Securing Helm Chart Deployments

Securing Helm Chart Deployments

Overview

Helm is the Kubernetes package manager. Securing Helm deployments requires validating chart provenance, scanning templates for security misconfigurations, enforcing pod security contexts, managing secrets securely, and controlling RBAC for Helm operations.

Prerequisites

• Helm 3.12+ installed
• kubectl with cluster access
• GnuPG for chart signing/verification
• kubesec or checkov for template scanning

Chart Provenance and Integrity

Sign a Helm Chart

# Generate GPG key for signing
gpg --full-generate-key

# Package and sign chart
helm package ./mychart --sign --key "helm-signing@example.com" --keyring ~/.gnupg/pubring.gpg

# Verify chart signature
helm verify mychart-0.1.0.tgz --keyring ~/.gnupg/pubring.gpg

Verify Chart Before Install

# Verify chart from repository
helm pull myrepo/mychart --verify --keyring /path/to/keyring.gpg

# Check chart provenance file
cat mychart-0.1.0.tgz.prov

Template Security Scanning

Render and Scan Templates

# Render templates without deploying
helm template myrelease ./mychart --values values-prod.yaml > rendered.yaml

# Scan with kubesec
kubesec scan rendered.yaml

# Scan with checkov
checkov -f rendered.yaml --framework kubernetes

# Scan with trivy
trivy config rendered.yaml

# Scan with kube-linter
kube-linter lint rendered.yaml

Helm Lint for Misconfigurations

# Lint chart
helm lint ./mychart --values values-prod.yaml --strict

# Lint with debug output
helm lint ./mychart --debug

Security Context Enforcement in values.yaml

# values.yaml - Security hardened defaults
securityContext:
  runAsNonRoot: true
  runAsUser: 1000
  runAsGroup: 3000
  fsGroup: 2000
  readOnlyRootFilesystem: true
  allowPrivilegeEscalation: false
  capabilities:
    drop:
      - ALL

podSecurityContext:
  seccompProfile:
    type: RuntimeDefault

resources:
  limits:
    cpu: 500m
    memory: 512Mi
  requests:
    cpu: 100m
    memory: 128Mi

networkPolicy:
  enabled: true

serviceAccount:
  create: true
  automountServiceAccountToken: false

image:
  pullPolicy: Always
  # Use digest instead of tag for immutability
  # tag: "1.0.0"
  # digest: "sha256:abc123..."

Template with Security Contexts

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "mychart.fullname" . }}
spec:
  template:
    spec:
      automountServiceAccountToken: {{ .Values.serviceAccount.automountServiceAccountToken }}
      securityContext:
        {{- toYaml .Values.podSecurityContext | nindent 8 }}
      containers:
        - name: {{ .Chart.Name }}
          securityContext:
            {{- toYaml .Values.securityContext | nindent 12 }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          resources:
            {{- toYaml .Values.resources | nindent 12 }}

Secrets Management

Use External Secrets (Not Helm Values)

# templates/external-secret.yaml
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: {{ include "mychart.fullname" . }}-secrets
spec:
  refreshInterval: 1h
  secretStoreRef:
    name: aws-secretsmanager
    kind: ClusterSecretStore
  target:
    name: {{ include "mychart.fullname" . }}-secrets
  data:
    - secretKey: db-password
      remoteRef:
        key: production/database
        property: password

helm-secrets Plugin

# Install helm-secrets plugin
helm plugin install https://github.com/jkroepke/helm-secrets

# Encrypt values file
helm secrets encrypt values-secrets.yaml

# Deploy with encrypted secrets
helm secrets install myrelease ./mychart -f values.yaml -f values-secrets.yaml

# Decrypt for editing
helm secrets edit values-secrets.yaml

RBAC for Helm Operations

# helm-deployer-role.yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: helm-deployer
  namespace: production
rules:
  - apiGroups: ["", "apps", "batch", "networking.k8s.io"]
    resources: ["deployments", "services", "configmaps", "secrets", "ingresses", "jobs"]
    verbs: ["get", "list", "create", "update", "patch", "delete"]
  - apiGroups: [""]
    resources: ["pods", "pods/log"]
    verbs: ["get", "list"]

---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: helm-deployer-binding
  namespace: production
subjects:
  - kind: ServiceAccount
    name: helm-deployer
    namespace: production
roleRef:
  kind: Role
  name: helm-deployer
  apiGroup: rbac.authorization.k8s.io

CI/CD Helm Security Pipeline

# .github/workflows/helm-security.yaml
name: Helm Chart Security
on:
  pull_request:
    paths: ['charts/**']

jobs:
  lint-and-scan:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Helm lint
        run: helm lint ./charts/mychart --strict

      - name: Render templates
        run: helm template test ./charts/mychart -f charts/mychart/values.yaml > rendered.yaml

      - name: Scan with kube-linter
        uses: stackrox/kube-linter-action@v1
        with:
          directory: rendered.yaml

      - name: Scan with trivy
        uses: aquasecurity/trivy-action@master
        with:
          scan-type: config
          scan-ref: rendered.yaml

      - name: Scan with checkov
        uses: bridgecrewio/checkov-action@master
        with:
          file: rendered.yaml
          framework: kubernetes

Best Practices

1. Sign charts with GPG and verify before installation
2. Render and scan templates before deploying to catch misconfigurations
3. Enforce security contexts in values.yaml defaults
4. Never store secrets in Helm values - use external secrets or helm-secrets plugin
5. Use image digests instead of tags for immutable references
6. Restrict Helm RBAC to least privilege per namespace
7. Pin chart versions in requirements - never use latest
8. Lint strictly in CI with --strict flag
9. Review third-party charts before deploying to production
10. Use Helm test hooks to validate deployments post-install