Re: Microsoft Windows 2000 WebDAV Buffer Overflow Vulnerability

[Gerardo Richarte <core.lists.pentest () corest com>]

Frank Knobbe wrote:

> However, those same folks said that it is not the LOCK method that is
> vulnerable, but in fact only the GET method. I heard reports from guys
> who just couldn't make WebDAV crash with GET, but didn't have a problem
> with SEARCH and PROPFIND. Personally, I'm wondering if ISS was just
> spreading misinformation to confuse the potential worm-writers, but I'm
> not making any such accusation. (Misinformation wouldn't be effective
> anyway. But then again, neither is holding back the details for a sig,
> but explaining how it works...:/

    In did, the problem is not in GET nor SEARCH nor LOCK nor any other
method. AFAIK.

    While writing the exploit, and heavily basing our work on Renaud's nessus script
(thanks Renaud)

http://cvs.nessus.org/cgi-bin/cvsweb.cgi/~checkout~/nessus-plugins/scripts/iis_webdav_overflow.nasl

    we found out that the problem is not in the method, it's rather in the embeded SQL sentence:

            ...
             '<g:sql>\r\n' +
             'Select "DAV:displayname" from scope()\r\n' +
             '</g:sql>\r\n' +
            ...

    the function scope() somehow is resolved to the Unicode string
scope('"c:\inetpub\wwwroot\AAAAAAAAAAAA...
(I think it's not unicode but rather just wchars, UTF-16, or however it's the official
name) and this is what's causing the overflow actually... well... I think...
mmm... let me try something... well... for us, it's not crashing with GET nor
LOCK nor PROPFIND nor XXX... only with SEARCH, but, I bet the tests
were too fast to be correct. I'll try again latter today, and if there is any
change I'll let you know.

    So, being that the problem is present when using an SQL statement calling
scope() I wonder how many other ways are there to call an SQL statement
(only SEARCH, or all the other methods also... or does IIS care about the method
at all?). Is there another vuln function like scope is? [apparently scope is calling
"strcat()" on a wchar string]. Is there another way to force the problem in
ntdll.dll without even having to send 64k bytes of data? (and just create an SQL
statement that will generate 64K of data)... who knows... is the patch correct
at all? heh, who knows... what's the patch patching?

    more $0.02 to the piggy bank
    gera



--- for a personal reply use: gera () corest com

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