Tetrate Istio SubscriptionVersion: Next

Istio and cert-manager integration

Istio provides different mechanisms to sign workload certificates for the purpose of mutual TLS (mTLS). The options include:

Istio Certificate Authority (CA) uses a self-signed root certificate
Istio CA uses an administrator-specified certificate and key with an administrator-specified root certificate
Custom CA issues keys and certificate files mounted into the sidecars
Custom CA integration uses Kubernetes CSR API
External CA uses Istio CA gRPC API (either through the Istiod Registration Authority (RA) model or directly authenticating workloads and validating Subject Alternative Name (SAN))

This guide explains how to integrate with cert-manager.

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.

Use a Private CA

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
metadata:
  name: selfsigned
spec:
  selfSigned: {}
---
apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
  name: istio-ca
spec:
  isCA: true
  duration: 2160h # 90d
  secretName: istio-ca
  commonName: istio-ca
  subject:
    organizations:
    - cert-manager
  issuerRef:
    name: selfsigned
    kind: Issuer
    group: cert-manager.io
---
apiVersion: cert-manager.io/v1
kind: Issuer
metadata:
  name: istio-ca
spec:
  ca:
    secretName: istio-ca
EOF

Verify the "istio-ca" and "self-signed" 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:

istioctl install -y -f - <<EOF
apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
metadata:
  namespace: istio-system
spec:
  values:
    global:
      # Changes the certificate provider to Cert Manager istio-csr
      caAddress: cert-manager-istio-csr.cert-manager.svc:443
  components:
    pilot:
      k8s:
        env:
          # Disables istiod CA Server functionality
        - name: ENABLE_CA_SERVER
          value: "false"
        overlays:
        - apiVersion: apps/v1
          kind: Deployment
          name: istiod
          patches:
            # 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]
            value:
              name: cert-manager
              mountPath: "/etc/cert-manager/tls"
              readOnly: true
          - path: spec.template.spec.containers.[name:discovery].volumeMounts[-1]
            value:
              name: ca-root-cert
              mountPath: "/etc/cert-manager/ca"
              readOnly: true
          - path: spec.template.spec.volumes[-1]
            value:
              name: cert-manager
              secret:
                secretName: istiod-tls
          - path: spec.template.spec.volumes[-1]
            value:
              name: ca-root-cert
              configMap:
                defaultMode: 420
                name: istio-ca-root-cert
EOF

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.
```
ISTIO_VERSION=1.18
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
metadata:
  name: "default"
spec:
  mtls:
    mode: STRICT
EOF
```
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 have successfully configured Istio to use cert-manager as a CA for mesh mTLS authentication.

Istio and cert-manager integration

cert-manager CA Integration​

Install cert-manager​

Configure cert-manager​

Install istio-csr​

Install Istio​

Test mTLS​

Visualize mTLS​

cert-manager CA Integration

Install cert-manager

Configure cert-manager

Install istio-csr

Install Istio

Test mTLS

Visualize mTLS