WP Cookies and Authenticated Access — at Initial Version
|Reported by:||filosofo||Owned by:|
This has been an issue for a while as far as I can tell, but it's been brought to my attention by the convergence of the admin bar and Firesheep.
Let's say you define FORCE_SSL_ADMIN to be true. This redirects login and wp-admin access to its equivalent SSL/TLS version, mostly. Good so far.
However, when you authenticate to WP thus you get two cookies:
- SECURE_AUTH_COOKIE (a secure cookie, to be transmitted only over a secure connection.)
- LOGGED_IN_COOKIE (a non-secure cookie, to be transmitted over both secure and insecure connections.)
When you request a front-end page, not over SSL, your browser sends the LOGGED_IN_COOKIE but not SECURE_AUTH_COOKIE. This is sufficient to authenticate you as a user, with all the capabilities of your user (such as manage_options or edit_posts).
Why We Should Be Concerned
On an insecure network (e.g., a coffee shop), it's easy enough to get someone's LOGGED_IN_COOKIE. This allows you to do a number of things, depending on the themes and plugins used:
- You can access user information, which ranges from the trivial (the admin bar's comment and update counts) to more significant (view draft posts).
- You can get the logout nonce at least, and possibly more. This opens up some XSS vectors.
- Make admin-ajax requests. All you need are the appropriate nonces, and you can perform any of the admin-ajax actions. Some of the admin-ajax actions require no nonces at all; you can e.g. query tag information.
- The sky's the limit with themes and plugins.
- Plugins like BuddyPress let you do practically everything on the front-end, including editing user information and handling users.
- More generally, plugins tend to check just capabilities and verify nonces; they don't usually care about whether the user is using secure authentication. With the advent of the admin bar, we can expect even more administrative functionality to appear on the front-end, courtesy of plugins that are adding to the admin bar.
- When a site is FORCE_SSL_ADMIN, do not allow LOGGED_IN_COOKIE to be insecure. Or better, just have one authentication cookie that is secure for FORCE_SSL_ADMIN.
- Generate different nonces depending on whether they're over SSL or not.
- From the admin, link to the SSL versions of front-end objects, so authenticated users can browse them, secure and authenticated.
- More Involved
- When FORCE_SSL_ADMIN, deny authentication for capabilities above a certain level. So maybe if you have subscriber capabilities you can get a LOGGED_IN_COOKIE but not above.
- When FORCE_SSL_ADMIN, return false for any capability check above a certain level, when is_ssl() is false. So for example, current_user_can( 'read' ) would be true, but current_user_can( 'edit_posts' ) returns true only if is_ssl().