Used jwt for our web app before - changed to session cookies. To make jwt secure for web apps it feels like you are reinventing session authentication.
I've never heard anyone say that's the problem, rather the issue is the network latency + dependency of hitting a cache/database for every future request. It's not a problem for everyone's apps, but pretending it's never a problem for anyone is shortsighted. Session cookies are just fine for many/most apps, and JWTs add new problems, so I dont recommend them. YMMV
On the other hand, a client can usefully send a JWT to any other service that has the secret key to validate it, and once validated, the information the service needs can be in the JWT itself, so there's not session lookup needed.
It's the difference between giving a friend your parking stub so they can go pick up your keys from the attendant and bring your car back vs giving the friend a copy of your key and having him get the car from wherever it might be.
This sounds like a database. Or if that's too slow for you, a Redis cache.
I try not to make blanket statements about software infrastructure, because we all work on a variety of systems. However, I'm having a hard time thinking of scenarios where session cookies are too hard or too slow.
If the receiver trusts the signer, they can use the data. Sometimes the two systems cannot share a database, or a cookie.
Like everything else, JWT is sometimes used inappropriately.
And of course it's not the only way to pass signed data between two systems. Sometimes it makes sense to create your own equivalent that supports only the pieces you need.
One popular criticism (and historical security risk) of JWT is that the spec allows signing algorithm flexibility. This is easily mitigated, but of course any tool that can be used improperly, will be, by someone.
But honestly, JWT is straightforward, simple, and has good library support across all popular languages. It's a good choice for an API that you expose to groups outside your organization.
The problem lay in 1. implementations blindly accepting the value in the alg field as sent by the client and 2. one of the allowed "algorithms" was 'none'. An attacker could create a JWT with the desired data and "alg" : "none" and the flawed implementations would then "validate" the data by applying "none" to verify the signature was "".
Oh, and the spec required conforming implementations to accept "none".
https://auth0.com/blog/critical-vulnerabilities-in-json-web-...
And most implementations did not include "none" in the default accepted algorithm list.
But yeah, the optics of that debacle were poor. And I can sympathize with those who instinctively avoid JWT due to concern that there are other design/spec flaws lurking.
(JWT is so simple though -- it's what you'd design if you designed a thing for signed, base64'ed messages and then added a couple of extra fields. Some people will respond: "So then do that instead!". :)
IMO, as long as you think of JWT as a simple and standardized signed message format, with broad cross-platform support, it's perfectly suited for its purpose.
There's lots of possibilities for signed messages to simplify some things that are complicated if tied with maintaining session state on a server.
One header chunk, one data chunk, one signature chunk. Base64-encoded and concatenated. Done.
You don't need a JWT library, although I guess I'm taking JSON parsing ability as a given. This seems reasonable -- anywhere JWT would make sense, JSON is likely established.
Some of the other associated standards (JOSE, JWKS, etc) can get complicated, but JWT is about as simple as it gets.
I used it for cross-server auth sign-in to B.com from A.com
> It just sounds really awesome until you realize that, no matter what, you're going to need to keep and fetch some information about the user on the server, and that it's really not helpful at all to offload user data into a client side token
I guess you always must unless you want to skip permission validation and stuff.
What if you aren't using a browser? What if you explicitly want to know that the contents of the auth token aren't modified? What if you want to work with a IdP that only provides JWTs to offer centralized authentication and user management?
> Cookie auth is much easier to implement without the need for a 3rd party library and is also more secure.
As long as you are in the browser, sure! In many cases you can use secure cookies and server side sessions and they work well. But as soon as you get into more distributed or larger systems, reaching out to multiple APIs, JWTs may make sense.
There's no difference between browser authentication via a cookie and app authentication via a token. The cookie stores the session token, the app store the session token.
What if you explicitly want to know that the contents of the auth token aren't modified
There is no content in an auth token — it's a random number.
What if you want to work with a IdP that only provides JWTs to offer centralized authentication and user management?
When there's no choice, there's no choice.
Wait what? Auth tokens may contain (signed) claims, and I believe this is what grandparent poster was referring to.
Using some kind of cryptographic token that can be validated without the database hit is much faster.