Ingress Sidecar TLS Termination

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In a regular Istio mesh deployment, the TLS termination for downstream requests is performed at the Ingress Gateway. Although this satisfies most use cases, for some (like an API Gateway in the mesh) the Ingress Gateway is not necessarily needed. This task shows how to eliminate the additional hop introduced by the Istio Ingress Gateway and let the Envoy sidecar, running alongside the application, perform TLS termination for requests coming from outside of the service mesh.

The example HTTPS service used for this task is a simple httpbin service. In the following steps you will deploy the httpbin service inside your service mesh and configure it.

Before you begin

  • Setup Istio by following the instructions in the Installation guide, enabling the experimental feature ENABLE_TLS_ON_SIDECAR_INGRESS.

    $ istioctl install --set profile=default --set values.pilot.env.ENABLE_TLS_ON_SIDECAR_INGRESS=true

  • Create the test namespace where the target httpbin service will be deployed. Make sure to enable sidecar injection for the namespace.

    $ kubectl create ns test
$ kubectl label namespace test istio-injection=enabled

Enable global mTLS

Apply the following PeerAuthentication policy to require mTLS traffic for all workloads in the mesh.

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

Disable PeerAuthentication for the externally exposed httpbin port

Disable PeerAuthentication for the port of the httpbin service which will perform ingress TLS termination at the sidecar. Note that this is the targetPort of the httpbin service which should be used exclusively for external communication.

$ kubectl -n test apply -f - <<EOF
apiVersion: security.istio.io/v1
kind: PeerAuthentication
metadata:
  name: disable-peer-auth-for-external-mtls-port
  namespace: test
spec:
  selector:
    matchLabels:
      app: httpbin
  mtls:
    mode: STRICT
  portLevelMtls:
    9080:
      mode: DISABLE
EOF

Generate CA cert, Server cert/key and Client cert/key

For this task you can use your favorite tool to generate certificates and keys. The commands below use openssl:

$ #CA is example.com
$ openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -subj '/O=example Inc./CN=example.com' -keyout example.com.key -out example.com.crt
$ #Server is httpbin.test.svc.cluster.local
$ openssl req -out httpbin.test.svc.cluster.local.csr -newkey rsa:2048 -nodes -keyout httpbin.test.svc.cluster.local.key -subj "/CN=httpbin.test.svc.cluster.local/O=httpbin organization"
$ openssl x509 -req -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 1 -in httpbin.test.svc.cluster.local.csr -out httpbin.test.svc.cluster.local.crt
$ #client is client.test.svc.cluster.local
$ openssl req -out client.test.svc.cluster.local.csr -newkey rsa:2048 -nodes -keyout client.test.svc.cluster.local.key -subj "/CN=client.test.svc.cluster.local/O=client organization"
$ openssl x509 -req -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 1 -in client.test.svc.cluster.local.csr -out client.test.svc.cluster.local.crt

Create k8s secrets for the certificates and keys

$ kubectl -n test create secret generic httpbin-mtls-termination-cacert --from-file=ca.crt=./example.com.crt
$ kubectl -n test create secret tls httpbin-mtls-termination --cert ./httpbin.test.svc.cluster.local.crt --key ./httpbin.test.svc.cluster.local.key

Deploy the httpbin test service

When the httpbin deployment is created, we need to use userVolumeMount annotations in the deployment to mount the certificates for the istio-proxy sidecar. Note that this step is only needed because Istio does not currently support credentialName in a sidecar configuration.

sidecar.istio.io/userVolume: '{"tls-secret":{"secret":{"secretName":"httpbin-mtls-termination","optional":true}},"tls-ca-secret":{"secret":{"secretName":"httpbin-mtls-termination-cacert"}}}'
sidecar.istio.io/userVolumeMount: '{"tls-secret":{"mountPath":"/etc/istio/tls-certs/","readOnly":true},"tls-ca-secret":{"mountPath":"/etc/istio/tls-ca-certs/","readOnly":true}}'

Use the following command to deploy the httpbin service with the required userVolumeMount configuration:

