»Vault CSI Provider

The Vault CSI Provider allows pods to consume Vault secrets using CSI Secrets Store volumes.

»Overview

At a high level, the CSI Secrets Store driver allows users to create SecretProviderClass objects. This object defines which secret provider to use and what secrets to retrieve. When pods requesting CSI volumes are created, the CSI Secrets Store driver will send the request to the Vault CSI Provider if the provider is vault. The Vault CSI Provider will then use Secret Class Provider specified and the pod's service account to retrieve the secrets from Vault, and mount them into the pod's CSI volume.

The secret is retrieved from Vault and populated to the CSI secrets store volume during the ContainerCreation phase. This means that pods will be blocked from starting until the secrets have been read from Vault and written to the volume.

»Features

The following features are supported by the Vault CSI Provider:

  • All Vault secret engines supported.
  • Authenticatation using the requesting pod's service account.
  • TLS/mTLS communciations with Vault.
  • Rendering Vault secrets to files.
  • Syncing secrets to Kubernetes secrets to be used as environment variables.
  • Installation via Vault Helm

»Authenticating with Vault

The primary method of authentication with Vault when using the Vault CSI Provider is the service account attached to the pod. At this time no other authentication methods are supported.

For Kubernetes authentication, the service account must be bound to a Vault role and a policy granting access to the secrets desired.

A service account must be present to use the Vault CSI Provider with the Kubernetes authentication method. It is not recommended to bind Vault roles to the default service account provided to pods if no service account is defined.

»Secret Provider Class Example

The following is an example of a Secret Provider Class using the vault provider:

---
apiVersion: secrets-store.csi.x-k8s.io/v1alpha1
kind: SecretProviderClass
metadata:
  name: vault-db-creds
spec:
  # Vault CSI Provider
  provider: vault
  parameters:
    # Vault role name to use during login
    roleName: 'app'
    # Vault's hostname
    vaultAddress: 'https://vault:8200'
    # TLS CA certification for validation
    vaultCACertPath: '/vault/tls/ca.crt'
    objects: |
      - objectName: "dbUsername"
        secretPath: "database/creds/db-app"
        secretKey: "username"
      - objectName: "dbPassword"
        secretPath: "database/creds/db-app"
        secretKey: "password"
    # "objectName" is an alias used within the SecretProviderClass to reference
    # that specific secret. This will also be the filename containing the secret.
    # "secretPath" is the path in Vault where the secret should be retrieved.
    # "secretKey" is the key within the Vault secret response to extract a value from.

»Using Secret Provider Classes

An application pod uses the example Secret Provider Class above by mounting it as a CSI volume:

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
  labels:
    app: demo
spec:
  selector:
    matchLabels:
      app: demo
  replicas: 1
  template:
    spec:
      serviceAccountName: app
      containers:
        - name: app
          image: my-app:1.0.0
          volumeMounts:
            - name: 'vault-db-creds'
              mountPath: '/mnt/secrets-store'
              readOnly: true
      volumes:
        - name: vault-db-creds
          csi:
            driver: 'secrets-store.csi.k8s.io'
            readOnly: true
            volumeAttributes:
              secretProviderClass: 'vault-db-creds'

In this example volumes.csi is created on the application deployment and references the Secret Provider Class named vault-db-creds.

»Learn

Refer to the Vault CSI Provider guide for a step-by-step tutorial.