DarkLoop.Azure.Functions.Authorization.Isolated 4.1.0-preview-240521-1

functions-authorization-isolated

Bringing AuthorizeAttribute Behavior to Azure Functions v4 in Isolated mode.

It hooks into .NET Core dependency injection container to enable authentication and authorization in the same way ASP.NET Core does.

Using the package

Installing the package

dotnet add package DarkLoop.Azure.Functions.Authorization.Isolated

Setting up authentication and authorization

The goal is to utilize the same authentication framework provided for ASP.NET Core

using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureFunctionsWebAppliction(builder =>
    {
        // Explicitly adding the extension middleware because
        // registering middleware when extension is loaded does not
        // place the middleware in the pipeline where required request
        // information is available.
        builder.UseFunctionsAuthorization();
    })
    .ConfigureServices(services =>
    {
        services
            .AddFunctionsAuthentication(JwtBearerDefaults.AuthenticationScheme)
            // This is important as Bearer scheme is used by the platform
            .AddJwtFunctionsBearer(options =>
            {
                options.Authority = "https://login.microsoftonline.com/your-tenant-id";
                options.Audience = "your-app-id-uri";
                ...
            });

        services.AddFunctionsAuthorization(options =>
        {
            options.AddPolicy("OnlyAdmins", policy => policy.RequireRole("Admin"));
        });

        // Add other services
    })
    .Build();

host.Run();

Starting with version 4.1.0, the default Bearer scheme is not supported by this framework. You can use a custom scheme or make use of AddJwtFunctionsBearer(Action<JwtBearerOptions>) as shown above. This one adds the "FunctionsBearer" scheme. Clients still submit token for Authorization header in the format: Bearer <token>.

Notice the call to UseFunctionsAuthorization in the ConfigureFunctionsWebAppliction method. This is required to ensure that the middleware is placed in the pipeline where required function information is available.`

Using the attribute

And now lets use FunctionAuthorizeAttribute the same way we use AuthorizeAttribute in our ASP.NET Core applications.

[FunctionAuthorize]
public class Functions
{
  [FunctionName("get-record")]
  public async Task<IActionResult> GetRecord(
    [HttpTrigger("get")] HttpRequest req, ILogger log)
  {
    var user = req.HttpContext.User;
    var record = GetUserData(user.Identity.Name);
    return new OkObjectResult(record);
  }

  [Authorize(Policy = "OnlyAdmins")]
  [FunctionName("get-all-records")]
  public async Task<IActionResult> GetAllRecords(
    [HttpTrigger("get")] HttpRequest req, ILogger log)
  {
    var records = GetAllData();
    return new OkObjectResult(records);
  }
}

Something really nice to notice is that for Functions in Isolated mode, the HttpTriggerAttribute default AuthenticationLevel is Anonymous, playing really well with the attribute.<br/> Also notice how the second function uses the AuthorizeAttribute attribute to apply a policy to the function. FunctionAuthorizeAttribute was left as part of the framework only to make it easier to migrate from In-Proc to Isolated, but they can be used interchangeably.