Egress Gateways
This example does not work in Minikube.
The Accessing External Services task shows how to configure Istio to allow access to external HTTP and HTTPS services from applications inside the mesh. There, the external services are called directly from the client sidecar. This example also shows how to configure Istio to call external services, although this time indirectly via a dedicated egress gateway service.
Istio uses ingress and egress gateways to configure load balancers executing at the edge of a service mesh. An ingress gateway allows you to define entry points into the mesh that all incoming traffic flows through. Egress gateway is a symmetrical concept; it defines exit points from the mesh. Egress gateways allow you to apply Istio features, for example, monitoring and route rules, to traffic exiting the mesh.
Use case
Consider an organization that has a strict security requirement that all traffic leaving the service mesh must flow through a set of dedicated nodes. These nodes will run on dedicated machines, separated from the rest of the nodes running applications in the cluster. These special nodes will serve for policy enforcement on the egress traffic and will be monitored more thoroughly than other nodes.
Another use case is a cluster where the application nodes don’t have public IPs, so the in-mesh services that run on them cannot access the Internet. Defining an egress gateway, directing all the egress traffic through it, and allocating public IPs to the egress gateway nodes allows the application nodes to access external services in a controlled way.
Before you begin
Setup Istio by following the instructions in the Installation guide.
The egress gateway and access logging will be enabled if you install the
demo
configuration profile.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})
The instructions in this task create a destination rule for the egress gateway in the default
namespace and assume that the client, SOURCE_POD
, is also running in the default
namespace. If not, the destination rule will not be found on the destination rule lookup path and the client requests will fail.
Deploy Istio egress gateway
Check if the Istio egress gateway is deployed:
$ kubectl get pod -l istio=egressgateway -n istio-system
If no pods are returned, deploy the Istio egress gateway by performing the following step.
If you used an
IstioOperator
CR to install Istio, add the following fields to your configuration:spec:
components:
egressGateways:
- name: istio-egressgateway
enabled: true
Otherwise, add the equivalent settings to your original
istioctl install
command, for example:$ istioctl install <flags-you-used-to-install-Istio> \
--set components.egressGateways[0].name=istio-egressgateway \
--set components.egressGateways[0].enabled=true
Egress gateway for HTTP traffic
First create a ServiceEntry
to allow direct traffic to an external service.
Define a
ServiceEntry
foredition.cnn.com
.DNS
resolution must be used in the service entry below. If the resolution isNONE
, the gateway will direct the traffic to itself in an infinite loop. This is because the gateway receives a request with the original destination IP address which is equal to the service IP of the gateway (since the request is directed by sidecar proxies to the gateway).With
DNS
resolution, the gateway performs a DNS query to get an IP address of the external service and directs the traffic to that IP address.$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
name: cnn
spec:
hosts:
- edition.cnn.com
ports:
- number: 80
name: http-port
protocol: HTTP
- number: 443
name: https
protocol: HTTPS
resolution: DNS
EOF
Verify that your
ServiceEntry
was applied correctly by sending an HTTP request to http://edition.cnn.com/politics.$ kubectl exec "$SOURCE_POD" -c sleep -- curl -sSL -o /dev/null -D - http://edition.cnn.com/politics
...
HTTP/1.1 301 Moved Permanently
...
location: https://edition.cnn.com/politics
...
HTTP/2 200
Content-Type: text/html; charset=utf-8
...
The output should be the same as in the TLS Origination for Egress Traffic example, without TLS origination.
Create an egress
Gateway
for edition.cnn.com, port 80, and a destination rule for traffic directed to the egress gateway.To direct multiple hosts through an egress gateway, you can include a list of hosts, or use
*
to match all, in theGateway
. Thesubset
field in theDestinationRule
should be reused for the additional hosts.$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
name: istio-egressgateway
spec:
selector:
istio: egressgateway
servers:
- port:
number: 80
name: http
protocol: HTTP
hosts:
- edition.cnn.com
---
apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
name: egressgateway-for-cnn
spec:
host: istio-egressgateway.istio-system.svc.cluster.local
subsets:
- name: cnn
EOF
Define a
VirtualService
to direct traffic from the sidecars to the egress gateway and from the egress gateway to the external service:$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
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: 80
weight: 100
EOF
Resend the HTTP request to http://edition.cnn.com/politics.
$ kubectl exec "$SOURCE_POD" -c sleep -- curl -sSL -o /dev/null -D - http://edition.cnn.com/politics
...
HTTP/1.1 301 Moved Permanently
...
location: https://edition.cnn.com/politics
...
