AssertionConsumerServiceUrl - Optional?

So I have a customer who would like to send their requests to any page on my site and become authenticated. They are the IdP and we are the SP. In the documentation it says that IdP-initiated SSO must go to a specific page specified by AssertionConsumerServiceUrl. Is this true? Or could I just try to catch a POST in my master page and call the AssertionConsumerServiceUrl “<a href=“””>" and that would work even if someone went to "<a href=“"?">”?

Hi Matt
Typically the SAML response is sent to a single endpoint - the assertion consumer service. This is how the SAML specification is written and what we would recommend.
With IdP-initiated SSO, along the SAML response, an optional relay state may be sent which specifies the URL the service provider should redirect to after SSO completes.
This is how you should support a user wishing to go to any page on your site. The SAML response and relay state are sent to the assertion consumer service and then once SSO completes you redirect to the page specified by the relay state.
However, if you want to catch the Post on your master page and call SAMLServiceProvider.ReceiveSSO that should work also but it’s not recommended.