cert-manager CA Integration

This task shows how to provision Control Plane and Workload Certificates with an external Certificate Authority using cert-manager. cert-manager is a x509 certificate operator for Kubernetes that supports a number of Issuers, representing Certificate Authorities that can sign certificates. The istio-csr project installs an agent that is responsible for verifying incoming certificate signing requests from Istio mesh workloads, and signs them through cert-manager via a configured Issuer.

Install cert-manager

First, cert-manager must be installed on the cluster using your preferred method.

helm repo add jetstack https://charts.jetstack.io
helm repo update
kubectl create namespace cert-manager
helm install -n cert-manager cert-manager jetstack/cert-manager --set installCRDs=true

Verify the cert-manager deployments have successfully rolled-out.

for i in cert-manager cert-manager-cainjector cert-manager-webhook; \
do kubectl rollout status deploy/$i -n cert-manager; done

Configure cert-manager

An Issuer must be created in the istio-system namespace to sign Istiod and mesh workload certificates. We will use a SelfSigned Issuer, though any supported Issuer can be used.

Note that publicly trusted certificates are strongly discouraged from being used, including ACME certificates.

kubectl create namespace istio-system
kubectl apply -n istio-system -f - <<EOF
apiVersion: cert-manager.io/v1
kind: Issuer
  name: selfsigned
  selfSigned: {}
apiVersion: cert-manager.io/v1
kind: Certificate
  name: istio-ca
  isCA: true
  duration: 2160h # 90d
  secretName: istio-ca
  commonName: istio-ca
    - cert-manager
    name: selfsigned
    kind: Issuer
    group: cert-manager.io
apiVersion: cert-manager.io/v1
kind: Issuer
  name: istio-ca
    secretName: istio-ca

Verify the “istio-ca” and “selfsigned” issuers are present and report READY=True:

kubectl get issuers -n istio-system

Once the issuers have become ready, istio-csr can be installed into the cluster.

Install istio-csr

helm install -n cert-manager cert-manager-istio-csr jetstack/cert-manager-istio-csr

Verify the istio-csr deployment has successfully rolled-out.

kubectl rollout status deploy/cert-manager-istio-csr -n cert-manager

Certificates “istio-ca” and “istiod” should be present and report READY=True.

kubectl get certificates -n istio-system

Install Istio

Istio must be configured to use cert-manager as the CA server for both workload and Istio control plane components. The following configuration uses the IstioOperator resource to install Istio with cert-manager integration:

getmesh istioctl install -y -f - <<EOF
apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
  namespace: istio-system
      # Changes the certificate provider to Cert Manager istio-csr
      caAddress: cert-manager-istio-csr.cert-manager.svc:443
          # Disables istiod CA Sever functionality
        - name: ENABLE_CA_SERVER
          value: "false"
        - apiVersion: apps/v1
          kind: Deployment
          name: istiod
            # Mounts istiod serving and webhook certificates from Secret
          - path: spec.template.spec.containers.[name:discovery].args[-1]
            value: "--tlsCertFile=/etc/cert-manager/tls/tls.crt"
          - path: spec.template.spec.containers.[name:discovery].args[-1]
            value: "--tlsKeyFile=/etc/cert-manager/tls/tls.key"
          - path: spec.template.spec.containers.[name:discovery].args[-1]
            value: "--caCertFile=/etc/cert-manager/ca/root-cert.pem"
          - path: spec.template.spec.containers.[name:discovery].volumeMounts[-1]
              name: cert-manager
              mountPath: "/etc/cert-manager/tls"
              readOnly: true
          - path: spec.template.spec.containers.[name:discovery].volumeMounts[-1]
              name: ca-root-cert
              mountPath: "/etc/cert-manager/ca"
              readOnly: true
          - path: spec.template.spec.volumes[-1]
              name: cert-manager
                secretName: istiod-tls
          - path: spec.template.spec.volumes[-1]
              name: ca-root-cert
                defaultMode: 420
                name: istio-ca-root-cert

The installation should complete, and the Istio control plane should become in a ready state.

kubectl get pods -n istio-system

Test mTLS

All workload certificates will now be requested through cert-manager using the configured Issuer. Let’s run an example workload to test mTLS. First, create a namespace and configure it for automatic sidecar injection:

kubectl create ns foo
kubectl label ns/foo istio-injection=enabled

Run the sample sleep and httpbin workloads.

kubectl apply -n foo -f https://raw.githubusercontent.com/istio/istio/release-$ISTIO_VERSION/samples/sleep/sleep.yaml
kubectl apply -n foo -f https://raw.githubusercontent.com/istio/istio/release-$ISTIO_VERSION/samples/httpbin/httpbin.yaml

Verify the sleep and httpbin deployments have successfully rolled-out.

for i in sleep httpbin; do kubectl rollout status -n foo deploy/$i; done

Verify the sidecar proxy was injected for each workload. Each workload pod should show 2/2 containers are READY.

for i in sleep httpbin; do kubectl get po -n foo -l app=$i; done

By default, Istio configures destination workloads using PERMISSIVE mode. This mode means a service can accept both plain text and mTLS connections. To ensure mTLS is being used between sleep and httpbin workloads, set the mode to STRICT for namespace “foo”.

kubectl apply -n foo -f - <<EOF
apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
  name: "default"
    mode: STRICT

Test mTLS from the sleep pod to the httpbin pod.

kubectl -n foo exec -it deploy/sleep -c sleep -- curl -o /dev/null -s -w '%{http_code}\n' http://httpbin.foo:8000/headers

You should receive an 200 response code.

Visualize mTLS

Optionally, you can run Kiali to visualize the mTLS connections.

kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-$ISTIO_VERSION/samples/addons/prometheus.yaml
kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-$ISTIO_VERSION/samples/addons/kiali.yaml

Verify the Kiali and Prometheus deployments successfully rolled-out.

for i in prometheus kiali; do kubectl rollout status -n istio-system deploy/$i; done

Open the Kiali dashboard.

istioctl dashboard kiali

Navigate to Workloads > Namespace:foo > httpbin. You should see the connection graph with padlocks to indicate mTLS is being used. If the graph is empty, adjust the “traffic metrics per refresh” dropdown list in the upper right-hand corner or regenerate connections.


Congratulations, you successfully configured Istio to use cert-manager as a CA for mesh mTLS authentication.