$ kubectl -n test apply -f - <<EOF
apiVersion: v1
kind: ServiceAccount
metadata:
  name: httpbin
---
apiVersion: v1
kind: Service
metadata:
  name: httpbin
  labels:
    app: httpbin
    service: httpbin
spec:
  ports:
  - port: 8443
    name: https
    targetPort: 9080
  - port: 8080
    name: http
    targetPort: 9081
  selector:
    app: httpbin
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpbin
spec:
  replicas: 1
  selector:
    matchLabels:
      app: httpbin
      version: v1
  template:
    metadata:
      labels:
        app: httpbin
        version: v1
      annotations:
        sidecar.istio.io/userVolume: '{"tls-secret":{"secret":{"secretName":"httpbin-mtls-termination","optional":true}},"tls-ca-secret":{"secret":{"secretName":"httpbin-mtls-termination-cacert"}}}'
        sidecar.istio.io/userVolumeMount: '{"tls-secret":{"mountPath":"/etc/istio/tls-certs/","readOnly":true},"tls-ca-secret":{"mountPath":"/etc/istio/tls-ca-certs/","readOnly":true}}'
    spec:
      serviceAccountName: httpbin
      containers:
      - image: docker.io/kennethreitz/httpbin
        imagePullPolicy: IfNotPresent
        name: httpbin
        ports:
        - containerPort: 80
EOF

Configure httpbin to enable external mTLS

This is the core step for this feature. Using the Sidecar API, configure the ingress TLS settings. The TLS mode can be SIMPLE or MUTUAL. This example uses MUTUAL.

$ kubectl -n test apply -f - <<EOF
apiVersion: networking.istio.io/v1
kind: Sidecar
metadata:
  name: ingress-sidecar
  namespace: test
spec:
  workloadSelector:
    labels:
      app: httpbin
      version: v1
  ingress:
  - port:
      number: 9080
      protocol: HTTPS
      name: external
    defaultEndpoint: 0.0.0.0:80
    tls:
      mode: MUTUAL
      privateKey: "/etc/istio/tls-certs/tls.key"
      serverCertificate: "/etc/istio/tls-certs/tls.crt"
      caCertificates: "/etc/istio/tls-ca-certs/ca.crt"
  - port:
      number: 9081
      protocol: HTTP
      name: internal
    defaultEndpoint: 0.0.0.0:80
EOF

Verification

Now that the httpbin server is deployed and configured, bring up two clients to test the end to end connectivity from both inside and outside of the mesh:

  1. An internal client (curl) in the same namespace (test) as the httpbin service, with sidecar injected.
  2. An external client (curl) in the default namespace (i.e., outside of the service mesh).
$ kubectl apply -f samples/curl/curl.yaml
$ kubectl -n test apply -f samples/curl/curl.yaml

Run the following commands to verify that everything is up and running, and configured correctly.

$ kubectl get pods
NAME                     READY   STATUS    RESTARTS   AGE
curl-557747455f-xx88g    1/1     Running   0          4m14s
$ kubectl get pods -n test
NAME                       READY   STATUS    RESTARTS   AGE
httpbin-5bbdbd6588-z9vbs   2/2     Running   0          8m44s
curl-557747455f-brzf6      2/2     Running   0          6m57s
$ kubectl get svc -n test
NAME      TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)             AGE
httpbin   ClusterIP   10.100.78.113   <none>        8443/TCP,8080/TCP   10m
curl      ClusterIP   10.110.35.153   <none>        80/TCP              8m49s

In the following command, replace httpbin-5bbdbd6588-z9vbs with the name of your httpbin pod.

