Azure Mobile App Authentication using Xamarin

Question

I read these two articles 1. here and 2. here to find out what is best way to perform authentication against an Azure Mobile App when the API on the server is using Claims based custom authorization and the Xamarin client calling it is using the MobileServiceClient framework. I am unable to finalize which of the two examples in those links is the better way to go.

In the first link there doesn't seem to be any dependency on platform specific code like it has in the second link, which means I don't need to write any code in the Driod or IOS or Windows projects and can get away with doing everything in a class library itself.(Am I right here?) Also, the first link seems to not require any provider like the second link does because I am invoking a direct service call to a Url. The second link on the other hand only seems to support Facebook, Twitter, MicrosoftAccount, Google and WindowsAzureActiveDirectory . The mandatory MobileServiceAuthenticationProvider parameter doesn't seem to provide for Custom Authentication against a sql server based User table. I am not sure about this part and cant find documentation that says otherwise.

If LoginAsync doesn't provide for Custom Authentication then its clear that I will need to follow the InvokeApiAsync route. If it does provide it then the question is: should I write platform specific(Droid/IOS/windows) code in each target project like in the second link or should I handle all the service calls in a class library as can be done in the example shown in the first link? In other words should I go with LoginAsync or InvokeApiAsync ? Which of the two is the recommended way?

Answer 1

The first article shows off custom authentication, as you intimated. The second article shows off App Service Authentication, which has a known list. If you need to do a custom username/password, then go with the former. If you need to go with social auth or enterprise auth, then go with the latter.

My general recommendation is don't require the user to create yet another username unless you have to - which means social authentication for consumer apps and enterprise authentication via AAD for enterprise apps.

My other recommendation is to always use the client SDK for doing the authentication part. This allows you to follow the very latest practices from the provider (facebook, twitter, etc.) in respect to security, refresh tokens and other authentication requirements. Once you have the provider token, it's easy to swap it for an Azure Mobile token by using LoginAsync() with a token. See the Azure Documentation for information on this.

In all cases, you are going to need platform specific code - that means using the DependencyService (as in the second example) to execute your login code. I generally create a singleton class that wraps the MobileServiceClient in the PCL. Then create an ILoginProvider interface which has LoginAsync/LogoutAsync code in it to handle the platform dependency code. My singleton class then calls the DependencyService to get the code. You can find an example in my GitHub Repository that covers iOS, Android and UWP.