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istio.io/content/en/docs/tasks/traffic-management/egress/egress-tls-origination/index.md

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title description keywords weight owner test aliases
Egress TLS Origination Describes how to configure Istio to perform TLS origination for traffic to external services.
traffic-management
egress
20 istio/wg-networking-maintainers yes
/docs/examples/advanced-gateways/egress-tls-origination/

The Accessing External Services task demonstrates how external, i.e., outside of the service mesh, HTTP and HTTPS services can be accessed from applications inside the mesh. As described in that task, a ServiceEntry is used to configure Istio to access external services in a controlled way. This example shows how to configure Istio to perform {{< gloss >}}TLS origination{{< /gloss >}} for traffic to an external service. Istio will open HTTPS connections to the external service while the original traffic is HTTP.

Use case

Consider a legacy application that performs HTTP calls to external sites. Suppose the organization that operates the application receives a new requirement which states that all the external traffic must be encrypted. With Istio, this requirement can be achieved just by configuration, without changing any code in the application. The application can send unencrypted HTTP requests and Istio will then encrypt them for the application.

Another benefit of sending unencrypted HTTP requests from the source, and letting Istio perform the TLS upgrade, is that Istio can produce better telemetry and provide more routing control for requests that are not encrypted.

Before you begin

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

  • Start the [sleep]({{< github_tree >}}/samples/sleep) sample which will be used as a test source for external calls.

    If you have enabled automatic sidecar injection, deploy the sleep application:

    {{< text bash >}} $ kubectl apply -f @samples/sleep/sleep.yaml@ {{< /text >}}

    Otherwise, you have to manually inject the sidecar before deploying the sleep application:

    {{< text bash >}} $ kubectl apply -f <(istioctl kube-inject -f @samples/sleep/sleep.yaml@) {{< /text >}}

    Note that any pod that you can exec and curl from will do for the procedures below.

  • Create a shell variable to hold the name of the source pod for sending requests to external services. If you used the [sleep]({{< github_tree >}}/samples/sleep) sample, run:

    {{< text bash >}} export SOURCE_POD=(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name}) {{< /text >}}

Configuring access to an external service

First start by configuring access to an external service, edition.cnn.com, using the same technique shown in the Accessing External Services task. This time, however, use a single ServiceEntry to enable both HTTP and HTTPS access to the service.

  1. Create a ServiceEntry to enable access to edition.cnn.com:

    {{< text syntax=bash snip_id=apply_simple >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: ServiceEntry metadata: name: edition-cnn-com spec: hosts:

    • edition.cnn.com ports:
    • number: 80 name: http-port protocol: HTTP
    • number: 443 name: https-port protocol: HTTPS resolution: DNS EOF {{< /text >}}

  2. Make a request to the external HTTP service:

    {{< text syntax=bash snip_id=curl_simple >}} kubectl exec "{SOURCE_POD}" -c sleep -- curl -sSL -o /dev/null -D - http://edition.cnn.com/politics HTTP/1.1 301 Moved Permanently ... location: https://edition.cnn.com/politics ...

    HTTP/2 200 ... {{< /text >}}

    The output should be similar to the above (some details replaced by ellipsis).

Notice the -L flag of curl which instructs curl to follow redirects. In this case, the server returned a redirect response (301 Moved Permanently) for the HTTP request to http://edition.cnn.com/politics. The redirect response instructs the client to send an additional request, this time using HTTPS, to https://edition.cnn.com/politics. For the second request, the server returned the requested content and a 200 OK status code.

Although the curl command handled the redirection transparently, there are two issues here. The first issue is the redundant request, which doubles the latency of fetching the content of http://edition.cnn.com/politics. The second issue is that the path of the URL, politics in this case, is sent in clear text. If there is an attacker who sniffs the communication between your application and edition.cnn.com, the attacker would know which specific topics of edition.cnn.com the application fetched. For privacy reasons, you might want to prevent such disclosure.

Both of these issues can be resolved by configuring Istio to perform TLS origination.

TLS origination for egress traffic

  1. Redefine your ServiceEntry from the previous section to redirect HTTP requests to port 443 and add a DestinationRule to perform TLS origination:

    {{< text syntax=bash snip_id=apply_origination >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: ServiceEntry metadata: name: edition-cnn-com spec: hosts:

    • edition.cnn.com ports:
    • number: 80 name: http-port protocol: HTTP targetPort: 443
    • number: 443 name: https-port protocol: HTTPS resolution: DNS

    apiVersion: networking.istio.io/v1alpha3 kind: DestinationRule metadata: name: edition-cnn-com spec: host: edition.cnn.com trafficPolicy: portLevelSettings: - port: number: 80 tls: mode: SIMPLE # initiates HTTPS when accessing edition.cnn.com EOF {{< /text >}}

    The above DestinationRule will perform TLS origination for HTTP requests on port 80 and the ServiceEntry will then redirect the requests on port 80 to target port 443.

