Ingress Gateway without TLS Termination

4 minute read

The Securing Gateways with HTTPS task describes how to configure HTTPS ingress access to an HTTP service. This example describes how to configure HTTPS ingress access to an HTTPS service, i.e., configure an ingress gateway to perform SNI passthrough, instead of TLS termination on incoming requests.

The example HTTPS service used for this task is a simple NGINX server. In the following steps you first deploy the NGINX service in your Kubernetes cluster. Then you configure a gateway to provide ingress access to the service via host nginx.example.com.

Generate client and server certificates and keys

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

Create a root certificate and private key to sign the certificate for your services:

$ 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

Create a certificate and a private key for nginx.example.com:

$ openssl req -out nginx.example.com.csr -newkey rsa:2048 -nodes -keyout nginx.example.com.key -subj "/CN=nginx.example.com/O=some organization"
$ openssl x509 -req -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 0 -in nginx.example.com.csr -out nginx.example.com.crt

Deploy an NGINX server

Create a Kubernetes Secret to hold the server’s certificate.

$ kubectl create secret tls nginx-server-certs --key nginx.example.com.key --cert nginx.example.com.crt

Create a configuration file for the NGINX server:

$ cat <<EOF > ./nginx.conf
events {
}

http {
  log_format main '$remote_addr - $remote_user [$time_local]  $status '
  '"$request" $body_bytes_sent "$http_referer" '
  '"$http_user_agent" "$http_x_forwarded_for"';
  access_log /var/log/nginx/access.log main;
  error_log  /var/log/nginx/error.log;

  server {
    listen 443 ssl;

    root /usr/share/nginx/html;
    index index.html;

    server_name nginx.example.com;
    ssl_certificate /etc/nginx-server-certs/tls.crt;
    ssl_certificate_key /etc/nginx-server-certs/tls.key;
  }
}
EOF

Create a Kubernetes ConfigMap to hold the configuration of the NGINX server:

$ kubectl create configmap nginx-configmap --from-file=nginx.conf=./nginx.conf

Deploy the NGINX server:

$ cat <<EOF | istioctl kube-inject -f - | kubectl apply -f -
apiVersion: v1
kind: Service
metadata:
  name: my-nginx
  labels:
    run: my-nginx
spec:
  ports:
  - port: 443
    protocol: TCP
  selector:
    run: my-nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-nginx
spec:
  selector:
    matchLabels:
      run: my-nginx
  replicas: 1
  template:
    metadata:
      labels:
        run: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx
        ports:
        - containerPort: 443
        volumeMounts:
        - name: nginx-config
          mountPath: /etc/nginx
          readOnly: true
        - name: nginx-server-certs
          mountPath: /etc/nginx-server-certs
          readOnly: true
      volumes:
      - name: nginx-config
        configMap:
          name: nginx-configmap
      - name: nginx-server-certs
        secret:
          secretName: nginx-server-certs
EOF

To test that the NGINX server was deployed successfully, send a request to the server from its sidecar proxy without checking the server’s certificate (use the -k option of curl). Ensure that the server’s certificate is printed correctly, i.e., common name is equal to nginx.example.com.

$ kubectl exec -it $(kubectl get pod  -l run=my-nginx -o jsonpath={.items..metadata.name}) -c istio-proxy -- curl -v -k --resolve nginx.example.com:443:127.0.0.1 https://nginx.example.com
...
SSL connection using TLS1.2 / ECDHE_RSA_AES_128_GCM_SHA256
  server certificate verification SKIPPED
  server certificate status verification SKIPPED
  common name: nginx.example.com (matched)
  server certificate expiration date OK
  server certificate activation date OK
  certificate public key: RSA
  certificate version: #3
  subject: CN=nginx.example.com; O=some organization
  start date: Wed, 15 Aug 2018 07:29:07 GMT
  expire date: Sun, 25 Aug 2019 07:29:07 GMT
  issuer: O=example Inc.; CN=example.com

> GET / HTTP/1.1
> User-Agent: curl/7.35.0
> Host: nginx.example.com
...
< HTTP/1.1 200 OK

< Server: nginx/1.15.2
...
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
...

Configure an ingress gateway

Define a Gateway with a server section for port 443. Note the PASSTHROUGH TLS mode which instructs the gateway to pass the ingress traffic AS IS, without terminating TLS.

$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: mygateway
spec:
  selector:
    istio: ingressgateway # use istio default ingress gateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    tls:
      mode: PASSTHROUGH
    hosts:
    - nginx.example.com
EOF

Configure routes for traffic entering via the Gateway:

$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: nginx
spec:
  hosts:
  - nginx.example.com
  gateways:
  - mygateway
  tls:
  - match:
    - port: 443
      sni_hosts:
      - nginx.example.com
    route:
    - destination:
        host: my-nginx
        port:
          number: 443
EOF

Follow the instructions in Determining the ingress IP and ports to define the SECURE_INGRESS_PORT and INGRESS_HOST environment variables.

Access the NGINX service from outside the cluster. Note that the correct certificate is returned by the server and it is successfully verified (SSL certificate verify ok is printed).

$ curl -v --resolve nginx.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST --cacert example.com.crt https://nginx.example.com:$SECURE_INGRESS_PORT
Server certificate:
  subject: CN=nginx.example.com; O=some organization
  start date: Wed, 15 Aug 2018 07:29:07 GMT
  expire date: Sun, 25 Aug 2019 07:29:07 GMT
  issuer: O=example Inc.; CN=example.com
  SSL certificate verify ok.

  < HTTP/1.1 200 OK
  < Server: nginx/1.15.2
  ...
  <html>
  <head>
  <title>Welcome to nginx!</title>

Cleanup

Remove created Kubernetes resources:

$ kubectl delete secret nginx-server-certs
$ kubectl delete configmap nginx-configmap
$ kubectl delete service my-nginx
$ kubectl delete deployment my-nginx
$ kubectl delete gateway mygateway
$ kubectl delete virtualservice nginx

Delete the certificates and keys:

$ rm example.com.crt example.com.key nginx.example.com.crt nginx.example.com.key nginx.example.com.csr

Delete the generated configuration files used in this example:
```
$ rm ./nginx.conf
```