---
title: External Authorization
description: Shows how to integrate and delegate access control to an external authorization system.
weight: 35
keywords: [security,access-control,rbac,authorization,custom, opa, oauth, oauth2-proxy]
owner: istio/wg-security-maintainers
test: yes
---

This task shows you how to set up an Istio authorization policy using a new value for the [action field](/docs/reference/config/security/authorization-policy/#AuthorizationPolicy-Action), `CUSTOM`,
to delegate the access control to an external authorization system. This can be used to integrate with [OPA authorization](https://www.openpolicyagent.org/docs/latest/envoy-introduction/),
[`oauth2-proxy`](https://github.com/oauth2-proxy/oauth2-proxy), your own custom external authorization server and more.

## Before you begin

Before you begin this task, do the following:

* Read the [Istio authorization concepts](/docs/concepts/security/#authorization).

* Follow the [Istio installation guide](/docs/setup/install/istioctl/) to install Istio.

* Deploy test workloads:

    This task uses two workloads, `httpbin` and `curl`, both deployed in namespace `foo`.
    Both workloads run with an Envoy proxy sidecar. Deploy the `foo` namespace
    and workloads with the following command:

    {{< text bash >}}
    $ kubectl create ns foo
    $ kubectl label ns foo istio-injection=enabled
    $ kubectl apply -f @samples/httpbin/httpbin.yaml@ -n foo
    $ kubectl apply -f @samples/curl/curl.yaml@ -n foo
    {{< /text >}}

* Verify that `curl` can access `httpbin` with the following command:

    {{< text bash >}}
    $ kubectl exec "$(kubectl get pod -l app=curl -n foo -o jsonpath={.items..metadata.name})" -c curl -n foo -- curl http://httpbin.foo:8000/ip -s -o /dev/null -w "%{http_code}\n"
    200
    {{< /text >}}

{{< warning >}}
If you don’t see the expected output as you follow the task, retry after a few seconds.
Caching and propagation overhead can cause some delay.
{{< /warning >}}

## Deploy the external authorizer

First, you need to deploy the external authorizer. For this, you will simply deploy the sample external authorizer in a standalone pod in the mesh.

1. Run the following command to deploy the sample external authorizer:

    {{< text bash >}}
    $ kubectl apply -n foo -f {{< github_file >}}/samples/extauthz/ext-authz.yaml
    service/ext-authz created
    deployment.apps/ext-authz created
    {{< /text >}}

1. Verify the sample external authorizer is up and running:

    {{< text bash >}}
    $ kubectl logs "$(kubectl get pod -l app=ext-authz -n foo -o jsonpath={.items..metadata.name})" -n foo -c ext-authz
    2021/01/07 22:55:47 Starting HTTP server at [::]:8000
    2021/01/07 22:55:47 Starting gRPC server at [::]:9000
    {{< /text >}}

Alternatively, you can also deploy the external authorizer as a separate container in the same pod of the application
that needs the external authorization or even deploy it outside of the mesh. In either case, you will also need to create a
service entry resource to register the service to the mesh and make sure it is accessible to the proxy.

The following is an example service entry for an external authorizer deployed in a separate container in the same pod
of the application that needs the external authorization.

{{< text yaml >}}
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-authz-grpc-local
spec:
  hosts:
  - "external-authz-grpc.local" # The service name to be used in the extension provider in the mesh config.
  endpoints:
  - address: "127.0.0.1"
  ports:
  - name: grpc
    number: 9191 # The port number to be used in the extension provider in the mesh config.
    protocol: GRPC
  resolution: STATIC
{{< /text >}}

## Define the external authorizer

In order to use the `CUSTOM` action in the authorization policy, you must define the external authorizer that is allowed to be
used in the mesh. This is currently defined in the [extension provider](https://github.com/istio/api/blob/a205c627e4b955302bbb77dd837c8548e89e6e64/mesh/v1alpha1/config.proto#L534)
in the mesh config.

Currently, the only supported extension provider type is the [Envoy `ext_authz`](https://www.envoyproxy.io/docs/envoy/v1.16.2/intro/arch_overview/security/ext_authz_filter) provider.
The external authorizer must implement the corresponding Envoy `ext_authz` check API.

In this task, you will use a [sample external authorizer]({{< github_tree >}}/samples/extauthz) which
allows requests with the header `x-ext-authz: allow`.

1. Edit the mesh config with the following command:

    {{< text bash >}}
    $ kubectl edit configmap istio -n istio-system
    {{< /text >}}

1. In the editor, add the extension provider definitions shown below:

    The following content defines two external providers `sample-ext-authz-grpc` and `sample-ext-authz-http` using the
    same service `ext-authz.foo.svc.cluster.local`. The service implements both the HTTP and gRPC check API as defined by
    the Envoy `ext_authz` filter. You will deploy the service in the following step.

