Configuration Validation Webhook

 5 minute read

Galley’s configuration validation ensures user authored Istio configuration is syntactically and semantically valid. It uses a Kubernetes ValidatingWebhook. The istio-galley ValidationWebhookConfiguration has two webhooks.

  • pilot.validation.istio.io - Served on path /admitpilot and is responsible for validating configuration consumed by Pilot (e.g. VirtualService, Authentication).

  • mixer.validation.istio.io - Served on path /admitmixer and is responsible for validating configuration consumed by Mixer.

Both webhooks are implemented by the istio-galley service on port 443. Each webhook has its own clientConfig, namespaceSelector, and rules section. Both webhooks are scoped to all namespaces. The namespaceSelector should be empty. Both rules apply to Istio Custom Resource Definitions (CRDs).

Seemingly valid configuration is rejected

Manually verify your configuration is correct, cross-referencing Istio API reference when necessary.

Invalid configuration is accepted

Verify the istio-galley validationwebhookconfiguration exists and is correct. The apiVersion, apiGroup, and resource of the invalid configuration should be listed in one of the two webhooks entries.

$ kubectl get validatingwebhookconfiguration istio-galley -o yaml
apiVersion: admissionregistration.k8s.io/v1beta1
kind: ValidatingWebhookConfiguration
metadata:
  labels:
    app: istio-galley
  name: istio-galley
  ownerReferences:
  - apiVersion: extensions/v1beta1
    blockOwnerDeletion: true
    controller: true
    kind: Deployment
    name: istio-galley
    uid: 5c64585d-91c6-11e8-a98a-42010a8001a8
webhooks:
- clientConfig:
    # caBundle should be non-empty. This is periodically (re)patched
    # every second by the webhook service using the ca-cert
    # from the mounted service account secret.
    caBundle: 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
    service:
      # service corresponds to the Kubernetes service that implements the
      # webhook, e.g. istio-galley.istio-system.svc:443
      name: istio-galley
      namespace: istio-system
      path: /admitpilot
  failurePolicy: Fail
  name: pilot.validation.istio.io
  namespaceSelector: {}
  rules:
  - apiGroups:
    - config.istio.io
    apiVersions:
    - v1alpha2
    operations:
    - CREATE
    - UPDATE
    resources:
    - httpapispecs
    - httpapispecbindings
    - quotaspecs
    - quotaspecbindings
  - apiGroups:
    - rbac.istio.io
    apiVersions:
    - '*'
    operations:
    - CREATE
    - UPDATE
    resources:
    - '*'
  - apiGroups:
    - authentication.istio.io
    apiVersions:
    - '*'
    operations:
    - CREATE
    - UPDATE
    resources:
    - '*'
  - apiGroups:
    - networking.istio.io
    apiVersions:
    - '*'
    operations:
    - CREATE
    - UPDATE
    resources:
    - destinationrules
    - envoyfilters
    - gateways
    - virtualservices
- clientConfig:
    # caBundle should be non-empty. This is periodically (re)patched
    # every second by the webhook service using the ca-cert
    # from the mounted service account secret.
    caBundle: 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
    service:
      # service corresponds to the Kubernetes service that implements the
      # webhook, e.g. istio-galley.istio-system.svc:443
      name: istio-galley
      namespace: istio-system
      path: /admitmixer
  failurePolicy: Fail
  name: mixer.validation.istio.io
  namespaceSelector: {}
  rules:
  - apiGroups:
    - config.istio.io
    apiVersions:
    - v1alpha2
    operations:
    - CREATE
    - UPDATE
    resources:
    - rules
    - attributemanifests
    - circonuses
    - deniers
    - fluentds
    - kubernetesenvs
    - listcheckers
    - memquotas
    - noops
    - opas
    - prometheuses
    - rbacs
    - servicecontrols
    - solarwindses
    - stackdrivers
    - statsds
    - stdios
    - apikeys
    - authorizations
    - checknothings
    - listentries
    - logentries
    - metrics
    - quotas
    - reportnothings
    - servicecontrolreports
    - tracespans

If the validatingwebhookconfiguration doesn’t exist, verify the istio-galley-configuration configmap exists. istio-galley uses the data from this configmap to create and update the validatingwebhookconfiguration.

