# File lib_doc/rucy/auth.rb, line 16
    def filter_open(context, script_name, request, response, logger)
      if (credentials = request.header('Authorization')) then
        if (credentials =~ /^Basic\s+/) then
          base64_user_pass = $'
          user_pass = base64_user_pass.unpack('m').first
          userid, password = user_pass.split(/:/, 2)
          if (@passwd.verify(userid, password)) then
            return
          end
        end
      end
      ex = HTTPError.new(401)
      ex.set_header('WWW-Authenticate', "Basic realm=#{@realm}")
      raise ex
    end