Can we use builder.Services.AddAuthentication() in azure Function app

Question

Hi Team,

I am using an azure function which has http triggers as a rest endpoints, i want to use microsoft jwt authentication for the http triggers, can i use some kind of authentication filter like we have in asp.net core web api in azure function app so that i don;t need to repeat my authnetication code every time on the function

can i use the builder.Services.AddAuthentication() at the functionstartup class which will apply to all functions similar to .net core web api

Answer 1

Hi anonymous user,

I haven't implemented this personally, but based on my research it appears that this is something you can do.

There is a blog post here by Jan Hajek where the author provides an example of adding builder.Services.AddAuthentication() in the functionstartup class.

 public class Startup : FunctionsStartup  
    {  
        public override void Configure(IFunctionsHostBuilder builder)  
        {  
            // This is configuration from environment variables, settings.json etc.  
            var configuration = builder.GetContext().Configuration;  
  
            builder.Services.AddAuthentication(sharedOptions =>  
            {  
                sharedOptions.DefaultScheme = "Bearer";  
                sharedOptions.DefaultChallengeScheme = "Bearer";  
            })  
                .AddMicrosoftIdentityWebApi(configuration)  
                    .EnableTokenAcquisitionToCallDownstreamApi()  
                    .AddInMemoryTokenCaches();  
        }  
    }  
}  

Based on some previous Github issues, it looks like support for this didn't exist before but was since added.

https://github.com/Azure/azure-functions-host/issues/6805
https://github.com/Azure/azure-functions-host/issues/4485
https://github.com/Azure/azure-functions-host/issues/5886

There is also a nuget package that was published for handling this scenario. https://www.nuget.org/packages/AzureFunctions.Authentication/

Let me know if you have any issues with the implementation, though.

-

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Answer 2

You can use DarkLoop.Azure.Functions.Authorization.Isolated for Isolated mode with ASP.NET Core integration and DarkLoop.Azure.Functions.Authorization.InProcess for In-Process mode.

This has the benefit of allowing you to have fine grained authorization rules (policies) for all functions in your class or on individual functions, using the same [Authorize] attribute you use in ASP.NET Core controllers.

You can read more here.