using AD app registration in http request in an azure function - azure-active-directory

Question

I am accessing azure API's (graph, inTune etc).
To do this I have created an App Registration with permissions against the azure API's.
I now want to encapsulate the call within an azure function.
To call a REST API from an azure function, I understand I need to use a HTTP Request.
But I cannot identify how to use the existing App Registration to authenticate against the API's.
Can anyone advise how this might be accomplished?

Answer 1

Few of the workarounds I used to call the Azure GRAPH API from the existing Azure Function App Registration activated the authentication with Microsoft Account in the AAD is:
Approach 1:
Initialized the Http Client to call the Azure Graph API.
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", graphToken);
var me = await client.GetStringAsync("https://graph.microsoft.com/v1.0/me/");
return new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StringContent(me, Encoding.UTF8, "application/json")
};
To obtain the graph token, go to graph.microsoft.io and Click on Graph Explorer > Click on Access Token to get the token value.
Run the Http Trigger Function to send the Http Request to the Azure Graph API:
**Result when running locally: **
Above approach is the token passed manually in the code which is not the good approach in the Cloud (Azure)
Approach 2:
In order to pass the bearer/access token in the Request Headers to Http Client Request for querying the Graph API in the Cloud (Azure - Azure Functions):
Http Trigger Function:
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, string graphToken, TraceWriter log)
{
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", graphToken);
return await client.GetAsync("https://graph.microsoft.com/v1.0/me/");
}
To query the Graph API on behalf of the user making the request, add the below snippet to the function.json:
{
"type": "token",
"direction": "in",
"name": "graphToken",
"resource": "https://graph.microsoft.com",
"identity": "userFromRequest"
}
Also, you can run the function with the ClientCredentials authentication mode as it runs as an application instead of in the context of a particular user.
References:
Microsoft Documentation of Azure Functions with Microsoft Graph API Call.
Calling Microsoft Graph API from inside Azure Functions - JavaScript