SNI Monitoring and Policies for TLS Egress Traffic

6 minute read

The Configure Egress Traffic using Wildcard Hosts example describes how to enable TLS egress traffic for a set of hosts in a common domain, in that case *.wikipedia.org. This example extends that example to show how to configure SNI monitoring and apply policies on TLS egress traffic.

Before you begin

Setup Istio by following the instructions in the Installation guide.
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
```
$ kubectl apply -f @samples/sleep/sleep.yaml@
```
Otherwise, manually inject the sidecar before deploying the sleep application with the following command:
Zip
```
$ 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})

Deploy Istio egress gateway.
Configure traffic to *.wikipedia.org by following the steps in Configure Egress Traffic using Wildcard Hosts example, with mutual TLS enabled.
Policy enforcement must be enabled in your cluster for this task. Follow the steps in Enabling Policy Enforcement to ensure that policy enforcement is enabled.

SNI monitoring and access policies

Since you configured the egress traffic to flow through the egress gateway, you can apply monitoring and access policy enforcement on the egress traffic, securely. In this section you will define a log entry and an access policy for the egress traffic to *.wikipedia.org.

Create logging configuration:

$ kubectl apply -f @samples/sleep/telemetry/sni-logging.yaml@

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

$ kubectl exec -it $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 mixer log. If Istio is deployed in the istio-system namespace, the command to print the log is:
```
$ kubectl -n istio-system logs -l istio-mixer-type=telemetry -c mixer | grep 'egress-access'
```
Define a policy that allows access to the hostnames matching *.wikipedia.org except for Wikipedia in English:
Zip
```
$ kubectl apply -f @samples/sleep/policy/sni-wikipedia.yaml@
```

Send an HTTPS request to the blacklisted Wikipedia in English:

$ kubectl exec -it $SOURCE_POD -c sleep -- sh -c 'curl -v https://en.wikipedia.org/wiki/Main_Page'
...
curl: (35) Unknown SSL protocol error in connection to en.wikipedia.org:443
command terminated with exit code 35

Access to Wikipedia in English is blocked according to the policy you defined.

Send HTTPS requests to some other Wikipedia sites, for example https://es.wikipedia.org and https://de.wikipedia.org:

$ kubectl exec -it $SOURCE_POD -c sleep -- sh -c 'curl -s https://es.wikipedia.org/wiki/Wikipedia:Portada | grep -o "<title>.*</title>"; curl -s https://de.wikipedia.org/wiki/Wikipedia:Hauptseite | grep -o "<title>.*</title>"'
<title>Wikipedia, la enciclopedia libre</title>
<title>Wikipedia – Die freie Enzyklopädie</title>

Access to Wikipedia sites in other languages is allowed, as expected.

Cleanup of monitoring and policy enforcement

$ kubectl delete -f @samples/sleep/telemetry/sni-logging.yaml@
$ kubectl delete -f @samples/sleep/policy/sni-wikipedia.yaml@

Monitor the SNI and the source identity, and enforce access policies based on them

Since you enabled mutual TLS between the sidecar proxies and the egress gateway, you can monitor the service identity of the applications that access external services, and enforce policies based on the identities of the traffic source. In Istio on Kubernetes, the identities are based on Service Accounts. In this subsection, you deploy two sleep containers, sleep-us and sleep-canada under two service accounts, sleep-us and sleep-canada, respectively. Then you define a policy that allows applications with the sleep-us identity to access the English and the Spanish versions of Wikipedia, and services with sleep-canada identity to access the English and the French versions.

Deploy two sleep containers, sleep-us and sleep-canada, with sleep-us and sleep-canada service accounts, respectively:

$ sed 's/: sleep/: sleep-us/g' @samples/sleep/sleep.yaml@ | kubectl apply -f -
$ sed 's/: sleep/: sleep-canada/g' @samples/sleep/sleep.yaml@ | kubectl apply -f -
serviceaccount "sleep-us" created
service "sleep-us" created
deployment "sleep-us" created
serviceaccount "sleep-canada" created
service "sleep-canada" created
deployment "sleep-canada" created

Create logging configuration:

$ kubectl apply -f @samples/sleep/telemetry/sni-logging.yaml@

Send HTTPS requests to Wikipedia sites in English, German, Spanish and French, from sleep-us:

