Calling Microsoft Graph from Taskpane Outlook plugin

Question

I have successfully managed to configure my plugin (and Azure app registration) for SSO, such that Office.auth.getAccessToken() returns an access token.

However, I cannot use this access token with Microsoft Graph. I get an error saying the audience is incorrect.

I know there is a way of using an intermediate web API server to call MS Graph (which I do not really want to do and have not investigated yet). Is there a way to simply call the Microsoft Graph API directly from the plugin using SSO?

Answer 1

The token returned by Office.auth.getAccessToken() does not give access to Microsoft Graph. It provides access to the add-in's own server-side APIs. The server-side code should use the OAuth 2.0 On-Behalf-Of flow (OBO) to request a new access token with permissions to Microsoft Graph. Please refer to https://learn.microsoft.com/en-us/office/dev/ad-ins/outlook/authentication to know about other authentication options on Outlook add-ins depending upon the use case.