fix(apiserver): probe SA permissions before loading admission-policy plugins#1842
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…plugins Fixes carvel-dev#1841 On Kubernetes 1.36+ the MutatingAdmissionPolicy admission plugin ships enabled by default. Its SharedInformer requires list+watch permission on mutatingadmissionpolicies and mutatingadmissionpolicybindings. If the deployed ClusterRole for the kapp-controller ServiceAccount lacks those permissions, the informer's cache never syncs, HasSynced() never returns true, and every mutating admission request into the aggregated apiserver fails permanently with 'not yet ready to handle request (reason: Forbidden)'. The existing serverResourceExists guard only confirms the API resource is present in cluster discovery, which is always true on k8s 1.36+ regardless of RBAC. This change extends the guard with a SelfSubjectAccessReview probe for both list and watch on the policy resource and its bindings resource before loading each admission-policy plugin. When the probe fails the plugin is skipped and an actionable warning is logged naming the missing (resource, verb) pair. The probe uses subjectaccessreviews/create, which is already granted in the shipped ClusterRole, no new RBAC required. Also applied to ValidatingAdmissionPolicy for symmetry; the same failure mode is possible on k8s 1.30+ if RBAC drifts. Signed-off-by: Neel Patel <neel5481@gmail.com>
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Fixes #1841
On Kubernetes 1.36+ the MutatingAdmissionPolicy admission plugin ships enabled by default. Its SharedInformer requires list+watch permission on mutatingadmissionpolicies and mutatingadmissionpolicybindings. If the deployed ClusterRole for the kapp-controller ServiceAccount lacks those permissions, the informer's cache never syncs, HasSynced() never returns true, and every mutating admission request into the aggregated apiserver fails permanently with 'not yet ready to handle request (reason: Forbidden)'.
Signed-off-by: Neel Patel
What this PR does / why we need it:
The existing serverResourceExists guard only confirms the API resource is present in cluster discovery, which is always true on k8s 1.36+ regardless of RBAC. This change extends the guard with a SelfSubjectAccessReview probe for both list and watch on the policy resource and its bindings resource before loading each admission-policy plugin. When the probe fails the plugin is skipped and an actionable warning is logged naming the missing (resource, verb) pair.
The probe uses subjectaccessreviews/create, which is already granted in the shipped ClusterRole, no new RBAC required.
Also applied to ValidatingAdmissionPolicy for symmetry; the same failure mode is possible on k8s 1.30+ if RBAC drifts.
Which issue(s) this PR fixes:
Fixes #1841
Does this PR introduce a user-facing change?
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