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TLS termination for TCPRoutes

          
Set up a TLS listener on the Gateway that terminates incoming TLS traffic and routes it using a TCPRoute. Unlike TLS termination for TLSRoutes, which uses SNI-based hostname matching, the TCPRoute does not perform hostname matching and routes traffic based on the listener port only.


Before you begin
    
    

  1. 

    Set up kgateway by following the Quick start or Installation guides.
    

    2. 

  2. 

    Deploy the httpbin sample app.
    

    3. 

  3. 

    Make sure that you have the OpenSSL version of openssl, not LibreSSL. The openssl version must be at least 1.1.
    

      

    1. 

      Check the openssl version that is installed. If you see LibreSSL in the output, continue to the next step.
      

      


      openssl version
      
  

      

      

      2. 

    2. 

      Install the OpenSSL version (not LibreSSL). For example, you might use Homebrew.
      

      


      brew install openssl
      
  

      

      

      3. 

    3. 

      Review the output of the OpenSSL installation for the path of the binary file. You can choose to export the binary to your path, or call the entire path whenever the following steps use an openssl command.
      

        

      • For example, openssl might be installed along the following path: /usr/local/opt/openssl@3/bin/
        • 

      • To run commands, you can append the path so that your terminal uses this installed version of OpenSSL, and not the default LibreSSL. /usr/local/opt/openssl@3/bin/openssl req -new -newkey rsa:4096 -x509 -sha256 -days 3650...
        • 

      

      4. 

    

    4. 

  4. 
Decide whether to set up a listener inline on the Gateway resource or as a separate ListenerSet resource. For more information, see the Listener overview.

    5. 



Install the experimental channel of the Kubernetes Gateway API so that you can use TCPRoutes.





kubectl apply -f https://github.com/kubernetes-sigs/gateway-api/releases/download/v1.5.1/experimental-install.yaml

  





Create a TLS certificate
    
    

  1. 

    Create a directory to store your TLS credentials in.
    

    


    mkdir example_certs
    
  

    

    

    2. 

  2. 

    Create a self-signed root certificate.
    

    


    openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 \
  -subj '/O=any domain/CN=*' \
  -keyout example_certs/root.key -out example_certs/root.crt
    
  

    

    

    3. 

  3. 

    Create an OpenSSL configuration for the app.example.com hostname.
    

    


    cat <<'EOF' > example_certs/gateway.cnf
[ req ]
default_bits = 2048
prompt = no
default_md = sha256
distinguished_name = dn
req_extensions = req_ext
[ dn ]
CN = *.example.com
O = any domain
[ req_ext ]
subjectAltName = @alt_names
[ alt_names ]
DNS.1 = *.example.com
DNS.2 = example.com
EOF
    
  

    

    

    4. 

  4. 

    Create and sign the gateway certificate.
    

    


    openssl req -new -nodes \
  -keyout example_certs/gateway.key \
  -out example_certs/gateway.csr \
  -config example_certs/gateway.cnf
openssl x509 -req -sha256 -days 365 \
  -CA example_certs/root.crt -CAkey example_certs/root.key -set_serial 0 \
  -in example_certs/gateway.csr -out example_certs/gateway.crt \
  -extfile example_certs/gateway.cnf -extensions req_ext
    
  

    

    

    5. 

  5. 

    Create a Kubernetes secret to store the gateway TLS certificate.
    

    


    kubectl create secret tls tls-terminate-tcp \
  -n kgateway-system \
  --key example_certs/gateway.key \
  --cert example_certs/gateway.crt
    
  

    

    

    6. 



Set up TLS termination
    
Set up a TLS listener on the Gateway with tls.mode: Terminate. The Gateway decrypts incoming TLS traffic using the certificate you created and forwards the plain traffic to the backend service. Unlike TLS termination with TLSRoutes, no hostname is required on the listener because TCPRoutes route based on port only.


    

  1. 

