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MSAL Error message AADSTS65005 when trying to get token for accessing custom api

I downloaded the example below to get an access token from MS Graph and it worked fine. Now I changed the code to get a token from a custom web API. On apps.dev.microsoft.com I registered a client application and an the API.
Client and server registration in AD
private static async Task<AuthenticationResult> GetToken()
{
const string clientId = "185adc28-7e72-4f07-a052-651755513825";
var clientApp = new PublicClientApplication(clientId);
AuthenticationResult result = null;
string[] scopes = new string[] { "api://f69953b0-2d7f-4523-a8df-01f216b55200/Test" };
try
{
result = await clientApp.AcquireTokenAsync(scopes, "", UIBehavior.SelectAccount, string.Empty);
}
catch (Exception x)
{
if (x.Message == "User canceled authentication")
{
}
return null;
}
return result;
}
When I run the code I login to AD via the dialog en get the following exception in the debugger:
Error: Invalid client Message = "AADSTS65005: The application
'CoreWebAPIAzureADClient' asked for scope 'offline_access' that
doesn't exist on the resource. Contact the app vendor.\r\nTrace ID:
56a4b5ad-8ca1-4c41-b961-c74d84911300\r\nCorrelation ID:
a4350378-b802-4364-8464-c6fdf105cbf1\r...
Error message
Help appreciated trying for days...

For anyone still striking this problem, please read this:
https://www.andrew-best.com/posts/please-sir-can-i-have-some-auth/
You'll feel better after this guy reflects all of your frustrations, except that he works it out...
If using adal.js, for your scope you need to use
const tokenRequest = {
scopes: ["https://management.azure.com/user_impersonation"]
};
I spent a week using
const tokenRequest = {
scopes: ["user_impersonation"]
};
.. since that is the format that the graph API scopes took

As of today, the V2 Endpoint does not support API access other than the Microsoft Graph. See the limitations of the V2 app model here.
Standalone Web APIs
You can use the v2.0 endpoint to build a Web API that is secured with
OAuth 2.0. However, that Web API can receive tokens only from an
application that has the same Application ID. You cannot access a Web
API from a client that has a different Application ID. The client
won't be able to request or obtain permissions to your Web API.
For the specific scenario that you are trying to accomplish, you need to use the V1 App Model (register apps on https://portal.azure.com).
In the very near future, V2 apps will be enabled to call other APIs other than Microsoft Graph, so your scenario will be supported, but that is just not the case today. You should keep an eye out on our documentation for this update.

In your (server) application registration in AAD, you need to specify your scopes in the oauth2Permissions element.
You may already have a user_impersonation scope set. Copy that as a baseline, give it a unique GUID and value, and then AAD will let your client request an access token with your new scope.

