Egress Gateways with TLS Origination

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The TLS Origination for Egress Traffic example shows how to configure Istio to perform TLS origination for traffic to an external service. The Configure an Egress Gateway example shows how to configure Istio to direct egress traffic through a dedicated egress gateway service. This example combines the previous two by describing how to configure an egress gateway to perform TLS origination for traffic to external services.

Before you begin

  • Setup Istio by following the instructions in the Installation guide.

  • Start the curl sample which will be used as a test source for external calls.

    If you have enabled automatic sidecar injection, do

    Zip
    $ kubectl apply -f @samples/curl/curl.yaml@

    otherwise, you have to manually inject the sidecar before deploying the curl application:

    Zip
    $ kubectl apply -f <(istioctl kube-inject -f @samples/curl/curl.yaml@)

    Note that any pod that you can exec and curl from would do.

  • Create a shell variable to hold the name of the source pod for sending requests to external services. If you used the curl sample, run:

    $ export SOURCE_POD=$(kubectl get pod -l app=curl -o jsonpath={.items..metadata.name})

  • For macOS users, verify that you are using openssl version 1.1 or later:

    $ openssl version -a | grep OpenSSL
OpenSSL 1.1.1g  21 Apr 2020

    If the previous command outputs a version 1.1 or later, as shown, your openssl command should work correctly with the instructions in this task. Otherwise, upgrade your openssl or try a different implementation of openssl, for example on a Linux machine.

  • Enable Envoy’s access logging if not already enabled. For example, using istioctl:

    $ istioctl install <flags-you-used-to-install-Istio> --set meshConfig.accessLogFile=/dev/stdout

  • If you are NOT using the Gateway API instructions, make sure to deploy the Istio egress gateway.

Perform TLS origination with an egress gateway

This section describes how to perform the same TLS origination as in the TLS Origination for Egress Traffic example, only this time using an egress gateway. Note that in this case the TLS origination will be done by the egress gateway, as opposed to by the sidecar in the previous example.

  1. Define a ServiceEntry for edition.cnn.com:

    $ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: cnn
spec:
  hosts:
  - edition.cnn.com
  ports:
  - number: 80
    name: http
    protocol: HTTP
  - number: 443
    name: https
    protocol: HTTPS
  resolution: DNS
EOF

  2. Verify that your ServiceEntry was applied correctly by sending a request to http://edition.cnn.com/politics.

    $ kubectl exec "${SOURCE_POD}" -c curl -- curl -sSL -o /dev/null -D - http://edition.cnn.com/politics
HTTP/1.1 301 Moved Permanently
...
location: https://edition.cnn.com/politics
...

    Your ServiceEntry was configured correctly if you see 301 Moved Permanently in the output.

  3. Create an egress Gateway for edition.cnn.com, port 80, and a destination rule for sidecar requests that will be directed to the egress gateway.

$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1
kind: Gateway
metadata:
  name: istio-egressgateway
spec:
  selector:
    istio: egressgateway
  servers:
  - port:
      number: 80
      name: https-port-for-tls-origination
      protocol: HTTPS
    hosts:
    - edition.cnn.com
    tls:
      mode: ISTIO_MUTUAL
---
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: egressgateway-for-cnn
spec:
  host: istio-egressgateway.istio-system.svc.cluster.local
  subsets:
  - name: cnn
    trafficPolicy:
      loadBalancer:
        simple: ROUND_ROBIN
      portLevelSettings:
      - port:
          number: 80
        tls:
          mode: ISTIO_MUTUAL
          sni: edition.cnn.com
EOF
  1. Configure route rules to direct traffic through the egress gateway:
$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: direct-cnn-through-egress-gateway
spec:
  hosts:
  - edition.cnn.com
  gateways:
  - istio-egressgateway
  - mesh
  http:
  - match:
    - gateways:
      - mesh
      port: 80
    route:
    - destination:
        host: istio-egressgateway.istio-system.svc.cluster.local
        subset: cnn
        port:
          number: 80
      weight: 100
  - match:
    - gateways:
      - istio-egressgateway
      port: 80
    route:
    - destination:
        host: edition.cnn.com
        port:
          number: 443
      weight: 100
EOF