    Create a Gateway with a TLS termination listener. Set the gatewayClassName to kgateway.
    

   
   
   
    
  
    

    

    

    kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: tls-terminate-tcp
  namespace: kgateway-system
  labels:
    example: tls-terminate-tcp
spec:
  gatewayClassName: kgateway
  listeners:
  - name: tls
    protocol: TLS
    port: 8443
    tls:
      mode: Terminate
      certificateRefs:
        - name: tls-terminate-tcp
          kind: Secret
    allowedRoutes:
      kinds:
        - kind: TCPRoute
      namespaces:
        from: All
EOF
    
  

    

    

    Review the following table to understand this configuration.
    

    
  
    
 
   
    
     Setting
     Description
   
    
     
 
   
    spec.gatewayClassNameThe name of the Kubernetes GatewayClass that you want to use to configure the Gateway. When you set up kgateway, a default GatewayClass is set up for you. Set the gatewayClassName to kgateway.
   
    
   
    spec.listenersConfigure the listeners for this Gateway. In this example, you configure a TLS listener that terminates incoming TLS traffic on port 8443. No hostname is set because TCPRoutes do not perform SNI-based hostname matching.
   
    
   
    spec.listeners.tls.modeThe TLS mode for incoming requests. In this example, TLS requests are terminated at the Gateway and the decrypted traffic is forwarded to the backend service.
   
    
   
    spec.listeners.tls.certificateRefsThe Kubernetes secret that holds the TLS certificate and key. The Gateway uses these to terminate the TLS connection.
   
    
   
    spec.listeners.allowedRoutes.kindsRestricts the listener to accept only TCPRoute resources.
   
    
     
  
    

    


    2. 

  2. 

    Check the status of the Gateway to make sure that your configuration is accepted.
    

    


    kubectl get gateway tls-terminate-tcp -n kgateway-system -o yaml
    
  

    

    

    3. 



Create a TCPRoute
    
Create a TCPRoute that routes traffic on port 8443 to the httpbin app.






  






kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: TCPRoute
metadata:
  name: tls-terminate-tcp-route
  namespace: httpbin
  labels:
    example: tls-terminate-tcp
spec:
  parentRefs:
    - name: tls-terminate-tcp
      namespace: kgateway-system
      sectionName: tls
  rules:
    - backendRefs:
        - name: httpbin
          port: 8000
EOF

  








Verify TLS termination traffic
    





  




    

  1. 

    Get the external address of the gateway and save it in an environment variable.
    

    

    export INGRESS_GW_ADDRESS=$(kubectl get svc -n kgateway-system tls-terminate-tcp -o jsonpath="{.status.loadBalancer.ingress[0]['hostname','ip']}")
echo $INGRESS_GW_ADDRESS
    
  

    

    

    2. 

  2. 

    Send a request to the app.example.com domain and verify that you get back a 200 HTTP response code. The TLS connection is terminated at the Gateway and the plain traffic is forwarded to the httpbin app.
    

      

    • 

      Load balancer IP:
      

      

      curl -vik --resolve "app.example.com:8443:${INGRESS_GW_ADDRESS}" \
  --cacert example_certs/root.crt \
  https://app.example.com:8443/status/200
      
  

      

      

      • 

    • 

      Load balancer hostname:
      

      

      curl -vik --resolve "app.example.com:8443:$(dig +short $INGRESS_GW_ADDRESS | head -n1)" \
  --cacert example_certs/root.crt \
  https://app.example.com:8443/status/200
      
  

      

      

      • 

    

    Example output:
    

    

    * Request completely sent off
< HTTP/1.1 200 OK
HTTP/1.1 200 OK
...

    
  

    

    

    3. 






Cleanup
    
You can remove the resources that you created in this guide.





  






kubectl delete -A gateways,tcproutes,secret -l example=tls-terminate-tcp
rm -rf example_certs

  








        

        

        
TLS passthroughTLS termination for TLSRoutes

        

  

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