livebook/lib/livebook_web/templates/auth/index.html.eex

<div class="h-screen flex items-center justify-center bg-gray-900">
  <div class="flex flex-col space-y-4 items-center">
    <a href="/">
      <img src="/logo.png" height="128" width="128" alt="livebook" />
    </a>
    <div class="text-2xl text-gray-50">
      Authentication required
    </div>

    <div class="max-w-2xl text-center text-gray-300">
      Type password to access the Livebook.
    </div>
    <div class="text-2xl text-gray-50 w-full pt-2">
      <form method="post" class="flex flex-col space-y-4 items-center">
        <input type="hidden" value="<%= Phoenix.Controller.get_csrf_token() %>" name="_csrf_token"/>
        <input type="password" name="password" class="input" placeholder="Password" />
        <button type="submit" class="button button-blue">
          Authenticate
        </button>
      </form>
    </div>
  </div>
</div>