Hi Arno,
it has nothing to do with ".php" in the file name. What the hacker did, was
uploading a .gif file with some malicious php code included to your
webserver. Then he called the .gif file from his own website by using a php
script containing some code like
require_once('http://www.yoursite.com/images/yourimage.gif'). At that moment
the php code inside the .gif file has been executed.
Steven
----- Original Message -----
From: "Arno Kuhl" <arno@xxxxxxxxxxxxxx>
To: "'Design in Motion Webdesign'" <info@xxxxxxxxxxxxxxxxx>;
<php-general@xxxxxxxxxxxxx>
Sent: Thursday, September 19, 2013 2:43 PM
Subject: RE: Apache's PHP handlers
For the past week I've been trying to get to the bottom of an exploit,
but
googling hasn't been much help so far, nor has my service provider.
Basically a file was uploaded with the filename xxx.php.pgif which
contained
nasty php code, and then the file was run directly from a browser. The
upload script used to upload this file checks that the upload filename
doesn't have a .php extension, which in this case it doesn't, so let it
through. I was under the impression apache would serve any file with an
extension not listed in its handlers directly back to the browser, but
instead it sent it to the php handler. Is this normal behaviour or is
there
a problem with my service provider's apache configuration? Trying this on
my localhost returns the file contents directly to the browser as
expected
and doesn't run the php code.
--
Arno,
the php file hidden as a gif will indeed not execute if opened directly
from
your website. But if opened from a page hosted elsewhere with some code
like
require($path_to_your_image), the php code inside the image will be sent
to
the php handler and will be executed.
Prevention is the best way to avoid hacking from image upload. Check the
file extention and the file content before upload.
Cheers.
Steven
--
Hi Steven, I agree the best way to avoid this is for the file upload
script
to check the file contents and that's something I'll have to sort out,
currently it just checks the extension. But it's still a concern that a
file
with any arbitrary extension can be processed as php script as long as it
has the text ".php" in the filename. I'm not worried about including the
file because that would require pre-existing malicious php code, I want to
prevent that malicious php code from running in the first place.
Cheers
Arno
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