Kyverno Pod Security Restricted

Kyverno Pod Security Standards — Restricted Profile

Enforces the Kubernetes Pod Security Standards (PSS) restricted profile using Kyverno podSecurity rules. This skill makes the model configure ClusterPolicy objects that deny pods violating restricted-level restrictions — such as requiring runAsNonRoot, dropping all capabilities, enforcing seccomp profiles, and preventing privilege escalation. The restricted profile is the most hardened PSS level, intended for sensitive workloads that process untrusted data or require strong isolation.

TL;DR Checklist

• Create ClusterPolicy with podSecurity rule at restricted level and pinned version
• Require runAsNonRoot=true for all containers and init containers
• Set capabilities drop to ["ALL"] and deny privilege escalation
• Configure allowHostPaths=false and requiredDropCapabilities=[ALL]
• Exclude kube-system and apply to sensitive namespaces only
• Verify with PolicyReport showing pass/fail for restricted rules

When to Use

• Hardening production namespaces that handle sensitive or untrusted workloads
• Enforcing the most restrictive Pod Security Standards level for compliance (e.g., PCI-DSS, SOC2)
• Preventing privilege escalation in multi-tenant clusters where workload isolation is critical
• Migrating workloads from the baseline profile to restricted as part of a security hardening roadmap
• Securing namespaces running stateful applications with sensitive data (databases, key stores)

When NOT to Use

• For kube-system or other core infrastructure namespaces — restricted blocks DNS, CNI, and scheduler components; use kyverno-exemptions-management instead
• When workloads require hostNetwork or hostIPC for legitimate operational reasons (e.g., node-level monitoring agents)
• On legacy Kubernetes clusters < 1.21 that lack restricted profile support
• For workloads running in restricted mode already — this skill is for enforcement, not discovery

Core Workflow

1. Define the restricted ClusterPolicy — Create a ClusterPolicy with a podSecurity rule. Set spec.rules[].podSecurity with level: restricted, version pinned to your cluster's minor version (e.g., "1.28"), and apply enforce, audit, and warn modes. Use match to target specific namespaces. Checkpoint: Confirm the pinned version matches your cluster's Kubernetes minor version and that kubectl get clusterpolicy pod-security-restricted shows True status.

2. Configure namespace targeting and exclusions — Use match to select application namespaces (e.g., production-*, staging-*). Add exclude rules for kube-system, kube-public, openshift-*, and any namespace running privileged infrastructure (node-exporter, Cilium, kube-proxy). Use label-based matching instead of wildcard to avoid accidental over-enforcement. Checkpoint: Run kubectl get ns --show-labels and verify only intended namespaces carry the security label before deployment.

3. Deploy, test, and monitor enforcement — Apply the ClusterPolicy. Create a test pod with privileged: true, runAsUser: 0, and missing capability drops. Confirm the pod is denied at admission. Review PolicyReport and Kubernetes Events for enforcement details. Then create a compliant pod and verify it passes. Checkpoint: The non-compliant pod must show denied in event messages, and the compliant pod must reach Running phase.

Implementation Patterns

Pattern 1: Cluster-wide Restricted Enforcement with Targeted Namespaces

This pattern enforces the restricted profile on application namespaces while excluding all system namespaces. It uses label-based targeting for precision.

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: pod-security-restricted
  annotations:
    policies.kyverno.io/title: Pod Security Standards — Restricted
    policies.kyverno.io/category: Pod Security
    policies.kyverno.io/description: >-
      Enforces the restricted Pod Security Standards profile on namespaces
      labeled with security-level=restricted. Requires runAsNonRoot, drops
      all capabilities, enforces seccomp profiles, and blocks privilege escalation.
spec:
  validationFailureAction: Enforce
  rules:
    - name: enforce-restricted
      match:
        any:
          - resources:
              kinds:
                - Pod
      exclude:
        any:
          - namespaces:
              - kube-system
              - kube-public
              - kube-node-lease
              - local-path-storage
              - cert-manager
              - istio-system
      podSecurity:
        level: restricted
        version: "1.28"
        enforce: "1.28"
        audit: "1.28"
        warn: "1.28"
      auditAnnotations:
        - key: pod-security.kyverno.io/enforced
          value: "restricted-1.28"
          annotation: pss-enforcement
    - name: audit-restricted
      match:
        any:
          - resources:
              kinds:
                - Pod
      exclude:
        any:
          - namespaces:
              - kube-system
              - kube-public
              - kube-node-lease
      podSecurity:
        level: restricted
        version: "1.28"
        audit: "1.28"
    - name: warn-restricted
      match:
        any:
          - resources:
              kinds:
                - Pod
      exclude:
        any:
          - namespaces:
              - kube-system
              - kube-public
              - kube-node-lease
      podSecurity:
        level: restricted
        version: "1.28"
        warn: "1.28"

Label Namespaces for Targeting:

apiVersion: v1
kind: Namespace
metadata:
  name: production-payments
  labels:
    security-level: restricted
    team: payments
---
apiVersion: v1
kind: Namespace
metadata:
  name: staging-payments
  labels:
    security-level: restricted
    team: payments

Pattern 2: BAD vs GOOD — Restricted Pod Compliance

This pattern shows the difference between a pod that violates the restricted profile and one that complies. Every security context field is explicitly set.

