Hacker News Reader

Comment by tptacek | Hacker News Reader

Apart from the JWT thing (please avoid JWT if possible), I agree with this comment 100%. Things I'd like to see in a Go web app example site:

1. Examples of using context values to pass things selectively to handlers.

2. An arbitrary trivial middleware example, like a specialized request logger, just to demonstrate Go middleware.

3. A Rails/Django-style session token done in the same middleware style.

4. Giving requests a notion of "current user".

5. Simplified user-visible vs. developer-visible error handling.

It's too much to ask for ORM-style database query examples, I know, but that too would be nice.

View on HN

> please avoid JWT if possible

That's why this Category #2 stuff is so important. People can agree without much controversy what "best practice" is for the Category #1 stuff, but at the next level it's just blog posts and discussion thread comments passionately arguing opposite statements.

I'm curious... if not JWT, then how would you approach the problem of authenticated sessions without server-side state? (assuming you aren't rejecting the overall premise entirely)

If you track authentication with a server-side session, then you have to either:

(1) Setup a backing store for your session state (e.g. Redis, relational database, proprietary app server solution, etc). Share the backing store across all instance nodes in your server-side cluster. Tune the inevitable performance issues and point-of-failure risks, and expect the worst if you're using a proprietary thing (they're all terrible).

(2) Use a hardware solution. Have the load balancer always route a given client's requests to the same server-side instance. Deal with failover scenarios when that instance goes down, have to drain traffic every time you want to do a deployment, etc.

JWT's ugly, but no uglier than either of those! Always on the lookout for other recipes...

The choice isn't "JWT" or "server-side sessions". It's client-side sessions versus server-side sessions, and JWT is just one (bad) option among many for client-side sessions.

'lvh and I are working on a piece about this for our clients, so I want to be careful not to write a crappy version of it in an HN comment first. But I think you'll find something close to a consensus on JWT/JWS/JWE/JWK among crypto engineers of our ilk.

I guess I'd close by saying: if you were writing a Rails app, it's almost certainly the case that you'd be better off just using ActiveSupport::MessageEncryptor to create an encrypted token than you would be building a shambolic equivalent of MessageEncryptor in JWT.

You didn't actually answer the why not JWT question there.

We're pretty heavily invested with using JWT wrapped inside OpenID Connect, and given you garner a lot of respect on such topics, I'd really be appreciate if you cited a source or gave us a reason. Anything would be better rather than just appealing to a vague consensus.

Why would my advice change because you're building something that uses JWT?

This thread, though, is about Go web applications. So I guess apropos this thread, I'd just say we probably don't need an example of how to use JWTs in Go. But session management, yes!

> Why would my advice change because you're building something that uses JWT?

I never said it would, I was simply stating my interest in your opinion on the topic. It seems a shame that you don't seem to be willing to expand though.

Is there anything wrong with encrypted cookies for client-side sessions?

Nope. If there was, virtually every Rails app would be doomed.

There's a sort of intuitive insecurity quotient for things that goes something like C/W_s where C is complexity and W_s is the number of people in the world who would be screwed if something was totally broken.

Encrypted session cookies have, as a design, relatively modest C and very, very high W_s.

JWT has extraordinarily high C and, at present, modest W_s (relative to session cookies).

(They also have a bunch of design flaws that amplify their complexity).

Yep. I was brought on to a project where the JWT secret was a 6 letter band name. It's the hotness newness in the JS community and there's a lot of tutorials out there that show how easy it is to set up without explaining the risks/trade-offs.

>"It's client-side sessions versus server-side sessions, and JWT is just one (bad) option among many for client-side sessions."

What you recommend then instead of JWT in a non-Rails environment?

The equivalent of ActiveSupport::MessageEncryptor. Virtually every platform has something. Go has crypto/cipher.AEAD. Python has fernet. Most platforms have access to Nacl's "secretbox". All of these things are simpler, safer, and just as effective as JWT.

And even that presumes you want to actually encrypt data to the client: many (most) JWT users are just signing tokens, which makes an alternative to JWTs even simpler.

token = data:expiry:hmac(key, data+expiry) is super simple in most languages, is robust, and nacl provides useful helpers for doing this as well.

Can you expand on JWT thing? Why should it be avoided?

Why avoid JWT? Has there been some new development regarding it that makes it unsuitable for auth? I just started using it in a new app...

