Allow users from my ASP.Net MVC site to access my private WordPress site

I ended up making the whole WP site private except to logged in users by using a plugin (Ultimate Member). Then I created a single login which would be used from the .Net site. The way it works is:

  1. User clicks on link within .Net site to access WordPress site
  2. Server-side: performs POST to /wp-login.php with credentials for single WP user
  3. Server-side: retrieve cookies from wp-login.php response
  4. Client-side: call to custom PHP page on WP site: /setcookies.php and set user’s session cookies for WP site domain using cookies from previous step
  5. Client-side: open WP site in iframe using session cookies