Google Data API Authorization Redirect URI Mismatch

Background
I am wanting to write a small, personal web app in .NET Core 1.1 to interact with YouTube and make some things easier for me to do and I am following the tutorials/samples in Google's YouTube documentation. Sounds simple enough, right? ;)
Authenticating with Google's APIs seems impossible! I have done the following:
Created an account in the Google Developer Console
Created a new project in the Google Developer Console
Created a Web Application OAuth Client ID and added my Web App debug URI to the list of approved redirect URIs
Saved the json file provided after generating the OAuth Client ID to my system
In my application, my debug server url is set (and when my application launches in debug, it's using the url I set which is http://127.0.0.1:60077).
However, when I attempt to authenticate with Google's APIs, I recieve the following error:
That’s an error.
Error: redirect_uri_mismatch
The redirect URI in the request, http://127.0.0.1:63354/authorize/,
does not match the ones authorized for the OAuth client.
Problem
So now, for the problem. The only thing I can find when searching for a solution for this is people that say
just put the redirect URI in your approved redirect URIs
Unfortunately, the issue is that every single time my code attempts to authenticate with Google's APIs, the redirect URI it is using changes (the port changes even though I set a static port in the project's properties). I cannot seem to find a way to get it to use a static port. Any help or information would be awesome!
NOTE: Please don't say things like "why don't you just do it this other way that doesn't answer your question at all".
The code
client_id.json
{
"web": {
"client_id": "[MY_CLIENT_ID]",
"project_id": "[MY_PROJECT_ID]",
"auth_uri": "https://accounts.google.com/o/oauth2/auth",
"token_uri": "https://accounts.google.com/o/oauth2/token",
"auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
"client_secret": "[MY_CLIENT_SECRET]",
"redirect_uris": [
"http://127.0.0.1:60077/authorize/"
]
}
}
Method That Is Attempting to Use API
public async Task<IActionResult> Test()
{
string ClientIdPath = #"C:\Path\To\My\client_id.json";
UserCredential credential;
using (var stream = new FileStream(ClientIdPath, FileMode.Open, FileAccess.Read))
{
credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
GoogleClientSecrets.Load(stream).Secrets,
new[] { YouTubeService.Scope.YoutubeReadonly },
"user",
CancellationToken.None,
new FileDataStore(this.GetType().ToString())
);
}
var youtubeService = new YouTubeService(new BaseClientService.Initializer()
{
HttpClientInitializer = credential,
ApplicationName = this.GetType().ToString()
});
var channelsListRequest = youtubeService.Channels.List("contentDetails");
channelsListRequest.Mine = true;
// Retrieve the contentDetails part of the channel resource for the authenticated user's channel.
var channelsListResponse = await channelsListRequest.ExecuteAsync();
return Ok(channelsListResponse);
}
Project Properties