That recommendation is due to JWT not taking revocation into account at all, if I remember tptacek's stance correctly. Personally, I agree.

This has been discussed on HN before and I remember talk about using "fancy" stuff like Bloom filters but as far as I know, no library offers anything for this out of the box and this is not something you want to roll yourself.

Lack of revocation is actually pretty far down my list of reasons, but it's a very common complaint other people have about JWT that I also agree with.

Can you remember where this was discussed? I was under the impression that JWT was becoming a new standard for many people. I guess that's not mutually exclusive to it being bad, but I would like to read more.

JWT is popular with application developers. I think that's because it's cross-stack. Rails developers already have solutions for 95% of the problems JWT solves in the real world. So do Django developers, and so do Go developers, and so do PHP developers. But there's no lingua franca for this problem.

Developers would like there to be one. Unfortunately, they've chosen a terrible standard --- just really, really bad --- to run with. You are better off doing something by hand than using JWT. If you're at all familiar with my ouvre on HN: that's how bad JWT is. I think you might seriously be better off DIY.

This is at least one discussion:

https://news.ycombinator.com/item?id=11895440

The recommendation seems to be using an encrypted cookie, with some format other than JWT.

Which is fine and well. But how does that take revocation into account?

You can store a token on the client side, in ANY format. The problem remains that you're either storing some server-side state about that token, or you aren't. If you are, then you're not really using client-side sessions. If you aren't, then you still don't have a good way to revoke. Because you can't really control the client-side after you've issued a token, and you can't revoke it from the server-side without state.

I'm sure there are good arguments to be made against the use of JWT. But their simply aren't any to be found in this thread, and no alternative client-side proposal that solves the revocation problem.

Revocation was something I did consider, but I am just using a users password hash as the token key, that way when the user changes his password, all previous tokens are invalidated.

Sort of funny, that is more or less exactly the stuff we needed for our internal candidate assessment app built on go/http. It just makes sense and is stuff you will want in any app, even a mostly CRUD one.

FWIW, gophish is a very clean app built using Gorilla packages that implements these patterns in a comprehensible way and I found it very helpful as I was implementing things.

Your first request is tricky because it can lead to issues down the road if done poorly, so it is hard to just give a quick example of it. I wrote about this subject recently (see https://www.calhoun.io/pitfalls-of-context-values-and-how-to... ) and there is a lot of info to cover. That said I could see value in doing an example and referencing a more in depth overview from the example.

Once you cover (1) most of the others fall into line. There is little reason to use context values outside of MW from my experience.

Re (3) - can you provide a link or example of what you mean?

(5) - again, can you elaborate? Are you referring to error types? Or just how the errors are rendered?

I ask all these questions because I write a lot about Go and I am interested in trying to make examples of these available, but I want to understand what you are asking for first.

Could you be a bit clearer about the "issues down the road" we're concerned about with overuse of context, or with use of context for non-request-scoped dependencies?

The end of your article advocates a little bit for just accepting code reuse, and the getter/setter/subfunction thing comes perilously close to GoF Java style for my taste. Further: I have seen, routinely, on pretty much every project I've worked on, serious production faults from errors and omissions in duplicated code. I'm not sure I've seen equivalently serious production faults (really: any faults) in overuse of things like "context".

Totally agree. It's because of stuff like this that I find Go to be fairly tedious for full stack web. JSON microservice that's blazing fast is great. High concurrency workload, great.

Full stack website that reuses template parts with live data, manages sessions and logins, images, JavaScript and CSS...not so much.

Just curious, what were the worst gaps in functionality and have you looked at it recently? I'm pretty happy with Go for full stack web apps, but it did take a little while to get up to speed and a few years ago there were fewer solutions for common problems available. A few areas where it required some more work:

Authentication - there are a few good examples out there, I think gorilla secure cookie is good, CSRF protection too.

Authorisation - had to write my own version of the ruby lib cancan, am now happy with the solution

Images - stdlib is pretty good but it'd be nice if it handled resizing images and exif orientation tags.

Javascript and CSS - there are some ports of minifiers in go so an asset pipeline is pretty easy.

ORM - I use a query builder and use the map columns->fields in code, not keen on the orms using reflection and/or struct tags to do so. This doesn't have to be complex though.

Migrations - there are a few libraries out there now, so this isn't bad, I prefer sql migrations.

