I’m linking this draft discussing BFF from oauth perspective.
https://datatracker.ietf.org/doc/html/draft-ietf-oauth-brows...
Keycloak, Angular, and the BFF Pattern
11–20 of 25 posts
Re: Keycloak, Angular, and the BFF Pattern
#12I don’t understand the benefit of adding this intermediate component vs just writing frontend code to interact with the APIs you’d otherwise already be calling. An HTTP server with sessions placed between clients and internal systems makes sense and is standard, but the weird callback-style “remote control” system seems completely unnecessary and inefficient to me. I don’t think client logic being married to some bac…
The article imo misuses the term BFF a bit, but perhaps its meaning has evolved over time. I was at SoundCloud when BFF was being introduced as an important piece of the microservice architecture--this post explains the purpose well[0]. BFFs can enable you to build more general-purpose and domain-specific services with few assumptions as to how they are used and their callers. BFFs then provide a composition layer you can use to, e.g., call one service to get a list of tracks, then call an authorization service w/ the list of track IDs to get geo-specific distribution rules for them, and compose that together in one materialized presentation view for the clients of the BFF.
Eventually I think there was some work to move to GraphQL, which can solve some of the same problems. But GraphQL is a technology, and BFF is more of a pattern. There is a later reflection on that blog that makes this distinction, which I only read today.[1] It makes another observation that I kind of forgot about, because it was hiding right in front of my face as a worker there:
"The defining characteristic of a BFF is that the API used by a client application is part of said application, owned by the same team that owns it, and it is not meant to be used by any other applications or clients."
The ownership model is indeed a big deal. In practice, it helped in many ways to have a sort of intermediate layer between the client applications and the rest of the architecture. For example, in the SoundCloud web application, when you load a page of playlists, only the first 5 tracks in the playlist are visible to the end-user. So the web BFF application had special logic to only partially load all the track metadata past track 5, which had significant impact on scalability and latency, especially when rendering a lot of playlists that had lots of tracks!
[0]: https://philcalcado.com/2015/09/18/the_back_end_for_front_en... [1]: https://philcalcado.com/2019/07/12/some_thoughts_graphql_bff...
Re: Keycloak, Angular, and the BFF Pattern
#13The BFF pattern is just "mostly microservices dedicated to a particular client type". It makes sense when you have drastically different needs between a desktop client and a mobile client (or maybe for a kiosk client or POS interface) Hosting a microservice is cheap, it avoids unnecessary workload on backend data stores, and teams can operate with more autonomy if they don't have to cooperatively update APIs in coord…
> The BFF pattern is just "mostly microservices dedicated to a particular client type". If you’re building dedicated APIs for just one client you’ve come full circle and building a monolith with a bunch of extra step. Why not just build a good old web app at that point?
No, you’re not. You’re building specialised tools for each job.
Also with GQL you can separate by business domain as opposed to consumer for example your customer apps/website could use one gateway, and your back office app could use another.
Also, if you have an old monolith in something like rails, and want to build new functionality in something different whilst migrating parts of it over, it makes sense to have a service oriented architecture. A gateway is a layer that exposes all of the services in a unified and consistent manner.
Re: Keycloak, Angular, and the BFF Pattern
#14I don’t understand the benefit of adding this intermediate component vs just writing frontend code to interact with the APIs you’d otherwise already be calling. An HTTP server with sessions placed between clients and internal systems makes sense and is standard, but the weird callback-style “remote control” system seems completely unnecessary and inefficient to me. I don’t think client logic being married to some bac…
The article imo misuses the term BFF a bit, but perhaps its meaning has evolved over time. I was at SoundCloud when BFF was being introduced as an important piece of the microservice architecture--this post explains the purpose well[0]. BFFs can enable you to build more general-purpose and domain-specific services with few assumptions as to how they are used and their callers. BFFs then provide a composition layer yo…
If you have lots of backend services, building a gateway API (aka BFF) using GraphQL is really nice. Your GQL handles composition of all the resources into exactly what the client needs for something, without having to define a REST endpoint for every single use case.
