Secure Gateways

8 minute read

This guide will help you get started using secure Gateways. The guide uses a self-signed CA, so it should be used for testing and demonstration purposes only.

Prerequisites

OpenSSL to generate TLS assets.

Installation

Follow the steps from the Quickstart Guide to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTP.

TLS Certificates

Generate the certificates and keys used by the Gateway to terminate client TLS connections.

Create a root certificate and private key to sign certificates:

openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -subj '/O=example Inc./CN=example.com' -keyout example.com.key -out example.com.crt

Create a certificate and a private key for www.example.com:

openssl req -out www.example.com.csr -newkey rsa:2048 -nodes -keyout www.example.com.key -subj "/CN=www.example.com/O=example organization"
openssl x509 -req -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 0 -in www.example.com.csr -out www.example.com.crt

Store the cert/key in a Secret:

kubectl create secret tls example-cert --key=www.example.com.key --cert=www.example.com.crt

Update the Gateway from the Quickstart guide to include an HTTPS listener that listens on port 443 and references the example-cert Secret:

kubectl patch gateway eg --type=json --patch '[{
   "op": "add",
   "path": "/spec/listeners/-",
   "value": {
      "name": "https",
      "protocol": "HTTPS",
      "port": 443,
      "tls": {
        "mode": "Terminate",
        "certificateRefs": [{
          "kind": "Secret",
          "group": "",
          "name": "example-cert",
        }],
      },
    },
}]'

Verify the Gateway status:

kubectl get gateway/eg -o yaml

Testing

Clusters without External LoadBalancer Support

Get the name of the Envoy service created the by the example Gateway:

export ENVOY_SERVICE=$(kubectl get svc -n envoy-gateway-system --selector=gateway.envoyproxy.io/owning-gateway-namespace=default,gateway.envoyproxy.io/owning-gateway-name=eg -o jsonpath='{.items[0].metadata.name}')

Port forward to the Envoy service:

kubectl -n envoy-gateway-system port-forward service/${ENVOY_SERVICE} 8443:443 &

Query the example app through Envoy proxy:

curl -v -HHost:www.example.com --resolve "www.example.com:8443:127.0.0.1" \
--cacert example.com.crt https://www.example.com:8443/get

Clusters with External LoadBalancer Support

Get the External IP of the Gateway:

export GATEWAY_HOST=$(kubectl get gateway/eg -o jsonpath='{.status.addresses[0].value}')

Query the example app through the Gateway:

curl -v -HHost:www.example.com --resolve "www.example.com:443:${GATEWAY_HOST}" \
--cacert example.com.crt https://www.example.com/get

Multiple HTTPS Listeners

Create a TLS cert/key for the additional HTTPS listener:

openssl req -out foo.example.com.csr -newkey rsa:2048 -nodes -keyout foo.example.com.key -subj "/CN=foo.example.com/O=example organization"
openssl x509 -req -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 0 -in foo.example.com.csr -out foo.example.com.crt

Store the cert/key in a Secret:

kubectl create secret tls foo-cert --key=foo.example.com.key --cert=foo.example.com.crt

Create another HTTPS listener on the example Gateway:

kubectl patch gateway eg --type=json --patch '[{
   "op": "add",
   "path": "/spec/listeners/-",
   "value": {
      "name": "https-foo",
      "protocol": "HTTPS",
      "port": 443,
      "hostname": "foo.example.com",
      "tls": {
        "mode": "Terminate",
        "certificateRefs": [{
          "kind": "Secret",
          "group": "",
          "name": "foo-cert",
        }],
      },
    },
}]'

Update the HTTPRoute to route traffic for hostname foo.example.com to the example backend service:

kubectl patch httproute backend --type=json --patch '[{
   "op": "add",
   "path": "/spec/hostnames/-",
   "value": "foo.example.com",
}]'

Verify the Gateway status:

kubectl get gateway/eg -o yaml

Follow the steps in the Testing section to test connectivity to the backend app through both Gateway listeners. Replace www.example.com with foo.example.com to test the new HTTPS listener.

Cross Namespace Certificate References

A Gateway can be configured to reference a certificate in a different namespace. This is allowed by a ReferenceGrant created in the target namespace. Without the ReferenceGrant, a cross-namespace reference is invalid.

Before proceeding, ensure you can query the HTTPS backend service from the Testing section.

