fix(kyverno): unblock CDI imports by SATISFYING the label requirement, not exempting it

Prod's UniFi VM has no disk. `DataVolume unifi/unifi-rootdisk` stuck in
ImportScheduled for hours, because Kyverno denied CDI's own generated pod:

  validate.kyverno.svc-fail denied Pod/unifi/importer-prime-<uid>
    require-auth-mode-label     (R-IDP-02)
    require-egress-class-label  (R-NET-05)

Both policies match any Pod in an `app-namespace: "true"` namespace with no
exclusion, and CDI generates `importer-*` itself — it cannot carry repo labels.
A COLD-START defect, not a prod quirk: dev's identical import Succeeded 9 days
ago, before the policies enforced, so dev has never exercised it and would hit it
on any rebuild. Fourth bug of this shape in two days.

MECHANISM: a MUTATE ClusterPolicy that ADDS
`egress-class: internet` + `auth-mode: none` (add-if-absent anchor) to Pods on
CREATE in app namespaces WHEN the requesting subject is ServiceAccount
`cdi/cdi-sa`. Both validate policies are untouched — no exclude, no exception,
`background: true` preserved on them.

Why mutate beats exempting: the requirement stays literally true ("every pod in an
app namespace declares both labels") and the values are HONEST — the importer does
pull over the default WAN path, and `internet` is the least-reach class (it does
not grant the VPN path); a transient worker pod with no UI genuinely is
`auth-mode: none`.

THE MATCH IS IDENTITY, NOT A NAME. `subjects: ServiceAccount cdi/cdi-sa` is the
AdmissionReview userInfo, taken from the real prod denial
(`system:serviceaccount:cdi:cdi-sa`, name importer-prime-…, op CREATE). A name
prefix is attacker-choosable; a requesting ServiceAccount is not — and the test
proves it, with a fixture `importer-prime-forged-by-an-app` that copies both the
name prefix AND CDI's labels and is still DENIED. Covers every CDI worker kind
(importer/uploader/cloner) without enumerating names that change per release.
Confirmed on prod that cdi-sa is the only cdi-namespace SA that can create pods.

REJECTED, and the first one is a trap worth recording:
  * PolicyException — the CRD EXISTS (v2/v2beta1, from the pre-applied bundle) but
    all controllers run `--enablePolicyException=false` (verified live on prod:
    admission, background and reports controllers all carry the flag). An exception
    would apply cleanly through Flux and be SILENTLY IGNORED. Enabling the gate is a
    cluster-wide capability change for no gain over the mutate.
  * `exclude` scoped to cdi-sa — sound identity, worse consequences: any userInfo
    match forces `background: false`, which would drop background scanning and
    policy-report coverage of R-NET-05/R-IDP-02 for ALL EXISTING PODS to fix one pod
    class. It also leaves the importer with no labels at all — the unlabelled
    fall-through that require-egress-class-label's own header calls a fail-open leak.
  * name-prefix / CDI-label matching — attacker-choosable, and proven walkable.

TWO-WAY PROOF, non-vacuous by construction — same resource, different requester,
opposite outcomes (verified by me, not just reported):
  userinfo cdi-sa   -> mutate pass, require-egress-class pass, require-auth-mode pass
  userinfo ordinary -> mutate SKIP,  require-egress-class FAIL, require-auth-mode FAIL
Kyverno L0 went 17 -> 29 tests passed, 0 failed. The mutate policy is deliberately
kept OUT of the existing tests/kyverno-test.yaml: that suite declares no userinfo,
and without userinfo the offline engine does not discriminate on subjects — it
mutates everything, which would have silently turned its negative rows into passes.

platform-config/kustomization.yaml is the live apply path for these ClusterPolicies;
without it the policy never reaches a cluster.

RESIDUAL TRADE-OFF, reversible by deleting one file: anything created by cdi-sa in
an app namespace now has these labels supplied rather than being rejected for not
declaring them — including a pod that is not a CDI worker. That identity already
holds `pods create/delete` cluster-wide via ClusterRole `cdi`, so it is not a new
capability; what changes is that for that one identity the declaration is assumed
rather than demanded. restrict-host-namespaces, the namespace default-deny baseline
and the CiliumNetworkPolicies all still apply.

FIRST resource-mutating policy on this cluster: kyverno-resource-mutating-webhook-cfg
holds 0 webhooks today; with autoUpdateWebhooks=true Kyverno registers
mutate.kyverno.svc-fail for Pods within seconds of this applying. Prod's
forceFailurePolicyIgnore=false makes it failurePolicy: Fail — same posture as the
validating webhook already in that path.

CDI retries importer creation on a loop, so the stuck import should proceed once
this lands. The detached prime-be3f9d1c-… 40 GiB scratch PVC is separate operator
cleanup; untouched, as is the DataVolume.

VERIFIED: full CI gate PASS. Nothing applied to any cluster.

Refs R-IDP-02, R-NET-05, R-PLAT-01.

Co-Authored-By: Claude Opus 5 <[email protected]>

platform/kyverno/tests/controller-worker-pods/resources/cdi-worker-pods.yaml

@@ -0,0 +1,53 @@
+# Fixtures for the CDI-worker-pod label mutation (policies/label-cdi-worker-pods.yaml).
+#
+# All three pods live in `app-ns` (../resources/namespaces.yaml — carries
+# homelab.keithjackson.dev/app-namespace: "true"), so all three are IN SCOPE of
+# require-egress-class-label + require-auth-mode-label. What separates them is WHO creates
+# them, which is the whole point of the mechanism: the two "forged" pods are byte-for-byte
+# as CDI-looking as the real one.
+#
+# ---- (a) the REAL CDI worker pod: shape copied from the pod CDI actually tried to create on
+#          prod (name importer-prime-<pvc-uid>, CDI's own labels, no platform labels). It is
+#          created by ServiceAccount cdi/cdi-sa — see userinfo-cdi-sa.yaml.
+apiVersion: v1
+kind: Pod
+metadata:
+  name: importer-prime-be3f9d1c-c3ce-455a-a450-3d9e95c7baa2
+  namespace: app-ns
+  labels:
+    app: containerized-data-importer
+    cdi.kubevirt.io: importer
+    # NOTE: no homelab.keithjackson.dev/* labels — CDI generates this pod itself, nothing in
+    # git can label it. This is exactly why the import was blocked.
+spec:
+  restartPolicy: OnFailure
+  containers:
+    - name: importer
+      image: quay.io/kubevirt/cdi-importer:v1.62.0
+---
+# ---- (b) FORGED: an ordinary pod that copies the importer's NAME PREFIX and CDI's labels.
+#          Proves that a name-prefix or label-based exemption would have been walkable, and
+#          that this ServiceAccount-scoped one is not.
+apiVersion: v1
+kind: Pod
+metadata:
+  name: importer-prime-forged-by-an-app
+  namespace: app-ns
+  labels:
+    app: containerized-data-importer
+    cdi.kubevirt.io: importer
+spec:
+  containers:
+    - name: app
+      image: registry.example/app:1.0.0
+---
+# ---- (c) a plain unlabelled application pod in the SAME namespace. Must still be DENIED.
+apiVersion: v1
+kind: Pod
+metadata:
+  name: plain-app-pod-no-labels
+  namespace: app-ns
+spec:
+  containers:
+    - name: app
+      image: registry.example/app:1.0.0