There could be a really easy solution to this, already implemented for a
MediaWiki hack (although I haven't tested your proposed vuln):
by: Sebastien Barre (Kitware, Inc.)
product: kwIncludeFile.php
[START]
// Can not open URL, bail out
if (!@fopen($url, 'r'))
{
return kwIncludeFileError(
"file not found ($url)");
}
// If we can "read" that URL, then it means it is in the local
filesystem
if (@is_readable($url))
{
return kwIncludeFileError(
"local access denied ($url)");
}
[END]
There might be something to this to confirm if the file being opened is a
valid file.
Better yet, I'm working on a project right now that includes checking the
mime type of a file using PHP's getimagesize:
http://php.net/getimagesize
GD is not required for this function. In it, you can check if a file is
actually an image or not against its mime/type:
image/jpeg
image/pjpeg
image/tiff
So there are a couple avenues one can take in assessing if the file that
[IMG][/IMG] is rendering is indeed an image.
Problem solved.
On Mon, 22 Aug 2005, h4cky0u wrote:
Hi,
Saw this one on www.waraxe.us (Discovered by Easyex) and i was
thinking if there are some more possibilities using the method
described. The POC below is for phpBB. -
==========
make yourself a folder on your host
rename the folder to signature.jpg
this will trick bbcode that its an image file.
example http://sitewithmaliciouscode/signature.jpg
inside that folder .. put this code ..
and rename it to index.php file.
Quote:
<?php
header("Location: http://hosttobeexploited/phpBB/login.php?logout=true";);
exit;
?>
this will make every visitor getting logout when they view the thread that
have image linked to this.
===================
This seems to be working on almost all the scripts using BBcode.
Successfully tested on vBulletin 3.0.7 and phpBB 2.0.17 when used the
image link to the folder with the malicious code as the forum
signature. What i was wondering is there anything more serious than
logging out the users that can be done with this? The admin folders of
ipb and phpbb need reauthentication. So nothing serious for them but
anything more innovative that could be done? And any way to fix this?
Regards,
--
Paul Laudanski http://castlecops.com
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