PHP – Securing your Web Application : More information and Summary

This is a last article in this series.

More Information

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

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 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:

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