Implementation of Azure Active Directory authentication with cross-platform development

Alexander Meijers | Lead Architect | April 21st, 2016

Why? – ADALXamarin – StepsDemo - Wrap up!

Why?• Securing your business applications• Access resources like Office 365, Yammer and Microsoft

Graph• You don’t need to have extensive

knowledge of authentication• Focus on building your app

Active Directory Authentication Library• Enables developers to easily authenticate users against the

cloud or on-premises AD• It handles mostly all complexity of the authentication• Returns access tokens to execute secure API calls• Many features like

• Handles the login screen (including your organization page)• Asynchronous support• Configurable token cache for storing access and refresh tokens• Automatic token refresh when access token expires

• Available on a variety of platforms like .NET, JavaScript, OSX, iOS, Android and node.js

Xamarin [‘zæmərɪn] • Allows developers using Visual Studio and C# shared

codebase to create cross-platform applications• Support of platforms as iOS, Android, Windows 8 and

Windows 10• Acquired by Microsoft on February 24th 2016• Use Portable Class Libraries or Shared Asset Projects to

write code once for all platforms• Possible to write platform specific code

Steps• Register your application in Azure AD• Setup Xamarin project• Implement ADAL• Create a login page• Implement code for

accessing Microsoft Groups

Register your application in Azure AD• Specify name, type of

application and redirect URL(s)• Select the permissions to other

applications• Client ID is generated

• Client ID and Redirect URL combination is used during authentication

Setup Xamarin project• Create a Xamarin project

• Since February 2016 it is possible to create Universal Windows app

• Use Xamarin.Forms Portable project• Remove any not used projects

• Install the NuGet package Microsoft.IndentityModel.Clients.ActiveDirectory• V3.9.302111717-alpha

Authenticate with ADALAuthenticationContext ac = new AuthenticationContext(string authority);• authority URL of the authority• Calling https://login.microsoftonline.com/common without the tenant id will allow your app to be multi-tenant

AuthenticationResult authResult = AcquireTokenAsync(string resource, string clientId, Uri redirectUri, IPlatformParameters parameters));• resource the URL of the requested resource• clientId and redirectUri Azure AD registration• parameters Platform specific parameters • Attempts to return a token for the requested resource

based on caching or refreshing old tokens• If necessary an Azure AD sign page is shown

to acquire a request token

PlatformParametersPlatform Parameter(s) Value

iOS Reference to a UIViewController

UIApplication.SharedApplication.KeyWindow.RootViewController

Android Reference to an Activity

(Activity)Forms.Context

Remark: You will need to override the OnActivityResult method in MainActivity.cs and call the WebAuthenticationBrokerContinuationHelper class.

Windows Phone No parameters N/A

Windows 10 (Universal)

PromptBehavior, OrganizationOnly

PromptBehavior.Auto, false

Implement ADAL• ADALAuthentication class• Contains the logic for authentication with ADAL

• IADALAuthenticator interface• Implement the interface per platform to provide the platform

specific PlatformParameters

Implement the IADALInterface• Implement the interface for iOS

• Implement the interface for Universal Windows

Create a login page• Use a Xaml forms content page• Place a (login) button on the page• Use DependencyService.Get<>(…) method

to retrieve an instance of that interfacewithin the current platform• Authenticate and request

access to Microsoft Graph using the resource URL and the information you got from your Azure AD registration

Implement code for accessing Microsoft Groups• Use the access token you got from your

authentication call• Define a request based on

• Get= https://graph.microsoft.com/v1.0/groups• Application/json• Bearer = access token

• Use NuGet package NewtonSoft.json

Demo time“Let’s hope the demo gods are with us”

Wrap up!• ADAL allows you to easily implement authentication in

your cross-platform application• Be aware of your implementation when using a PCL.

Platform specific code is not allowed in your PCL• PlatformParameters differ per platform

• For a complete walkthrough check my post http://www.appzinside.com/2016/02/22/implement-adal-for-cross-platform-xamarin-applications/