Device Code Flow

Note: this feature is not yet available in the public release of MSAL

Principle of Device Code Flow

The application obtains tokens through a two steps process especially designed for devices and operating systems that do not provide a Web browser (See ). Examples of such applications are applications running on iOT, or Command-Line tools (CLI). The idea is that:

1. Whenever a user authentication is required, the app provides a code and asks the user to use another device (such as an internet-connected smartphone) to navigate to a URL (for instance http://microsoft.com/devicelogin), where the user will be prompted to enter the code. That done, the web page will lead the user through a normal authentication experience, including consent prompts and multi factor authentication if necessary.

2. Upon successful authentication, the command-line app will receive the required tokens through a back channel and will use it to perform the web API calls it needs.

How to use it?

PublicClientApplicationcontains the method AcquireTokenWithDeviceCodeAsync. This method contains:

• the scopes to request an access token for
• a string enabling passing extra query parameters. This can be useful for globalization (see below). you can pass string.Empty
• a callback that will receive the DeviceCodeResult
• an optional CancellationToken in case you want the enable the application to cancel the call.

The following sample presents the most current case, with explanations of the kind of exceptions you can get, and their mitigations

static async Task GetATokenForGraph()
{
 // This code should be in your application startup / main function.
 ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

 string authority = "https://login.microsoftonline.com/contoso.com";
 string[] scopes = new string[] { "user.read" };
 PublicClientApplication app = new PublicClientApplication(clientId, authority);

 try
 {
  AuthenticationResult result = await app.AcquireTokenWithDeviceCodeAsync(scopes,
      string.Empty, deviceCodeCallback =>
  {
       // This will print the message on the console which tells the user where to go sign-in using 
       // a separate browser and the code to enter once they sign in.
       // The AcquireTokenWithDeviceCodeAsync() method will poll the server after firing this
       // device code callback to look for the successful login of the user via that browser.
       // This background polling (whose interval and timeout data is also provided as fields in the 
       // deviceCodeCallback class) will occur until:
       // * The user has successfully logged in via browser and entered the proper code
       // * The timeout specified by the server for the lifetime of this code (typically ~15 minutes) has been reached
       // * The developing application calls the Cancel() method on a CancellationToken sent into the method.
       //   If this occurs, an OperationCanceledException will be thrown (see catch below for more details).
       Console.WriteLine(deviceCodeCallback.Message);
  }, CancellationToken.None);

  Console.WriteLine(result.Account.Username);
 }
 catch (MsalServiceException ex)
 {
  // Kind of errors you could have (in ex.Message)

  // AADSTS50059: No tenant-identifying information found in either the request or implied by any provided credentials.
  // Mitigation: as explained in the message from Azure AD, the authoriy needs to be tenanted. you have probably created
  // your public client application with the following authorities:
  // https://login.microsoftonline.com/common or https://login.microsoftonline.com/organizations

  // AADSTS90133: Device Code flow is not supported under /common or /consumers endpoint.
  // Mitigation: as explained in the message from Azure AD, the authority needs to be tenanted

  // AADSTS90002: Tenant <tenantId or domain you used in the authority> not found. This may happen if there are 
  // no active subscriptions for the tenant. Check with your subscription administrator.
  // Mitigation: if you have an active subscription for the tenant this might be that you have a typo in the 
  // tenantId (GUID) or tenant domain name.
 }
 catch (OperationCanceledException ex)
 {
  // If you use a CancellationToken, and call the Cancel() method on it, then this may be triggered
  // to indicate that the operation was cancelled. 
  // See https://docs.microsoft.com/en-us/dotnet/standard/threading/cancellation-in-managed-threads 
  // for more detailed information on how C# supports cancellation in managed threads.
 }
}