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 Provider Class 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.
• Authentication using the requesting pod's service account.
• TLS/mTLS communications with Vault.
• Rendering Vault secrets to files.
• Dynamic lease caching and renewal performed by Agent.
• Syncing secrets to Kubernetes secrets to be used as environment variables.
• Installation via Vault Helm

Supported kubernetes versions

The following Kubernetes minor releases are currently supported. The latest version is tested against each Kubernetes version. It may work with other versions of Kubernetes, but those are not supported.

• 1.26
• 1.25
• 1.24
• 1.23
• 1.22

Authenticating with Vault

The Vault CSI Provider will authenticate with Vault as the service account of the pod that mounts the CSI volume. Kubernetes and JWT auth methods are supported. The pod's service account must be bound to a Vault role and a policy granting access to the secrets desired.

It is highly recommended to run pods with dedicated Kubernetes service accounts to ensure applications cannot access more secrets than they require.

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 address and TLS connection config is normally best configured by the
    # helm chart, but can be overridden per SecretProviderClass:
    # 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.

Tutorial

Refer to the Vault CSI Provider tutorial to learn how to set up Vault and its dependencies with a Helm chart.