  2. Send an HTTP request to http://edition.cnn.com/politics, as in the previous section:

    {{< text syntax=bash snip_id=curl_origination_http >}} kubectl exec "{SOURCE_POD}" -c sleep -- curl -sSL -o /dev/null -D - http://edition.cnn.com/politics HTTP/1.1 200 OK ... {{< /text >}}

    This time you receive 200 OK as the first and the only response. Istio performed TLS origination for curl so the original HTTP request was forwarded to edition.cnn.com as HTTPS. The server returned the content directly, without the need for redirection. You eliminated the double round trip between the client and the server, and the request left the mesh encrypted, without disclosing the fact that your application fetched the politics section of edition.cnn.com.

    Note that you used the same command as in the previous section. For applications that access external services programmatically, the code does not need to be changed. You get the benefits of TLS origination by configuring Istio, without changing a line of code.

  3. Note that the applications that used HTTPS to access the external service continue to work as before:

    {{< text syntax=bash snip_id=curl_origination_https >}} kubectl exec "{SOURCE_POD}" -c sleep -- curl -sSL -o /dev/null -D - https://edition.cnn.com/politics HTTP/2 200 ... {{< /text >}}

Additional security considerations

Because the traffic between the application pod and the sidecar proxy on the local host is still unencrypted, an attacker that is able to penetrate the node of your application would still be able to see the unencrypted communication on the local network of the node. In some environments a strict security requirement might state that all the traffic must be encrypted, even on the local network of the nodes. With such a strict requirement, applications should use HTTPS (TLS) only. The TLS origination described in this example would not be sufficient.

Also note that even with HTTPS originated by the application, an attacker could know that requests to edition.cnn.com are being sent by inspecting Server Name Indication (SNI). The SNI field is sent unencrypted during the TLS handshake. Using HTTPS prevents the attackers from knowing specific topics and articles but does not prevent attackers from learning that edition.cnn.com is accessed.

Cleanup the TLS origination configuration

Remove the Istio configuration items you created:

{{< text bash >}}
$ kubectl delete serviceentry edition-cnn-com
$ kubectl delete destinationrule edition-cnn-com
{{< /text >}}

Mutual TLS origination for egress traffic

This section describes how to configure a sidecar to perform TLS origination for an external service, this time using a service that requires mutual TLS. This example is considerably more involved because it requires the following setup:

  1. Generate client and server certificates
  2. Deploy an external service that supports the mutual TLS protocol
  3. Configure the client (sleep pod) to use the credentials created in Step 1

Once this setup is complete, you can then configure the external traffic to go through the sidecar which will perform TLS origination.

Generate client and server certificates and keys

Follow these steps in the Egress Gateway TLS Origination task.

Deploy a mutual TLS server

Follow these steps in the Egress Gateway TLS Origination task.

Configure the client (sleep pod)

  1. Create Kubernetes Secrets to hold the client's certificates:

    {{< text bash >}} $ kubectl create secret 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 {{< /text >}}

    The secret must be created in the same namespace as the client pod is deployed in, default in this case.

  2. Create required RBAC to make sure the secret created in the above step is accessible to the client pod, which is sleep in this case.

    {{< text bash >}} $ kubectl create role client-credential-role --resource=secret --verb=list $ kubectl create rolebinding client-credential-role-binding --role=client-credential-role --serviceaccount=default:sleep {{< /text >}}

Configure mutual TLS origination for egress traffic at sidecar

  1. Add a DestinationRule to perform mutual TLS origination

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: DestinationRule metadata: name: originate-mtls-for-nginx spec: workloadSelector: matchLabels: app: sleep 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, and works only when DR has a workloadSelector sni: my-nginx.mesh-external.svc.cluster.local # this is optional EOF {{< /text >}}

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

    {{< text bash >}} kubectl exec "(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name})" -c sleep -- curl -sS http://my-nginx.mesh-external.svc.cluster.local:443

    <html> <head> ... {{< /text >}}

  3. Check the log of the sleep pod for a line corresponding to our request.

    {{< text bash >}} $ kubectl logs -l app=sleep -c istio-proxy | grep 'my-nginx.mesh-external.svc.cluster.local' {{< /text >}}

    You should see a line similar to the following:

    {{< text plain>}} [2022-05-19T10:01:06.795Z] "GET / HTTP/1.1" 200 - via_upstream - "-" 0 615 1 0 "-" "curl/7.83.1-DEV" "96e8d8a7-92ce-9939-aa47-9f5f530a69fb" "my-nginx.mesh-external.svc.cluster.local:443" "10.107.176.65:443" {{< /text >}}

Cleanup the mutual TLS origination configuration

  1. Remove created Kubernetes resources:

    {{< text bash >}} $ kubectl delete secret nginx-server-certs nginx-ca-certs -n mesh-external $ kubectl delete secret client-credential $ 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 $ kubectl delete serviceentry originate-mtls-for-nginx $ kubectl delete destinationrule originate-mtls-for-nginx {{< /text >}}

  2. Delete the certificates and private keys:

    {{< text bash >}} $ 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 {{< /text >}}

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

    {{< text bash >}} $ rm ./nginx.conf {{< /text >}}

Cleanup common configuration

Delete the sleep service and deployment:

{{< text bash >}} $ kubectl delete service sleep $ kubectl delete deployment sleep {{< /text >}}