Comment by fc417fc802
3 days ago
> This is exactly the same as you'd normally do implicitly by handing a CI/CD system a long-lived API token, except without the long-lived API token.
The other difference is being subjected to a whitelisting approach. That wasn't previously the case.
It's frustrating that seemingly every time better authentication schemes get introduced they come with functionality for client and third party service attestation baked in. All we ever really needed was a standardized way to limit the scope of a given credential coupled with a standardized challenge format to prove possession of a private key.
> The other difference is being subjected to a whitelisting approach. That wasn't previously the case.
You are not being subjected to one. Again: you can always use an API token with PyPI, even on a CI/CD platform that PyPI knows how to do Trusted Publishing against. It's purely optional.
> All we ever really needed was a standardized way to limit the scope of a given credential coupled with a standardized challenge format to prove possession of a private key.
That is what OIDC is. Well, not for a private key, but for a set of claims that constitute a machine identity, which the relying party can then do whatever it wants with.
But standards and interoperability don't mean that any given service will just choose to federate with every other service out there. Federation always has up-front and long-term costs that need to be balanced with actual delivered impact/value; for a single user on their own server, the actual value of OIDC federation versus an API token is nil.
Right, I meant that the new scheme is subject to a whitelist. I didn't mean to imply that you can't use the old scheme anymore.
> Federation always has up-front and long-term costs
Not particularly? For example there's no particular cost if I accept email from outlook today but reverse that decision and ban it tomorrow. I don't immediately see a technical reason to avoid a default accept policy here.
> for a single user on their own server, the actual value of OIDC federation versus an API token is nil.
The value is that you can do away with long lived tokens that are prone to theft. You can MFA with your (self hosted) OIDC service and things should be that much more secure. Of course your (single user) OIDC service could get pwned but that's no different than any other account compromise.
I guess there's some nonzero risk that a bunch of users all decide to use the same insecure OIDC service. But you might as well worry that a bunch of them all decide to use an insecure password manager.
> Well, not for a private key, but for a set of claims that constitute a machine identity
What's the difference between "set of claims" and "private key" here?
That last paragraph in GP was more a tangential rant than directly on topic BTW. I realize that OIDC makes sense here. The issue is that as an end user I have more flexibility and ease of use with my SSH keys than I do with something like a self hosted OIDC service. I can store my SSH keys on a hardware token, or store them on my computer blinded so that I need a hardware token or TPM to unlock them, or lots of other options. The service I'm connecting to doesn't need to know anything about my workflow. Whereas self hosting something like OIDC managing and securing the service becomes an entire thing on top of which many services arbitrarily dictate "thou shalt not self host".
It's a general trend that as new authentication schemes have been introduced they have generally included undesirable features from the perspective of user freedom. Adding insult to injury those unnecessary features tend to increase the complexity of the specification. In contrast, it's interesting to think how things might work if what we had instead was a single widely accepted challenge scheme such as SSH has. You could implement all manner of services such as OIDC on top of such a primitive while end users would retain the ability to directly use the equivalent of an SSH key.
> Not particularly? For example there's no particular cost if I accept email from outlook today but reverse that decision and ban it tomorrow. I don't immediately see a technical reason to avoid a default accept policy here.
Accepting email isn't really the same thing. I've linked some resources elsewhere in this thread that explain why OIDC federation isn't trivial in the context of machine identities.
> The value is that you can do away with long lived tokens that are prone to theft. You can MFA with your (self hosted) OIDC service and things should be that much more secure. Of course your (single user) OIDC service could get pwned but that's no different than any other account compromise.
You can already do this by self-attenuating your PyPI API token, since it's a Macaroon. We designed PyPI's API tokens with exactly this in mind.
(This isn't documented particularly well, since nobody has clearly articulated a threat model in which a single user runs their own entire attenuation service only to restrict a single or small subset of credentials that they already have access to. But you could do it, I guess.)
> What's the difference between "set of claims" and "private key" here?
A private key is a cryptographic object; a "set of claims" is (very literally) a JSON object that was signed over as the payload of a JWT. You can't sign (or encrypt, or whatever) with a set of claims naively; it's just data.
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