ssbe_authenticator.rb

require 'rubygems'
require 'httpauth'
require 'addressable/uri'

class SSBEAuthenticator

  attr_reader :username, :password, :realm, :domain, :challenge

  def initialize(username, password)
    @username, @password = username, password
    @realm = 'SystemShepherd'
    @domain = nil
  end

  def update_credentials(challenge_response)
    @domain = Addressable::URI.parse(challenge_response.uri).host
    @challenge = HTTPAuth::Digest::Challenge.from_header(challenge_response.header['WWW-Authenticate'].first)
  end

  def valid_for?(challenge_response)
    return false unless challenge_header = challenge_response.header['WWW-Authenticate']
    begin
      challenge = HTTPAuth::Digest::Challenge.from_header(challenge_header.first)
    rescue HTTPAuth::UnwellformedHeader
      return false
    end
    challenge.realm == @realm
  end

  def can_handle?(request)
    Addressable::URI.parse(request.uri).host == @domain
  end

  def add_credentials_to(request)
    request.header['Authorization'] = credentials_for(request)
  end

  def credentials_for(request)
    HTTPAuth::Digest::Credentials.from_challenge(@challenge, 
                                                 :username => @username,
                                                 :password => @password,
                                                 :method   => request.method.to_s.upcase,
                                                 :uri      => Addressable::URI.parse(request.uri).path).to_header
  end

end