HTTP/2 200
Content-Type: text/html; charset=utf-8
...
The output should be the same as in the step 2.
Check the log of the
istio-egressgateway
pod for a line corresponding to our request. If Istio is deployed in theistio-system
namespace, the command to print the log is:$ kubectl logs -l istio=egressgateway -c istio-proxy -n istio-system | tail
You should see a line similar to the following:
[2019-09-03T20:57:49.103Z] "GET /politics HTTP/2" 301 - "-" "-" 0 0 90 89 "10.244.2.10" "curl/7.64.0" "ea379962-9b5c-4431-ab66-f01994f5a5a5" "edition.cnn.com" "151.101.65.67:80" outbound|80||edition.cnn.com - 10.244.1.5:80 10.244.2.10:50482 edition.cnn.com -
Note that you only redirected the traffic from port 80 to the egress gateway. The HTTPS traffic to port 443 went directly to edition.cnn.com.
Cleanup HTTP gateway
Remove the previous definitions before proceeding to the next step:
$ kubectl delete gateway istio-egressgateway
$ kubectl delete serviceentry cnn
$ kubectl delete virtualservice direct-cnn-through-egress-gateway
$ kubectl delete destinationrule egressgateway-for-cnn
Egress gateway for HTTPS traffic
In this section you direct HTTPS traffic (TLS originated by the application) through an egress gateway. You need to specify port 443 with protocol TLS
in a corresponding ServiceEntry
, an egress Gateway
and a VirtualService
.
Define a
ServiceEntry
foredition.cnn.com
:$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
name: cnn
spec:
hosts:
- edition.cnn.com
ports:
- number: 443
name: tls
protocol: TLS
resolution: DNS
EOF
Verify that your
ServiceEntry
was applied correctly by sending an HTTPS request to https://edition.cnn.com/politics.$ kubectl exec "$SOURCE_POD" -c sleep -- curl -sSL -o /dev/null -D - https://edition.cnn.com/politics
...
HTTP/2 200
Content-Type: text/html; charset=utf-8
...
Create an egress
Gateway
for edition.cnn.com, a destination rule and a virtual service to direct the traffic through the egress gateway and from the egress gateway to the external service.To direct multiple hosts through an egress gateway, you can include a list of hosts, or use
*
to match all, in theGateway
. Thesubset
field in theDestinationRule
should be reused for the additional hosts.$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
name: istio-egressgateway
spec:
selector:
istio: egressgateway
servers:
- port:
number: 443
name: tls
protocol: TLS
hosts:
- edition.cnn.com
tls:
mode: PASSTHROUGH
---
apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
name: egressgateway-for-cnn
spec:
host: istio-egressgateway.istio-system.svc.cluster.local
subsets:
- name: cnn
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
name: direct-cnn-through-egress-gateway
spec:
hosts:
- edition.cnn.com
gateways:
- mesh
- istio-egressgateway
tls:
- match:
- gateways:
- mesh
port: 443
sniHosts:
- edition.cnn.com
route:
- destination:
host: istio-egressgateway.istio-system.svc.cluster.local
subset: cnn
port:
number: 443
- match:
- gateways:
- istio-egressgateway
port: 443
sniHosts:
- edition.cnn.com
route:
- destination:
host: edition.cnn.com
port:
number: 443
weight: 100
EOF
Send an HTTPS request to https://edition.cnn.com/politics. The output should be the same as before.
$ kubectl exec "$SOURCE_POD" -c sleep -- curl -sSL -o /dev/null -D - https://edition.cnn.com/politics
...
HTTP/2 200
Content-Type: text/html; charset=utf-8
...
Check the log of the egress gateway’s proxy. If Istio is deployed in the
istio-system
namespace, the command to print the log is:$ kubectl logs -l istio=egressgateway -n istio-system
You should see a line similar to the following:
[2019-01-02T11:46:46.981Z] "- - -" 0 - 627 1879689 44 - "-" "-" "-" "-" "151.101.129.67:443" outbound|443||edition.cnn.com 172.30.109.80:41122 172.30.109.80:443 172.30.109.112:59970 edition.cnn.com
Cleanup HTTPS gateway
$ kubectl delete serviceentry cnn
$ kubectl delete gateway istio-egressgateway
$ kubectl delete virtualservice direct-cnn-through-egress-gateway
$ kubectl delete destinationrule egressgateway-for-cnn
Additional security considerations
Note that defining an egress Gateway
in Istio does not in itself provides any special treatment for the nodes on which the egress gateway service runs. It is up to the cluster administrator or the cloud provider to deploy the egress gateways on dedicated nodes and to introduce additional security measures to make these nodes more secure than the rest of the mesh.
