Tag: PHP Security Summary

This is a last article in this series.

More Information

The following resources can help you expand on this brief introduction:

• Essential PHP Security by Chris Shiflett (O’Reilly) and its companion website at http://phpsecurity.org/
• The Open Web Application Security Project at https://www.owasp.org/
• The PHP Security Consortium at http://phpsec.org/

Security Recap and Summary

Because security is such an important issue, we want to reiterate the main points of this series of tutorials as well as add a few additional tips:

• Filter input to be sure that all data you receive from remote sources is the data you expect. Remember, the stricter your filtering logic, the safer your application.
• Escape output in a context-aware manner to be sure that your data isn’t misinterpreted by a remote system.
• Always initialize your variables. This is especially important when the register_globals directive is enabled.
• Disable register_globals, magic_quotes_gpc, and allow_url_fopen. See http://www.php.net for details on these directives.
• Whenever you construct a filename, check the components with basename() and realpath().
• Store includes outside of the document root. It is better to not name your included files with the .inc extension. Name them with a .php extension, or some other less obvious extension.
• Always call session_regenerate_id() whenever a user’s privilege level changes.
• Whenever you construct a filename from a user-supplied component, check the components with basename() and realpath().
• Don’t create a file and then change its permissions. Instead, set umask() so that the file is created with the correct permissions.
• Don’t use user-supplied data with eval(), preg_replace() with the /e option, or any of the system commands— exec(), system(), popen(), passthru(), and the backtick (`) operator.

Here is the list of of Article in this Series:

• PHP – Securing your Web Application : Introduction
• PHP – Securing your Web Application : Filter Input
• PHP – Securing your Web Application : Cross-Site Scripting
• PHP – Securing your Web Application : SQL Injection
• PHP – Securing your Web Application : Escape Output
• PHP – Securing your Web Application : Filenames
• PHP – Securing your Web Application : Session Fixation
• PHP – Securing your Web Application : File Uploads
• PHP – Securing your Web Application : File Access
• PHP – Securing your Web Application : PHP Code
• PHP – Securing your Web Application : Shell Commands
• PHP – Securing your Web Application : More information and Summary

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Thanks Kevin Tatroe, Peter MacIntyre and Rasmus Lerdorf. Special Thanks to O’Relly.