Decode base64 headers

Automatically decode base64 values in request headers and add the decoded value as a response header.

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 response header.

Before you begin

1. Follow the Get started guide to install Gloo Gateway, 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.

   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 RouteOption or 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 -f- <<EOF
   apiVersion: gateway.solo.io/v1
   kind: RouteOption
   metadata:
     name: transformation
     namespace: httpbin
   spec:
     targetRefs:
     - group: gateway.networking.k8s.io
       kind: HTTPRoute
       name: httpbin
     options:
       transformations:
         responseTransformation:
           transformationTemplate:
             headers:
               x-base64-decoded:
                 text: '{{substring(base64_decode(request_header("x-base64-encoded")), 11)}}'
   EOF

   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.

   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:

   * 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

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

kubectl delete virtualhostoption transformation -n gloo-system
kubectl delete routeoption transformation -n httpbin