Request Access Token in Postman for Azure Function App protected by Azure AD B2C

Question

I have an AspNetCore 2.0 MVC web API secured by an Azure Active Directory B2C tenant. I have been able to use Postman to test the API end points by following this SO posting: Request Access Token in Postman for Azure AD B2C (in particular, the Microsoft documented steps referenced in SpottedMahn's comments: https://docs.microsoft.com/en-us/aspnet/core/security/authentication/azure-ad-b2c-webapi#use-postman-to-get-a-token-and-test-the-api )

Now, I am working on a serverless version of the above - the app is pretty much identical expect that the endpoints have been implemented by Azure functions in an Azure Functions App

The Functions App has Authentication on, Log in with Azure Active Directory and the following settings:

This is how i have set up the Application in the Azure B2C tenant:

If I access the functions endpoint via a browser, I get successfully routed to the Azure AD B2C login page and can log in, then see the results from the API endpoint. So I'm pretty confident all is good wrt the Azure AD B2C <-> Function App configuration.

However, I can't use the Request Access Token technique linked above to get a token and inspect the endpoint in Postman

If I take the token obtained after authentication (for example by using fiddler and observing the id_token being returned), and in Postman I choose Bearer authentication and supply that id_token, then Postman successfully hits my endpoint. However, if I follow the steps in the linked document above, I do get the "login" popup and then do get a valid [looking] token, but when I click Use Token and run the request, I get

You do not have permission to view this directory or page.

I'd really like to be able to request an access token from postman just like I can with my aspnetcore 2.0 app (really just for the consistency so I don't have to remember lots of different techniques). Is that possible for Azure Function Apps and if so, any clues what I'm doing wrong in the above?

Answer 1

Ah I stumbled upon it. I fixed it by adding the Postman API client id (note: the postman API client id, not the postman App client id) [those references will make sense in the context of the Microsoft how-to linked above], under "ALLOWED TOKEN AUDIENCES" (visible in screenshot in question above).