Assuming a SP-initiated Single sign-on with SAML. After the SSO session is established, which possibilities do I have to establish a communication between the Service Provider (SP) and Identity Provider (IdP) using SAML? As I understood, there are following related protocols:
a) Assertion Query and Request
b) Artifact Resolution
But in my use case, I would like to send some data from SP to IdP after the SSO session is established and get a response with an updated assertion from IdP. The IdP would use the received data, check the SSO session, update the assertion if required and send it back to the SP. It is assumed, that the IdP and SP understand the format of sent data.
In my opinion I could use the Assertion Query and Request protocol. But can I send my own XML-data formats to the IdP within that protocol? Are there any other possiblities?
Thanks in Advance.