How restrict under password all my pages through the landing page

Good afternoon,

I would like to know if there is any possiblities to restrict all my pages using the landing page as a page with the password. If I put the landing page with the password, it covered only that page. I would like to covered all my pages. I know than I can put the password one by one, but I would like to have to put the password only once on the landing page. If I wrote to http//:www my domain/about or /contact for example, it will show to anybody the content. But I would like to block it by the landing page password. Is there anything without pluigin how to do it?

Thank you.

Kind regards,

Veronika