Auto-authenticating to iframe-embedded Kibana dashboard

I have a Shield-protected Kibana 4.5 dashboard that I'm embedding via iframe. Is there any way to programmatically provide the user/password so that the user automatically auths and the dashboard is displayed?

I've attempted the following with no luck:
<iframe src="https://username:password@myKibanaHost....>
<iframe src="https://myKibanaHost?embed=true&username=myuser&password=mypass>

I know this isn't best idea to embed credentials in the iframe, but this is an internal system and we don't want users to have to authenticate twice (once to our site, once to Kibana).

Or is there another way?