To demonstrate cross namespace certificate references, create a ReferenceGrant that allows Gateways from the “default” namespace to reference Secrets in the “envoy-gateway-system” namespace:

$ cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: ReferenceGrant
metadata:
  name: example
  namespace: envoy-gateway-system
spec:
  from:
  - group: gateway.networking.k8s.io
    kind: Gateway
    namespace: default
  to:
  - group: ""
    kind: Secret
EOF

Delete the previously created Secret:

kubectl delete secret/example-cert

The Gateway HTTPS listener should now surface the Ready: False status condition and the example HTTPS backend should no longer be reachable through the Gateway.

kubectl get gateway/eg -o yaml

Recreate the example Secret in the envoy-gateway-system namespace:

kubectl create secret tls example-cert -n envoy-gateway-system --key=www.example.com.key --cert=www.example.com.crt

Update the Gateway HTTPS listener with namespace: envoy-gateway-system, for example:

$ cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: eg
spec:
  gatewayClassName: eg
  listeners:
    - name: http
      protocol: HTTP
      port: 80
    - name: https
      protocol: HTTPS
      port: 443
      tls:
        mode: Terminate
        certificateRefs:
          - kind: Secret
            group: ""
            name: example-cert
            namespace: envoy-gateway-system
EOF

The Gateway HTTPS listener status should now surface the Ready: True condition and you should once again be able to query the HTTPS backend through the Gateway.

Lastly, test connectivity using the above Testing section.

Clean-Up

Follow the steps from the Quickstart Guide to uninstall Envoy Gateway and the example manifest.

Delete the Secrets:

kubectl delete secret/example-cert
kubectl delete secret/foo-cert

RSA + ECDSA Dual stack certificates

This section gives a walkthrough to generate RSA and ECDSA derived certificates and keys for the Server, which can then be configured in the Gateway listener, to terminate TLS traffic.

Prerequisites

Follow the steps from the Quickstart Guide to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTP.

Follow the steps in the TLS Certificates section in the guide to generate self-signed RSA derived Server certificate and private key, and configure those in the Gateway listener configuration to terminate HTTPS traffic.

Pre-checks

While testing in Cluster without External LoadBalancer Support, we can query the example app through Envoy proxy while enforcing an RSA cipher, as shown below:

curl -v -HHost:www.example.com --resolve "www.example.com:8443:127.0.0.1" \
--cacert example.com.crt https://www.example.com:8443/get  -Isv --ciphers ECDHE-RSA-CHACHA20-POLY1305 --tlsv1.2 --tls-max 1.2

Since the Secret configured at this point is an RSA based Secret, if we enforce the usage of an ECDSA cipher, the call should fail as follows

$ curl -v -HHost:www.example.com --resolve "www.example.com:8443:127.0.0.1" \
--cacert example.com.crt https://www.example.com:8443/get  -Isv --ciphers ECDHE-ECDSA-CHACHA20-POLY1305 --tlsv1.2 --tls-max 1.2

* Added www.example.com:8443:127.0.0.1 to DNS cache
* Hostname www.example.com was found in DNS cache
*   Trying 127.0.0.1:8443...
* Connected to www.example.com (127.0.0.1) port 8443 (#0)
* ALPN: offers h2
* ALPN: offers http/1.1
* Cipher selection: ECDHE-ECDSA-CHACHA20-POLY1305
*  CAfile: example.com.crt
*  CApath: none
* (304) (OUT), TLS handshake, Client hello (1):
* error:1404B410:SSL routines:ST_CONNECT:sslv3 alert handshake failure
* Closing connection 0

Moving forward in the doc, we will be configuring the existing Gateway listener to accept both kinds of ciphers.

TLS Certificates

Reuse the CA certificate and key pair generated in the Secure Gateways guide and use this CA to sign both RSA and ECDSA Server certificates. Note the CA certificate and key names are example.com.crt and example.com.key respectively.

