If you installed Kibana in the same host with ES, this is the problem.
About Kibana authentication without ROR PRO/Enterprise
Yeah I hear you, but without the Kibana plugin is pretty hard. Kibana will ask you to re-authenticate every now and then because it “forgets” to forward your basic auth password. By all means, try it out yourself. Maybe it’s not that bad for you, but this is the single reason I created the Kibana plugin (ROR PRO).