feat(sec): constrain the conformance CI trigger at admission (R-SEC-02)

Implements the credential model the operator chose for wiring L2/L3 into CI: a narrow trigger SA bounded by a fail-closed Kyverno admission policy, rather than the zero-credential GitOps-native alternative (plan section 4, primary model). THE ESCALATION THIS CLOSES. Kubernetes places NO `use` check on a Job's serviceAccountName. Any principal that can `create jobs` in ns conformance can create a Job running as conformance-runner -- nodes/patch, pods/exec, namespaces/patch -- with an arbitrary command. A CI token with plain `create jobs` IS that privileged identity no matter how narrow its own Role looks. RBAC cannot fix this; only constraining the SHAPE of what the trigger may create can. Adds: * SA/Role/RoleBinding conformance-trigger -- create+get+list+watch jobs, get pods and pods/log, nothing else. Namespaced. No delete (a trigger that can delete can hide a failed run), no exec, no secrets. Results come back as a tarball on stdout read via pods/log, so no execution channel into the runner pod is ever granted. * ClusterPolicy conformance-trigger-job-shape -- Enforce, failurePolicy: Fail. It does NOT use ${KYVERNO_VALIDATION_ACTION}: a security boundary an overlay can downgrade to Audit is not a boundary. It constrains ONLY conformance-trigger, so a mistake here cannot wedge the rest of the cluster. * Flux Kustomization `conformance` -> ./conformance/incluster, wait:false and non-gating like apps-vms, so a test identity can never stall the platform or app tiers. * A kyverno test with seven cases, six of them real escalation paths. VERIFIED by `kyverno apply` (pass: 10, fail: 6, error: 0), not assumed: evil-command DENIED at /spec/template/spec/containers/0/command/ <- THE attack evil-image DENIED at .../image/ tag-not-digest DENIED at .../image/ (mutable tag is republishable) host-namespaces DENIED at /spec/template/spec/hostPID/ extra-volume DENIED by the volumes foreach injected-args DENIED by the args foreach good-run ADMITTED ALSO FIXES A FAIL-OPEN IN THE GATE ITSELF. `kyverno test` does NOT fail when a policy cannot LOAD: every row becomes "Skip / Invalid Policy" and it still prints "N tests passed" and exits 0. Measured while writing this policy -- a schema error (subjects in a separate match.all entry from resources) produced exactly that, and ci/l0.sh would have certified a security policy that does not load as green. This is not specific to this policy: a typo in restrict-host-namespaces or secret-provenance would silently disable it with the gate still green. ci/l0.sh now scans for "Invalid Policy" and fails. Proven: broken policy -> l0 rc=1, restored -> rc=0. IMAGE PINNING, HONEST LIMIT: the plan specifies pinning the exact runner image digest. That image does not exist yet, so this enforces the enforceable half -- the image must be under the conformance repository path AND digest-pinned, never a mutable tag. Residual surface: anyone who can PUSH to that path could publish a different digest. Tighten to the literal digest when the image is built; it is a one-line change to the pattern, reviewed in a PR, which is where a change to a security boundary belongs. NOT YET WIRED, deliberately: no runner image, no trigger kubeconfig, no CLUSTER_AVAILABLE. The identities here are inert until those exist, and PR #12 makes CLUSTER_AVAILABLE=true block rather than fake a green in the meantime. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
2026-09-29 03:22:41 -05:00
1 parent e8e6b9c681
commit 8eb5baffa4
@@ -0,0 +1,14 @@
+# Reconciled by clusters/base/conformance.yaml (non-gating, wait:false).
+#
+# RBAC ONLY. chainsaw-job.yaml is deliberately NOT listed: that manifest is a TEMPLATE the CI
+# trigger renders and submits per run (with the commit SHA and the touched --requirements). Flux
+# reconciling it would create a permanent Job object and fight the trigger for ownership.
+#
+# The identities here are inert without
+# platform/kyverno/admission/conformance-trigger-job-shape.yaml, which is what actually bounds
+# the trigger to the committed run shape. RBAC is the necessary half, that policy the sufficient
+# half — see the header of rbac.yaml.
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+  - rbac.yaml
@@ -174,3 +174,68 @@ subjects:
  - kind: ServiceAccount
    name: conformance-runner
    namespace: conformance
+---
+# =============================================================================
+# THE TRIGGER IDENTITY — deliberately NOT conformance-runner.
+#
+# THE ESCALATION THIS EXISTS TO CLOSE (docs/plans/l2-l3-conformance-ci-wiring.md §4):
+# Kubernetes places NO `use` check on a Pod/Job's `serviceAccountName`. So any principal
+# that can `create jobs` in this namespace can create a Job with
+# `serviceAccountName: conformance-runner` and an ARBITRARY command — i.e. run arbitrary
+# code with the runner's privileges (nodes/patch, pods/exec, namespaces/patch, jobs).
+# A CI-held token with plain `create jobs` therefore IS the privileged identity, no matter
+# how narrow its own RBAC looks. That would break R-SEC-02 ("CI holds no broad cluster
+# access") while appearing to satisfy it.
+#
+# RBAC ALONE CANNOT FIX THIS. The real boundary is the admission policy
+# platform/kyverno/admission/conformance-trigger-job-shape.yaml, which admits Jobs from
+# THIS ServiceAccount only when they match the committed conformance shape. This Role is
+# the necessary half; that policy is the sufficient half. Neither works alone — do not
+# grant this Role without that policy reconciled and ENFORCING.
+#
+# Namespaced Role, bound only in `conformance`. No ClusterRole, deliberately.
+# =============================================================================
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: conformance-trigger
+  namespace: conformance
+  labels:
+    app.kubernetes.io/part-of: conformance
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: Role
+metadata:
+  name: conformance-trigger
+  namespace: conformance
+  labels:
+    app.kubernetes.io/part-of: conformance
+rules:
+  # Create the run, and watch it to completion.
+  - apiGroups: [batch]
+    resources: [jobs]
+    verbs: [create, get, list, watch]
+  # Read the Job's pod and its log — this is how results come back. Deliberately NOT
+  # pods/exec and NOT `kubectl cp`: the run tars its artifacts to stdout and CI decodes
+  # them from the log, so no execution channel into the runner pod is ever granted.
+  - apiGroups: [""]
+    resources: [pods, pods/log]
+    verbs: [get, list, watch]
+  # NOTHING ELSE. In particular NO delete on jobs (a trigger that can delete can hide a
+  # failed run), no secrets, no configmaps, no exec, no create on pods.
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: RoleBinding
+metadata:
+  name: conformance-trigger
+  namespace: conformance
+  labels:
+    app.kubernetes.io/part-of: conformance
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: Role
+  name: conformance-trigger
+subjects:
+  - kind: ServiceAccount
+    name: conformance-trigger
+    namespace: conformance
@@ -216,6 +216,20 @@ def is_literal_base(host: str) -> bool:
 DELIVERY_ROOTS = ("apps", "platform", "platform-config", "platform-config-cdi",
                  "runbooks", "clusters", "bootstrap", "catalog")

