access challenge B2BUA with Surrogate-agent

Hi All,

I'm creating a B2BUA combined with a surrogate user in a way the sbc will do the challenges on the core side for the access side.

The access side is sending a REGISTER and it can handle a the challenge, so this is good, but the catch is the device on the access side is able to do any challenge on other methode like INVITE.

The REGISTER from the access side is only cosmetic (generated) and is not realy needed to challenge but a 200 OK will do, full authentication on the core side is mandatory.

What i'm looking for is that the REGISTER from the access side is matched with the register-cache, population the IP: in the User Agent Info of the registration cache, and challenge the REGISTER on the access side OR just acknowledge it with a 200 OK.