Egress using Wildcard Hosts

The Accessing External Services task and the Configure an Egress Gateway example describe how to configure egress traffic for specific hostnames, like edition.cnn.com. This example shows how to enable egress traffic for a set of hosts in a common domain, for example *.wikipedia.org, instead of configuring each and every host separately.

Background

Suppose you want to enable egress traffic in Istio for the wikipedia.org sites in all languages. Each version of wikipedia.org in a particular language has its own hostname, e.g., en.wikipedia.org and de.wikipedia.org in the English and the German languages, respectively. You want to enable egress traffic by common configuration items for all the Wikipedia sites, without the need to specify every language’s site separately.

Before you begin

  • Install Istio using the demo configuration profile and with the blocking-by-default outbound traffic policy:

    1. $ istioctl install --set profile=demo --set meshConfig.outboundTrafficPolicy.mode=REGISTRY_ONLY

    You can run this task on an Istio configuration other than the demo profile as long as you make sure to deploy the Istio egress gateway, enable Envoy’s access logging, and apply the blocking-by-default outbound traffic policy in your installation. You will also need to add the second gateway using your own IstioOperator CR instead of the one shown in setup egress gateway with SNI proxy.

  • Deploy the sleep sample app to use as a test source for sending requests. If you have automatic sidecar injection enabled, run the following command to deploy the sample app:

    Zip

    1. $ kubectl apply -f @samples/sleep/sleep.yaml@

    Otherwise, manually inject the sidecar before deploying the sleep application with the following command:

    Zip

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

    You can use any pod with curl installed as a test source.

  • Set the SOURCE_POD environment variable to the name of your source pod:

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

Configure direct traffic to a wildcard host

The first, and simplest, way to access a set of hosts within a common domain is by configuring a simple ServiceEntry with a wildcard host and calling the services directly from the sidecar. When calling services directly (i.e., not via an egress gateway), the configuration for a wildcard host is no different than that of any other (e.g., fully qualified) host, only much more convenient when there are many hosts within the common domain.

Note that the configuration below can be easily bypassed by a malicious application. For a secure egress traffic control, direct the traffic through an egress gateway.

Note that the DNS resolution cannot be used for wildcard hosts. This is why the NONE resolution (omitted since it is the default) is used in the service entry below.

  1. Define a ServiceEntry for *.wikipedia.org:

    1. $ kubectl apply -f - <<EOF
    2. apiVersion: networking.istio.io/v1alpha3
    3. kind: ServiceEntry
    4. metadata:
    5.   name: wikipedia
    6. spec:
    7.   hosts:
    8.   - "*.wikipedia.org"
    9.   ports:
    10.   - number: 443
    11.     name: https
    12.     protocol: HTTPS
    13. EOF

  2. Send HTTPS requests to https://en.wikipedia.org and https://de.wikipedia.org:

    1. $ kubectl exec "$SOURCE_POD" -c sleep -- sh -c 'curl -s https://en.wikipedia.org/wiki/Main_Page | grep -o "<title>.*</title>"; curl -s https://de.wikipedia.org/wiki/Wikipedia:Hauptseite | grep -o "<title>.*</title>"'
    2. <title>Wikipedia, the free encyclopedia</title>
    3. <title>Wikipedia – Die freie Enzyklopädie</title>

Cleanup direct traffic to a wildcard host

  1. $ kubectl delete serviceentry wikipedia

Wildcard configuration for a single hosting server

When all wildcard hosts are served by a single server, the configuration for egress gateway-based access to a wildcard host is very similar to that of any host, with one exception: the configured route destination will not be the same as the configured host, i.e., the wildcard. It will instead be configured with the host of the single server for the set of domains.

  1. Create an egress Gateway for \.wikipedia.org*, a destination rule and a virtual service to direct the traffic through the egress gateway and from the egress gateway to the external service.