Istio cannot securely enforce that all egress traffic actually flows through the egress gateways. Istio only enables such flow through its sidecar proxies. If attackers bypass the sidecar proxy, they could directly access external services without traversing the egress gateway. Thus, the attackers escape Istio’s control and monitoring. The cluster administrator or the cloud provider must ensure that no traffic leaves the mesh bypassing the egress gateway. Mechanisms external to Istio must enforce this requirement. For example, the cluster administrator can configure a firewall to deny all traffic not coming from the egress gateway. The Kubernetes network policies can also forbid all the egress traffic not originating from the egress gateway (see the next section for an example). Additionally, the cluster administrator or the cloud provider can configure the network to ensure application nodes can only access the Internet via a gateway. To do this, the cluster administrator or the cloud provider can prevent the allocation of public IPs to pods other than gateways and can configure NAT devices to drop packets not originating at the egress gateways.
Apply Kubernetes network policies
This section shows you how to create a Kubernetes network policy to prevent bypassing of the egress gateway. To test the network policy, you create a namespace, test-egress
, deploy the sleep sample to it, and then attempt to send requests to a gateway-secured external service.
Follow the steps in the Egress gateway for HTTPS traffic section.
Create the
test-egress
namespace:$ kubectl create namespace test-egress
Deploy the sleep sample to the
test-egress
namespace.$ kubectl apply -n test-egress -f @samples/sleep/sleep.yaml@
Check that the deployed pod has a single container with no Istio sidecar attached:
$ kubectl get pod "$(kubectl get pod -n test-egress -l app=sleep -o jsonpath={.items..metadata.name})" -n test-egress
NAME READY STATUS RESTARTS AGE
sleep-776b7bcdcd-z7mc4 1/1 Running 0 18m
Send an HTTPS request to https://edition.cnn.com/politics from the
sleep
pod in thetest-egress
namespace. The request will succeed since you did not define any restrictive policies yet.$ kubectl exec "$(kubectl get pod -n test-egress -l app=sleep -o jsonpath={.items..metadata.name})" -n test-egress -c sleep -- curl -s -o /dev/null -w "%{http_code}\n" https://edition.cnn.com/politics
200
Label the namespaces where the Istio components (the control plane and the gateways) run. If you deployed the Istio components to
istio-system
, the command is:$ kubectl label namespace istio-system istio=system
Label the
kube-system
namespace.$ kubectl label ns kube-system kube-system=true
Define a
NetworkPolicy
to limit the egress traffic from thetest-egress
namespace to traffic destined toistio-system
, and to thekube-system
DNS service (port 53):$ cat <<EOF | kubectl apply -n test-egress -f -
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: allow-egress-to-istio-system-and-kube-dns
spec:
podSelector: {}
policyTypes:
- Egress
egress:
- to:
- namespaceSelector:
matchLabels:
kube-system: "true"
ports:
- protocol: UDP
port: 53
- to:
- namespaceSelector:
matchLabels:
istio: system
EOF
Network policies are implemented by the network plugin in your Kubernetes cluster. Depending on your test cluster, the traffic may not be blocked in the following step.
Resend the previous HTTPS request to https://edition.cnn.com/politics. Now it should fail since the traffic is blocked by the network policy. Note that the
sleep
pod cannot bypassistio-egressgateway
. The only way it can accessedition.cnn.com
is by using an Istio sidecar proxy and by directing the traffic toistio-egressgateway
. This setting demonstrates that even if some malicious pod manages to bypass its sidecar proxy, it will not be able to access external sites and will be blocked by the network policy.$ kubectl exec "$(kubectl get pod -n test-egress -l app=sleep -o jsonpath={.items..metadata.name})" -n test-egress -c sleep -- curl -v -sS https://edition.cnn.com/politics
Hostname was NOT found in DNS cache
Trying 151.101.65.67...
Trying 2a04:4e42:200::323...
Immediate connect fail for 2a04:4e42:200::323: Cannot assign requested address
Trying 2a04:4e42:400::323...
Immediate connect fail for 2a04:4e42:400::323: Cannot assign requested address
Trying 2a04:4e42:600::323...
Immediate connect fail for 2a04:4e42:600::323: Cannot assign requested address
Trying 2a04:4e42::323...