On the frontend you compose the various schemas that each component needs (fragments) and can in one request pull exactly the data needed with one request to the gateway which will use the minimum required calls to the upstream services, and execute them in the most efficient order.
Re: Keycloak, Angular, and the BFF Pattern
#15I've looked over the code, and some things seem a little odd to me.
The article starts by mentioning how insecure the browser is, apparently even cookies aren't secure. But then the API to talk to the BFF uses.... a server-side session tracked via a client cookie. If the BFF is holding the oauth credentials, then someone could steal the client cookie to make requests to the BFF to do whatever it can do.
It's not impossible to secure the browser from having credentials stolen from inside it, but it can be tricky to ensure that when the browser sends the credential in the request it doesn't leak somehow.
There's some irony as OAuth has DPoP now which can reduce the usefulness of stolen in-flight credentials but that can't be used in this BFF setup because the browser client needs the private key to sign the requests.
Properly securing the browser content on a login page, or the subdomain handling authentication credentials is definitely a challenge, and many don't like having to eliminate/audit any 3rd party JS they include on the page. I can see the appeal of a solution like this, but the trade-off isn't great.
Re: Keycloak, Angular, and the BFF Pattern
#16And I thought it's best friends forever! SCNR
Re: Keycloak, Angular, and the BFF Pattern
#17Formally proving that you can't be authenticated to a service without actually holding some type of authentication token is trivial.
Whatever you replace it with (a short-lived access token, a session cookie, a JWT, or whatever else) becomes the authentication token — if you add other properties (like short expiry), you are mostly trading convenience for security (eg. people will get logged out, or you'll need to implement refresh token dance in your app).
So it's really confusing to me how can someone pretend that there is something you can do on the unsafe client side, because you really can't (sure, there are obvious things you shouldn't do, like keep a plain text password in a cookie or localStorage, but an auth token is pretty much the same thing other than expiry).
Re: Keycloak, Angular, and the BFF Pattern
#18Earlier quoted context omitted.
The article imo misuses the term BFF a bit, but perhaps its meaning has evolved over time. I was at SoundCloud when BFF was being introduced as an important piece of the microservice architecture--this post explains the purpose well[0]. BFFs can enable you to build more general-purpose and domain-specific services with few assumptions as to how they are used and their callers. BFFs then provide a composition layer yo…
If you have lots of backend services, building a gateway API (aka BFF) using GraphQL is really nice. Your GQL handles composition of all the resources into exactly what the client needs for something, without having to define a REST endpoint for every single use case. On the frontend you compose the various schemas that each component needs (fragments) and can in one request pull exactly the data needed with one requ…
> gateway API (aka BFF)
A gateway API is an API that gates other APIs. A BFF is a gateway API used for a particular purpose, clearly identified by the name ("backend for frontend").
Thus, they are not the same: one is a wider term, another is a focused implementation of that concept.
Re: Keycloak, Angular, and the BFF Pattern
#19Earlier quoted context omitted.
If you have lots of backend services, building a gateway API (aka BFF) using GraphQL is really nice. Your GQL handles composition of all the resources into exactly what the client needs for something, without having to define a REST endpoint for every single use case. On the frontend you compose the various schemas that each component needs (fragments) and can in one request pull exactly the data needed with one requ…
> gateway API (aka BFF) A gateway API is an API that gates other APIs. A BFF is a gateway API used for a particular purpose, clearly identified by the name ("backend for frontend"). Thus, they are not the same: one is a wider term, another is a focused implementation of that concept.
And you can have multiple Backeds for Frontends different types of clients (i.e. browser, mobile)
Re: Keycloak, Angular, and the BFF Pattern
#20I’m surprised that the author chose to configure a public OIDC client for this scenario. Part of the benefit of this pattern is that it’s possible to use a confidential client, since the BFF can securely hold the client secret.