Skip to main content

Improve the security of your GraphQL API’s - Part 3–Authorization

As a GraphQL API gives you a lot of extra power and possibilities, it also introduces some new attack vectors. Nothing prevents the user of your (web) application to open the developer console and start creating and sending other queries to your GraphQL backend. By using the authentication token already available, he/she can call your API. So without further mitigations a user can create and run any query he/she can think of.

Luckily there are multiple ways to control this attack vector. I already talked about

Today I will focus on authorization.

Remark: I expect that you already have a kind of authentication built into your GraphQL API. So I'll ignore that part.

Doing an authorization check for a REST API is easy. As every REST call maps to a specific invocation requesting specific data, you have all the information you need to check if a user is allowed to fetch a specific set of data.

In ASP.NET Core this translates to the action level of a specific controller (or a specific endpoint if you are using minimal api's):

When using GraphQL you have a lot more flexibility at the query level so you don't know exactly what data will be fetched. Especially when you have created a rich graph, a lot of possible paths exist to get to a specific set of data.

So there is no single place where you can validate the authorization for the query the user wants to execute.

Authorization at the resolver level

A first option is to define authorization at the resolver level. In that case we use individual field resolvers to check user roles and make decisions as to what to return for each user.

HotChocolate builds further on the ASP.NET Core authorization middleware. It introduces an @authorize directive that can be applied to fields and types to denote that they require authorization.

If we do not specify any arguments to the @authorize directive, it will only enforce that the requestor is authenticated. But it is also possible to specify one or more roles or an an ASP.NET Core authorization policy:

Authorization at the business logic layer level

Doing authorization at the resolver level is fine for simple use cases. Thanks to the support for ASP.NET Core Authorization policies we can avoid duplication and decouple the authorization rules from the resolvers.

However you can go one step further and handle authorization at the business layer level. This helps to keep your resolvers thin, and put all of your business logic (including authorization) in one place.

Popular posts from this blog

.NET 8–Keyed/Named Services

A feature that a lot of IoC container libraries support but that was missing in the default DI container provided by Microsoft is the support for Keyed or Named Services. This feature allows you to register the same type multiple times using different names, allowing you to resolve a specific instance based on the circumstances. Although there is some controversy if supporting this feature is a good idea or not, it certainly can be handy. To support this feature a new interface IKeyedServiceProvider got introduced in .NET 8 providing 2 new methods on our ServiceProvider instance: object? GetKeyedService(Type serviceType, object? serviceKey); object GetRequiredKeyedService(Type serviceType, object? serviceKey); To use it, we need to register our service using one of the new extension methods: Resolving the service can be done either through the FromKeyedServices attribute: or by injecting the IKeyedServiceProvider interface and calling the GetRequiredKeyedServic...

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.

Kubernetes–Limit your environmental impact

Reducing the carbon footprint and CO2 emission of our (cloud) workloads, is a responsibility of all of us. If you are running a Kubernetes cluster, have a look at Kube-Green . kube-green is a simple Kubernetes operator that automatically shuts down (some of) your pods when you don't need them. A single pod produces about 11 Kg CO2eq per year( here the calculation). Reason enough to give it a try! Installing kube-green in your cluster The easiest way to install the operator in your cluster is through kubectl. We first need to install a cert-manager: kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.14.5/cert-manager.yaml Remark: Wait a minute before you continue as it can take some time before the cert-manager is up & running inside your cluster. Now we can install the kube-green operator: kubectl apply -f https://github.com/kube-green/kube-green/releases/latest/download/kube-green.yaml Now in the namespace where we want t...