Found this one while searching how to secure php-fpm.

Consider a situation where remote users can upload their own pictures to the site. Lets say that an attacker uploads an image to http://www.bambookites.com/uploads/random.gif. What happens, given the server block above, if the attacker then browses to http://www.bambookites.com/uploads/random.gif/somefilename.php?

  1. nginx will look at the URL, see that it ends in .php, and pass the path along to the PHP fastcgi handler.
  2. PHP will look at the path, find the .gif file in the filesystem, and store /somefilename.php in $_SERVER['PATH_INFO'], executing the contents of the GIF as PHP.

Since GIFs and other image types can contain arbitrary content within them, it?s possible to craft a malicious image that contains valid PHP. That is how the attacker was able to compromise the server: he or she uploaded a malicious image containing PHP code to the site, then browsed to the file in a way that caused it to be parsed as PHP.
This issue was first discovered almost a year ago. The original report can be found in Chinese at http://www.80sec.com/nginx-securit.html. There is also a discussion about it on the nginx forums.
This issue can be mitigated in a number of ways, but there are downsides associated with each of the possibilities:

  1. Set cgi.fix_pathinfo to false in php.ini (it?s set to true by default). This change appears to break any software that relies on PATH_INFO being set properly (eg: WordPress).
  2. Add try_files $uri =404; to the location block in your nginx config. This only works when nginx and the php-fcgi workers are on the same physical server.
  3. Add a new location block that tries to detect malicious URLs. Unfortunately, detecting based on the URL alone is impossible: files don?t necessarily need to have extensions (eg: README, INSTALL, etc).
  4. Explicitly exclude upload directories using an if statement in your location block. The disadvantage here is the use of a blacklist: you have to keep updating your nginx configuration every time you install a new application that allows uploads.
  5. Don?t store uploads on the same server as your PHP. The content is static anyway: serve it up from a separate (sub)domain. Of course, this is easier said than done: not all web applications make this easy to do.

Source: https://nealpoole.com/blog/2011/04/s...configuration/
masterb56 Reviewed by masterb56 on . Securing php-fpm with nginx Found this one while searching how to secure php-fpm. Source: https://nealpoole.com/blog/2011/04/setting-up-php-fastcgi-and-nginx-dont-trust-the-tutorials-check-your-configuration/ Rating: 5