Custom Token Validation Provider for Azure Functions

A custom access token validation provider for Azure Functions via Dependency Injection. Inspired by https://github.com/BenMorris/FunctionsCustomSercuity with extra implementation for Firebase Auth.

NuGet

Custom Token Validator

Add in your Function's Startup.cs

using Microsoft.Azure.Functions.Extensions.DependencyInjection;
using Microsoft.Azure.Functions.Extensions.JwtCustomHandler;
using Microsoft.Azure.Functions.Extensions.JwtCustomHandler.Interface;
using Microsoft.Extensions.DependencyInjection;
using System;

[assembly: FunctionsStartup(typeof(ExampleFunction.Startup))]
namespace ExampleFunction
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            /// Custom Token Validator
            builder.Services.AddSingleton<IClaimsTokenProvider, CustomTokenProvider>(provider => new CustomTokenProvider(
                issuer: Environment.GetEnvironmentVariable("issuer"),
                audience: Environment.GetEnvironmentVariable("audience"),
                issuerSigningKey: Environment.GetEnvironmentVariable("issuerSigningKey")));
        }
    }
}

Inside your Function Class

public class ExamplesFunction
{
    private readonly IClaimsTokenProvider IClaimsTokenProvider;
    public ExamplesFunction(IClaimsTokenProvider provider) => IClaimsTokenProvider = provider;

    [FunctionName("Example_Function")]
    public IActionResult HelloWorldFunction([HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = null)] HttpRequest req)
    {
        try
        {
            if (req.Headers is null)
                throw new NullReferenceException();
            else if (req.Body is null)
                throw new NullReferenceException();

            AccessTokenResult _tokenResult = IClaimsTokenProvider.ValidateToken(req);
            if (_tokenResult.Status != AccessTokenStatus.Valid)
                return new UnauthorizedResult();

            return new OkObjectResult($"Hello there, ${req.Query["name"]}");
        }
        catch (Exception)
        { return new BadRequestObjectResult("Web server encountered an error."); }
    }
}

or you can use the

Firebase Auth Id Token Validator

Add in your Function's Startup.cs

using Microsoft.Azure.Functions.Extensions.DependencyInjection;
using Microsoft.Azure.Functions.Extensions.JwtCustomHandler;
using Microsoft.Azure.Functions.Extensions.JwtCustomHandler.Interface;
using Microsoft.Extensions.DependencyInjection;
using System;

[assembly: FunctionsStartup(typeof(ExampleFunction.Startup))]
namespace ExampleFunction
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            /// Firebase Id Token Validator
            builder.Services.AddSingleton<IFirebaseTokenProvider, CustomTokenProvider>(provider => new CustomTokenProvider(
                issuer: "https://securetoken.google.com/<your-firebase-app-name>",
                audience: "<your-firebase-app-name>"));
        }
    }
}

Inside your Function Class

public class ExamplesFunction
{
    private readonly IFirebaseTokenProvider IFirebaseTokenProvider;
    public ExamplesFunction(IFirebaseTokenProvider provider) => IFirebaseTokenProvider = provider;

    [FunctionName("Example_Function")]
    public async Task<IActionResult> HelloWorldFunction(
        [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = null)] HttpRequest req)
    {
        try
        {
            if (req.Headers is null)
                throw new NullReferenceException();
            else if (req.Body is null)
                throw new NullReferenceException();

            AccessTokenResult _tokenResult = await IFirebaseTokenProvider.ValidateToken(req);
            if (_tokenResult.Status != AccessTokenStatus.Valid)
                return new UnauthorizedResult();

            return new OkObjectResult($"Hello there, ${req.Query["name"]}");
        }
        catch (Exception)
        { return new BadRequestObjectResult("Web server encountered an error."); }
    }
}

Contributors

• kuromukira

Install the following to get started

IDE

1. Visual Studio Code
2. Visual Studio Community

Exntesions

1. C# Language Extension for VSCode

Frameworks

1. .NET

Do you want to contribute? Send me an email or DM me in twitter.