+# NARROW EXEMPTION to (0), for reconciled trees that deliberately serve NOTHING.
+# `conformance/incluster` (the L2/L3 runner + CI-trigger identities, R-SEC-02) is reconciled
+# by clusters/base/conformance.yaml but contains only a Namespace, ServiceAccounts, RBAC and
+# an admission-bounded Job template. Adding "conformance" to DELIVERY_ROOTS instead would be
+# wrong for the reason stated above: it would sweep in this harness's synthetic fixture
+# routes and make (8) demand the operator's dashboard link them.
+#
+# THE EXEMPTION POLICES ITSELF. An unchecked allowlist is how (0) would rot into a fail-open —
+# add a tree here, later put an HTTPRoute in it, and the forward direction goes quietly green
+# on a hidden service. So each exempted tree is ASSERTED below to declare no route and no
+# hostname-publishing Service. If that ever stops being true the check fails and the tree must
+# become a real delivery root.
+NON_SERVING_RECONCILED = ("conformance/incluster",)
+

 def tracked_yaml() -> list[Path]:
    out = subprocess.run(["git", "ls-files", "-z", "--", "*.yaml", "*.yml"],
@@ -262,12 +276,31 @@ flux_ks = [(p, d) for p, d in docs_all()
 # a Kustomization declared elsewhere); they name no source and reconcile nothing, so requiring
 # a path of them would fail on a file that is correct.
 reconcilers = [(p, d) for p, d in flux_ks if (d.get("spec", {}) or {}).get("sourceRef")]
+def _reconciled_path(d):
+    return (d.get("spec", {}) or {}).get("path", "").lstrip("./").rstrip("/")
+
+
 unscanned = sorted({
    f"{p.relative_to(ROOT)}:{(d.get('spec', {}) or {}).get('path', '') or '(no path)'}"
    for p, d in reconcilers
-    if (d.get("spec", {}) or {}).get("path", "").lstrip("./").split("/")[0]
-    not in DELIVERY_ROOTS
+    if _reconciled_path(d).split("/")[0] not in DELIVERY_ROOTS
+    and _reconciled_path(d) not in NON_SERVING_RECONCILED
 })
+
+# The exemption's own guard: an exempted tree must actually serve nothing.
+exempt_serving = sorted({
+    f"{p.relative_to(ROOT)} ({d.get('kind')})"
+    for p, d in docs_all()
+    if any(str(p.relative_to(ROOT)).startswith(t + "/") for t in NON_SERVING_RECONCILED)
+    and (d.get("kind") == "HTTPRoute"
+         or (d.get("kind") == "Service"
+             and any("hostname" in str(k).lower()
+                     for k in ((d.get("metadata", {}) or {}).get("annotations", {}) or {}))))
+})
+check(not exempt_serving,
+      f"(0b) every NON_SERVING_RECONCILED tree really serves nothing — an exempted tree that "
+      f"gains a route would hide a service from this check entirely "
+      f"{exempt_serving if exempt_serving else ''}")
 check(len(reconcilers) >= 10 and not unscanned,
      f"(0) all {len(reconcilers)} Flux-reconciled path(s) lie inside a scanned root — a "
      f"reconciled tree this check does not read is a service it cannot require a link for "