The Original Answer works, but it is NOT the best way to do this for an ASP.NET Web Application. See the update below for a better way to handle the flow for an ASP.NET Web Application.
Original Answer
So, I figured this out. The issue is that Google thinks of a web app as a JavaScript based web application and NOT a web app with server side processing. Thus, you CANNOT create a Web Application OAuth Client ID in the Google Developer Console for a server based web application.
The solution is to select the type Other when creating an OAuth Client ID in the Google Developer Console. This will have Google treat it as an installed application and NOT a JavaScript application, thus not requiring a redirect URI to handle the callback.
It's somewhat confusing as Google's documentation for .NET tells you to create a Web App OAuth Client ID.
Feb 16, 2018 Updated Better Answer:
I wanted to provide an update to this answer. Though, what I said above works, this is NOT the best way to implement the OAuth workflow for a ASP.NET solution. There is a better way which actually uses a proper OAuth 2.0 flow. Google's documentation is terrible in regards to this (especially for .NET), so I'll provide a simple implementation example here. The sample is using ASP.NET core, but it's easily adapted to the full .NET framework :)
Note: Google does have a Google.Apis.Auth.MVC package to help simplifiy this OAuth 2.0 flow, but unfortunately it's coupled to a specific MVC implementation and does not work for ASP.NET Core or Web API. So, I wouldn't use it. The example I'll be giving will work for ALL ASP.NET applications. This same code flow can be used for any of the Google APIs you've enabled as it's dependent on the scopes you are requesting.
Also, I am assuming you have your application set up in your Google Developer dashboard. That is to say that you have created an application, enabled the necessary YouTube APIs, created a Web Application Client, and set your allowed redirect urls properly.
The flow will work like this:
The user clicks a button (e.g. Add YouTube)
The View calls a method on the Controller to obtain an Authorization URL
On the controller method, we ask Google to give us an Authorization URL based on our client credentials (the ones created in the Google Developer Dashboard) and provide Google with a Redirect URL for our application (this Redirect URL must be in your list of accepted Redirect URLs for your Google Application)
Google gives us back an Authorization URL
We redirect the user to that Authorization URL
User grants our application access
Google gives our application back a special access code using the Redirect URL we provided Google on the request
We use that access code to get the Oauth tokens for the user
We save the Oauth tokens for the user
You need the following NuGet Packages
Google.Apis
Google.Apis.Auth
Google.Apis.Core
Google.apis.YouTube.v3
The Model
public class ExampleModel
{
public bool UserHasYoutubeToken { get; set; }
}
The Controller
public class ExampleController : Controller
{
// I'm assuming you have some sort of service that can read users from and update users to your database
private IUserService userService;
public ExampleController(IUserService userService)
{
this.userService = userService;
}
public async Task<IActionResult> Index()
{
var userId = // Get your user's ID however you get it
// I'm assuming you have some way of knowing if a user has an access token for YouTube or not
var userHasToken = this.userService.UserHasYoutubeToken(userId);
var model = new ExampleModel { UserHasYoutubeToken = userHasToken }
return View(model);
}
// This is a method we'll use to obtain the authorization code flow
private AuthorizationCodeFlow GetGoogleAuthorizationCodeFlow(params string[] scopes)
{
var clientIdPath = #"C:\Path\To\My\client_id.json";
using (var fileStream = new FileStream(clientIdPath, FileMode.Open, FileAccess.Read))
{
var clientSecrets = GoogleClientSecrets.Load(stream).Secrets;
var initializer = new GoogleAuthorizationCodeFlow.Initializer { ClientSecrets = clientSecrets, Scopes = scopes };
var googleAuthorizationCodeFlow = new GoogleAuthorizationCodeFlow(initializer);
return googleAuthorizationCodeFlow;
}
}
// This is a route that your View will call (we'll call it using JQuery)
[HttpPost]
public async Task<string> GetAuthorizationUrl()
{
// First, we need to build a redirect url that Google will use to redirect back to the application after the user grants access
var protocol = Request.IsHttps ? "https" : "http";
var redirectUrl = $"{protocol}://{Request.Host}/{Url.Action(nameof(this.GetYoutubeAuthenticationToken)).TrimStart('/')}";
// Next, let's define the scopes we'll be accessing. We are requesting YouTubeForceSsl so we can manage a user's YouTube account.
var scopes = new[] { YouTubeService.Scope.YoutubeForceSsl };
// Now, let's grab the AuthorizationCodeFlow that will generate a unique authorization URL to redirect our user to
var googleAuthorizationCodeFlow = this.GetGoogleAuthorizationCodeFlow(scopes);
var codeRequestUrl = googleAuthorizationCodeFlow.CreateAuthorizationCodeRequest(redirectUrl);
codeRequestUrl.ResponseType = "code";
// Build the url
var authorizationUrl = codeRequestUrl.Build();
// Give it back to our caller for the redirect
return authorizationUrl;
}
public async Task<IActionResult> GetYoutubeAuthenticationToken([FromQuery] string code)
{
if(string.IsNullOrEmpty(code))
{
/*
This means the user canceled and did not grant us access. In this case, there will be a query parameter
on the request URL called 'error' that will have the error message. You can handle this case however.
Here, we'll just not do anything, but you should write code to handle this case however your application
needs to.
*/
}
// The userId is the ID of the user as it relates to YOUR application (NOT their Youtube Id).
// This is the User ID that you assigned them whenever they signed up or however you uniquely identify people using your application
var userId = // Get your user's ID however you do (whether it's on a claim or you have it stored in session or somewhere else)
// We need to build the same redirect url again. Google uses this for validaiton I think...? Not sure what it's used for
// at this stage, I just know we need it :)
var protocol = Request.IsHttps ? "https" : "http";
var redirectUrl = $"{protocol}://{Request.Host}/{Url.Action(nameof(this.GetYoutubeAuthenticationToken)).TrimStart('/')}";
// Now, let's ask Youtube for our OAuth token that will let us do awesome things for the user
var scopes = new[] { YouTubeService.Scope.YoutubeForceSsl };
var googleAuthorizationCodeFlow = this.GetYoutubeAuthorizationCodeFlow(scopes);
var token = await googleAuthorizationCodeFlow.ExchangeCodeForTokenAsync(userId, code, redirectUrl, CancellationToken.None);
// Now, you need to store this token in rlation to your user. So, however you save your user data, just make sure you
// save the token for your user. This is the token you'll use to build up the UserCredentials needed to act on behalf
// of the user.
var tokenJson = JsonConvert.SerializeObject(token);
await this.userService.SaveUserToken(userId, tokenJson);
// Now that we've got access to the user's YouTube account, let's get back
// to our application :)
return RedirectToAction(nameof(this.Index));
}
}
The View
#using YourApplication.Controllers
#model YourApplication.Models.ExampleModel
<div>
#if(Model.UserHasYoutubeToken)
{
<p>YAY! We have access to your YouTube account!</p>
}
else
{
<button id="addYoutube">Add YouTube</button>
}
</div>
<script>
$(document).ready(function () {
var addYoutubeUrl = '#Url.Action(nameof(ExampleController.GetAuthorizationUrl))';
// When the user clicks the 'Add YouTube' button, we'll call the server
// to get the Authorization URL Google built for us, then redirect the
// user to it.
$('#addYoutube').click(function () {
$.post(addYoutubeUrl, function (result) {
if (result) {
window.location.href = result;
}
});
});
});
</script>

