Did anyone implemented Siteminder integration with Drupal 8? Any documents related to this or any links will be greatly appreciated.
We don't have any documentation integrating with Druple.
However, Given that Drupal is a web application that runs on a web server that supports PHP, I would want to know what Web Server are you going to run Drupal under.
If your using a certified web server, Apache for instance, you can start with the Agent for Apache, and protect the Drupal Application.
You can also look at SSO Access Gateway (Secure Proxy Server), using that to protect Drupal.
Implementing CA Access Gateway - CA Single Sign-On - 12.7 - CA Technologies Documentation
I also did a quick search on drupal.org and found this module.
Siteminder | Drupal.org .
That being stated, if your going to have registered users within the web application, in this case Drupal, you would want to find out if it can use a header value and trust CA SSO (Siteminder).
I hope this helps.