External authorization (ext_authz) filter
The External Authorization sandbox demonstrates Envoy’s ext_authz filter capability to delegate authorization of incoming requests through Envoy to an external services.
While ext_authz can also be employed as a network filter, this sandbox is limited to exhibit ext_authz HTTP Filter, which supports to call HTTP or gRPC service.
The setup of this sandbox is very similar to front-proxy deployment, however calls to upstream
service behind the proxy will be checked by an external HTTP or gRPC service. In this sandbox,
for every authorized call, the external authorization service adds additional x-current-user
header entry to the original request headers to be forwarded to the upstream service.
Step 1: Start all of our containers
Change to the examples/ext_authz directory.
To build this sandbox example and start the example services, run the following commands:
$ pwd
envoy/examples/ext_authz
$ docker compose pull
$ docker compose up --build -d
$ docker compose ps
Name Command State Ports
--------------------------------------------------------------------------------------------------------------------
ext_authz_ext_authz-grpc-service_1 /app/server -users /etc/us Up
ext_authz_ext_authz-http-service_1 docker-entrypoint.sh node Up
ext_authz_front-envoy_1 /docker-entrypoint.sh /bin Up 10000/tcp, 0.0.0.0:8000->8000/tcp
ext_authz_upstream-service_1 python3 /code/service.py Up (healthy)
Note
This sandbox has multiple setup controlled by FRONT_ENVOY_YAML environment variable which
points to the effective Envoy configuration to be used. The default value of FRONT_ENVOY_YAML
can be defined in the .env file or provided inline when running the docker compose up
command.
For more information, please take a look at environment variables in Compose documentation.
By default, FRONT_ENVOY_YAML points to config/grpc-service/v3.yaml
file which bootstraps front-envoy with ext_authz HTTP filter with gRPC service V3 (this is specified by
transport_api_version field).
The possible values of FRONT_ENVOY_YAML can be found inside the config
directory.
For example, to run Envoy with ext_authz HTTP filter with HTTP service will be:
$ pwd
envoy/examples/ext_authz
$ docker compose pull
$ # Tearing down the currently running setup
$ docker compose down
$ FRONT_ENVOY_YAML=config/http-service.yaml docker compose up --build -d
$ # Or you can update the .env file with the above FRONT_ENVOY_YAML value, so you don't have to specify it when running the "up" command.
Step 4: Access the upstream-service behind the Front Envoy
You can now try to send a request to upstream-service via the front-envoy as follows:
$ curl -v localhost:8000/service
* Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8000 (#0)
> GET /service HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/7.58.0
> Accept: */*
>
< HTTP/1.1 403 Forbidden
< date: Fri, 19 Jun 2020 15:02:24 GMT
< server: envoy
< content-length: 0
As observed, the request failed with 403 Forbidden status code. This happened since the ext_authz
filter employed by Envoy rejected the call. To let the request reach the upstream service, you need
to provide a Bearer token via the Authorization header.
Note
A complete list of users is defined in auth/users.json
file. For example, the token1 used in the below example is corresponding to user1.
An example of successful requests can be observed as follows:
$ curl -v -H "Authorization: Bearer token1" localhost:8000/service
* Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8000 (#0)
> GET /service HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/7.58.0
> Accept: */*
> Authorization: Bearer token1
>
< HTTP/1.1 200 OK
< content-type: text/html; charset=utf-8
< content-length: 24
< server: envoy
< date: Fri, 19 Jun 2020 15:04:29 GMT
< x-envoy-upstream-service-time: 2
<
* Connection #0 to host localhost left intact
Hello user1 from behind Envoy!
We can also employ Open Policy Agent server (with envoy_ext_authz_grpc plugin enabled) as the authorization server. To run this example:
$ pwd
envoy/examples/ext_authz
$ docker compose pull
$ # Tearing down the currently running setup
$ docker compose down
$ FRONT_ENVOY_YAML=config/opa-service/v3.yaml docker compose up --build -d
And sending a request to the upstream service (via the Front Envoy) gives:
$ curl localhost:8000/service --verbose
* Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8000 (#0)
> GET /service HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/7.64.1
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: text/html; charset=utf-8
< content-length: 28
< server: envoy
< date: Thu, 02 Jul 2020 06:29:58 GMT
< x-envoy-upstream-service-time: 2
<
* Connection #0 to host localhost left intact
Hello OPA from behind Envoy!
From the logs, we can observe the policy decision message from the Open Policy Agent server (for
the above request against the defined policy in
config/opa-service/policy.rego):
$ docker compose logs ext_authz-opa-service | grep decision_id -A 30
ext_authz-opa-service_1 | "decision_id": "8143ca68-42d8-43e6-ade6-d1169bf69110",
ext_authz-opa-service_1 | "input": {
ext_authz-opa-service_1 | "attributes": {
ext_authz-opa-service_1 | "destination": {
ext_authz-opa-service_1 | "address": {
ext_authz-opa-service_1 | "Address": {
ext_authz-opa-service_1 | "SocketAddress": {
ext_authz-opa-service_1 | "PortSpecifier": {
ext_authz-opa-service_1 | "PortValue": 8000
ext_authz-opa-service_1 | },
ext_authz-opa-service_1 | "address": "172.28.0.6"
ext_authz-opa-service_1 | }
ext_authz-opa-service_1 | }
ext_authz-opa-service_1 | }
ext_authz-opa-service_1 | },
ext_authz-opa-service_1 | "metadata_context": {},
ext_authz-opa-service_1 | "request": {
ext_authz-opa-service_1 | "http": {
ext_authz-opa-service_1 | "headers": {
ext_authz-opa-service_1 | ":authority": "localhost:8000",
ext_authz-opa-service_1 | ":method": "GET",
ext_authz-opa-service_1 | ":path": "/service",
ext_authz-opa-service_1 | "accept": "*/*",
ext_authz-opa-service_1 | "user-agent": "curl/7.64.1",
ext_authz-opa-service_1 | "x-forwarded-proto": "http",
ext_authz-opa-service_1 | "x-request-id": "b77919c0-f1d4-4b06-b444-5a8b32d5daf4"
ext_authz-opa-service_1 | },
ext_authz-opa-service_1 | "host": "localhost:8000",
ext_authz-opa-service_1 | "id": "16617514055874272263",
ext_authz-opa-service_1 | "method": "GET",
ext_authz-opa-service_1 | "path": "/service",
Trying to send a request with method other than GET gives a rejection:
$ curl -X POST localhost:8000/service --verbose
* Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8000 (#0)
> PUT /service HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/7.64.1
> Accept: */*
>
< HTTP/1.1 403 Forbidden
< date: Thu, 02 Jul 2020 06:46:13 GMT
< server: envoy
< content-length: 0
See also
- ext_authz filter
Learn more about using Envoy’s
ext_authzfilter.- Open Policy Agent
Policy-based control for cloud native environments.
- envoy_ext_authz_grpc
Open Policy Agent Envoy plugin.
- environment variables in Compose documentation.
Further information about using env variables with Docker Compose.