Templates - love the context-sensitive escaping, would be nice if it handled layout/partial but this is doable with some tweaks.

Forms - generation of views with text/template is pretty handy to handle things like CRUD forms for models.

This is where frameworks are useful - they present best-practices for the above details and more that you have to handle in a full-scale webapp.

I think those are the areas I'd like to see more tutorials on for beginners coming to Go, but there are solutions out there nowadays (far more than even a few years ago).Most of the things you mention are not in the std library so I guess people feel a little lost when they first arrive in Go land, but there are a few libraries out there like gorilla which cover most of this stuff or you can write your own, and once you have it's a really pleasant language to write traditional server-side apps with.

So with the above caveats I'm really happy with it for full stack web development.

I'd love to see some blog posts about this. The lack of any good resources on full-stack web frameworks is what has kept me from really diving deep into Go. I still believe (pretty strongly) in traditional, server-rendered, low JS overhead websites / app.

My biggest issue was with server rendered applications. I think it's a good fit for SPA's where each piece is rendered to the browser independently.

Just as an example, my go to test for most programming languages is to rebuild my personal site with it (http://brightball.com/). Just provides me with a good exercise in running through a simple project that I've done in multiple languages and provides a good basis for comparison without getting too fancy.

If you'll look at the page layout, you'll see the main content area with a list of articles, some sidebar elements that are loaded from the database and a list of primary tags in the footer (also pulled from the database).

The biggest pain point was the reusable elements (sidebar and footer) with the template system. In most other template systems it's pretty trivial to write parts that have code attached to them and tell a layout to call those pieces with some arguments. With Go, that was a bit of a pain requiring all of the data that that would appear on the page to be retrieved before starting the rendering process. That led to a lot of repetition to pull in that data on every path to the layout.

So the layout/partial system would be my biggest pain point. My first instinct was to go and reach for a framework but so much stuff that I read on Go boards gave the impression that the community seemed to have a very negative impression there.

Additionally, there wasn't a clear winner among frameworks which made me hesitate. That's a problem you see in languages that have so much stuff for the web built in like PHP and Javascript. It becomes so easy to do-it-yourself on the framework front that there are a million different flavors and no clear path.

With Ruby, Python, Elixir, Groovy, etc there are clear and dominant frameworks for the language. If you learn this language, you should know framework "X". When there isn't that clear winner, it's hard to justify investing in developing around it.

To try to get around that issue and the sense that with Go you were supposed to sort of assemble your own parts, not commit to a framework, etc I tried https://github.com/runemadsen/ok-go since it's basically a framework of assembled and replaceable parts.

After a while I just gave up on it and started looking at porting to Hugo before I found out about Elixir and gave it a shot. Ultimately, that was exactly what I was looking for (http://brightball.com/articles/insanity-with-elixir-phoenix-...).

Most of the issues I describe are non-issues if Go is backing a React/Angular app instead. I just found it to be a huge pain for entirely server side applications.

My biggest issue was with server rendered applications.

Thanks, this is what I'm talking about too (server-side web apps), I've found it a good fit, but do understand the initial difficulties with html/template - it is not very user friendly and was not designed for the sort of layout/partial arrangement that almost every web framework uses, however it can be used in that way with a little tweaking. That data has to be retrieved somehow though for the sidebar say, so I don't mind having to pass it in explicitly - it at least makes all the work being done explicit.

Agreed on the frameworks issue, frankly I find the hostility to frameworks on places like /r/golang tiresome and cultish - there is the kernel of a good idea in rejecting frameworks (they can after all straightjacket your code and invert control), but there can be many benefits to them and they provide essential pointers for those new to the language. I think for Go to grow it does need people to start to coalesce around solutions so that beginners don't have to reinvent rails again for every app or (worse IMO) start using JS for frontend and Go for backend - then you have two problems (or 400,000 if you use npm). I prefer server-side only and am happy with Go for that.

Elixir is on my list to check out, thanks for the link.

The templating is fast and safe but a pain to use. For example, an HTML Select needs a 3-value list: id,text,selected bool. You can't evaluate a comparison (if...) or call a function in the template. It's unpleasant.

You can call functions and methods in templates, and you can use if else, they actually have all the tools you need to do things like provide helper functions and produce a full html select with something like:

    {{ select "Order" "form_name" .value .options }}

Granted those helper functions don't exist in the base templates, but the tools are there to build them.

Reply on news.ycombinator.com