Hi all,
We've been going over keystone gaps that need to be addressed for edge use cases every Tuesday. Since Berlin, Oath has open-sourced some of their custom authentication plugins for keystone that help them address these gaps.
The basic idea is that users authenticate to some external identity provider (Athenz in Oath's case), and then present an Athenz token to keystone. The custom plugins decode the token from Athenz to determine the user, project, roles assignments, and other useful bits of information. After that, it creates any resources that don't exist in keystone already. Ultimately, a user can authenticate against a keystone node and have specific resources provisioned automatically. In Berlin, engineers from Oath were saying they'd like to move away from Athenz tokens altogether and use x509 certificates issued by Athenz instead. The auto-provisioning approach is very similar to a feature we have in keystone already. In Berlin, and shortly after, there was general agreement that if we could support x509 authentication with auto-provisioning via keystone federation, that would pretty much solve Oath's use case without having to maintain custom keystone plugins.
Last week, Colleen started digging into keystone's existing x509 authentication support. I'll start with the good news, which is x509 authentication works, for the most part. It's been a feature in keystone for a long time, and it landed after we implemented federation support around the Kilo release. Chances are there won't be a need for a keystone specification like we were initially thinking in the edge meetings. Unfortunately, the implementation for x509 authentication has outdated documentation, is extremely fragile, hard to set up, and hasn't been updated with improvements we've made to the federation API since the original implementation (like shadow users or auto-provisioning, which work with other federated protocols like OpenID Connect and SAML). We've started tracking the gaps with bugs [0] so that we have things written down.
I think the good thing is that once we get this cleaned up, we'll be able to re-use some of the newer federation features with x509 authentication/federation. These updates would make x509 a first-class federated protocol. The approach, pending the bug fixes, would remove the need for Oath's custom authentication plugins. It could be useful for edge deployments, or even deployments with many regions, by allowing users to be auto-provisioned in each region. Although, it doesn't necessarily solve the network partition issue.
Now that we have an idea of where to start and some bug reports [0], I'm wondering if anyone is interested in helping with the update or refactor. Because this won't require a specification, we can get started on it sooner, instead of having to wait for Train development and a new specification. I'm also curious if anyone has comments or questions about the approach.
Thanks,
Lance
[0] https://bugs.launchpad.net/keystone/+bugs?field.tag=x509