Full Path Disclosure

Overview

Full Path Disclose (AKA, FPD) vulnerabilities enable the attacker to see the path to the webroot/file. Eg: /home/omg/htdocs/file/. Certain vulnerabilities such as using the load_file() query to view page sources require the attacker to have the full path to the file they wish to view.

Severity

Low to Medium (circumstantial)

Exploit Likely-Hood

Extremely High

Examples

• Empty Array

If we have a site that uses a method of requesting a page like this:

http://site.com/index.php?page=about

We can use a method of opening and closing braces and causing the page to output an error. This method would look like this:

http://site.com/index.php?page[]=about

This renders the page defunct thus spitting out an error:

Warning: opendir(Array): failed to open dir: No such file or directory in /home/omg/htdocs/index.php on line 84
Warning: pg_num_rows(): supplied argument ... in /usr/home/example/html/pie/index.php on line 131

• Null Session Cookie

Another popular and very reliable method of producing errors containing a FPD is to give the page a nulled session using Javascript Injections. A simple injection using this method would look something like so:

javascript:void(document.cookie="PHPSESSID=");

By simply setting the PHPSESSID cookie to nothing (null) we get an error.

Warning: session_start() [function.session-start]: The session id contains illegal characters, 
valid characters are a-z, A-Z, 0-9 and '-,' in /home/example/public_html/includes/functions.php on line 2

Preventing

This vulnerability is prevented simply by turning error reporting off so your code does not spit out errors.

error_reporting(0);