Create an ECDSA certificate and a private key for www.example.com:

openssl ecparam -noout -genkey -name prime256v1 -out www.example.com.ecdsa.key
openssl req -new -SHA384 -key www.example.com.ecdsa.key -nodes -out www.example.com.ecdsa.csr -subj "/CN=www.example.com/O=example organization"
openssl x509 -req -SHA384  -days 365 -in www.example.com.ecdsa.csr -CA example.com.crt -CAkey example.com.key -CAcreateserial -out www.example.com.ecdsa.crt

Store the cert/key in a Secret:

kubectl create secret tls example-cert-ecdsa --key=www.example.com.ecdsa.key --cert=www.example.com.ecdsa.crt

Patch the Gateway with this additional ECDSA Secret:

kubectl patch gateway eg --type=json --patch '[{
   "op": "add",
   "path": "/spec/listeners/1/tls/certificateRefs/-",
   "value": {
      "name": "example-cert-ecdsa",
    },
}]'

Verify the Gateway status:

kubectl get gateway/eg -o yaml

Testing

Again, while testing in Cluster without External LoadBalancer Support, we can query the example app through Envoy proxy while enforcing an RSA cipher, which should work as it did before:

curl -v -HHost:www.example.com --resolve "www.example.com:8443:127.0.0.1" \
--cacert example.com.crt https://www.example.com:8443/get  -Isv --ciphers ECDHE-RSA-CHACHA20-POLY1305 --tlsv1.2 --tls-max 1.2

...
* TLSv1.2 (IN), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-CHACHA20-POLY1305
...

Additionally, querying the example app while enforcing an ECDSA cipher should also work now:

curl -v -HHost:www.example.com --resolve "www.example.com:8443:127.0.0.1" \
--cacert example.com.crt https://www.example.com:8443/get  -Isv --ciphers ECDHE-ECDSA-CHACHA20-POLY1305 --tlsv1.2 --tls-max 1.2

...
* TLSv1.2 (IN), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-ECDSA-CHACHA20-POLY1305
...

SNI based Certificate selection

This sections gives a walkthrough to generate multiple certificates corresponding to different FQDNs. The same Gateway listener can then be configured to terminate TLS traffic for multiple FQDNs based on the SNI matching.

Prerequisites

Follow the steps from the Quickstart Guide to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTP.

Additional Configurations

Using the TLS Certificates section in the guide we first generate additional Secret for another Host www.sample.com.

openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -subj '/O=sample Inc./CN=sample.com' -keyout sample.com.key -out sample.com.crt

openssl req -out www.sample.com.csr -newkey rsa:2048 -nodes -keyout www.sample.com.key -subj "/CN=www.sample.com/O=sample organization"
openssl x509 -req -days 365 -CA sample.com.crt -CAkey sample.com.key -set_serial 0 -in www.sample.com.csr -out www.sample.com.crt

kubectl create secret tls sample-cert --key=www.sample.com.key --cert=www.sample.com.crt

Note that all occurrences of example.com were just replaced with sample.com

Next we update the Gateway configuration to accommodate the new Certificate which will be used to Terminate TLS traffic:

kubectl patch gateway eg --type=json --patch '[{
   "op": "add",
   "path": "/spec/listeners/1/tls/certificateRefs/-",
   "value": {
      "name": "sample-cert",
    },
}]'

Finally, we update the HTTPRoute to route traffic for hostname www.sample.com to the example backend service:

kubectl patch httproute backend --type=json --patch '[{
  "op": "add",
  "path": "/spec/hostnames/-",
  "value": "www.sample.com",
}]'

Testing

Clusters without External LoadBalancer Support

Get the name of the Envoy service created the by the example Gateway:

export ENVOY_SERVICE=$(kubectl get svc -n envoy-gateway-system --selector=gateway.envoyproxy.io/owning-gateway-namespace=default,gateway.envoyproxy.io/owning-gateway-name=eg -o jsonpath='{.items[0].metadata.name}')

Port forward to the Envoy service:

kubectl -n envoy-gateway-system port-forward service/${ENVOY_SERVICE} 8443:443 &

Query the example app through Envoy proxy:

curl -v -HHost:www.example.com --resolve "www.example.com:8443:127.0.0.1" \
--cacert example.com.crt https://www.example.com:8443/get -I

Similarly, query the sample app through the same Envoy proxy:

curl -v -HHost:www.sample.com --resolve "www.sample.com:8443:127.0.0.1" \
--cacert sample.com.crt https://www.sample.com:8443/get -I

Since the multiple certificates are configured on the same Gateway listener, Envoy was able to provide the client with appropriate certificate based on the SNI in the client request.

Clusters with External LoadBalancer Support

Refer to the steps mentioned earlier in the guide under Testing in clusters with External LoadBalancer Support

Next Steps

Checkout the Developer Guide to get involved in the project.

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Last modified December 20, 2024: chore: fix typo (#4958) (2a10d47)