Redfinger: A Ruby WebFinger Gem

Just yesterday, Google turned on webfinger for all GMail accounts. Today, we’re releasing a RubyGem to help you use the new protocol!

What’s a WebFinger?

WebFinger is a new protocol for extracting public information about a person via their e-mail address. It is meant to complement systems such as OpenID as well as give a simple way to get basic information about a user without having to ask them for it.

E-Mail providers can implement WebFinger by creating a special URL (specifically at /.well-known/host-meta) that is an XRD XML document telling the requester a URL at which they can find out more about e-mail addresses on their domain. Google’s, for example, is{uri}. When the WebFinger endpoint is requested with an e-mail address in place of {uri}, Google looks up information about that e-mail’s public profile and provides it in a standardized XRD XML format.

So why WebFinger when OpenID already exists? Users are used to associating their e-mail address with their identity. It’s natural since an e-mail address is (usually) for a specific person. By putting a protocol in place to find out more about an e-mail address without requiring additional input from the user, a host of options become available.

For instance, if I’m an application looking to authenticate using OpenID, I can ask a user for their e-mail address instead of their OpenID URL (something that will confuse mainstream users to no end). Or, if I want to automatcially fill in basic profile information, I can check to see if a parseable profile page is available in a format such as hCard.

Enter Redfinger

Redfinger is a library built to easily consume the WebFinger protocol. Installing it is simple:

gem install redfinger

Using it is just as simple:

require 'rubygems' require 'redfinger'  finger = Redfinger.finger('') finger.open_id.first.to_s # => ""

Redfinger will query the host of the e-mail domain specified, and, if the Webfinger protocol is supported, retrieve information about that e-mail address including such links as OpenID Provider, hCard URL, and more.

How can you use this today? Well, if you’re an OpenID consumer you can use the above code to try to “intelligently find” an OpenID endpoint from an e-mail address. Of course, it will just about only work with Google at the moment (this is an alpha protocol, after all). Or, you could install the mofo gem (a gem for parsing microformats for web pages) and do some neat things with microformats:

require 'rubygems' require 'mofo' require 'redfinger'  finger = Redfinger.finger('') card = hCard.find(finger.hcard.first.to_s) card.fn # => "That GMail user's full name" card.title # => "The title he/she entered on Google Profile"

Here Redfinger determines a URL that will have hCard information about the e-mail address specified, and the Mofo gem goes out and fetches that address, parsing out the information.

WebFinger is still brand new (Google calls it “alpha”) but it shows some promise for being a great way to make the open web more seamless for users. As always, the Redfinger source code is available on GitHub and RDoc Documentation is available. Check it out!