I'm trying to build a setup where my Xamarin forms app authenticates with Facebook, and when done gets a token from the Azure AD B2C to use when requesting data from my API.
So far I have native Facebook login up and running, meaning no web UI login, but uses the user's Facebook app and I get a the Facebook access token. This is the one I want to use when requesting a token from the Azure AD B2C
My issue now is how I should integrate this with Azure AD B2C. I want the API to be protected using Azure AD B2C and that part is enabled too, but I need the App to request a token before it can access my API. This is the part where I'm not sure if it is possible yet, with out letting the Azure AD popup with some UI.....
At this time, Azure AD B2C does not support acknowledging authentication that occurred outside of B2C.
You should request either support for the Facebook SDK and/or more broadly, supporting swapping tokens obtained outside of B2C for B2C tokens via the Azure AD B2C feedback forum