SharePoint Framework: Calling AAD secured Azure Function on behalf of a user

Recently, after long last, the support for easily calling Azure AD secured custom APIs was released in the latest version of the SharePoint Framework (v1.4.1). Here are the details if you want to learn more: https://docs.microsoft.com/en-us/sharepoint/dev/spfx/use-aadhttpclient

In this post, let's have a look at how to secure our custom API (Azure Function) with Azure AD and then call the custom API from within a SharePoint Framework web part on behalf of the currently logged in user. We will be able to get the current user identity/claims in the custom API to know which user made the call to the Azure Function.



So let's quickly jump into how we are going to achieve this:

1) Create an Azure AD app registration

Go to Azure AD > App registrations > New application registration and create a new app registration. I am calling my app "User Details Custom API for SPFx"



By default the app registration will have the Sign in and read user profile scope on the Windows Azure Active Directory API. For the purpose of this post, those permissions are enough for us. We don't need to modify anything here right now.

Make a note of the Application ID of the app registration. This is the Client ID which we will use later.

As a subscription admin, Grant permissions to the App registration for all users so that each user does not have to do this individually:

2) Create an Azure Function App and configure it

Go to App Services > Add > Function App and create a new Azure Function App which we will use to host our Azure Function


Once the Function App is created, we need to secure it with our Azure AD app registration.

Go to Function App > Platform Features > Authentication / Authorization


In the Authentication / Authorization pane, for "Action to take when request is not authenticated" select "Log in with Azure Active Directory".

For Authentication Provider, click on Azure AD > Advanced and for Client ID, paste the Client ID (Application ID) of our Azure AD app registration we created earlier.


Click Ok and Save the Configuration.

Go to Function App > Platform Features > CORS and add the SharePoint Online domain from which your SPFx webpart will make a call to the Azure Function.

3) Create the Azure Function

Now let's actually create the Azure Function which we will deploy to the Function App as our custom API.

Using Visual Studio 2017, I have created a precompiled .NET Framework Azure Function project. As we are going to use this function as an API, I have selected an Http Triggered function:

Notice that the Authorization level for the function itself is set to Anonymous. This is because we are using Azure AD at the Function App level to secure it.

All this function does is returns the claims of the current authenticated user in JSON format.

Publish the function to the Azure Function App we created earlier.

4) Create the SharePoint Framework web part

Before going ahead with this step, make sure you have the latest version of the SharePoint Framework yeoman generator (1.4.1 at the time of this writing) This page should contain all the current versions of the generator, npm and node supported by the SharePoint Framework: https://docs.microsoft.com/en-us/sharepoint/dev/spfx/set-up-your-development-environment

Once you have all the latest packages, create the SPFx web part with yo @microsoft/sharepoint


To keep it simple, I am making it a tenant scoped solution with no JavaScript framework.

5) Request permissions for the SPFx web part

Once the SPFx web part solution is created, navigate to the config/package-solution.json file and add the webApiPermissionRequests property:

The resource will be the name of the Azure AD app registration we used to secure our Azure Function and the scope will be user_impersonation as we want to make a call on behalf of the current user.

6) Using AadHttpClient to call the custom Azure Function

Now in your SPFx webpart, include the following imports:

and the code to use the AadHttpClient to make a request to your custom Azure Function:

To display the table properly, add the following to the .scss file of your web part:

7) Installing and running the SPFx package 

Since we are going to run the SPFx solution in debug mode, we will run the commands without the --ship or --production switch. This will enable us to debug the solution locally.

Run the following commands to build and package your solution:

gulp build

gulp bundle

gulp package-solution

Start local debugging with

gulp serve --nobrowser

Now, upload the .sppkg file from the sharepoint/solution folder to the App Catalog:


Select the checkbox and Click on Deploy.

8) Granting permissions using the SPO Admin API management page

9) Add web part to page

 

Now go to any modern page and add your web part to it. Since we have deployed a tenant scoped solution, no need to install it individually on each site.

This is probably my least favourite part of the process. You will need to enable pop-ups so that SPFx and the underlying ADAL.js can authenticate the current user with the custom API.