Ext Authz server implements the external server for the Envoy ext_authz filter as an example of integrating custom authorization system into Istio.

The Ext Authz server supports authorization check request using either HTTP (port 8000) or gRPC v2/v3 (port 9000) API and will allow the request if it includes the header x-ext-authz: allow or if the service account of the source workload is a. Note that a is just a default value for testing. It can be changed with the flag -allow_service_account when running the ext authz server.

1. Deploy the Ext Authz service in a dedicated pod:

   $ kubectl apply -f ext-authz.yaml
   service/ext-authz created
   deployment.apps/ext-authz created

   Note, you can also deploy the Ext Authz service locally with the application container in the same pod, see the example in local-ext-authz.yaml.

2. Verify the Ext Authz server is up and running:

   Deploy a sleep pod to send the request:

   $ kubectl apply -f ../sleep/sleep.yaml

   Send a check request with header x-ext-authz: allow to the Ext Authz server:

   $ kubectl exec -it $(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name}) -c sleep -- curl -v ext-authz:8000 -H "x-ext-authz: allow"
      *   Trying 10.97.88.183:8000...
      * Connected to ext-authz-server (10.97.88.183) port 8000 (#0)
      > GET / HTTP/1.1
      > Host: ext-authz-server:8000
      > User-Agent: curl/7.73.0-DEV
      > Accept: */*
      > x-ext-authz: allow
      >
      * Mark bundle as not supporting multiuse
      < HTTP/1.1 200 OK
      < x-ext-authz-result: allowed
      < date: Tue, 03 Nov 2020 03:06:11 GMT
      < content-length: 0
      < x-envoy-upstream-service-time: 19
      < server: envoy
      <
      * Connection #0 to host ext-authz-server left intact

   As you observe, the check request with header x-ext-authz: allow is allowed by the Ext Authz server.

   Send another check request with x-ext-authz: blabla to the Ext Authz server:

   $ kubectl exec -it $(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name}) -c sleep -- curl -v ext-authz:8000 -H "x-ext-authz: bla"
       > GET / HTTP/1.1
       > Host: ext-authz-server:8000
       > User-Agent: curl/7.73.0-DEV
       > Accept: */*
       > x-ext-authz: allowx
       >
       * Mark bundle as not supporting multiuse
       < HTTP/1.1 403 Forbidden
       < x-ext-authz-check-result: denied
       < date: Tue, 03 Nov 2020 03:14:02 GMT
       < content-length: 76
       < content-type: text/plain; charset=utf-8
       < x-envoy-upstream-service-time: 44
       < server: envoy
       <
       * Connection #0 to host ext-authz-server left intact
       denied by ext_authz for not found header `x-ext-authz: allow` in the request

   As you observe, the check request with header x-ext-authz: bla is denied by the Ext Authz server.

3. To clean up, execute the following commands:

   $ kubectl delete -f ../sleep/sleep.yaml
   $ kubectl delete -f ext-authz.yaml

The Ext Authz server supports the following advanced features that are useful for testing:

• The ext authz server will add the x-ext-authz-check-received header to the user request. The content is the dump of the check request it received from the ext-authz filter. This header is useful in verifying the ext-authz filter sending the expected request to the ext authz server.

• The ext authz server will add (or override if it already exists) the header x-ext-authz-additional-header-override to the user request. The value of the header depends on the type of ext-authz server. The ext authz HTTP server will set it to the value of the same x-ext-authz-additional-header-override header in the check request. The ext authz gRPC server will set it to the constant value grpc-additional-header-override-value. This header is useful in verifying the header override behavior in the ext-authz filter.