

from html.parser import HTMLParser

js检测也是如此,如果回显内容在JavaScript脚本中,发送随机flag后,通过js语法解析只需要确定IdentifierLiteral这两个类型中是否包含,如果flag是Identifier类型,就能直接判断存在xss,payload是alert(1)//,如果flag是Literal类型,再通过单双引号来闭合进行检测。

Debug之旅

整个xss扫描代码不过1000行,但debug的过程是道阻且长。

本地靶机测试后就对在线的靶机进行了测试 https://brutelogic.com.br/knoxss.html

查漏补缺后就就开始了自动化扫描。

整个自动化架构如下

1\. 提供url -> 爬虫爬取 -> 参数入库 -> 消息队列 -> xss扫描器
                                -> 子域名入库
                                -> url入库

1.爬虫使用的crawlergo,效果挺不错的,但还是不太满足我的需求(造轮子的心态又膨胀了)

2.数据库使用的mongodb

3.用celery分散调用,由于用到了celery,又用到了rabbitmq消息编码,鲜花监控

4.用了服务器酱进行微信推送(得到一个扩展微信就会响一次)

刚开始打把游戏微信就会不停的响,然后就查找误报,优化逻辑,随之而来

经过了不懈的改造,优化了检测逻辑,加入了去重处理后,现在既扫描的慢且推动的消息也变少了。

一些成果

经过缩短对src的扫描后,成功还是挺多的(很多都归功于爬虫)

2.png

甚至发现了微软分站某处xss

3.png

未完,待续。。。

*本文作者:w7ay @知道创宇404实验室,转载请注明来自FreeBuf.COM


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