I'm trying to create a FB tab app. It's supposed to have an Edit Settings page, which is obviously supposed to be accessible only to page admins. If the admin is watching the tab - he's supposed to see a link to that page. I can do something like that with jQuery:
var is_admin = "<?php echo isset( $page['admin'] ) && $page['admin'] == 1 ? true : false; ?>";
if(is_admin)
$("<div id='div_edit_settings'>Edit Settings</div>").appendTo("some_div");
And later I can detect when this link was clicked and present the page (it's supposed to be displayed inside the tab as well, but since it's stored on the server it's also accessible through a browser).
The problem is that JS is visible to Firebug and other browser developer tools, so somebody could just insert a code line and see that link. So what can I do to make sure that only admins can see that Edit page and that only admins are editing the settings? How can I protect the link and the Edit page itself?
You should use PHP to insert the link into your page, something like:
<?php if ( isset( $page['admin'] ) && $page['admin'] == 1 ) : ?>
<div id='div_edit_settings'>Edit Settings</div>
<?php endif; ?>
You should also save the admin status to a session (with a name that isn't obvious, possible random string you can later check for), so that you can verify on other pages if the user viewing the link is actually an admin (you lost access to $page['admin'] when accessing other pages, unless you pass the signed_request to subsequent page calls.