As referred here, you need to specify a fix port for the ASP.NET development server like How to fix a port number in asp.NET development server and add this url with the fix port to the allowed urls. Also as stated in this thread, when your browser redirects the user to Google's oAuth page, you should be passing as a parameter the redirect URI you want Google's server to return to with the token response.

I noticed that there is easy non-programmatic way around.
If you have typical monotlith application built in typical MS convention(so not compatible with 12factor and typical DDD) there is an option to tell your Proxy WWW server to rewrite all requests from HTTP to HTTPS so even if you have set up Web App on http://localhost:5000 and then added in Google API url like: http://your.domain.net/sigin-google, it will work perfectly and it is not that bas because it is much safer to set up main WWW to rewrite all to HTTPS.
It is not very good practice I guess however it makes sense and does the job.

I've struggled with this issue for hours in a .net Core application. What finally fixed it for me was, in the Google developers console, to create and use a credential for "Desktop app" instead of a "Web application".

Yeah!! Using credentials of desktop app instead of web app worked for me fine. It took me more than 2 days to figure out this problem. The main problem is that google auth library dose not adding or supporting http://localhost:8000 as redirect uri for web app creds but credentials of desktop app fixed that issue. Cause its supporting http://___ connection instead of https: connection for redirect uri

Use google credentials to login into UWP C# app

I'm trying to make a login for a UWP app that I'm developing for a client that has a #<theircompay>.com email that uses G Suite. It doesn't have to access any user data, they just want it as an authentication so that only people that have a company email can access the app.
It would be great if they could login from within the app without having to use a web browser, and even better if it could remember them so they wouldn't have to login every single time.
I've been looking at OAuth 2.0 and several other solutions google has but can't really understand which one to use and much less how.
I looked into this answer but it doesn't seem like a good idea to ship your certificate file with your app.
So basically if this can be done, what (if any) certificates or credentials do I need to get from Google, and how would I handle them and the login through my C# code?
Edit
The app is 100% client side, no server backend

