external-secrets/docs/provider/kubernetes.md

External Secrets Operator allows to retrieve secrets from a Kubernetes Cluster - this can be either a remote cluster or the local one where the operator runs in.

A SecretStore points to a specific namespace in the target Kubernetes Cluster. You are able to retrieve all secrets from that particular namespace given you have the correct set of RBAC permissions.

The SecretStore reconciler checks if you have read access for secrets in that namespace using SelfSubjectRulesReview. See below on how to set that up properly.

External Secret Spec

This provider supports the use of the Property field. With it you point to the key of the remote secret. If you leave it empty it will json encode all key/value pairs.

apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: database-credentials
spec:
  refreshInterval: 1h
  secretStoreRef:
    kind: SecretStore
    name: k8s-store             # name of the SecretStore (or kind specified)
  target:
    name: database-credentials  # name of the k8s Secret to be created
  data:
  - secretKey: username
    remoteRef:
      key: database-credentials
      property: username

  - secretKey: password
    remoteRef:
      key: database-credentials
      property: password

find by tag & name

You can fetch secrets based on labels or names matching a regexp:

apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: fetch-tls-and-nginx
spec:
  refreshInterval: 1h
  secretStoreRef:
    kind: SecretStore
    name: k8s-store
  target:
    name: fetch-tls-and-nginx
  dataFrom:
  - find:
      name:
        # match secret name with regexp
        regexp: "tls-.*"
  - find:
      tags:
        # fetch secrets based on label combination
        app: "nginx"

Target API-Server Configuration

The servers url can be omitted and defaults to kubernetes.default. You have to provide a CA certificate in order to connect to the API Server securely. For your convenience, each namespace has a ConfigMap kube-root-ca.crt that contains the CA certificate of the internal API Server (see RootCAConfigMap feature gate). Use that if you want to connect to the same API server. If you want to connect to a remote API Server you need to fetch it and store it inside the cluster as ConfigMap or Secret. You may also define it inline as base64 encoded value using the caBundle property.

apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: k8s-store-default-ns
spec:
  provider:
    kubernetes:
      # with this, the store is able to pull only from `default` namespace
      remoteNamespace: default
      server:
        url: "https://myapiserver.tld"
        caProvider:
          type: ConfigMap
          name: kube-root-ca.crt
          key: ca.crt

Authentication

It's possible to authenticate against the Kubernetes API using client certificates, a bearer token or service account. The operator enforces that exactly one authentication method is used. You can not use the service account that is mounted inside the operator, this is by design to avoid reading secrets across namespaces.

NOTE: SelfSubjectRulesReview permission is required in order to validation work properly. Please use the following role as reference:

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: default
  name: eso-store-role
rules:
- apiGroups: [""]
  resources:
  - secrets
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - authorization.k8s.io
  resources:
  - selfsubjectrulesreviews
  verbs:
  - create

Authenticating with BearerToken

Create a Kubernetes secret with a client token. There are many ways to acquire such a token, please refer to the Kubernetes Authentication docs.

apiVersion: v1
kind: Secret
metadata:
  name: my-token
data:
  token: "...."

Create a SecretStore: The auth section indicates that the type token will be used for authentication, it includes the path to fetch the token. Set remoteNamespace to the name of the namespace where your target secrets reside.

apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: k8s-store-token-auth
spec:
  provider:
    kubernetes:
      # with this, the store is able to pull only from `default` namespace
      remoteNamespace: default
      server:
        # ...
      auth:
        token:
          bearerToken:
            name: my-token
            key: token

Authenticating with ServiceAccount

Create a Kubernetes Service Account, please refer to the Service Account Tokens Documentation on how they work and how to create them.

$ kubectl create serviceaccount my-store

This Service Account needs permissions to read Secret and create SelfSubjectRulesReview resources. Please see the above role.

$ kubectl create rolebinding my-store --role=eso-store-role --serviceaccount=default:my-store

Create a SecretStore: the auth section indicates that the type serviceAccount will be used for authentication.

apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: k8s-store-sa-auth
spec:
  provider:
    kubernetes:
      # with this, the store is able to pull only from `default` namespace
      remoteNamespace: default
      server:
        # ...
      auth:
        serviceAccount:
          name: "my-store"

Authenticating with Client Certificates

Create a Kubernetes secret which contains the client key and certificate. See Generate Certificates Documentations on how to create them.

$ kubectl create secret tls tls-secret --cert=path/to/tls.cert --key=path/to/tls.key

Reference the tls-secret in the SecretStore

apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: k8s-store-cert-auth
spec:
  provider:
    kubernetes:
      # with this, the store is able to pull only from `default` namespace
      remoteNamespace: default
      server:
        # ...
      auth:
        cert:
          clientCert:
            name: "tls-secret"
            key: "tls.crt"
          clientKey:
            name: "tls-secret"
            key: "tls.key"