# File lib/httpclient/auth.rb, line 725
    def get(req)
      target_uri = req.header.request_uri
      return nil unless @challengeable[nil] or @challengeable.find { |uri, ok|
        Util.uri_part_of(target_uri, uri) and ok
      }
      config = get_config(target_uri) || @config
      return nil unless config
      calc_cred(req, config)
    end