$ istioctl proxy-config secret httpbin-5bbdbd6588-z9vbs.test
RESOURCE NAME                                                           TYPE           STATUS     VALID CERT     SERIAL NUMBER                               NOT AFTER                NOT BEFORE
file-cert:/etc/istio/tls-certs/tls.crt~/etc/istio/tls-certs/tls.key     Cert Chain     ACTIVE     true           1                                           2023-02-14T09:51:56Z     2022-02-14T09:51:56Z
default                                                                 Cert Chain     ACTIVE     true           329492464719328863283539045344215802956     2022-02-15T09:55:46Z     2022-02-14T09:53:46Z
ROOTCA                                                                  CA             ACTIVE     true           204427760222438623495455009380743891800     2032-02-07T16:58:00Z     2022-02-09T16:58:00Z
file-root:/etc/istio/tls-ca-certs/ca.crt                                Cert Chain     ACTIVE     true           14033888812979945197                        2023-02-14T09:51:56Z     2022-02-14T09:51:56Z

Verify internal mesh connectivity on port 8080

$ export INTERNAL_CLIENT=$(kubectl -n test get pod -l app=curl -o jsonpath={.items..metadata.name})
$ kubectl -n test exec "${INTERNAL_CLIENT}" -c curl -- curl -IsS "http://httpbin:8080/status/200"
HTTP/1.1 200 OK
server: envoy
date: Mon, 24 Oct 2022 09:04:52 GMT
content-type: text/html; charset=utf-8
access-control-allow-origin: *
access-control-allow-credentials: true
content-length: 0
x-envoy-upstream-service-time: 5

Verify external to internal mesh connectivity on port 8443

To verify mTLS traffic from an external client, first copy the CA certificate and client certificate/key to the curl client running in the default namespace.

$ export EXTERNAL_CLIENT=$(kubectl get pod -l app=curl -o jsonpath={.items..metadata.name})
$ kubectl cp client.test.svc.cluster.local.key default/"${EXTERNAL_CLIENT}":/tmp/
$ kubectl cp client.test.svc.cluster.local.crt default/"${EXTERNAL_CLIENT}":/tmp/
$ kubectl cp example.com.crt default/"${EXTERNAL_CLIENT}":/tmp/ca.crt

Now that the certificates are available for the external curl client, you can verify connectivity from it to the internal httpbin service using the following command.

$ kubectl exec "${EXTERNAL_CLIENT}" -c curl -- curl -IsS --cacert /tmp/ca.crt --key /tmp/client.test.svc.cluster.local.key --cert /tmp/client.test.svc.cluster.local.crt -HHost:httpbin.test.svc.cluster.local "https://httpbin.test.svc.cluster.local:8443/status/200"
server: istio-envoy
date: Mon, 24 Oct 2022 09:05:31 GMT
content-type: text/html; charset=utf-8
access-control-allow-origin: *
access-control-allow-credentials: true
content-length: 0
x-envoy-upstream-service-time: 4
x-envoy-decorator-operation: ingress-sidecar.test:9080/*

In addition to verifying external mTLS connectivity via the ingress port 8443, it is also important to verify that port 8080 does not accept any external mTLS traffic.

$ kubectl exec "${EXTERNAL_CLIENT}" -c curl -- curl -IsS --cacert /tmp/ca.crt --key /tmp/client.test.svc.cluster.local.key --cert /tmp/client.test.svc.cluster.local.crt -HHost:httpbin.test.svc.cluster.local "http://httpbin.test.svc.cluster.local:8080/status/200"
curl: (56) Recv failure: Connection reset by peer
command terminated with exit code 56

Cleanup the mutual TLS termination example

  1. Remove created Kubernetes resources:

    $ kubectl delete secret httpbin-mtls-termination httpbin-mtls-termination-cacert -n test
$ kubectl delete service httpbin curl -n test
$ kubectl delete deployment httpbin curl -n test
$ kubectl delete namespace test
$ kubectl delete service curl
$ kubectl delete deployment curl

  2. Delete the certificates and private keys:

    $ rm example.com.crt example.com.key httpbin.test.svc.cluster.local.crt httpbin.test.svc.cluster.local.key httpbin.test.svc.cluster.local.csr \
    client.test.svc.cluster.local.crt client.test.svc.cluster.local.key client.test.svc.cluster.local.csr

  3. Uninstall Istio from your cluster:

    $ istioctl uninstall --purge -y
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