XLogin

XLogin enhances the WordPress login page (usually wp-login.php) to
allow users to authenticate with the following external services:

• Facebook Login
• Google Sign-In
• Yahoo! OAuth

These services can be enabled or disabled individually. XLogin adds a
button to the WordPress login page for each enabled service. Clicking
the button sends the browser to the corresponding external service
where the user can authorize the WordPress site to access their
information. Having been granted access to, for example, the Facebook
public profile of a user, XLogin retrieves their email address to
find a matching WordPress user to complete the login process.

XLogin also maintains a list of external aliases. They are additional
email addresses for mapping to WordPress users. Some scenarios where
external aliases can be handy include:

1. A user’s email address in his WordPress profile is not used in any
   of the external services. For example, a corporate WordPress site
   may mandate the use of company email addresses in user
   profiles. If a user has for example his Gmail address in the
   external alias list, they can still nevertheless sign in Google.

2. A WordPress user account is shared by a group of actual
   users. With XLogin it is not necessary to have the users share a
   single password. Instead just register their email addresses (as
   known by the external services) as external aliases; it becomes a
   simple matter to add and remove user.

XLogin has the option to restrict an external service to only users with
external aliases. This allows tight control on who can use external
services to login.

A user’s profile in WordPress and in the external service may be
different. Email address is one, and display name (or its component
family and given names) is another. XLogin offers the option to import
the external profile information into the current session. The imported
display name will be tagged with the external service name. For
example, if a user has display name ‘John Doe’ in WordPress, but is
known as ‘Johnny D’ in his Facebook account, then he would be
displayed as ‘Johnny D (Facebook)’ (instead of ‘John Doe’) in his
WordPress session when he logs in with Facebook.

Finally XLogin has the notion of ‘guest’ user. When an email address
provided by an external service does not correspond to a specific
WordPress user, XLogin will proceed with a guest WordPress user
configured for the service. There are plugins that control access to
content based on user roles; a site can combine such with XLogin to
control what is visible to guests. Note that guest WordPress users
should have minimal privileges. XLogin has safeguards to ensure, for
example, that a guest cannot edit posts. It also filters out guest’s
permission to access the dashboard or to update their own profile.