Taking a look at Google's GitHub it seems that .Net API is still not ready for UWP (however if you traverse the issues you will find that they are working on it, so it's probably a matter of time when official version is ready and this answer would be obsolete).
As I think getting simple accessToken (optionaly refresing it) to basic profile info should be sufficient for this case. Basing on available samples from Google I've build a small project (source at GitHub), that can help you.
So first of all you have to define your app at Google's developer console and obtain ClientID and ClientSecret. Once you have this you can get to coding. To obtain accessToken I will use a WebAuthenticationBroker:
string authString = "https://accounts.google.com/o/oauth2/auth?client_id=" + ClientID;
authString += "&scope=profile";
authString += $"&redirect_uri={RedirectURI}";
authString += $"&state={state}";
authString += $"&code_challenge={code_challenge}";
authString += $"&code_challenge_method={code_challenge_method}";
authString += "&response_type=code";
var receivedData = await WebAuthenticationBroker.AuthenticateAsync(WebAuthenticationOptions.UseTitle, new Uri(authString), new Uri(ApprovalEndpoint));
switch (receivedData.ResponseStatus)
{
case WebAuthenticationStatus.Success:
await GetAccessToken(receivedData.ResponseData.Substring(receivedData.ResponseData.IndexOf(' ') + 1), state, code_verifier);
return true;
case WebAuthenticationStatus.ErrorHttp:
Debug.WriteLine($"HTTP error: {receivedData.ResponseErrorDetail}");
return false;
case WebAuthenticationStatus.UserCancel:
default:
return false;
}
If everything goes all right and user puts correct credentials, you will have to ask Google for tokens (I assume that you only want the user to put credentials once). For this purpose you have the method GetAccessToken:
// Parses URI params into a dictionary - ref: http://stackoverflow.com/a/11957114/72176
Dictionary<string, string> queryStringParams = data.Split('&').ToDictionary(c => c.Split('=')[0], c => Uri.UnescapeDataString(c.Split('=')[1]));
StringContent content = new StringContent($"code={queryStringParams["code"]}&client_secret={ClientSecret}&redirect_uri={Uri.EscapeDataString(RedirectURI)}&client_id={ClientID}&code_verifier={codeVerifier}&grant_type=authorization_code",
Encoding.UTF8, "application/x-www-form-urlencoded");
HttpResponseMessage response = await httpClient.PostAsync(TokenEndpoint, content);
string responseString = await response.Content.ReadAsStringAsync();
if (!response.IsSuccessStatusCode)
{
Debug.WriteLine("Authorization code exchange failed.");
return;
}
JsonObject tokens = JsonObject.Parse(responseString);
accessToken = tokens.GetNamedString("access_token");
foreach (var item in vault.RetrieveAll().Where((x) => x.Resource == TokenTypes.AccessToken.ToString() || x.Resource == TokenTypes.RefreshToken.ToString())) vault.Remove(item);
vault.Add(new PasswordCredential(TokenTypes.AccessToken.ToString(), "MyApp", accessToken));
vault.Add(new PasswordCredential(TokenTypes.RefreshToken.ToString(), "MyApp", tokens.GetNamedString("refresh_token")));
TokenLastAccess = DateTimeOffset.UtcNow;
Once you have the tokens (I'm saving them in PasswordVault for safety), you can later then use them to authenticate without asking the user for his credentials. Note that accessToken has limited lifetime, therefore you use refreshToken to obtain a new one:
if (DateTimeOffset.UtcNow < TokenLastAccess.AddSeconds(3600))
{
// is authorized - no need to Sign In
return true;
}
else
{
string token = GetTokenFromVault(TokenTypes.RefreshToken);
if (!string.IsNullOrWhiteSpace(token))
{
StringContent content = new StringContent($"client_secret={ClientSecret}&refresh_token={token}&client_id={ClientID}&grant_type=refresh_token",
Encoding.UTF8, "application/x-www-form-urlencoded");
HttpResponseMessage response = await httpClient.PostAsync(TokenEndpoint, content);
string responseString = await response.Content.ReadAsStringAsync();
if (response.IsSuccessStatusCode)
{
JsonObject tokens = JsonObject.Parse(responseString);
accessToken = tokens.GetNamedString("access_token");
foreach (var item in vault.RetrieveAll().Where((x) => x.Resource == TokenTypes.AccessToken.ToString())) vault.Remove(item);
vault.Add(new PasswordCredential(TokenTypes.AccessToken.ToString(), "MyApp", accessToken));
TokenLastAccess = DateTimeOffset.UtcNow;
return true;
}
}
}
The code above is only a sample (with some shortcuts) and as mentioned above - a working version with some more error handling you will find at my GitHub. Please also note, that I haven't spend much time on this and it will surely need some more work to handle all the cases and possible problems. Though hopefully will help you to start.