  1. Define a DestinationRule to perform TLS origination for requests to edition.cnn.com:

    $ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: originate-tls-for-edition-cnn-com
spec:
  host: edition.cnn.com
  trafficPolicy:
    loadBalancer:
      simple: ROUND_ROBIN
    portLevelSettings:
    - port:
        number: 443
      tls:
        mode: SIMPLE # initiates HTTPS for connections to edition.cnn.com
EOF

  2. Send an HTTP request to http://edition.cnn.com/politics.

    $ kubectl exec "${SOURCE_POD}" -c curl -- curl -sSL -o /dev/null -D - http://edition.cnn.com/politics
HTTP/1.1 200 OK
...

    The output should be the same as in the TLS Origination for Egress Traffic example, with TLS origination: without the 301 Moved Permanently message.

  3. Check the log of the egress gateway’s proxy.

If Istio is deployed in the istio-system namespace, the command to print the log is:

$ kubectl logs -l istio=egressgateway -c istio-proxy -n istio-system | tail

You should see a line similar to the following:

[2020-06-30T16:17:56.763Z] "GET /politics HTTP/2" 200 - "-" "-" 0 1295938 529 89 "10.244.0.171" "curl/7.64.0" "cf76518d-3209-9ab7-a1d0-e6002728ef5b" "edition.cnn.com" "151.101.129.67:443" outbound|443||edition.cnn.com 10.244.0.170:54280 10.244.0.170:8080 10.244.0.171:35628 - -

Cleanup the TLS origination example

Remove the Istio configuration items you created:

$ kubectl delete gw istio-egressgateway
$ kubectl delete serviceentry cnn
$ kubectl delete virtualservice direct-cnn-through-egress-gateway
$ kubectl delete destinationrule originate-tls-for-edition-cnn-com
$ kubectl delete destinationrule egressgateway-for-cnn

Perform mutual TLS origination with an egress gateway

Similar to the previous section, this section describes how to configure an egress gateway to perform TLS origination for an external service, only this time using a service that requires mutual TLS.

This example is considerably more involved because you need to first:

  1. generate client and server certificates
  2. deploy an external service that supports the mutual TLS protocol
  3. redeploy the egress gateway with the needed mutual TLS certs

Only then can you configure the external traffic to go through the egress gateway which will perform TLS origination.

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

  1. 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

  2. Create a certificate and a private key for my-nginx.mesh-external.svc.cluster.local:

    $ openssl req -out my-nginx.mesh-external.svc.cluster.local.csr -newkey rsa:2048 -nodes -keyout my-nginx.mesh-external.svc.cluster.local.key -subj "/CN=my-nginx.mesh-external.svc.cluster.local/O=some organization"
$ openssl x509 -req -sha256 -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 0 -in my-nginx.mesh-external.svc.cluster.local.csr -out my-nginx.mesh-external.svc.cluster.local.crt

    Optionally, you can add SubjectAltNames to the certificate if you want to enable SAN validation for the destination. For example:

    $ cat > san.conf <<EOF
[req]
distinguished_name = req_distinguished_name
req_extensions = v3_req
x509_extensions = v3_req
prompt = no
[req_distinguished_name]
countryName = US
[v3_req]
keyUsage = critical, digitalSignature, keyEncipherment
extendedKeyUsage = serverAuth, clientAuth
basicConstraints = critical, CA:FALSE
subjectAltName = critical, @alt_names
[alt_names]
DNS = my-nginx.mesh-external.svc.cluster.local
EOF
$
$ openssl req -out my-nginx.mesh-external.svc.cluster.local.csr -newkey rsa:4096 -nodes -keyout my-nginx.mesh-external.svc.cluster.local.key -subj "/CN=my-nginx.mesh-external.svc.cluster.local/O=some organization" -config san.conf
$ openssl x509 -req -sha256 -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 0 -in my-nginx.mesh-external.svc.cluster.local.csr -out my-nginx.mesh-external.svc.cluster.local.crt -extfile san.conf -extensions v3_req

