design of website with membership to restricted content - php

Question

I have a web site which currently has over 900 html articles currently viewable to anyone. I want to change it to restrict viewing of certain articles by membership only. I have the articles in sql database with flag if restricted. There is an article index with links to each article. The process will be to check if article is restricted, check if user is member logged in, then display, otherwise send to login or subscribe pages. Since there is so many articles, I can't just add some php to not display if the article is accessed directly. My question is where in my web directory to I put these article pages, and how do you protect someone from directly accessing the page, but allow access once the user is authenticated? Any input is appreciated. Anyone know of good reference books on this either?

Answer 1

Move the files so that they're above your document root, and therefore inaccessible through the web server. Or, move the files to a directory which you protect with a password (.htaccess/.htpasswd pair). You never give out that password, it's only there to prevent direct access of the files.
Then, write a script which proxies the articles. That script checks if the user is logged in. If not, it redirects them to the login page. If it is, it reads the article HTML from its actual location, and sends it through.
Ex: http://www.example.com/article.php?view=cooking.html
session_start();
if (!isset($_SESSION['logged_in'])) {
header("Location: login.php");
} else {
readfile("/path/to/articles/" . $_GET['view']);
}
You'll want to do some kind of sanitation on $_GET['view'] to make sure it doesn't contain anything but the name of an article.
You can even keep your current URLs and links to the articles by rewriting them to the proxy script in your .httaccess/httpd.conf with mod_rewrite. Something like this:
RewriteEngine On
RewriteRule article/(.*)\.html articles.php?view=$1 [L]

Answer 2

If you don't already have any existing framework for PHP development that would help with security matters, you might consider something simpler than even using PHP to restrict access. Read up about .htaccess files, and how you can create a protected directory in which you could place all the restricted articles. Then you can setup user account and require people to authenticate themselves before they can read the restricted articles.
Here's a tutorial on how to setup .htaccess for user authorization/authentication:
http://www.javascriptkit.com/howto/htaccess3.shtml

Answer 3

You have a couple of basic options:
Add the code to each page. You can probably automate this, so its not as bad as it sounds. It really shouldn't be more than a single include.
Figure out how to get your web server software (e.g., apache) to do the authentication checks. Depending on how complicated your checks are, a mod_rewrite external mapping program may be able to do it. Other than that, there are existing authentication modules, or writing a fairly simple shim isn't that hard (if you know C)
Feed all page loads through PHP. This will probably break existing URLs, unfortunately. You pass the page you want to see as a parameter or part of the path (depending on server config), then do you checks inside your script, and finally send the page if the checks pass.

Answer 4

The simplest way would probably be to move all the aricle files outside the web root, and then use PHP to fetch them if the client is allowed to see it.
For example:
<?php
if (isset($_GET['id']))
{
$articleDir = "/var/articles/";
// Assuming a "?id=1" query string is used to pass a numberic ID of
// an article. (Like: example.com/showArticle.php?id=1)
$articleID = (int)$_GET['id'];
$articleFile = "article_{$articleID}.html";
// Look through your SQL database to see if the article is restricted.
// I'll leave the codeing to that up to you though.
if (!$isRestricted || $isLoggedIn)
{
$path = $articleDir . $articleFile;
if (file_exists($path))
{
include $path;
}
else
{
echo "The requested article does not exist.";
}
}
else
{
echo "You have to be logged in to see this article.";
}
}
else
{
echo "No article ID was passed. Did you perhaps follow a bad link?";
}
?>
Note that if you want to keep the old links alive, you can use Apache's mod_rewrite to rewrite incoming requests and route them to your PHP file.
Edit
This may help if you are new to mod_rewrite and/or regular expressions:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^article_(\d+)\.html$ fetchArticle.php?id=$1 [L]
</IfModule>
Routs any link such as example.com/article_123.html to example.com/fetchArticle.php?id=123 without the client noticing it.
Similar to what Dan Grossman did, but this one fetches only numbers.