Adauth provides Windows Active Directory authentication for Rails. To install it simply add this to your Gemfile
Then create config/initializers/adauth.rb and put this in it:
Adauth.configure do |c| c.domain = "example.com" c.server = "dc.example.com" c.base = "dc=example, dc=com" end
And thats it!
You can now authenticate users against the domain by calling:
Adauth does have a lot more config available, such as group/ou filtering.