Description

I'm currently working on an implementation for RIOT of the ACE framework (RFC 9200) with the DTLS profile (RFC 9202). For this I need the information which credentials were used to set up the DTLS connection between server and client. As far as I know it is currently not possible for an application to get the credentials used for a request.
The knowledge about the credentials is needed to determine the previously uploaded access token and with it the access rights that the client has. (RFC 9202 3.3.2)

What would be the best way to bring this feature in?

Useful links

https://www.rfc-editor.org/rfc/rfc9200.html
https://www.rfc-editor.org/rfc/rfc9202.html