$ kubectl -n istio-system get configmap istio-galley-configuration -o jsonpath='{.data}'
map[validatingwebhookconfiguration.yaml:apiVersion: admissionregistration.k8s.io/v1beta1
kind: ValidatingWebhookConfiguration
metadata:
  name: istio-galley
  namespace: istio-system
  labels:
    app: istio-galley
    chart: galley-1.0.0
    release: istio
    heritage: Tiller
webhooks:
  - name: pilot.validation.istio.io
    clientConfig:
      service:
        name: istio-galley
        namespace: istio-system
        path: "/admitpilot"
      caBundle: ""
    rules:
      - operations:
      (... snip ...)

If the webhook array in istio-galley-configuration is empty and you’re using helm template or helm install, verify --set galley.enabled and --set global.configValidation=true options are set. If you’re not using helm, you’ll need to find a generate YAML that includes the populated webhook array.

The istio-galley validation configuration is fail-close. If configuration exists and is scoped properly, the webhook will be invoked. A missing caBundle, bad certificate, or network connectivity problem will produce an error message when the resource is created/updated. If you don’t see any error message and the webhook wasn’t invoked and the webhook configuration is valid, your cluster is misconfigured.

Creating configuration fails with x509 certificate errors

x509: certificate signed by unknown authority related errors are typically caused by an empty caBundle in the webhook configuration. Verify that it is not empty (see verify webhook configuration). The istio-galley deployment consciously reconciles webhook configuration used the istio-galley-configuration configmap and root certificate mounted from istio.istio-galley-service-account secret in the istio-system namespace.

  1. Verify the istio-galley pod(s) are running:

    $  kubectl -n istio-system get pod -listio=galley
NAME                            READY     STATUS    RESTARTS   AGE
istio-galley-5dbbbdb746-d676g   1/1       Running   0          2d

  2. Verify you’re using Istio version >= 1.0.0. Older version of Galley did not properly re-patch the caBundle. This typically happened when the istio.yaml was re-applied, overwriting a previously patched caBundle.

    $ for pod in $(kubectl -n istio-system get pod -listio=galley -o jsonpath='{.items[*].metadata.name}'); do \
    kubectl -n istio-system exec ${pod} -it /usr/local/bin/galley version| grep ^Version; \
done
Version: 1.0.0

  3. Check the Galley pod logs for errors. Failing to patch the caBundle should print an error.

    $ for pod in $(kubectl -n istio-system get pod -listio=galley -o jsonpath='{.items[*].metadata.name}'); do \
    kubectl -n istio-system logs ${pod} \
done

  4. If the patching failed, verify the RBAC configuration for Galley:

    $ kubectl get clusterrole istio-galley-istio-system -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
    app: istio-galley
  name: istio-galley-istio-system
rules:
- apiGroups:
  - admissionregistration.k8s.io
  resources:
  - validatingwebhookconfigurations
  verbs:
  - '*'
- apiGroups:
  - config.istio.io
  resources:
  - '*'
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - '*'
  resourceNames:
  - istio-galley
  resources:
  - deployments
  verbs:
  - get

    istio-galley needs validatingwebhookconfigurations write access to create and update the istio-galley validatingwebhookconfiguration.

Creating configuration fails with no such hosts or no endpoints available errors

Validation is fail-close. If the istio-galley pod is not ready, configuration cannot be created and updated. In such cases you’ll see an error about no endpoints available.

Verify the istio-galley pod(s) are running and endpoints are ready.

$  kubectl -n istio-system get pod -listio=galley
NAME                            READY     STATUS    RESTARTS   AGE
istio-galley-5dbbbdb746-d676g   1/1       Running   0          2d

$ kubectl -n istio-system get endpoints istio-galley
NAME           ENDPOINTS                          AGE
istio-galley   10.48.6.108:10514,10.48.6.108:443   3d

If the pods or endpoints aren’t ready, check the pod logs and status for any indication about why the webhook pod is failing to start and serve traffic.

$ for pod in $(kubectl -n istio-system get pod -listio=galley -o jsonpath='{.items[*].metadata.name}'); do \
    kubectl -n istio-system logs ${pod} \
done

$ for pod in $(kubectl -n istio-system get pod -listio=galley -o name); do \
    kubectl -n istio-system describe ${pod} \
done