Answer from Roamsz is great but didnt work for me because I found some conflicts or at least with the latest build 17134 as target, it doesn't work. Here are the problem, in his Github sample, he is using returnurl as urn:ietf:wg:oauth:2.0:oob . this is the type of url, you can't use with web application type when you create new "Create OAuth client ID" in the google or firebase console. you must use "Ios" as shown below. because web application requires http or https urls as return url.
from google doc
According to his sample he is using Client secret to obtain access token, this is not possible if you create Ios as type. because Android and Ios arent using client secret. It is perfectly described over here
client_secret The client secret obtained from the API Console. This
value is not needed for clients registered as Android, iOS, or Chrome
applications.
So you must use type as Ios, No Client Secret needed and return url is urn:ietf:wg:oauth:2.0:oob or urn:ietf:wg:oauth:2.0:oob:auto difference is that auto closes browser and returns back to the app. other one, code needs to be copied manually. I prefer to use urn:ietf:wg:oauth:2.0:oob:auto
Regarding code: please follow his github code. Just remove the Client Secret from the Access Token Request.
EDIT: it looks like I was right that even offical sample is not working after UWP version 15063, somebody created an issue on their github
https://github.com/Microsoft/Windows-universal-samples/issues/642

I'm using pretty straightforward code with Google.Apis.Oauth2.v2 Nuget package. Note, that I'm using v.1.25.0.859 of that package. I tried to update to the lastest version (1.37.0.1404), but this surprisingly doesn't work with UWP. At the same time v. 1.25.0.859 works just fine.
So, unless there's a better option, I would recommend to use a bit old, but working version of Nuget package.
This is my code:
credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
new Uri("ms-appx:///Assets/User/Auth/google_client_secrets.json"),
new[] { "profile", "email" },
"me",
CancellationToken.None);
await GoogleWebAuthorizationBroker.ReauthorizeAsync(credential, CancellationToken.None);
Then you can retrieve access token from: credential.Token.AccessToken.

Is there a way to generate an access token from within Identity Server without using the endpoints?

I'm building an identity server deployment (Identity Server 4, hosted in an ASP.NET Core MVC application). As a part of the new user registration process, I need the identity server application to make a request against another API. I'd like to use, basically, the client credential flow to make this request, but instead of having the identity server make an http request against its own endpoint, would it be possible to just programmatically generate the token in C#?
What I'd like to do would be something like this:
public class AccountController : Controller
{
[HttpPost("register")]
public async Task<IActionResult> Register(UserRegistrationModel model)
{
// do stuff like validate model, create user, update database, etc
// generate access token for other API
var client = identityServer4DbContext.Clients.FirstOrDefault(c => c.Id = "myself");
var token = tokenService.CreateAccessToken(client, StandardScopes.All.Concat(scopeForMyOtherApi));
var httpClient = new HttpClient();
httpClient.BaseAddress = new Uri("https://myotherapi/");
var result = await httpClient.GetAsync("resource/info-i-need");
// do something with result.
}
}
I saw that there is an ITokenService in IdentityServer4, but it requires a TokenCreationRequest populated with stuff you only get when you have an http request (for a token) to handle, so it seems that it is only useful to IdentityServer4 itself.
I also recognize that I could use the IdentityModel client to make a request against my own endpoint, but that would involve a bit more configuration that I'd like to avoid - not to mention that it seems like I shouldn't have to do that from within the identity server application itself.

In IdentityServer 3 it was possible to call IssueClientToken() OWIN extension method.
In IdSrv 4, use IdentityServerTools.IssueJwtAsync() and IssueClientJwtAsync().

