Decode base64 headers

In the following example, you combine multiple Inja functions to accomplish the following tasks:

• Extract a base64-encoded value from a specific request header.
• Decode the base64-encoded value.
• Trim the decoded value and only capture everything starting from the 11th character.
• Add the captured string as a response header.

Before you begin

1. Follow the Get started guide to install K8sGateway, set up a gateway resource, and deploy the httpbin sample app.

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

   Cloud Provider LoadBalancerPort-forward for local testing

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

   kubectl port-forward deployment/gloo-proxy-http -n gloo-system 8080:8080

Decode base64 headers

1. Encode a string to base64.

   echo -n "transformation test" | base64

   Example output:

   dHJhbnNmb3JtYXRpb24gdGVzdA==

2. Create a VirtualHostOption resource with your transformation rules. In the following example, you decode the base64-encoded value from the x-base64-encoded request header and populate the decoded value into an x-base64-decoded header starting from the 11th character.

   kubectl apply -n gloo-system -f- <<EOF
   apiVersion: gateway.solo.io/v1
   kind: VirtualHostOption
   metadata:
     name: transformation
     namespace: gloo-system
   spec:
     options:
       transformations:
         responseTransformation:
           transformationTemplate:
             headers:
               x-base64-decoded:
                 text: '{{substring(base64_decode(request_header("x-base64-encoded")), 11)}}'
     targetRefs:
     - group: gateway.networking.k8s.io
       kind: Gateway
       name: http
       namespace: gloo-system
   EOF

3. Send a request to the httpbin app and include your base64-encoded string in the x-base64-encoded request header. Verify that you get back a 200 HTTP response code and that you see the trimmed decoded value of your base64-encoded string in the x-base64-decoded response header.

   Cloud Provider LoadBalancerPort-forward for local testing

   curl -vik http://$INGRESS_GW_ADDRESS:8080/response-headers \
    -H "host: www.example.com:8080" \
    -H "x-base64-encoded: dHJhbnNmb3JtYXRpb24gdGVzdA==" 

   curl -vik localhost:8080/response-headers \
   -H "host: www.example.com" \
   -H "x-base64-encoded: dHJhbnNmb3JtYXRpb24gdGVzdA==" 

   Example output:

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

   * Mark bundle as not supporting multiuse < HTTP/1.1 200 OK HTTP/1.1 200 OK < access-control-allow-credentials: true access-control-allow-credentials: true < access-control-allow-origin: * access-control-allow-origin: * < content-type: application/json; encoding=utf-8 content-type: application/json; encoding=utf-8 < date: Wed, 26 Jun 2024 02:54:48 GMT date: Wed, 26 Jun 2024 02:54:48 GMT < content-length: 3 content-length: 3 < x-envoy-upstream-service-time: 2 x-envoy-upstream-service-time: 2 < server: envoy server: envoy < x-envoy-decorator-operation: httpbin.httpbin.svc.cluster.local:8000/* x-envoy-decorator-operation: httpbin.httpbin.svc.cluster.local:8000/* < x-base64-decoded: ion test x-base64-decoded: ion test

Cleanup

kubectl delete virtualhostoption transformation -n gloo-system