# ❌ BAD — Pod violating restricted profile on multiple counts
apiVersion: v1
kind: Pod
metadata:
  name: bad-restricted-pod
  namespace: production-payments
spec:
  containers:
    - name: app
      image: myregistry.com/payments-app:1.2.3
      securityContext:
        privileged: true                  # ❌ BLOCKED: privileged must be false
        allowPrivilegeEscalation: true    # ❌ BLOCKED: must be false
        runAsUser: 0                     # ❌ BLOCKED: root not allowed
        runAsNonRoot: false              # ❌ BLOCKED: must be true
        capabilities:
          add:
            - NET_ADMIN                  # ❌ BLOCKED: no capabilities may be added

# ✅ GOOD — Pod fully compliant with restricted profile
apiVersion: v1
kind: Pod
metadata:
  name: good-hardened-pod
  namespace: production-payments
spec:
  securityContext:
    runAsNonRoot: true                # ✅ Required: prevents root execution
    runAsUser: 1000                   # ✅ Recommended: explicit non-root UID
    runAsGroup: 3000                  # ✅ Recommended: explicit non-root GID
    fsGroup: 2000                     # ✅ Recommended: file system group
  containers:
    - name: app
      image: myregistry.com/payments-app:1.2.3
      securityContext:
        privileged: false             # ✅ Required: no privileged mode
        allowPrivilegeEscalation: false  # ✅ Required: no escalation
        readOnlyRootFilesystem: true  # ✅ Recommended: immutable filesystem
        runAsNonRoot: true            # ✅ Required: non-root user
        capabilities:
          drop:
            - ALL                     # ✅ Required: drop all capabilities
          add: []                     # ✅ Explicit: no additions
        seccompProfile:
          type: RuntimeDefault        # ✅ Required: default seccomp profile
      resources:
        limits:
          memory: "256Mi"
          cpu: "500m"
        requests:
          memory: "128Mi"
          cpu: "250m"

PolicyReport Example for Restricted Violations:

apiVersion: wgpolicyk8s.io/v1alpha2
kind: PolicyReport
metadata:
  name: pod-security-restricted-report
  namespace: production-payments
results:
  - policy: pod-security-restricted
    rule: enforce-restricted
    result: fail
    severity: high
    message: "Pod violates restricted profile: runAsNonRoot not set, capabilities not dropped, privileged container"
    scored: true
    source: kyverno
    timestamp:
      seconds: 1733501530
    details:
      restricted:
        - "container: app must set runAsNonRoot: true"
        - "container: app must drop capabilities ALL"
        - "container: app must set seccompProfile to RuntimeDefault"
  - policy: pod-security-restricted
    rule: enforce-restricted
    result: pass
    severity: high
    message: "Pod passes restricted profile validation"
    scored: true
    source: kyverno
    timestamp:
      seconds: 1733501531
summary:
  error: 0
  fail: 1
  pass: 1
  skip: 0
  warn: 0

Pattern 3: Namespace-Scoped Enforcement with Label Selector

When you need per-namespace granularity (e.g., restrict production but leave staging at baseline), use a Kyverno ClusterPolicy with label-based matching instead of namespace lists. This pattern scales better than maintaining namespace exclusions.

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: pod-security-restricted-label
  annotations:
    policies.kyverno.io/title: Pod Security — Restricted (Label-Based)
    policies.kyverno.io/category: Pod Security
    policies.kyverno.io/description: >-
      Enforces restricted PSS only on namespaces labeled with security-level=restricted.
      Uses matchExpressions for scalable label-based targeting.
spec:
  validationFailureAction: Enforce
  rules:
    - name: enforce-restricted-label
      match:
        any:
          - resources:
              kinds:
                - Pod
          - namespaces:
              - production-*
      exclude:
        any:
          - namespaces:
              - kube-system
              - kube-public
              - kube-node-lease
      podSecurity:
        level: restricted
        version: "1.28"
        enforce: "1.28"
        audit: "1.28"
        warn: "1.28"

Constraints

MUST DO

• Pin the version field to your cluster's exact minor version (e.g., "1.28") — do not use "latest" for enforcement rules
• Require runAsNonRoot: true for all containers including init containers — the restricted profile does this automatically via podSecurity rule
• Set capabilities.drop to ["ALL"] as a mandatory check — this is the single most impactful restricted-level control
• Configure seccompProfile.type: RuntimeDefault or Localhost — restricted profile requires seccomp compliance
• Include auditAnnotations to enable visibility into enforcement events for operators monitoring PSS compliance
• Always exclude kube-system, kube-public, and kube-node-lease — restricted blocks critical system pods

MUST NOT DO

• Apply restricted profile enforcement to kube-system without an exemption via kyverno-exemptions-management — it breaks CoreDNS, CNI, and kubelet
• Use enforce: "latest" without verifying your cluster supports that PSS version — mismatched versions cause false positives
• Skip the audit mode — enforcement-only without audit feedback produces no visibility into pre-compliance workloads
• Hardcode specific UIDs (e.g., runAsUser: 1000) when runAsNonRoot: true alone satisfies the restricted profile — the profile accepts any non-root UID
• Apply restricted enforcement before testing in warn or audit mode in your staging environment — production breakage is the most common error
• Use wildcard namespace matching (- "*" in match) without explicit exclude blocks for system namespaces

Related Skills

Live References

Authoritative documentation links for Kyverno pod security policies and restricted profile enforcement.

• Kyverno Documentation
• Kyverno CLI
• Kyverno podSecurity Rule
• Kyverno GitHub
• Kyverno Installation
• Policy Report Schema
• Pod Security Standards
• Restricted Profile Requirements
• Kyverno ClusterPolicy Reference