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@digibase.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@digibase.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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