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Vault Secrets Operator

Vault Secrets Operator (VSO) is HashiCorp's official Kubernetes operator for synchronizing secrets from HashiCorp Vault into Kubernetes Secrets. It provides deep integration with Vault's features including dynamic secrets, automatic secret rotation, and Vault's audit capabilities.

VSO is designed as the successor to the Vault Agent Sidecar Injector, offering a more Kubernetes-native approach to secret management.

Key Features​

  • Native Kubernetes integration using Custom Resources.
  • Automatic secret synchronization from Vault to Kubernetes Secrets.
  • Dynamic secret support with automatic rotation.
  • PKI certificate management with automatic renewal.
  • Vault Enterprise features support (namespaces, KMIP).
  • Kubernetes authentication using service accounts.

Installation​

Using Helm​

helm repo add hashicorp https://helm.releases.hashicorp.com
helm install vault-secrets-operator hashicorp/vault-secrets-operator \
  --namespace vault-secrets-operator-system \
  --create-namespace

Configuration Values​

# values.yaml
defaultVaultConnection:
  enabled: true
  address: "https://vault.example.com"
  skipTLSVerify: false

controller:
  replicas: 2
  
defaultAuthMethod:
  enabled: true
  method: kubernetes
  mount: kubernetes
  kubernetes:
    role: vault-secrets-operator
    serviceAccount: default

Core Concepts​

VaultConnection​

Defines how to connect to a Vault server:

apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultConnection
metadata:
  name: vault-connection
  namespace: vault-secrets-operator-system
spec:
  address: https://vault.example.com
  skipTLSVerify: false
  caCertSecretRef: vault-ca-cert

VaultAuth​

Defines authentication method to Vault:

apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultAuth
metadata:
  name: vault-auth
  namespace: production
spec:
  method: kubernetes
  mount: kubernetes
  kubernetes:
    role: app-role
    serviceAccount: app-sa
    audiences:
      - vault
  vaultConnectionRef: vault-connection

VaultStaticSecret​

Synchronizes static KV secrets:

apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultStaticSecret
metadata:
  name: database-creds
  namespace: production
spec:
  vaultAuthRef: vault-auth
  mount: secret
  type: kv-v2
  path: production/database
  destination:
    name: database-secret
    create: true
  refreshAfter: 30s

VaultDynamicSecret​

Synchronizes dynamic secrets with automatic rotation:

apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultDynamicSecret
metadata:
  name: aws-creds
  namespace: production
spec:
  vaultAuthRef: vault-auth
  mount: aws
  path: creds/my-role
  destination:
    name: aws-credentials
    create: true
  renewalPercent: 67

VaultPKISecret​

Manages PKI certificates:

apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultPKISecret
metadata:
  name: app-tls
  namespace: production
spec:
  vaultAuthRef: vault-auth
  mount: pki
  role: app-role
  commonName: app.example.com
  altNames:
    - app.production.svc.cluster.local
  ttl: 24h
  destination:
    name: app-tls-secret
    create: true
  expiryOffset: 1h

Vault Configuration​

Enable Kubernetes Auth​

# Enable Kubernetes auth method
vault auth enable kubernetes

# Configure Kubernetes auth
vault write auth/kubernetes/config \
  kubernetes_host="https://$KUBERNETES_HOST:443" \
  kubernetes_ca_cert=@/var/run/secrets/kubernetes.io/serviceaccount/ca.crt

Create Vault Role​

vault write auth/kubernetes/role/app-role \
  bound_service_account_names=app-sa \
  bound_service_account_namespaces=production \
  policies=app-policy \
  ttl=1h

Create Vault Policy​

# app-policy.hcl
path "secret/data/production/*" {
  capabilities = ["read"]
}

path "aws/creds/my-role" {
  capabilities = ["read"]
}

path "pki/issue/app-role" {
  capabilities = ["create", "update"]
}
vault policy write app-policy app-policy.hcl

Usage Examples​

Static Secret Synchronization​

# Store a secret in Vault
# vault kv put secret/production/database username=admin password=secret123

apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultStaticSecret
metadata:
  name: database-secret
  namespace: production
spec:
  vaultAuthRef: vault-auth
  mount: secret
  type: kv-v2
  path: production/database
  destination:
    name: db-credentials
    create: true
    labels:
      app: myapp
    annotations:
      managed-by: vault-secrets-operator
  refreshAfter: 60s

Dynamic AWS Credentials​

apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultDynamicSecret
metadata:
  name: aws-creds
  namespace: production
spec:
  vaultAuthRef: vault-auth
  mount: aws
  path: creds/s3-readonly
  destination:
    name: aws-credentials
    create: true
    transformation:
      excludeRaw: true
      templates:
        AWS_ACCESS_KEY_ID:
          text: "{{ .Secrets.access_key }}"
        AWS_SECRET_ACCESS_KEY:
          text: "{{ .Secrets.secret_key }}"
  renewalPercent: 67

Automatic TLS Certificate​

apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultPKISecret
metadata:
  name: nginx-tls
  namespace: production
spec:
  vaultAuthRef: vault-auth
  mount: pki
  role: web-server
  commonName: nginx.production.svc.cluster.local
  altNames:
    - nginx.example.com
  ipSans:
    - 10.0.0.100
  ttl: 720h
  destination:
    name: nginx-tls-secret
    create: true
    type: kubernetes.io/tls
  expiryOffset: 24h

Secret Transformation​

Transform secrets during synchronization:

spec:
  destination:
    name: transformed-secret
    transformation:
      excludeRaw: true
      excludes:
        - internal_key
      templates:
        FORMATTED_URL:
          text: "postgresql://{{ .Secrets.username }}:{{ .Secrets.password }}@db:5432/mydb"

Monitoring​

Check VaultStaticSecret Status​

kubectl get vaultstaticsecret -n production
kubectl describe vaultstaticsecret database-secret -n production

View Operator Logs​

kubectl logs -n vault-secrets-operator-system -l app.kubernetes.io/name=vault-secrets-operator

Prometheus Metrics​

VSO exposes metrics at /metrics:

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: vault-secrets-operator
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: vault-secrets-operator
  endpoints:
    - port: metrics

Best Practices​

  • Use Kubernetes authentication: Avoid static tokens; use service account authentication.
  • Scope roles narrowly: Grant minimum necessary permissions in Vault policies.
  • Enable audit logging: Configure Vault audit logging for compliance and troubleshooting.
  • Set appropriate refresh intervals: Balance security needs with Vault API load.
  • Use dynamic secrets: Prefer dynamic secrets over static when supported by the target system.
  • Implement rotation: Configure renewalPercent for automatic credential rotation before expiry.

Comparison: VSO vs Vault Agent Sidecar​

FeatureVault Secrets OperatorVault Agent Sidecar
ArchitectureCentralized operatorPer-pod sidecar
Resource usageLower (shared operator)Higher (sidecar per pod)
Secret deliveryKubernetes SecretsFiles in shared volume
Dynamic secretsNative supportTemplate rendering
Certificate managementVaultPKISecret CRDAgent templates
Kubernetes nativeYes (CRDs)No

References​

This article is based on information from the following official sources:

  1. Vault Secrets Operator Documentation - HashiCorp
  2. Vault Secrets Operator GitHub Repository - HashiCorp
  3. Vault Kubernetes Auth Method - HashiCorp