Control Headers and Routing

Control Headers and Routing

This task demonstrates how to use a policy adapter to manipulate request headers and routing.

Before you begin

Set up Istio on Kubernetes by following the instructions in theInstallation guide.

Policy enforcement must be enabled in your cluster for this task. Follow the steps inEnabling Policy Enforcement to ensure that policy enforcement is enabled.

Follow the set-up instructions in the ingress task to configure an ingress using a gateway.
Customize the virtual serviceconfiguration for the httpbin service containing two route rules that allow traffic for paths /headers and/status:

$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: httpbin
spec:
  hosts:
  - "*"
  gateways:
  - httpbin-gateway
  http:
  - match:
    - uri:
        prefix: /headers
    - uri:
        prefix: /status
    route:
    - destination:
        port:
          number: 8000
        host: httpbin
EOF

Output-producing adapters

In this task, we are using a sample policy adapter keyval. In addition toa policy check result, this adapter returns an output with a single fieldcalled value. The adapter is configured with a lookup table, which it uses topopulate the output value, or return NOT_FOUND error status if the inputinstance key is not present in the lookup table.

Deploy the demo adapter:

$ kubectl run keyval --image=gcr.io/istio-testing/keyval:release-1.1 --namespace istio-system --port 9070 --expose

Enable the keyval adapter by deploying its template and configuration descriptors:

Zip Zip

$ kubectl apply -f @samples/httpbin/policy/keyval-template.yaml@
$ kubectl apply -f @samples/httpbin/policy/keyval.yaml@

Create a handler for the demo adapter with a fixed lookup table:

$ kubectl apply -f - <<EOF
apiVersion: config.istio.io/v1alpha2
kind: handler
metadata:
  name: keyval
  namespace: istio-system
spec:
  adapter: keyval
  connection:
    address: keyval:9070
  params:
    table:
      jason: admin
EOF

Create an instance for the handler with the user request header as a lookup key:

$ kubectl apply -f - <<EOF
apiVersion: config.istio.io/v1alpha2
kind: instance
metadata:
  name: keyval
  namespace: istio-system
spec:
  template: keyval
  params:
    key: request.headers["user"] | ""
EOF

Request header operations

Ensure the httpbin service is accessible through the ingress gateway:

$ curl http://$INGRESS_HOST:$INGRESS_PORT/headers
{
  "headers": {
    "Accept": "*/*",
    "Content-Length": "0",
    ...
    "X-Envoy-Internal": "true"
  }
}

The output should be the request headers as they are received by the httpbin service.

Create a rule for the demo adapter:

$ kubectl apply -f - <<EOF
apiVersion: config.istio.io/v1alpha2
kind: rule
metadata:
  name: keyval
  namespace: istio-system
spec:
  actions:
  - handler: keyval.istio-system
    instances: [ keyval ]
    name: x
  requestHeaderOperations:
  - name: user-group
    values: [ x.output.value ]
EOF

Issue a new request to the ingress gateway with the header key set to value jason:

$ curl -Huser:jason http://$INGRESS_HOST:$INGRESS_PORT/headers
{
  "headers": {
    "Accept": "*/*",
    "Content-Length": "0",
    "User": "jason",
    "User-Agent": "curl/7.58.0",
    "User-Group": "admin",
    ...
    "X-Envoy-Internal": "true"
  }
}

Note the presence of the user-group header with the value derived from therule application of the adapter. The expression x.output.value in the ruleevaluates to the populated value field returned by the keyval adapter.

Modify the rule to rewrite the URI path to a different virtual service routeif the check succeeds:

$ kubectl apply -f - <<EOF
apiVersion: config.istio.io/v1alpha2
kind: rule
metadata:
  name: keyval
  namespace: istio-system
spec:
  match: source.labels["istio"] == "ingressgateway"
  actions:
  - handler: keyval.istio-system
    instances: [ keyval ]
  requestHeaderOperations:
  - name: :path
    values: [ '"/status/418"' ]
EOF

Repeat the request to the ingress gateway:

$ curl -Huser:jason -I http://$INGRESS_HOST:$INGRESS_PORT/headers
HTTP/1.1 418 Unknown
server: istio-envoy
...

Note that the ingress gateway changed the route after the rule applicationof the policy adapter. The modified request may use a different route anddestination and is subject to the traffic management configuration.

The modified request is not checked again by the policy engine within thesame proxy. Therefore, we recommend to use this feature in gateways, sothat the server-side policy checks take effect.

Cleanup

Delete the policy resources for the demo adapter:

$ kubectl delete rule/keyval handler/keyval instance/keyval adapter/keyval template/keyval -n istio-system
$ kubectl delete service keyval -n istio-system
$ kubectl delete deployment keyval -n istio-system

Complete the clean-up instructions in ingress task.

Control Headers and Routing

Control Headers and Routing

Before you begin

Output-producing adapters

Request header operations

Cleanup

See also