Azure web api Unauthorized 401 - api

Question

I have some code that used to call Azure Scheduler to get a token, then using that token, make restful calls. Works a treat.
So i decided to adopt the code into a new app but this time call my own web api hosted on azure. The API is registered in Active directory I have created a secret key etc. When i initiliaze my static httpclient it fetches a token succesfully.
But when i make a call to the API using the token for auth, the response is a 401 "unauthorized", below is the code.
public static class SchedulerHttpClient
{
const string SPNPayload = "resource={0}&client_id={1}&grant_type=client_credentials&client_secret={2}";
private static Lazy<Task<HttpClient>> _Client = new Lazy<Task<HttpClient>>(async () =>
{
string baseAddress = ConfigurationManager.AppSettings["BaseAddress"];
var client = new HttpClient();
client.BaseAddress = new Uri(baseAddress);
await MainAsync(client).ConfigureAwait(false);
return client;
});
public static Task<HttpClient> ClientTask => _Client.Value;
private static async Task MainAsync(HttpClient client)
{
string tenantId = ConfigurationManager.AppSettings["AzureTenantId"];
string clientId = ConfigurationManager.AppSettings["AzureClientId"];
string clientSecret = ConfigurationManager.AppSettings["AzureClientSecret"];
string token = await AcquireTokenBySPN(client, tenantId, clientId, clientSecret).ConfigureAwait(false);
client.DefaultRequestHeaders.Add("Authorization", "Bearer " + token); //TODO ssmith: const or localization
}
private static async Task<string> AcquireTokenBySPN(HttpClient client, string tenantId, string clientId, string clientSecret)
{
var payload = String.Format(SPNPayload,
WebUtility.UrlEncode(ConfigurationManager.AppSettings["ARMResource"]),
WebUtility.UrlEncode(clientId),
WebUtility.UrlEncode(clientSecret));
var body = await HttpPost(client, tenantId, payload).ConfigureAwait(false);
return body.access_token;
}
private static async Task<dynamic> HttpPost(HttpClient client, string tenantId, string payload)
{
var address = String.Format(ConfigurationManager.AppSettings["TokenEndpoint"], tenantId);
var content = new StringContent(payload, Encoding.UTF8, "application/x-www-form-urlencoded");
using (var response = await client.PostAsync(address, content).ConfigureAwait(false))
{
if (!response.IsSuccessStatusCode)
{
Console.WriteLine("Status: {0}", response.StatusCode);
Console.WriteLine("Content: {0}", await response.Content.ReadAsStringAsync().ConfigureAwait(false));
}//TODO: start removing tests
response.EnsureSuccessStatusCode();
return await response.Content.ReadAsAsync<dynamic>().ConfigureAwait(false);
}
}
}
The above code is the class that creates a httpclient and gets its authorization.
public virtual async Task<T> GetAsync(string apiURL)
{
try
{
_client = await SchedulerHttpClient.ClientTask;
var response = await _client.GetAsync(apiURL);
response.EnsureSuccessStatusCode();
var responseContent = await response.Content.ReadAsAsync<T>().ConfigureAwait(false);
return responseContent;
}
catch (Exception e)
{
return default(T);
}
}
The above code is a quick lift of my old code simply to test if i can get any results. but as stated it returns a 401.
My question is, is my old code to get authorization incorrect?
<add key="ARMResource" value="https://management.core.windows.net/" />
<add key="TokenEndpoint" value="https://login.windows.net/{0}/oauth2/token" />
<add key="BaseAddress" value="https://mysite.azurewebsites.net" />

Answer 1

As suspected, This particular issue was cause by the incorrect "ARMresource" in the case of a web api it required me to change it to the client id.
Source of answer
Seems my issue was the same, however i suspect i may be able to omit the resource entirely from my SPNPayload string.