How to: Proxy TCP traffic over TLS by SNI

Prerequisites

Kong Konnect

If you don’t have a Konnect account, you can get started quickly with our onboarding wizard.

The following Konnect items are required to complete this tutorial:
- Personal access token (PAT): Create a new personal access token by opening the Konnect PAT page and selecting Generate Token.
Set the personal access token as an environment variable:
```
export KONNECT_TOKEN='YOUR KONNECT TOKEN'
```

Enable the Gateway API

Install the experimental Gateway API CRDs before installing Kong Ingress Controller:

kubectl apply -f https://github.com/kubernetes-sigs/gateway-api/releases/download/v1.3.0/experimental-install.yaml

Create a Gateway and GatewayClass instance to use.

echo "
apiVersion: v1
kind: Namespace
metadata:
  name: kong
---
apiVersion: gateway.networking.k8s.io/v1
kind: GatewayClass
metadata:
  name: kong
  annotations:
    konghq.com/gatewayclass-unmanaged: 'true'
spec:
  controllerName: konghq.com/kic-gateway-controller
---
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: kong
spec:
  gatewayClassName: kong
  listeners:
  - name: proxy
    port: 80
    protocol: HTTP
    allowedRoutes:
      namespaces:
         from: All
" | kubectl apply -n kong -f -

Create a KIC Control Plane

Use the Konnect API to create a new CLUSTER_TYPE_K8S_INGRESS_CONTROLLER Control Plane:

CONTROL_PLANE_DETAILS=$(curl -X POST "https://us.api.konghq.com/v2/control-planes" \
     -H "Authorization: Bearer $KONNECT_TOKEN" \
     --json '{
       "name": "My KIC CP",
       "cluster_type": "CLUSTER_TYPE_K8S_INGRESS_CONTROLLER"
     }')

We’ll need the id and telemetry_endpoint for the values.yaml file later. Save them as environment variables:

CONTROL_PLANE_ID=$(echo $CONTROL_PLANE_DETAILS | jq -r .id)
CONTROL_PLANE_TELEMETRY=$(echo $CONTROL_PLANE_DETAILS | jq -r '.config.telemetry_endpoint | sub("https://";"")')

Create mTLS certificates

Kong Ingress Controller talks to Konnect over a connected secured with TLS certificates.

Generate a new certificate using openssl:

openssl req -new -x509 -nodes -newkey rsa:2048 -subj "/CN=kongdp/C=US" -keyout ./tls.key -out ./tls.crt

The certificate needs to be a single line string to send it to the Konnect API with curl. Use awk to format the certificate:

export CERT=$(awk 'NF {sub(/\r/, ""); printf "%s\\n",$0;}' tls.crt);

Next, upload the certificate to Konnect:

curl -X POST "https://us.api.konghq.com/v2/control-planes/$CONTROL_PLANE_ID/dp-client-certificates" \
     -H "Authorization: Bearer $KONNECT_TOKEN" \
     --json '{
       "cert": "'$CERT'"
     }'

Finally, store the certificate in a Kubernetes secret so that Kong Ingress Controller can read it:

kubectl create namespace kong -o yaml --dry-run=client | kubectl apply -f -
kubectl create secret tls konnect-client-tls -n kong --cert=./tls.crt --key=./tls.key

Kong Ingress Controller running

Add the Kong Helm charts:

helm repo add kong https://charts.konghq.com
helm repo update

Install Kong Ingress Controller using Helm:

helm install kong kong/ingress -n kong --create-namespace --set controller.ingressController.env.feature_gates="GatewayAlpha=true"

Set $PROXY_IP as an environment variable for future commands:

export PROXY_IP=$(kubectl get svc --namespace kong kong-gateway-proxy -o jsonpath='{range .status.loadBalancer.ingress[0]}{@.ip}{@.hostname}{end}')
echo $PROXY_IP

Required Kubernetes resources

This how-to requires some Kubernetes services to be available in your cluster. These services will be used by the resources created in this how-to.

kubectl apply -f https://developer.konghq.com/manifests/kic/echo-service.yaml -n kong

Expose additional ports

Kong Gateway doesn’t include any TCP listen configuration by default. To expose TCP listens, update the Deployment’s environment variables and port configuration.

Set the KONG_STREAM_LISTEN environment variable and expose port 9443 in the Deployment:

 kubectl patch deploy -n kong kong-gateway --patch '{
   "spec": {
     "template": {
       "spec": {
         "containers": [
           {
             "name": "proxy",
             "env": [
               {
                 "name": "KONG_STREAM_LISTEN",
                 "value": "0.0.0.0:9443 ssl"
               }
             ],
             "ports": [
               {
                 "containerPort": 9443,
                 "name": "stream9443",
                 "protocol": "TCP"
               }
             ]
           }
         ]
       }
     }
   }
 }'

The ssl parameter after the 9443 listener instructs Kong Gateway to expect TLS-encrypted TCP traffic on that port.