$ kubectl exec -it $(kubectl get pod -l app=sleep-us -o jsonpath='{.items[0].metadata.name}') -c sleep-us -- 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>"; curl -s https://es.wikipedia.org/wiki/Wikipedia:Portada | grep -o "<title>.*</title>"; curl -s https://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Accueil_principal | grep -o "<title>.*</title>"'
<title>Wikipedia, the free encyclopedia</title>
<title>Wikipedia – Die freie Enzyklopädie</title>
<title>Wikipedia, la enciclopedia libre</title>
<title>Wikipédia, l'encyclopédie libre</title>

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

$ kubectl -n istio-system logs -l istio-mixer-type=telemetry -c mixer | grep 'egress-access'
{"level":"info","time":"2019-01-10T17:33:55.559093Z","instance":"egress-access.instance.istio-system","connectionEvent":"open","destinationApp":"","requestedServerName":"en.wikipedia.org","source":"istio-egressgateway-with-sni-proxy","sourceNamespace":"default","sourcePrincipal":"cluster.local/ns/default/sa/sleep-us","sourceWorkload":"istio-egressgateway-with-sni-proxy"}
{"level":"info","time":"2019-01-10T17:33:56.166227Z","instance":"egress-access.instance.istio-system","connectionEvent":"open","destinationApp":"","requestedServerName":"de.wikipedia.org","source":"istio-egressgateway-with-sni-proxy","sourceNamespace":"default","sourcePrincipal":"cluster.local/ns/default/sa/sleep-us","sourceWorkload":"istio-egressgateway-with-sni-proxy"}
{"level":"info","time":"2019-01-10T17:33:56.779842Z","instance":"egress-access.instance.istio-system","connectionEvent":"open","destinationApp":"","requestedServerName":"es.wikipedia.org","source":"istio-egressgateway-with-sni-proxy","sourceNamespace":"default","sourcePrincipal":"cluster.local/ns/default/sa/sleep-us","sourceWorkload":"istio-egressgateway-with-sni-proxy"}
{"level":"info","time":"2019-01-10T17:33:57.413908Z","instance":"egress-access.instance.istio-system","connectionEvent":"open","destinationApp":"","requestedServerName":"fr.wikipedia.org","source":"istio-egressgateway-with-sni-proxy","sourceNamespace":"default","sourcePrincipal":"cluster.local/ns/default/sa/sleep-us","sourceWorkload":"istio-egressgateway-with-sni-proxy"}

Note the requestedServerName attribute, and sourcePrincipal, it must be cluster.local/ns/default/sa/sleep-us.

Define a policy that will allow access to Wikipedia in English and Spanish for applications with the sleep-us service account and to Wikipedia in English and French for applications with the sleep-canada service account. Access to other Wikipedia sites will be blocked.
Zip
```
$ kubectl apply -f @samples/sleep/policy/sni-serviceaccount.yaml@
```

Resend HTTPS requests to Wikipedia sites in English, German, Spanish and French, from sleep-us:

$ kubectl exec -it $(kubectl get pod -l app=sleep-us -o jsonpath='{.items[0].metadata.name}') -c sleep-us -- 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>"; curl -s https://es.wikipedia.org/wiki/Wikipedia:Portada | grep -o "<title>.*</title>"; curl -s https://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Accueil_principal | grep -o "<title>.*</title>";:'
<title>Wikipedia, the free encyclopedia</title>
<title>Wikipedia, la enciclopedia libre</title>

Note that only the allowed Wikipedia sites for sleep-us service account are allowed, namely Wikipedia in English and Spanish.

$ kubectl delete pod -n istio-system -l istio-mixer-type=policy

Resend HTTPS requests to Wikipedia sites in English, German, Spanish and French, from sleep-canada:

$ kubectl exec -it $(kubectl get pod -l app=sleep-canada -o jsonpath='{.items[0].metadata.name}') -c sleep-canada -- 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>"; curl -s https://es.wikipedia.org/wiki/Wikipedia:Portada | grep -o "<title>.*</title>"; curl -s https://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Accueil_principal | grep -o "<title>.*</title>";:'
<title>Wikipedia, the free encyclopedia</title>
<title>Wikipédia, l'encyclopédie libre</title>

Note that only the allowed Wikipedia sites for sleep-canada service account are allowed, namely Wikipedia in English and French.

Cleanup of monitoring and policy enforcement of SNI and source identity

$ kubectl delete service sleep-us sleep-canada
$ kubectl delete deployment sleep-us sleep-canada
$ kubectl delete serviceaccount sleep-us sleep-canada
$ kubectl delete -f @samples/sleep/telemetry/sni-logging.yaml@
$ kubectl delete -f @samples/sleep/policy/sni-serviceaccount.yaml@

Cleanup

Perform the cleanup steps from Configure Egress Traffic using Wildcard Hosts example.

Shutdown the sleep service:

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