Call an Identity Provider API post Auth0 authentication - auth0

Question

I am trying to follow the list of set of steps at https://auth0.com/docs/what-to-do-once-the-user-is-logged-in/calling-an-external-idp-api but despite my best effort am not able to get the access token as I am getting a error as follows:
POST https://r***s.eu.auth0.com/oauth/token 401 (Unauthorized)
when I try to obtain the access token.
My code is the following:
var data = {
client_id : '****',
client_secret : '****',
audience : 'https://r****.eu.auth0.com/api/v2/',
grant_type : 'client_credentials'
};
var config = {
json: true,
headers : {
'Content-Type': 'application/json;'
};
}
$http.post('https://r***.eu.auth0.com/oauth/token',data, config).then (
function(response) { console.log(response); }
);

Answer 1

The problem is that you're setting an incorrect Content-Type when doing your POST request.
The correct content type for a JSON request is the following: application/json
You're appending an extra ; character at the end which is causing the server to issue a 401 response.
Additionally, that code snippet seems to be from an AngularJS application. If that's the case there's two additional problems, due to CORS limitation unless the application domain is white-listed in the Allowed Origins (CORS) list in the client settings (Auth0 Dashboard), you won't be able to perform the request anyway. This is the first problem, but not the biggest one... if you solve this by adding the domain to the white-list you now have a client identifier and secret stored on a client-side application which means anyone can access it just by looking at the code. In almost all (probably 99.9%) situations this is just wrong.