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:$ 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.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:
$ kubectl apply -f @samples/sleep/sleep.yaml@
Otherwise, manually inject the sidecar before deploying the
sleep
application with the following command:$ 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:$ export SOURCE_POD=$(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name})
Configure direct traffic to a wildcard host
The first, and simplest, way to access a set of hosts within a common domain is by configuring a simple ServiceEntry
with a wildcard host and calling the services directly from the sidecar. When calling services directly (i.e., not via an egress gateway), the configuration for a wildcard host is no different than that of any other (e.g., fully qualified) host, only much more convenient when there are many hosts within the common domain.
Note that the configuration below can be easily bypassed by a malicious application. For a secure egress traffic control, direct the traffic through an egress gateway.
Note that the DNS
resolution cannot be used for wildcard hosts. This is why the NONE
resolution (omitted since it is the default) is used in the service entry below.
Define a
ServiceEntry
for*.wikipedia.org
:$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
name: wikipedia
spec:
hosts:
- "*.wikipedia.org"
ports:
- number: 443
name: https
protocol: HTTPS
EOF
Send HTTPS requests to https://en.wikipedia.org and https://de.wikipedia.org:
$ 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>"'
<title>Wikipedia, the free encyclopedia</title>
<title>Wikipedia – Die freie Enzyklopädie</title>
Cleanup direct traffic to a wildcard host
$ kubectl delete serviceentry wikipedia
Configure egress gateway traffic to a wildcard host
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.
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.$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
name: istio-egressgateway
spec:
selector:
istio: egressgateway
servers:
- port:
number: 443
name: https
protocol: HTTPS
hosts:
- "*.wikipedia.org"
tls:
mode: PASSTHROUGH
---
apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
name: egressgateway-for-wikipedia
spec:
host: istio-egressgateway.istio-system.svc.cluster.local
subsets:
- name: wikipedia
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
name: direct-wikipedia-through-egress-gateway
spec:
hosts:
- "*.wikipedia.org"
gateways:
- mesh
- istio-egressgateway
tls:
- match:
- gateways:
- mesh
port: 443
sniHosts:
- "*.wikipedia.org"
route:
- destination:
host: istio-egressgateway.istio-system.svc.cluster.local
subset: wikipedia
port:
number: 443
weight: 100
- match:
- gateways:
- istio-egressgateway
port: 443
sniHosts:
- "*.wikipedia.org"
route:
- destination:
host: www.wikipedia.org
port:
number: 443
weight: 100
EOF
Create a
ServiceEntry
for the destination server, www.wikipedia.org.$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
name: www-wikipedia
spec:
hosts:
- www.wikipedia.org
ports:
- number: 443
name: https
protocol: HTTPS
resolution: DNS
EOF
Send HTTPS requests to https://en.wikipedia.org and https://de.wikipedia.org:
$ kubectl exec "$SOURCE_POD" -c sleep -- sh -c 'curl -s https://en.wikipedia.org/wiki/Main_Page | grep -o "<title>.*</title>"; curl -s https://de.wikipedia.org/wiki/Wikipedia:Hauptseite | grep -o "<title>.*</title>"'
<title>Wikipedia, the free encyclopedia</title>
<title>Wikipedia – Die freie Enzyklopädie</title>
Check the statistics of the egress gateway’s proxy for the counter that corresponds to your requests to *.wikipedia.org. If Istio is deployed in the
istio-system
namespace, the command to print the counter is:$ 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:'
outbound|443||www.wikipedia.org::208.80.154.224:443::cx_total::2
Cleanup egress gateway traffic to a wildcard host
$ kubectl delete serviceentry www-wikipedia
$ kubectl delete gateway istio-egressgateway
$ kubectl delete virtualservice direct-wikipedia-through-egress-gateway
$ kubectl delete destinationrule egressgateway-for-wikipedia