# File lib/httpclient/auth.rb, line 483
    def get(req)
      return nil unless SSPIEnabled
      target_uri = req.header.request_uri
      domain_uri, param = @challenge.find { |uri, v|
        Util.uri_part_of(target_uri, uri)
      }
      return nil unless param
      state = param[:state]
      authenticator = param[:authenticator]
      authphrase = param[:authphrase]
      case state
      when :init
        authenticator = param[:authenticator] = Win32::SSPI::NegotiateAuth.new
        return authenticator.get_initial_token(@scheme)
      when :response
        @challenge.delete(domain_uri)
        return authenticator.complete_authentication(authphrase)
      end
      nil
    end