  3. Generate client certificate and private key:

    $ openssl req -out client.example.com.csr -newkey rsa:2048 -nodes -keyout client.example.com.key -subj "/CN=client.example.com/O=client organization"
$ openssl x509 -req -sha256 -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 1 -in client.example.com.csr -out client.example.com.crt

Deploy a mutual TLS server

To simulate an actual external service that supports the mutual TLS protocol, deploy an NGINX server in your Kubernetes cluster, but running outside of the Istio service mesh, i.e., in a namespace without Istio sidecar proxy injection enabled.

  1. Create a namespace to represent services outside the Istio mesh, namely mesh-external. Note that the sidecar proxy will not be automatically injected into the pods in this namespace since the automatic sidecar injection was not enabled on it.

    $ kubectl create namespace mesh-external

  2. Create Kubernetes Secrets to hold the server’s and CA certificates.

    $ kubectl create -n mesh-external secret tls nginx-server-certs --key my-nginx.mesh-external.svc.cluster.local.key --cert my-nginx.mesh-external.svc.cluster.local.crt
$ kubectl create -n mesh-external secret generic nginx-ca-certs --from-file=example.com.crt

  3. 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 my-nginx.mesh-external.svc.cluster.local;
    ssl_certificate /etc/nginx-server-certs/tls.crt;
    ssl_certificate_key /etc/nginx-server-certs/tls.key;
    ssl_client_certificate /etc/nginx-ca-certs/example.com.crt;
    ssl_verify_client on;
  }
}
EOF

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

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

  5. Deploy the NGINX server:

    $ kubectl apply -f - <<EOF
apiVersion: v1
kind: Service
metadata:
  name: my-nginx
  namespace: mesh-external
  labels:
    run: my-nginx
spec:
  ports:
  - port: 443
    protocol: TCP
  selector:
    run: my-nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-nginx
  namespace: mesh-external
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
        - name: nginx-ca-certs
          mountPath: /etc/nginx-ca-certs
          readOnly: true
      volumes:
      - name: nginx-config
        configMap:
          name: nginx-configmap
      - name: nginx-server-certs
        secret:
          secretName: nginx-server-certs
      - name: nginx-ca-certs
        secret:
          secretName: nginx-ca-certs
EOF

Configure mutual TLS origination for egress traffic

  1. Create a Kubernetes Secret in the same namespace as the egress gateway is deployed in, to hold the client’s certificates:
$ kubectl create secret -n istio-system generic client-credential --from-file=tls.key=client.example.com.key \
  --from-file=tls.crt=client.example.com.crt --from-file=ca.crt=example.com.crt

To support integration with various tools, Istio supports a few different Secret formats. In this example, a single generic Secret with keys tls.key, tls.crt, and ca.crt is used.

