I was asked if given the HRD screen is just "buttons" and there was a "link" behind that and users always picked the same one. could they not simply add the "link" to their web site and avoid the HRD screen altogether?
The basic problem with this is that the link is not static – it’s actually dynamic.
Take SAML-P as a example.
Assume the HRD screen has two entries; ADFS A and ADFS B.
The SAML request from the application to ADFS A gives:
And then selecting ADFS B via HRD gives:
The SAML request itself is different because as the packet goes through each ADFS, it’s signed with that ADFS’s signing key.
So the "link" would have to be updated every time a signing certificate changed.
In addition, a section of the SAML AuthnRequest contains:
The request contains the time the request was sent – which is dynamic.
There is an ADFS parameter for SAML called “clock skew”.
ADFS rejects the request when the skew between the server clock and the time in the request is more than 30 seconds (by default).
So nice try but no cigar!