active-directory-javascript-singlepageapp-angular | use MSAL Angular to login logout | Azure library

TL;DR

How can I delegate my user permissions to a service principal in Azure Ad when the usual interactive way (e.g. web app with consent screen popup) is not feasible? This is because I cannot configure the MSI in the Azure Portal properly to work that way.

More detail

I want to grant an application permission to access the Graph API on behalf of a user. Usually, this is a well-documented scenario in which you create an app registration, acquire delegated user permissions by asking permission for the needed scopes, and then use these permissions in the app.

The app that needs Graph access is a background service that is to work on its own without user intervention/activity. For this use case, the common approach is to use application permissions. In my case this is not feasible, because application permissions require admin-consent and are all-or-nothing kind of permissions. There is no way this will be granted for me. Rightfully so, because its overkill.

But on the other hand that's really a pity. A pity, because I've found an example on how to assign Graph API application permissions directly to a Managed Service Identity rather than to a self-registered app. And my service (as an Azure Functions app) already has a MSI assigned to it. So this would be the perfect fit, b then again, there is no way I'll get those application permissions.

So what is the workaround? We have this one user principal which has all the required permissions we need for our background service. What I want to do is to delegate this user's permissions to the Function App/MSI. In order to do this, I used this SPA-template by the MSAL team to have something that will prompt me the permissions popup.

This however failed because the implicit oauth flow was not enabled. To remedy this, you usually need to update the app manifest in the portal. However, since this is a MANAGED service identity, and not a self-registered one, the MSI is not listed in the portal under app registrations. So I cannot set this property to true.

Doing the same via Azure CLI also failed because apparently the MSI is not identified as an app.