alt Hacker News> Necessary qualifier: for browser-based user sessions.
> Plenty of good uses for JWTs for service-to-service communication.
This is the sensible conclusion right there. I agree JWTs are the wrong tool for the use case of user sessions in the browser.
To give some more arguments:
All the signature and encryption stuff in JWTs is complex. While common JWT libraries have now mostly got their stuff together, this has not always been the case. There were plenty of libraries accepting the "none" algorithm [1] or allowing attackers to forge tokens by using a public key as a shared secret [2]. This is the direct result of the complexity criticized in the linked blog post.
JWTs also cannot do some stuff you want for user sessions. You can't invalidate them without keeping a revocation list somewhere. But if you have to check an identifier for revocation on every request you could just use an opaque session ID and look that up on every request instead! Sure, you can use short-lived tokens and refresh them all the time, but why bother with that for a typical application that has to keep some state anyway?
All that being said, I wholeheartedly agree that there are use cases in distributed systems and machine-to-machine communication where signed tokens can be useful. Just please don't confuse the two cases.
[1] https://nvd.nist.gov/vuln/detail/cve-2022-23540
[2] https://nvd.nist.gov/vuln/detail/CVE-2024-54150 (just a random example from googling, I don't know what library made this one infamous)
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The design I've landed over the years is to use both. The cookie is a session token and that's where you handle refresh tokens. Then there's an endpoint where you can mint a short-lived tenant-sepecific JWT. This holds the scopes & tenant id. The session token only lets you access the web assets & mint JWT tokens.
> While common JWT libraries have now mostly got their stuff together, this has not always been the case. There were plenty of libraries accepting the "none" algorithm [1] or allowing attackers to forge tokens by using a public key as a shared secret [2]. This is the direct result of the complexity criticized in the linked blog post.
I'm a bit surprised at this. These are extremely simple to solve - the first time I ever did a JWT-reading implementation I specified the right defaults, which are very simple, even for a mid-level backend person I would say, and they haven't needed changing in 8 years or whatever it's been. It really isn't very complex.
A revocation list defeats the purpose of JWTs. If you find yourself needing one, JWTs were probably the wrong choice to begin with.
Come on, it’s not like the two are even within the same magnitude or three
“But if you have to check an identifier for revocation on every request you could just use an opaque session ID and look that up on every request instead!”
If you don't understand conceptually how to verify a signature with a public key the very first thing you should do is get that working and then work from there. It's completely unacceptable to ship without this.
Stateless JWT revocation: https://blog.nellcorp.com/new-aproach-to-jwt-revocation/
> if you have to check an identifier for revocation on every request you could just use an opaque session ID and look that up on every request instead!
One reason could be the size. A revocation list only needs to keep session IDs of recently logged-out sessions, for which the token's TTL hasn't yet expired. It may be a much smaller list than a list of every active session.
Also, a JWT (or a Macaroon, etc) can store a large amount of details about the session in a cryptographically secure, unforgeable way. This rids you of the necessity to store all that in your active session database, again cutting the size.