Essential PHP Security Book Cover
Essential PHP Security by Chris Shiflett
About | Contents | Buy Now | Reviews | Errata | Code
  1. Foreword
  2. Preface
  1. Introduction
  2. Forms and URLs
          ch02.pdf
  3. Databases and SQL
  4. Sessions and Cookies
          ch04.pdf
  5. Includes
  6. Files and Commands
  7. Authentication and Authorization
  8. Shared Hosting
  1. Configuration Directives
  2. Functions
  3. Cryptography
  4. Index

Enforce User-Agent Consistency

(Chapter 4, Sessions and Cookies - Pg 48)

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<?php

session_start();

if (isset($_SESSION['HTTP_USER_AGENT']))
{
    if ($_SESSION['HTTP_USER_AGENT'] != md5($_SERVER['HTTP_USER_AGENT']))
    {
        /* Prompt for password. */
        exit;
    }
}
else
{
    $_SESSION['HTTP_USER_AGENT'] = md5($_SERVER['HTTP_USER_AGENT']);
}

?>