Update the proxy Service to indicate the new ports:

kubectl patch service -n kong kong-gateway-proxy --patch '{
  "spec": {
    "ports": [
      {
        "name": "stream9443",
        "port": 9443,
        "protocol": "TCP",
        "targetPort": 9443
      }
    ]
  }
}'

Generate a TLS certificate

Create a test certificate for the tls9443.kong.example hostname. This will be used to secure TLS traffic.

openssl req -subj '/CN=tls9443.kong.example' -new -newkey rsa:2048 -sha256 \
   -days 365 -nodes -x509 -keyout server.key -out server.crt \
   -addext "subjectAltName = DNS:tls9443.kong.example" \
   -addext "keyUsage = digitalSignature" \
   -addext "extendedKeyUsage = serverAuth" 2> /dev/null;
   openssl x509 -in server.crt -subject -noout

openssl req -subj '/CN=tls9443.kong.example' -new -newkey rsa:2048 -sha256 \
   -days 365 -nodes -x509 -keyout server.key -out server.crt \
   -extensions EXT -config <( \
    printf "[dn]\nCN=tls9443.kong.example\n[req]\ndistinguished_name = dn\n[EXT]\nsubjectAltName=DNS:tls9443.kong.example\nkeyUsage=digitalSignature\nextendedKeyUsage=serverAuth") 2>/dev/null;
   openssl x509 -in server.crt -subject -noout

Older OpenSSL versions, including the version provided with macOS Monterey, require using the alternative version of this command.

Create a Secret containing the certificate:

 kubectl create secret -n kong tls tls9443.kong.example --cert=./server.crt --key=./server.key

Attach the TLS certificate to the echo service

The echo service does not listen on the TLS port by default as it requires a certificate stored in a Kubernetes Secret. Patch the echo deployment to mount the Secret in the pod and set the TLS_CERT_FILE and TLS_KEY_FILE environment variables to allow the echo service to terminate TLS:

kubectl patch -n kong --type=json deployment echo -p='[
    {
        "op":"add",
        "path":"/spec/template/spec/containers/0/env/-",
        "value":{
            "name": "TLS_PORT",
            "value": "1030"
        }
    },
    {
        "op":"add",
        "path":"/spec/template/spec/containers/0/env/-",
        "value":{
            "name": "TLS_CERT_FILE",
            "value": "/var/run/certs/tls.crt"
        }
    },
    {
        "op":"add",
        "path":"/spec/template/spec/containers/0/env/-",
        "value":{
            "name": "TLS_KEY_FILE",
            "value": "/var/run/certs/tls.key"
        }
    },
    {
        "op":"add",
        "path":"/spec/template/spec/containers/0/volumeMounts",
        "value":[{
            "mountPath": "/var/run/certs",
            "name": "secret-test",
            "readOnly": true
        }]
    },
    {
        "op":"add",
        "path":"/spec/template/spec/volumes",
        "value":[{
            "name": "secret-test",
            "secret": {
              "defaultMode": 420,
              "secretName": "tls9443.kong.example"
            }
        }]
    }
]'

Route TCP traffic

To reconcile the TLSRoute, configure an additional TLS listener on your Gateway resource:

kubectl patch -n kong --type=json gateway kong -p='[
    {
        "op":"add",
        "path":"/spec/listeners/-",
        "value":{
            "name":"stream9443",
            "port":9443,
            "protocol":"TLS",
            "hostname":"tls9443.kong.example",
            "allowedRoutes": {
              "namespaces": {
                "from": "All"
              }
            },
            "tls": {
              "mode": "Passthrough",
              "certificateRefs":[{
                "group":"",
                "kind":"Secret",
                "name":"tls9443.kong.example"
              }]
            }
        }
    }
]'

Next, create a TLSRoute:

echo "apiVersion: gateway.networking.k8s.io/v1alpha2
kind: TLSRoute
metadata:
  name: echo-tls
  namespace: kong
spec:
  parentRefs:
    - name: kong
      sectionName: stream9443
  hostnames:
    - tls9443.kong.example
  rules:
    - backendRefs:
      - name: echo
        port: 1030
" | kubectl apply -f -

This configuration instructs Kong Gateway to forward all traffic it receives on port 9000 to the echo service on port 1030.

Validate your configuration

You can now access the echo service on port 9443 with SNI tls9443.kong.example.

In real-world usage, you would create a DNS record for tls9443.kong.example pointing to your proxy Service’s public IP address, which causes TLS clients to add a SNI automatically. For this demo, add it manually using the OpenSSL CLI.

echo "hello" | openssl s_client -connect $PROXY_IP:9443 -servername tls9443.kong.example -quiet 2>/dev/null

Press Ctrl+C to exit.

The results should look like this:

Welcome, you are connected to node kind-control-plane.
Running on Pod echo-5f44d4c6f9-krnhk.
In namespace default.
With IP address 10.244.0.26.
hello

Cleanup

Delete created Kubernetes resources

kubectl delete -n kong -f https://developer.konghq.com/manifests/kic/echo-service.yaml

Uninstall KIC from your cluster

helm uninstall kong -n kong

Proxy TCP traffic over TLS by SNI