Mutual TLS Migration

This task shows how to ensure your workloads only communicate using mutual TLS as they are migrated to Istio.

Istio automatically configures workload sidecars to use mutual TLS when calling other workloads. By default, Istio configures the destination workloads using PERMISSIVE mode. When PERMISSIVE mode is enabled, a service can accept both plaintext and mutual TLS traffic. In order to only allow mutual TLS traffic, the configuration needs to be changed to STRICT mode.

You can use the Grafana dashboard to check which workloads are still sending plaintext traffic to the workloads in PERMISSIVE mode and choose to lock them down once the migration is done.

Before you begin

• Understand Istio authentication policy and related mutual TLS authentication concepts.

• Read the authentication policy task to learn how to configure authentication policy.

• Have a Kubernetes cluster with Istio installed, without global mutual TLS enabled (for example, use the default configuration profile as described in installation steps).

In this task, you can try out the migration process by creating sample workloads and modifying the policies to enforce STRICT mutual TLS between the workloads.

Set up the cluster

• Create two namespaces, foo and bar, and deploy httpbin and curl with sidecars on both of them:

  ZipZipZipZip

  $ kubectl create ns foo
  $ kubectl apply -f <(istioctl kube-inject -f @samples/httpbin/httpbin.yaml@) -n foo
  $ kubectl apply -f <(istioctl kube-inject -f @samples/curl/curl.yaml@) -n foo
  $ kubectl create ns bar
  $ kubectl apply -f <(istioctl kube-inject -f @samples/httpbin/httpbin.yaml@) -n bar
  $ kubectl apply -f <(istioctl kube-inject -f @samples/curl/curl.yaml@) -n bar

• Create another namespace, legacy, and deploy curl without a sidecar:

  Zip

  $ kubectl create ns legacy
  $ kubectl apply -f @samples/curl/curl.yaml@ -n legacy

• Verify the setup by sending http requests (using curl) from the curl pods, in namespaces foo, bar and legacy, to httpbin.foo and httpbin.bar. All requests should succeed with return code 200.

  $ for from in "foo" "bar" "legacy"; do for to in "foo" "bar"; do kubectl exec "$(kubectl get pod -l app=curl -n ${from} -o jsonpath={.items..metadata.name})" -c curl -n ${from} -- curl http://httpbin.${to}:8000/ip -s -o /dev/null -w "curl.${from} to httpbin.${to}: %{http_code}\n"; done; done
  curl.foo to httpbin.foo: 200
  curl.foo to httpbin.bar: 200
  curl.bar to httpbin.foo: 200
  curl.bar to httpbin.bar: 200
  curl.legacy to httpbin.foo: 200
  curl.legacy to httpbin.bar: 200

Lock down to mutual TLS by namespace

After migrating all clients to Istio and injecting the Envoy sidecar, you can lock down workloads in the foo namespace to only accept mutual TLS traffic.

$ kubectl apply -n foo -f - <<EOF
apiVersion: security.istio.io/v1
kind: PeerAuthentication
metadata:
  name: default
spec:
  mtls:
    mode: STRICT
EOF

Now, you should see the request from curl.legacy to httpbin.foo failing.

$ for from in "foo" "bar" "legacy"; do for to in "foo" "bar"; do kubectl exec "$(kubectl get pod -l app=curl -n ${from} -o jsonpath={.items..metadata.name})" -c curl -n ${from} -- curl http://httpbin.${to}:8000/ip -s -o /dev/null -w "curl.${from} to httpbin.${to}: %{http_code}\n"; done; done
curl.foo to httpbin.foo: 200
curl.foo to httpbin.bar: 200
curl.bar to httpbin.foo: 200
curl.bar to httpbin.bar: 200
curl.legacy to httpbin.foo: 000
command terminated with exit code 56
curl.legacy to httpbin.bar: 200

If you installed Istio with values.global.proxy.privileged=true, you can use tcpdump to verify traffic is encrypted or not.

$ kubectl exec -nfoo "$(kubectl get pod -nfoo -lapp=httpbin -ojsonpath={.items..metadata.name})" -c istio-proxy -- sudo tcpdump dst port 80  -A
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes

You will see plain text and encrypted text in the output when requests are sent from curl.legacy and curl.foo respectively.

If you can’t migrate all your services to Istio (i.e., inject Envoy sidecar in all of them), you will need to continue to use PERMISSIVE mode. However, when configured with PERMISSIVE mode, no authentication or authorization checks will be performed for plaintext traffic by default. We recommend you use Istio Authorization to configure different paths with different authorization policies.

Lock down mutual TLS for the entire mesh

You can lock down workloads in all namespaces to only accept mutual TLS traffic by putting the policy in the system namespace of your Istio installation.

$ kubectl apply -n istio-system -f - <<EOF
apiVersion: security.istio.io/v1
kind: PeerAuthentication
metadata:
  name: default
spec:
  mtls:
    mode: STRICT
EOF

Now, both the foo and bar namespaces enforce mutual TLS only traffic, so you should see requests from curl.legacy failing for both.

$ for from in "foo" "bar" "legacy"; do for to in "foo" "bar"; do kubectl exec "$(kubectl get pod -l app=curl -n ${from} -o jsonpath={.items..metadata.name})" -c curl -n ${from} -- curl http://httpbin.${to}:8000/ip -s -o /dev/null -w "curl.${from} to httpbin.${to}: %{http_code}\n"; done; done

Clean up the example

1. Remove the mesh-wide authentication policy.

   $ kubectl delete peerauthentication -n foo default
   $ kubectl delete peerauthentication -n istio-system default

2. Remove the test namespaces.

   $ kubectl delete ns foo bar legacy
   Namespaces foo bar legacy deleted.