Persistent authentication across UWP app and Azure Mobile Service

Building on the example here I'm attempting to authenticate an MSA login on the client, and have it authenticate service-side as well. The difference with mine is I'm using the new WebAccount-related API's in Windows 10 instead of the now deprecated Live SDK.
So far I've got:
var provider = await WebAuthenticationCoreManager.FindAccountProviderAsync("https://login.microsoft.com", "consumers");
var request = new WebTokenRequest(provider, "service::wl.basic wl.emails::DELEGATION", "none");
var result = await WebAuthenticationCoreManager.RequestTokenAsync(request);
if (result.ResponseStatus == WebTokenRequestStatus.Success)
{
string token = result.ResponseData[0].Token;
//This calls my custom wrappers around the Live REST API v5 and runs successfully with this token
var acc = await LiveApi.GetLiveAccount(token);
var jtoken = new JObject
{
{"authenticationToken", token}
};
try
{
//Shouldn't this work? but raises a 401
await App.MobileService.LoginAsync(MobileServiceAuthenticationProvider.MicrosoftAccount, jtoken);
//Alternate method? Also raises a 401
//await App.MobileService.LoginWithMicrosoftAccountAsync(token);
}
}
As I mentioned in the comments, all I get are 401s.
As far as I can tell the application is configured correctly in Microsoft Account dev center:
I'm using the client ID and secret from the same app in the Azure portal.
JWT issuing is not restricted.
Redirect URL is of the format https://{appname}.azurewebsites.net/.auth/login/microsoftaccount/callback
Authentication works fine when I switch to use purely server-side authentication. i.e.
await App.MobileService.LoginAsync(MobileServiceAuthenticationProvider.MicrosoftAccount);
Any ideas? Am I missing something? Any help would be appreciated.
UPDATED:
The token I get back in the WebTokenRequestResult is 877 characters long and does not appear to be in the JWT format, with the dot (.) separators and I'm quite certain that this is the issue. The following error gets logged in service when the client calls the code above:
JWT validation failed: IDX10708: 'System.IdentityModel.Tokens.JwtSecurityTokenHandler' cannot read this string: 'EwCQAq1DBAAUGCCXc8wU/zFu9QnLdZXy+...Zz9TbuxCowNxsEPPOvXwE='.
Application: The string needs to be in compact JSON format, which is of the form: '<Base64UrlEncodedHeader>.<Base64UrlEndcodedPayload>.<OPTIONAL, Base64UrlEncodedSignature>'..
Application: 2015-12-07T17:47:09 PID[5740] Information Sending response: 401.71 Unauthorized
What format is the token currently in? Can it be transformed to a JWT?
Still no closer to a solution, so any help is appreciated.

Anyone feel free to correct me, but it looks like RequestTokenAsync gets you an access token which you can't use to login the backend. You need an authentication token for that, and as far as I can see RequestTokenAsync doesn't get you that.
There's some info here about the tokens.

If people end up here searching for a solution for App Service Mobile, the update to MobileService. Then there is now a solution
The code replicated here is:
async Task<string> GetDataAsync()
{
try
{
return await App.MobileService.InvokeApiAsync<string>("values");
}
catch (MobileServiceInvalidOperationException e)
{
if (e.Response.StatusCode != HttpStatusCode.Unauthorized)
{
throw;
}
}
// Calling /.auth/refresh will update the tokens in the token store
// and will also return a new mobile authentication token.
JObject refreshJson = (JObject)await App.MobileService.InvokeApiAsync(
"/.auth/refresh",
HttpMethod.Get,
null);
string newToken = refreshJson["authenticationToken"].Value<string>();
App.MobileService.CurrentUser.MobileServiceAuthenticationToken
= newToken;
return await App.MobileService.InvokeApiAsync<string>("values");
}
Hope it saves somebody time !