full-disclosure - Re: Apache/PHP REQUEST

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Date: Tue, 24 Apr 2007 17:26:21 +0200
From: "Michał Majchrowicz" <mmajchrowicz@...il.com>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: Apache/PHP REQUEST_METHOD XSS Vulnerability

If you use htmlentitles it is still exploitable. The problem is that
Apache accepts chars wich it shouldn't.
Regards Michal.

On 4/24/07, Kradorex Xeron <admin@...ibase.ca> wrote:
> This isn't only a problem with that specific variable, it is also a problem
> with any user-defined variable, i.e.
>
> <?
> echo $_GET['page'];
> ?>
> can be XSS'd with script.php?page=<b>blah</b>
>
> However:
>
> <?
> echo htmlentities($_GET['page']);
> ?>
> is much harder to exploit to inject malicious code.
>
> I beleive the following: If your program/script accepts any user input, never
> assume something else will block the exploit of your program, always
> impliment sanity checks, and/or strip nonsense out of the input.
>
> On Monday 23 April 2007 18:21, Michał Majchrowicz wrote:
> > I agree. But (as a programmer) would you assume that there can be such
> > things in the REQUEST_METHOD? The flaw is that Apache accepts anything
> > after the valid request i.e. GET. There should be an error the the
> > request was not correct.
> > Regards Michal.
> >
> > On 4/24/07, Kradorex Xeron <admin@...ibase.ca> wrote:
> > > This is a case of poor-programming, on the script coder's part, it is not
> > > so much a vunerability.
> > >
> > > That variable only contains what it is sent by apache. it doesn't parse
> > > it. nor is it supposed to. If you want to ensure there is no XSS going
> > > on, parse the variable, escape characters, etc as it IS user input.
> > >
> > > This CAN be a vulnerability with individual scripts, however, it is not a
> > > vuln with PHP or Apache.
> > >
> > > On Monday 23 April 2007 17:31, Michal Majchrowicz wrote:
> > > > There exist a flaw in a way how Apache and php combination handle the
> > > > $_SERVER array.
> > > > If the programmer writes scrip like this:
> > > > <?php
> > > >               echo $_SERVER['REQUEST_METHOD'];
> > > > ?>
> > > > He will assume that REQUEST_METHOD can only by: GET,POST,OPTIONS,TRACE
> > > > and all that stuff. However this is not true, since Apache accepts
> > > > requests that look like this:
> > > > GET<script>alert(document.coookie);</script> /test.php HTTP/1.0
> > > > And the output for this would be:
> > > > GET<script>alert(document.coookie);</script>
> > > > Of course it is hard to exploit (I think some Flash might help ;)) and
> > > > I don't know if it is exploitable at all. But programmers should be
> > > > warned about this behaviour. You can't trust any  variable in the
> > > > $_SERVER table!
> > > > Regards Michal Majchrowicz.
> > > >
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