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allow_url_fopen

Test Description

This test checks to see if allow_url_fopen is enabled.

Security Implications

If enabled, allow_url_fopen allows PHP's file functions -- such as file_get_contents() and the include and require statements -- can retrieve data from remote locations, like an FTP or web site. Programmers frequently forget this and don't do proper input filtering when passing user-provided data to these functions, opening them up to code injection vulnerabilities. A large number of code injection vulnerabilities reported in PHP-based web applications are caused by the combination of enabling allow_url_fopen and bad input filtering.
allow_url_fopen is on by default.

Recommendations

You should disable allow_url_fopen in the php.ini file:

; Disable allow_url_fopen for security reasons
allow_url_fopen = 'off'

The setting can also be disabled in apache's httpd.conf file:

# Disable allow_url_fopen for security reasons
php_flag  allow_url_fopen  off

For remote file access, consider using the cURL functions that PHP provides.

More Information

• PHP.net manual: allow_url_fopen
• PHP.net manual: Using remote files
• PHP.net manual: CURL, Client URL Library Functions

REFERENCES
http://phpsec.org/projects/phpsecinfo/tests/allow_url_fopen.html
http://www.google.ca/#q=allow_url_fopen+on&hl=en&prmd=df&ei=bjJjTMTmDszGOP6CpbsK&start=0&sa=N&fp=e6a957a020d2d8f6