    1. $ kubectl apply -f - <<EOF
    2. apiVersion: networking.istio.io/v1alpha3
    3. kind: Gateway
    4. metadata:
    5.   name: istio-egressgateway
    6. spec:
    7.   selector:
    8.     istio: egressgateway
    9.   servers:
    10.   - port:
    11.       number: 443
    12.       name: https
    13.       protocol: HTTPS
    14.     hosts:
    15.     - "*.wikipedia.org"
    16.     tls:
    17.       mode: PASSTHROUGH
    18. ---
    19. apiVersion: networking.istio.io/v1alpha3
    20. kind: DestinationRule
    21. metadata:
    22.   name: egressgateway-for-wikipedia
    23. spec:
    24.   host: istio-egressgateway.istio-system.svc.cluster.local
    25.   subsets:
    26.     - name: wikipedia
    27. ---
    28. apiVersion: networking.istio.io/v1alpha3
    29. kind: VirtualService
    30. metadata:
    31.   name: direct-wikipedia-through-egress-gateway
    32. spec:
    33.   hosts:
    34.   - "*.wikipedia.org"
    35.   gateways:
    36.   - mesh
    37.   - istio-egressgateway
    38.   tls:
    39.   - match:
    40.     - gateways:
    41.       - mesh
    42.       port: 443
    43.       sniHosts:
    44.       - "*.wikipedia.org"
    45.     route:
    46.     - destination:
    47.         host: istio-egressgateway.istio-system.svc.cluster.local
    48.         subset: wikipedia
    49.         port:
    50.           number: 443
    51.       weight: 100
    52.   - match:
    53.     - gateways:
    54.       - istio-egressgateway
    55.       port: 443
    56.       sniHosts:
    57.       - "*.wikipedia.org"
    58.     route:
    59.     - destination:
    60.         host: www.wikipedia.org
    61.         port:
    62.           number: 443
    63.       weight: 100
    64. EOF

  2. Create a ServiceEntry for the destination server, www.wikipedia.org.

    1. $ kubectl apply -f - <<EOF
    2. apiVersion: networking.istio.io/v1alpha3
    3. kind: ServiceEntry
    4. metadata:
    5.   name: www-wikipedia
    6. spec:
    7.   hosts:
    8.   - www.wikipedia.org
    9.   ports:
    10.   - number: 443
    11.     name: https
    12.     protocol: HTTPS
    13.   resolution: DNS
    14. EOF

  3. Send HTTPS requests to https://en.wikipedia.org and https://de.wikipedia.org:

    1. $ kubectl exec "$SOURCE_POD" -c sleep -- sh -c 'curl -s https://en.wikipedia.org/wiki/Main_Page | grep -o "<title>.*</title>"; curl -s https://de.wikipedia.org/wiki/Wikipedia:Hauptseite | grep -o "<title>.*</title>"'
    2. <title>Wikipedia, the free encyclopedia</title>
    3. <title>Wikipedia – Die freie Enzyklopädie</title>

  4. Check the statistics of the egress gateway’s proxy for the counter that corresponds to your requests to \.wikipedia.org*. If Istio is deployed in the istio-system namespace, the command to print the counter is:

    1. $ kubectl exec "$(kubectl get pod -l istio=egressgateway -n istio-system -o jsonpath='{.items[0].metadata.name}')" -c istio-proxy -n istio-system -- pilot-agent request GET clusters | grep '^outbound|443||www.wikipedia.org.*cx_total:'
    2. outbound|443||www.wikipedia.org::208.80.154.224:443::cx_total::2

Cleanup wildcard configuration for a single hosting server

  1. $ kubectl delete serviceentry www-wikipedia
  2. $ kubectl delete gateway istio-egressgateway
  3. $ kubectl delete virtualservice direct-wikipedia-through-egress-gateway
  4. $ kubectl delete destinationrule egressgateway-for-wikipedia

Cleanup

  • Shutdown the sleep service:

    Zip

    1. $ kubectl delete -f @samples/sleep/sleep.yaml@

  • Uninstall Istio from your cluster:

    1. $ istioctl x uninstall --purge