Authentication from sub-folder non-wp cookie WordPress

Question

I have a question about user authentication in my WordPress Multisite site.

My site is http://www.drezzy.it that has its own user db with a login and logout system. This is a non-WP website. When you login, it gives a cookie which include the email and the password of the user.

I created a WordPress Multisite website inside this one, http://www.drezzy.it/community/speciale/ that can have access to the cookie.

My questions are:

1. How can I allow WordPress to log in users by using the main site's cookie, so that they don't have to register or log in again? A sort of bridge between the main site and WP that would enable to log in only once for all.

2. How can I create a new user in WP for each user logged in the main website?

P.S. I'm sorry for my English, if you have some troubles with understand it, ask me, I will explain better! :D

Answer 1

Here is a quick function I had lying around that does exactly what your talking about. It uses some core WP functions to get the job done and you'll have to modify it to fit your needs, maybe double-check on the security of the thing but it should give you a head start.

function auto_function() {
    if ( isset( $_GET['username'] ) && isset( $_GET['email'] ) ){

        $user_name   = $_GET['username'];
        $user_email  = $_GET['email'];

        $user_id = username_exists( $user_name );
        if ( ! $user_id and email_exists( $user_email ) == false ) {
            $random_password = wp_generate_password( $length=12, $include_standard_special_chars=false );
            $user_id         = wp_create_user( $user_name, $random_password, $user_email );

            $creds = array();
            $creds['user_login'] = $user_name;
            $creds['user_password'] = $random_password;
            $creds['remember'] = true;
            $user = wp_signon( $creds, false );

            $meta_key = 'some_meta_key';
            $meta =& get_user_meta($user, $meta_key, true);
            $site_allowance = 3;

            add_user_meta( $user->id, $meta_key, $site_allowance , TRUE );

            #Redirect to help page
            wp_redirect( site_url('/user-profile/') ); exit;

        } else {
            $random_password = __('User already exists.  Password inherited.');
        }
    }
}