There are lots of articles and opinions on this subject but most recent documentation points to id tokens being provided purely as a convenience after authentication and only access tokens should be used to call api’s.
Currently we have 2 front end applications (vuejs) and 2 API’s which they consume. The APIs are configured as oauth2 resource servers using Spring Security. Authorization is determined by the roles a user has (defined in our application) and again Spring security is configured to handle this i.e. restrict endpoints to specific roles as well as more fine grained permissions. Both APIs are not publicly exposed (internal dns) and are accessed via an API gateway.
After a user authenticates, the short-lived id token is obtained and set in a secure http-only cookie. The api gateway picks up the cookie and sets the Bearer header to pass onto the APIs. Each API verifies and converts the token to a Spring Authentication instance with a principal and their granted authorities.
The only information I need from a token is the email address of the user, which exists in the id token. Auth0 documentation is steering me towards using access tokens but I’m struggling to see the benefit in requesting another token which doesn’t contain the email address and so would require me to either pass the email address from the id token in a header as well as the access token or call the /userinfo endpoint from the APIs.
Is using the id token for this scenario acceptable usage or am I missing something.