2019
[deleted]
Stop Using JWTs
31–40 of 335 posts
Re: Stop Using JWTs
#32A whole lot of nonsense from a web guy.
Please, keep using JWTs, they do their job well: giving you an access or ID token that you can pass between applications and trust based on cryptographic signatures from an identity provider.
Re: Stop Using JWTs
#33Security doesn't start or end with JWTs.
A user wants to access a read-only resource with an invalid JWT? Envoy bounces it without passing the request through to the backend. Valid JWT? Let the request through without having to look up any session information. No DB, no cache, no session server hit. Fast.
A user wants to change a password, email address, or add an authenticator? First, require a password, second, require a second factor. If all of that checks out, look for the JWT access token in a revocation list that is only accessed during sensitive, infrequent, requests like these. If the token has been revoked, 403.
Tokens are dropped from the revocation list once the original access token's TTL has passed. Which should be low. I use 5 minutes. Most sessions on my site last 4-10 minutes.
Worst case scenario, a malicious user is able to access certain read-only resources for a few minutes.
Re: Stop Using JWTs
#34Earlier quoted context omitted.
>> You are essentially powerless, and cannot 'kill' a session without building complex (and stateful!) infrastructure to explicitly detect and reject them, defeating the entire point of using stateless JWT tokens to begin with. > I'm not sure that this is entirely true. You can be sure it is not true, because it is utter BS. JWTs have an "iat" timestamp field (issued at) and in the described case that an attacker has…
> your validation logic simply should refuse any token before $NOW. Well, this approach throws out a lot of babies with the bathwater. You invalidate tons of legitimate tokens along with the one that you wanted to invalidate and get a thundering herd [0] of clients wishing to re-authenticate. This is probably not good in case of a really high load. And if you don't have a really high load, then there is no good reaso…
I edited my comment after I posted it to clearify you do this on a per-identity basis. I.e. every user/identity has a minimum_issued_at field. A user can "sign out from all devices", and that will simply update minimum_issued_at with $NOW.
You are not throwing out a lot of babies with the bathwater if you would do it in a case of a known attack. You would invalidate ALL tokens of a user, which is a sane default especially since usually you wouldn't be able to rule out what other tokens were compromised. And yes, if it later turned out ALL your users and all their token were possibly compromised because you had some kind of security flaw, setting a global minimum_issued_at is exactly what you would do after you fixed the flaw. And yes, that means all your users must reauthenticate.
Re: Stop Using JWTs
#35Necessary qualifier: for browser-based user sessions. Plenty of good uses for JWTs for service-to-service communication. edit: I read some of the linked stuff, e.g. https://paragonie.com/blog/2017/03/jwt-json-web-tokens-is-ba... . Please, if JWTs are such a horrifically insecure standard, go ahead and publish your means for hacking AWS STS's AssumeRoleWithWebIdentity , or don't publish and just exploit it by launchin…
I agree with your first part but your edit is a logic fallacy. I don't need to be able to hack something to say that it is insecure.
For example: I don't know how to exploit SAML but I know it is a terrible standard dur to making all of the XML parser an attack surface. I am not a security researcher so I dont know how to find exploits in XML parsers but I know having a huge attack surface is bad.
Re: Stop Using JWTs
#36Necessary qualifier: for browser-based user sessions. Plenty of good uses for JWTs for service-to-service communication. edit: I read some of the linked stuff, e.g. https://paragonie.com/blog/2017/03/jwt-json-web-tokens-is-ba... . Please, if JWTs are such a horrifically insecure standard, go ahead and publish your means for hacking AWS STS's AssumeRoleWithWebIdentity , or don't publish and just exploit it by launchin…
> 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 no…
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.
Re: Stop Using JWTs
#37Earlier quoted context omitted.
> 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 no…
> 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…
As someone who operates a PostgreSQL database containing 27 billion SSL certificates, each 1-2kb each, with a bunch of secondary indexes that get inserted in random order, I find it pretty incredible that people see the need to optimize their session database. At what scale does the size of the session database actually matter?
Those stateless tokens may be "unforgeable", but they are replayable, and if you're not mindful of that you can have security vulnerabilities.
Re: Stop Using JWTs
#38[dead]
Re: Stop Using JWTs
#39PASETO is great but there's not enough ecosystem support
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Re: Stop Using JWTs
#40In sessions vs. JWT revocation lists, there is an argument in favor of JWT revocation lists. JWTs have a limited expiry timestamp, so you only ever need to maintain a revocation list for tokens not expired yet. Given that you probably only have a fraction of JWTs revoked compare to valid JWTs in circulation, you only need to query a very small dataset for each request.
When using sessions, your list of valid sessions is probably orders of magnitudes higher that the revocation list - thus the data lookup costs and the storage cost of that statefulness is higher.
Plus, the article mentions JWTs are stateless but that is usually not true. You mostly not only validate the JWT, but also obtain a matching identity object (i.e. user details) for each request to see if the user is still enabled/authorized to do whatever he does. You can leverage stuff such as per-user revocation lists, or a minimum_issued_at that will validate any JWT iat field. This allows the "Logout from all devices" pattern, where that action will simply set a user's minimum_issued_at field to $NOW. All previous tokens will thus be revoked, without individuall revocation list checks.