This commit is the main API piece of KEP-3257 (ClusterTrustBundles).
This commit:
* Adds the certificates.k8s.io/v1alpha1 API group
* Adds the ClusterTrustBundle type.
* Registers the new type in kube-apiserver.
* Implements the type-specfic validation specified for
ClusterTrustBundles:
- spec.pemTrustAnchors must always be non-empty.
- spec.signerName must be either empty or a valid signer name.
- Changing spec.signerName is disallowed.
* Implements the "attest" admission check to restrict actions on
ClusterTrustBundles that include a signer name.
Because it wasn't specified in the KEP, I chose to make attempts to
update the signer name be validation errors, rather than silently
ignored.
I have tested this out by launching these changes in kind and
manipulating ClusterTrustBundle objects in the resulting cluster using
kubectl.
This change updates the CSR API to add a new, optional field called
expirationSeconds. This field is a request to the signer for the
maximum duration the client wishes the cert to have. The signer is
free to ignore this request based on its own internal policy. The
signers built-in to KCM will honor this field if it is not set to a
value greater than --cluster-signing-duration. The minimum allowed
value for this field is 600 seconds (ten minutes).
This change will help enforce safer durations for certificates in
the Kube ecosystem and will help related projects such as
cert-manager with their migration to the Kube CSR API.
Future enhancements may update the Kubelet to take advantage of this
field when it is configured in a way that can tolerate shorter
certificate lifespans with regular rotation.
Signed-off-by: Monis Khan <mok@vmware.com>
