IRULE to validate cooke and its source URL

Want to write an irule where F5 need to validate that when we get a POST into our application with the security token in a cookie it is coming exclusively from Secure Auth (url).

 

Could someone one help me on this.

 

In detail:

 

We have an application which is hosted in F5. when client access this application it goes to server and server will get it redirect to secureauth and get the preauthtoken cookie. The cookie set bye secure auth will be used by server to post with preauthtoken and get to the webpage.