  1. Create an egress Gateway for my-nginx.mesh-external.svc.cluster.local, port 443, and a destination rule for sidecar requests that will be directed to the egress gateway:
$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1
kind: Gateway
metadata:
  name: istio-egressgateway
spec:
  selector:
    istio: egressgateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    hosts:
    - my-nginx.mesh-external.svc.cluster.local
    tls:
      mode: ISTIO_MUTUAL
---
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: egressgateway-for-nginx
spec:
  host: istio-egressgateway.istio-system.svc.cluster.local
  subsets:
  - name: nginx
    trafficPolicy:
      loadBalancer:
        simple: ROUND_ROBIN
      portLevelSettings:
      - port:
          number: 443
        tls:
          mode: ISTIO_MUTUAL
          sni: my-nginx.mesh-external.svc.cluster.local
EOF
  1. Configure route rules to direct traffic through the egress gateway:
$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: direct-nginx-through-egress-gateway
spec:
  hosts:
  - my-nginx.mesh-external.svc.cluster.local
  gateways:
  - istio-egressgateway
  - mesh
  http:
  - match:
    - gateways:
      - mesh
      port: 80
    route:
    - destination:
        host: istio-egressgateway.istio-system.svc.cluster.local
        subset: nginx
        port:
          number: 443
      weight: 100
  - match:
    - gateways:
      - istio-egressgateway
      port: 443
    route:
    - destination:
        host: my-nginx.mesh-external.svc.cluster.local
        port:
          number: 443
      weight: 100
EOF
  1. Add a DestinationRule to perform mutual TLS origination:
$ kubectl apply -n istio-system -f - <<EOF
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: originate-mtls-for-nginx
spec:
  host: my-nginx.mesh-external.svc.cluster.local
  trafficPolicy:
    loadBalancer:
      simple: ROUND_ROBIN
    portLevelSettings:
    - port:
        number: 443
      tls:
        mode: MUTUAL
        credentialName: client-credential # this must match the secret created earlier to hold client certs
        sni: my-nginx.mesh-external.svc.cluster.local
        # subjectAltNames: # can be enabled if the certificate was generated with SAN as specified in previous section
        # - my-nginx.mesh-external.svc.cluster.local
EOF
  1. Verify that the credential is supplied to the egress gateway and active:
$ istioctl -n istio-system proxy-config secret deploy/istio-egressgateway | grep client-credential
kubernetes://client-credential            Cert Chain     ACTIVE     true           1                                          2024-06-04T12:46:28Z     2023-06-05T12:46:28Z
kubernetes://client-credential-cacert     Cert Chain     ACTIVE     true           16491643791048004260                       2024-06-04T12:46:28Z     2023-06-05T12:46:28Z

  1. Send an HTTP request to http://my-nginx.mesh-external.svc.cluster.local:

    $ kubectl exec "$(kubectl get pod -l app=curl -o jsonpath={.items..metadata.name})" -c curl -- curl -sS http://my-nginx.mesh-external.svc.cluster.local
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
...

  2. Check the log of the egress gateway’s proxy:

If Istio is deployed in the istio-system namespace, the command to print the log is:

$ kubectl logs -l istio=egressgateway -n istio-system | grep 'my-nginx.mesh-external.svc.cluster.local' | grep HTTP

You should see a line similar to the following:

[2018-08-19T18:20:40.096Z] "GET / HTTP/1.1" 200 - 0 612 7 5 "172.30.146.114" "curl/7.35.0" "b942b587-fac2-9756-8ec6-303561356204" "my-nginx.mesh-external.svc.cluster.local" "172.21.72.197:443"

Cleanup the mutual TLS origination example

  1. Remove the NGINX mutual TLS server resources:

    $ kubectl delete secret nginx-server-certs nginx-ca-certs -n mesh-external
$ kubectl delete configmap nginx-configmap -n mesh-external
$ kubectl delete service my-nginx -n mesh-external
$ kubectl delete deployment my-nginx -n mesh-external
$ kubectl delete namespace mesh-external

  2. Remove the gateway configuration resources:

$ kubectl delete secret client-credential -n istio-system
$ kubectl delete gw istio-egressgateway
$ kubectl delete virtualservice direct-nginx-through-egress-gateway
$ kubectl delete destinationrule -n istio-system originate-mtls-for-nginx
$ kubectl delete destinationrule egressgateway-for-nginx

  1. Delete the certificates and private keys:

    $ rm example.com.crt example.com.key my-nginx.mesh-external.svc.cluster.local.crt my-nginx.mesh-external.svc.cluster.local.key my-nginx.mesh-external.svc.cluster.local.csr client.example.com.crt client.example.com.csr client.example.com.key

  2. Delete the generated configuration files used in this example:

    $ rm ./nginx.conf

Cleanup

Delete the curl service and deployment:

Zip
$ kubectl delete -f @samples/curl/curl.yaml@
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