MVC5 app using Azure Active Directory + REST API -- to auth for PowerBI / O365 - oauth

Question

I'm trying to adapt the WebAPI example shown here, to use in MVC5:
https://msdn.microsoft.com/en-US/library/dn931282.aspx#Configure
I have a regular AccountController based login system, but I also need the user to login via OAuth into PowerBI, so I can pull datasets via the PowerBI REST API. However, I'm gettting the ClaimsPrincipal.Current.FindFirst(..) to be null.
private static async Task<string> getAccessToken()
{
// Create auth context (note: token is not cached)
AuthenticationContext authContext = new AuthenticationContext(Settings.AzureADAuthority);
// Create client credential
var clientCredential = new ClientCredential(Settings.ClientId, Settings.Key);
// Get user object id
var userObjectId = ClaimsPrincipal.Current.FindFirst(Settings.ClaimTypeObjectIdentifier).Value;
// Get access token for Power BI
// Call Power BI APIs from Web API on behalf of a user
return authContext.AcquireToken(Settings.PowerBIResourceId, clientCredential, new UserAssertion(userObjectId, UserIdentifierType.UniqueId.ToString())).AccessToken;
}
It all works fine in the sample app (a WebAPI project). I've also configured the OWIN app.UseOpenIdConnectAuthentication stuff in Startup.Auth.cs.
It seems the issue is the only type of Claim I have in 'ClaimsPrincipal.Current' is a 'CookieAuthentication' - it is missing the http://schemas.microsoft.com/identity/claims/objectidentifier Claim.
Also...the Microsoft OAuth window never opens in the browser...however, the error is within the ActiveDirectory related code...that code shouldn't need an OAuth token in the first place, right?

Answer 1

The recommended way to do this is to use the code that the Open ID Connect middleware will automatically retrieve for you. There is relevant sample here:
https://github.com/AzureADSamples/WebApp-WebAPI-OpenIDConnect-DotNet
This sample uses OAuth to get a token for the AAD Graph API. I don't know PowerBI but I believe that this is exactly analogous to getting a token for PowerBI.
Pay attention in particular to this file:
https://github.com/AzureADSamples/WebApp-WebAPI-OpenIDConnect-DotNet/blob/master/TodoListWebApp/App_Start/Startup.Auth.cs
AuthorizationCodeReceived = (context) =>
{
var code = context.Code;
ClientCredential credential = new ClientCredential(clientId, appKey);
string userObjectID = context.AuthenticationTicket.Identity.FindFirst("http://schemas.microsoft.com/identity/claims/objectidentifier").Value;
AuthenticationContext authContext = new AuthenticationContext(Authority, new NaiveSessionCache(userObjectID));
AuthenticationResult result = authContext.AcquireTokenByAuthorizationCode(code, new Uri(HttpContext.Current.Request.Url.GetLeftPart(UriPartial.Path)), credential, graphResourceId);
return Task.FromResult(0);
},
The code above is called on every successful authentication, and ADAL is used to retrieve a token to the Graph API. At this point the only reason to get a token for the Graph API is to exchange the short lived auth code for a longer lived refresh token and get that stored in the cache. That is why the 'result' is never used.
Later, in the following file, the cache is employed to retrieve the token and use it to access the graph:
https://github.com/AzureADSamples/WebApp-WebAPI-OpenIDConnect-DotNet/blob/master/TodoListWebApp/Controllers/UserProfileController.cs
string tenantId = ClaimsPrincipal.Current.FindFirst(TenantIdClaimType).Value;
string userObjectID = ClaimsPrincipal.Current.FindFirst("http://schemas.microsoft.com/identity/claims/objectidentifier").Value;
AuthenticationContext authContext = new AuthenticationContext(Startup.Authority, new NaiveSessionCache(userObjectID));
ClientCredential credential = new ClientCredential(clientId, appKey);
result = authContext.AcquireTokenSilent(graphResourceId, credential, new UserIdentifier(userObjectID, UserIdentifierType.UniqueId));
This time the token is actually used.
Substitute PowerBI for Graph API in the sample and I think you should be good to go.
Note that one other thing to pay attention to is the cache implementation. This file contains an appropriately name NaiveSessionCache.
https://github.com/AzureADSamples/WebApp-WebAPI-OpenIDConnect-DotNet/blob/master/TodoListWebApp/Utils/NaiveSessionCache.cs
If you have multiple front ends you will need to implement your own, less naive, session cache so that all the front ends can share the same cache.

Answer 2

A potential workaround, at least for me, is to use the "native app" setup on Azure AD and follow this workflow, instead of the web app + oauth workflow:
https://msdn.microsoft.com/en-US/library/dn877545.aspx