AzureFunctions.Authentication 4.0.6

AzureFunctions.Authentication

Provides Azure Functions friendly ASP.NET Core Authentication/Authorization

https://www.nuget.org/packages/AzureFunctions.Authentication

Problem

Azure Function have ability to use Startup.cs class with Dependecy Injection same as ASP.NET Core applications, it is not working as expected out of the box though. The reason for that is default/internal (admin) features of Azure Functions Web Host that are protected with the exact same ASP.NET Core Authentication/Authorization registrations which will be overriden once you register yours and you'll start seeing such problem in Azure Portal . Moreover, predefined Azure Functions AuthorizationLevel policies wont work neither.

Root cause of a problem

Please read this issue to get more context: https://github.com/Azure/azure-functions-host/issues/6805.

Workaround

Register ASP.NET Core Authentication/Authorization in such a way that it is not replacing nor dropping existing configurations/schemas/handlers but extend it instead. This is achieved with "Dynamic schema registration", see example here: https://github.com/aspnet/AuthSamples/tree/master/samples/DynamicSchemes.

Solution

1. Expose custom Authentication/Authorization builder extensions that dont override existing one but registers all needed services
2. Provide custom extension that derives from IExtensionConfigProvider
3. Re-configure already configured Authentication/Authorization by Azure Functions
4. Dynamically inject new authentication schema and handler since Bearer schema is used by Azure Functions with their handler
5. Override IAuthorizationHandlerProvider to merge Azure Functions handlers with application handlers

Example

1. Add/replace existing AddAuthentication/AddAuthorization extension methods to AddFunctionAuthentication/AddFunctionAuthorization
2. Register IAuthorizationHandler handlers
3. Inject all needed services IAuthenticationSchemeProvider/IAuthorizationPolicyProvider/IPolicyEvaluator to authenticate & authorize request inside function. Alternative, encourage you to try nice package out there to simplify this process https://www.nuget.org/packages/DarkLoop.Azure.Functions.Authorize
4. Enjoy 😄

Important

! Do not try to use the "Bearer" scheme name since it is already used by AzureFunction host internally, provide any other name like: "CustomBearer", "B2B", etc.

Code snippet

private static void ConfigureAuthorization(IFunctionsHostBuilder builder)
    {
        var configuration = builder.GetContext().Configuration;

        builder.Services.AddFunctionAuthentication(
            configuration,
            defaultAuthenticationScheme: "CustomBearer");

        builder.Services.AddFunctionAuthorization(
            configuration,
            configureDefaultPolicy: policy => policy.RequireRole("Admin"),
            configureOptions: options =>
            {
                options.AddPolicy(
                    "Organizatiuon",
                    builder => builder
                        .Combine(options.DefaultPolicy)
                        .AddRequirements(new OrganizationRequirement()));
            });

        builder.Services.AddScoped<IAuthorizationHandler, OrganizationAuthorizationHandler>();
    }