Possible widespread PHP configuration issue - security risk
raina at thequeensmen.com
Fri Aug 27 20:58:39 MSD 2010
Hey Ed W,
Just want to say that while I'm not participating in this dialog since
it is over my head, I am listening and I do appreciate your asking
these questions, as well as your general commitment to Nginx and its
Hopefully I am part of a silent majority in this regard.
On Fri, Aug 27, 2010 at 11:49 AM, Ed W <lists at wildgooses.com> wrote:
> I'm not sure why a bunch of people are attacking me over this?
> The problem is clearly worded. I have taken some time to try and explain
> the issue. I have appealed for help designing a solution and yet half the
> responses are flames?
> Look, I'm reasonably sure *my* servers are fine. I don't really care if
> thousands of people I don't know get their servers taken over. However, I
> have taken the time to try and help here and try to encourage discussion on
> a new and better baseline config - I don't see why I'm getting attacked over
> Ed W
> On 27/08/2010 16:22, Ed W wrote:
>> Look, not had a lot of success raising this quietly. The Nginx wiki has
>> a number of very insecure PHP configuration suggestions. Anyone using these
>> example configurations should immediately review their configuration and
>> ensure that they aren't vulnerable to an upload attack where uploaded files
>> might be accidentally treated as executable files by nginx
>> The core of the problem is that most of the example configurations enable
>> php scripts in *all* directories on the server. Coupled with relatively
>> poor upload handling (in most PHP apps) and you have an upload attack
>> waiting to blow up on you.
>> Try the following:
>> 1) PHP Uploads allows (erk...)
>> Create a file test.php containing:
>> <?php echo 'hello' ?>
>> Try and upload this. If you can then probably turn off the server until
>> you fix the issue...
>> The attack is to construct a URL which points to the uploads directory,
>> 2) JPG uploads allowed, and wildcard ~ .php execution allowed
>> Create a test file test.jpg as follows:
>> # echo -e "\xff\xd8\xff\xe0\n<?php echo 'hello'; ?>" > test.jpg
>> # file test.jpg
>> test.jpg: JPEG image data
>> Now try and upload this test.jpg file to your server. If it succeeds then
>> probably turn off the server until you fix the issue...
>> The attack is to construct a URL which points to the uploads directory and
>> then append /.php on the URL, eg
>> Under *certain* configurations (wildcard php without a specific SCRIPT_URL
>> set) this will cause the execution of test.jpg by the php interpreter
>> The correct solution is where possible:
>> - Enable PHP only on files in certain directories (if possible). Exclude
>> upload dirs!
>> - Specifically disable (lots of) stuff on any upload locations!! Remember
>> configuration ordering in nginx puts regexp before named locations (order is
>> - Use try_files and other techniques to additionally lock down uri to file
>> - Check for any Apache .htaccess files shipped with your app and translate
>> to nginx config where appropriate (eg blocking certain locations completely)
>> There are plenty of examples of dangerous configuration on the nginx wiki.
>> eg the Wordpress initially presented configuration seems vulnerable, but
>> further down that page a more secure config is presented:
>> The Media wiki example seems to show the same vulnerability:
>> Please just treat your uploads directory carefully. It's a huge attack
>> Any volunteers to help improve the Wiki? Anyone got some better example
>> configurations (which are secure)? I don't use most of the PHP apps listed,
>> so hard to test their configurations?
>> Note this is not a problem with Nginx, this is a *configuration issue*.
>> However, the docs recommend such an insecure default configuration that
>> there must surely be loads of people vulnerable here...
>> Ed W
>> nginx mailing list
>> nginx at nginx.org
> nginx mailing list
> nginx at nginx.org
More information about the nginx