3 ms·

I've seen this argument often on the topic of JWTs, which are also mentioned in the tweets here. In many situations there are simpler methods than JWTs that don

I've seen this argument often on the topic of JWTs, which are also mentioned in the tweets here. In many situations there are simpler methods than JWTs that don't require any cryptography, e.g. simply storing session ids server-side. With these simple methods there isn't anything cryptographic that could break or be misused. The TLS encryption is of course assumed here, but that is nothing most developers ever really touch in a way that could break it. And arguably this part falls under the "you absolutely need it" exception.

jaywalk 5y ago
Server-side session storage isn't necessarily a replacement for JWTs. It can be in many cases, but it's not one to one. JWTs do have advantages.
- fabian2k 5y ago
  That's why I wrote "in many cases". The problem is more that for a while at least JWT were pretty much sold as the new and shiny replacement for classic sessions, which they're not. They absolutely have their uses, but they also have additional attack surface.
slaymaker1907 5y ago
You can still use encryption with JWTs if you use a symmetric key. I believe HS256 just uses a symmetric key HMAC with SHA256. If you go beyond JWT, Kerberos only uses symmetric cryptography while not being as centralized as other solutions. Obviously, the domain controller is centralized, but it allows for various services to use common authentication without compromising the whole domain if any one service is compromised (assuming correct configuration which is admittedly difficult with Kerberos).
deleted 5y ago
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er4hn 5y ago
The biggest problem with JWTs is not what cryptography you use (though there was a long standing issue where "none" was something that clients could enter as a client side attack...) but rather revocation. x509 certificates have several revocation mechanisms since having something being marked as "do not use" before the end of its lifetime is well understood. JWTs are not quite there.
- codebje 5y ago
  JWT is just a container for authenticated data. it's comparable to the ASN.1 encoding of an x509 certificate, not to the entire x509 public key infrastructure. You could compare x509 with revocation to something like oauth with JWT access tokens, though. In that case, x509 certificates are typically expensive to renew and have lifetimes measured in years. Revocation involves clients checking a revocation service. JWT access tokens are cheap to renew and have lifetimes measured in minutes. Revocation involves denying a refresh token when the access token needs renewing. Clients can also choose to renew access tokens much more frequently if a 'revocation server' experience is desirable. Given the spotty history of CRLDP reliability, I think oauth+JWT are doing very well in comparison. I'm pretty damn confident that when I revoke an application in Google or similar it will lose access very quickly.
  - tialaramex 5y ago
    > x509 certificates are typically expensive to renew and have lifetimes measured in years In the Web PKI thanks to Certificate Transparency we can measure, the typical X509 certificate was issued by ISRG (Let's Encrypt) and thus cost well under one dollar (free to the subscriber, that cost is borne by the donors) and has a lifetime of precisely 90 days.
    - codebje 5y ago
      > In the Web PKI thanks to Certificate Transparency we can measure, the typical X509 certificate was issued by ISRG (Let's Encrypt) and thus cost well under one dollar (free to the subscriber, that cost is borne by the donors) and has a lifetime of precisely 90 days. Yes, it's true that in the past few years Let's Encrypt has substantially altered the typical lifetime of web server certificates, as well as substantially eased the burden of refreshing a certificate in what I would guess to be the majority of use cases. Revocation, however, is still a mess. OCSP services are slow and a privacy leak, and are largely ignored by browsers - in 2021 Firefox was still checking OCSP services but given they're so unreliable if it can't contact a service it assumes the certificate is fine. OCSP winds up being a trade-off between allowing an attacker to conduct a denial of service on all certificates or blocking revocations. In practice the major browser vendors all do more or less the same thing - build their own proprietary list of revoked certificates and distribute it to browsers from time to time, with varying sources and granularity on what they will and won't include in their centralised CRLs. I would have little faith in a timely revocation of a compromised server certificate.

jaywalk 5y ago

Server-side session storage isn't necessarily a replacement for JWTs. It can be in many cases, but it's not one to one. JWTs do have advantages.

fabian2k 5y ago
That's why I wrote "in many cases". The problem is more that for a while at least JWT were pretty much sold as the new and shiny replacement for classic sessions, which they're not. They absolutely have their uses, but they also have additional attack surface.

slaymaker1907 5y ago

You can still use encryption with JWTs if you use a symmetric key. I believe HS256 just uses a symmetric key HMAC with SHA256. If you go beyond JWT, Kerberos only uses symmetric cryptography while not being as centralized as other solutions. Obviously, the domain controller is centralized, but it allows for various services to use common authentication without compromising the whole domain if any one service is compromised (assuming correct configuration which is admittedly difficult with Kerberos).

deleted 5y ago

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er4hn 5y ago

The biggest problem with JWTs is not what cryptography you use (though there was a long standing issue where "none" was something that clients could enter as a client side attack...) but rather revocation. x509 certificates have several revocation mechanisms since having something being marked as "do not use" before the end of its lifetime is well understood. JWTs are not quite there.

codebje 5y ago
JWT is just a container for authenticated data. it's comparable to the ASN.1 encoding of an x509 certificate, not to the entire x509 public key infrastructure. You could compare x509 with revocation to something like oauth with JWT access tokens, though. In that case, x509 certificates are typically expensive to renew and have lifetimes measured in years. Revocation involves clients checking a revocation service. JWT access tokens are cheap to renew and have lifetimes measured in minutes. Revocation involves denying a refresh token when the access token needs renewing. Clients can also choose to renew access tokens much more frequently if a 'revocation server' experience is desirable. Given the spotty history of CRLDP reliability, I think oauth+JWT are doing very well in comparison. I'm pretty damn confident that when I revoke an application in Google or similar it will lose access very quickly.
- tialaramex 5y ago
  > x509 certificates are typically expensive to renew and have lifetimes measured in years In the Web PKI thanks to Certificate Transparency we can measure, the typical X509 certificate was issued by ISRG (Let's Encrypt) and thus cost well under one dollar (free to the subscriber, that cost is borne by the donors) and has a lifetime of precisely 90 days.
  - codebje 5y ago
    > In the Web PKI thanks to Certificate Transparency we can measure, the typical X509 certificate was issued by ISRG (Let's Encrypt) and thus cost well under one dollar (free to the subscriber, that cost is borne by the donors) and has a lifetime of precisely 90 days. Yes, it's true that in the past few years Let's Encrypt has substantially altered the typical lifetime of web server certificates, as well as substantially eased the burden of refreshing a certificate in what I would guess to be the majority of use cases. Revocation, however, is still a mess. OCSP services are slow and a privacy leak, and are largely ignored by browsers - in 2021 Firefox was still checking OCSP services but given they're so unreliable if it can't contact a service it assumes the certificate is fine. OCSP winds up being a trade-off between allowing an attacker to conduct a denial of service on all certificates or blocking revocations. In practice the major browser vendors all do more or less the same thing - build their own proprietary list of revoked certificates and distribute it to browsers from time to time, with varying sources and granularity on what they will and won't include in their centralised CRLs. I would have little faith in a timely revocation of a compromised server certificate.