"Insufficient privileges to complete the operation" when trying to connect to Microsoft Graph

Question

I want to configure my Symfony4 application to read and send e-mails using the msgraph-sdk-php library.

My app would be reading and sending e-mail from a single account, whose password I don't want to expose to my app's users. Thus, I wouldn't be using OAuth for login.

My first experience was this piece of code (to retrieve mailbox user profile):

<?php

namespace App\Graph;

use Microsoft\Graph\Exception\GraphException;
use Microsoft\Graph\Graph;
use Microsoft\Graph\Model\User;

class GraphService
{
    function sentTestMessage() {
        $userId = "************************************";
        $tenantId = "************************************";
        $clientId = "************************************";
        $clientSecret = "***************************";


        $guzzle = new \GuzzleHttp\Client();
        $url = 'https://login.microsoftonline.com/' . $tenantId . '/oauth2/token?api-version=1.0';
        $token = json_decode($guzzle->post($url, [
            'form_params' => [
                'client_id' => $clientId,
                'client_secret' => $clientSecret,
                'resource' => 'https://graph.microsoft.com/',
                'grant_type' => 'client_credentials',
            ],
        ])->getBody()->getContents());
        $accessToken = $token->access_token;


        $graph = new Graph();
        $graph->setAccessToken($accessToken);

        $user=new \stdClass();
        try {
            $user = $graph->createRequest("GET", "/users/".$userId)
                ->setReturnType(User::class)
                ->execute();
        } catch (GraphException $e) {
            $user->getGivenName=$e->getMessage();
        }

        return "Hello, I am $user->getGivenName() ";

    }
}

But then Symfony shows me an exception page with this message:

Client error: GET https://graph.microsoft.com/v1.0/users/... resulted in a 403 Forbidden response:

{

"error": {

"code": "Authorization_RequestDenied",

"message": "Insufficient privileges to complete the ope (truncated...)

Now the same query works when run in https://developer.microsoft.com/en-us/graph/graph-explorer with the same user logged in.

These are the permissions I gave the app:

What should I do to overcome the problem above described?

Answer 1

You used client credentials flow to get access token in your code, so you need application permission instead of delegated permission.