Immediate connect fail for 2a04:4e42::323: Cannot assign requested address
connect to 151.101.65.67 port 443 failed: Connection timed out
Now inject an Istio sidecar proxy into the
sleep
pod in thetest-egress
namespace by first enabling automatic sidecar proxy injection in thetest-egress
namespace:$ kubectl label namespace test-egress istio-injection=enabled
Then redeploy the
sleep
deployment:$ kubectl delete deployment sleep -n test-egress
$ kubectl apply -f @samples/sleep/sleep.yaml@ -n test-egress
Check that the deployed pod has two containers, including the Istio sidecar proxy (
istio-proxy
):$ kubectl get pod "$(kubectl get pod -n test-egress -l app=sleep -o jsonpath={.items..metadata.name})" -n test-egress -o jsonpath='{.spec.containers[*].name}'
sleep istio-proxy
Create a similar destination rule as used for the
sleep
pod in thedefault
namespace, to direct thetest-egress
namespace traffic through the egress gateway:$ kubectl apply -n test-egress -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
name: egressgateway-for-cnn
spec:
host: istio-egressgateway.istio-system.svc.cluster.local
subsets:
- name: cnn
EOF
Send an HTTPS request to https://edition.cnn.com/politics. Now it should succeed since the traffic flows to
istio-egressgateway
in theistio-system
namespace, which is allowed by the Network Policy you defined.istio-egressgateway
forwards the traffic toedition.cnn.com
.$ kubectl exec "$(kubectl get pod -n test-egress -l app=sleep -o jsonpath={.items..metadata.name})" -n test-egress -c sleep -- curl -sS -o /dev/null -w "%{http_code}\n" https://edition.cnn.com/politics
200
Check the log of the egress gateway’s proxy. If Istio is deployed in the
istio-system
namespace, the command to print the log is:$ kubectl logs -l istio=egressgateway -n istio-system
You should see a line similar to the following:
[2020-03-06T18:12:33.101Z] "- - -" 0 - "-" "-" 906 1352475 35 - "-" "-" "-" "-" "151.101.193.67:443" outbound|443||edition.cnn.com 172.30.223.53:39460 172.30.223.53:443 172.30.223.58:38138 edition.cnn.com -
Cleanup network policies
Delete the resources created in this section:
$ kubectl delete -f @samples/sleep/sleep.yaml@ -n test-egress
$ kubectl delete destinationrule egressgateway-for-cnn -n test-egress
$ kubectl delete networkpolicy allow-egress-to-istio-system-and-kube-dns -n test-egress
$ kubectl label namespace kube-system kube-system-
$ kubectl label namespace istio-system istio-
$ kubectl delete namespace test-egress
Follow the steps in the Cleanup HTTPS gateway section.
Troubleshooting
If mutual TLS Authentication is enabled, verify the correct certificate of the egress gateway:
$ kubectl exec -i -n istio-system "$(kubectl get pod -l istio=egressgateway -n istio-system -o jsonpath='{.items[0].metadata.name}')" -- cat /etc/certs/cert-chain.pem | openssl x509 -text -noout | grep 'Subject Alternative Name' -A 1
X509v3 Subject Alternative Name:
URI:spiffe://cluster.local/ns/istio-system/sa/istio-egressgateway-service-account
For HTTPS traffic (TLS originated by the application), test the traffic flow by using the openssl command. openssl has an explicit option for setting the SNI, namely
-servername
.$ kubectl exec "$SOURCE_POD" -c sleep -- openssl s_client -connect edition.cnn.com:443 -servername edition.cnn.com
CONNECTED(00000003)
...
Certificate chain
0 s:/C=US/ST=California/L=San Francisco/O=Fastly, Inc./CN=turner-tls.map.fastly.net
i:/C=BE/O=GlobalSign nv-sa/CN=GlobalSign CloudSSL CA - SHA256 - G3
1 s:/C=BE/O=GlobalSign nv-sa/CN=GlobalSign CloudSSL CA - SHA256 - G3
i:/C=BE/O=GlobalSign nv-sa/OU=Root CA/CN=GlobalSign Root CA
---
Server certificate
-----BEGIN CERTIFICATE-----
...
If you get the certificate as in the output above, your traffic is routed correctly. Check the statistics of the egress gateway’s proxy and see a counter that corresponds to your requests (sent by openssl and curl) to edition.cnn.com.
$ 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 stats | grep edition.cnn.com.upstream_cx_total
cluster.outbound|443||edition.cnn.com.upstream_cx_total: 2
Cleanup
Shutdown the sleep service:
$ kubectl delete -f @samples/sleep/sleep.yaml@