    {{< text yaml >}}
    data:
      mesh: |-
        # Add the following content to define the external authorizers.
        extensionProviders:
        - name: "sample-ext-authz-grpc"
          envoyExtAuthzGrpc:
            service: "ext-authz.foo.svc.cluster.local"
            port: "9000"
        - name: "sample-ext-authz-http"
          envoyExtAuthzHttp:
            service: "ext-authz.foo.svc.cluster.local"
            port: "8000"
            includeRequestHeadersInCheck: ["x-ext-authz"]
    {{< /text >}}

    Alternatively, you can modify the extension provider to control the behavior of the `ext_authz` filter for things like
    what headers to send to the external authorizer, what headers to send to the application backend, the status to return
    on error and more.
    For example, the following defines an extension provider that can be used with the [`oauth2-proxy`](https://github.com/oauth2-proxy/oauth2-proxy):

    {{< text yaml >}}
    data:
      mesh: |-
        extensionProviders:
        - name: "oauth2-proxy"
          envoyExtAuthzHttp:
            service: "oauth2-proxy.foo.svc.cluster.local"
            port: "4180" # The default port used by oauth2-proxy.
            includeRequestHeadersInCheck: ["authorization", "cookie"] # headers sent to the oauth2-proxy in the check request.
            headersToUpstreamOnAllow: ["authorization", "path", "x-auth-request-user", "x-auth-request-email", "x-auth-request-access-token"] # headers sent to backend application when request is allowed.
            headersToDownstreamOnAllow: ["set-cookie"] # headers sent back to the client when request is allowed.
            headersToDownstreamOnDeny: ["content-type", "set-cookie"] # headers sent back to the client when request is denied.
    {{< /text >}}

## Enable with external authorization

The external authorizer is now ready to be used by the authorization policy.

1. Enable the external authorization with the following command:

    The following command applies an authorization policy with the `CUSTOM` action value for the `httpbin` workload. The policy enables the external authorization for
    requests to path `/headers` using the external authorizer defined by `sample-ext-authz-grpc`.

    {{< text bash >}}
    $ kubectl apply -n foo -f - <<EOF
    apiVersion: security.istio.io/v1
    kind: AuthorizationPolicy
    metadata:
      name: ext-authz
    spec:
      selector:
        matchLabels:
          app: httpbin
      action: CUSTOM
      provider:
        # The provider name must match the extension provider defined in the mesh config.
        # You can also replace this with sample-ext-authz-http to test the other external authorizer definition.
        name: sample-ext-authz-grpc
      rules:
      # The rules specify when to trigger the external authorizer.
      - to:
        - operation:
            paths: ["/headers"]
    EOF
    {{< /text >}}

    At runtime, requests to path `/headers` of the `httpbin` workload will be paused by the `ext_authz` filter, and a
    check request will be sent to the external authorizer to decide whether the request should be allowed or denied.

1. Verify a request to path `/headers` with header `x-ext-authz: deny` is denied by the sample `ext_authz` server:

    {{< text bash >}}
    $ kubectl exec "$(kubectl get pod -l app=curl -n foo -o jsonpath={.items..metadata.name})" -c curl -n foo -- curl "http://httpbin.foo:8000/headers" -H "x-ext-authz: deny" -s
    denied by ext_authz for not found header `x-ext-authz: allow` in the request
    {{< /text >}}

1. Verify a request to path `/headers` with header `x-ext-authz: allow` is allowed by the sample `ext_authz` server:

    {{< text bash >}}
    $ kubectl exec "$(kubectl get pod -l app=curl -n foo -o jsonpath={.items..metadata.name})" -c curl -n foo -- curl "http://httpbin.foo:8000/headers" -H "x-ext-authz: allow" -s | jq '.headers'
    ...
      "X-Ext-Authz-Check-Result": [
        "allowed"
      ],
    ...
    {{< /text >}}

1. Verify a request to path `/ip` is allowed and does not trigger the external authorization:

    {{< text bash >}}
    $ kubectl exec "$(kubectl get pod -l app=curl -n foo -o jsonpath={.items..metadata.name})" -c curl -n foo -- curl "http://httpbin.foo:8000/ip" -s -o /dev/null -w "%{http_code}\n"
    200
    {{< /text >}}

1. Check the log of the sample `ext_authz` server to confirm it was called twice (for the two requests). The first one was allowed and the second one was denied:

    {{< text bash >}}
    $ kubectl logs "$(kubectl get pod -l app=ext-authz -n foo -o jsonpath={.items..metadata.name})" -n foo -c ext-authz
    2021/01/07 22:55:47 Starting HTTP server at [::]:8000
    2021/01/07 22:55:47 Starting gRPC server at [::]:9000
    2021/01/08 03:25:00 [gRPCv3][denied]: httpbin.foo:8000/headers, attributes: source:{address:{socket_address:{address:"10.44.0.22"  port_value:52088}}  principal:"spiffe://cluster.local/ns/foo/sa/curl"}  destination:{address:{socket_address:{address:"10.44.3.30"  port_value:80}}  principal:"spiffe://cluster.local/ns/foo/sa/httpbin"}  request:{time:{seconds:1610076306  nanos:473835000}  http:{id:"13869142855783664817"  method:"GET"  headers:{key:":authority"  value:"httpbin.foo:8000"}  headers:{key:":method"  value:"GET"}  headers:{key:":path"  value:"/headers"}  headers:{key:"accept"  value:"*/*"}  headers:{key:"content-length"  value:"0"}  headers:{key:"user-agent"  value:"curl/7.74.0-DEV"}  headers:{key:"x-b3-sampled"  value:"1"}  headers:{key:"x-b3-spanid"  value:"377ba0cdc2334270"}  headers:{key:"x-b3-traceid"  value:"635187cb20d92f62377ba0cdc2334270"}  headers:{key:"x-envoy-attempt-count"  value:"1"}  headers:{key:"x-ext-authz"  value:"deny"}  headers:{key:"x-forwarded-client-cert"  value:"By=spiffe://cluster.local/ns/foo/sa/httpbin;Hash=dd14782fa2f439724d271dbed846ef843ff40d3932b615da650d028db655fc8d;Subject=\"\";URI=spiffe://cluster.local/ns/foo/sa/curl"}  headers:{key:"x-forwarded-proto"  value:"http"}  headers:{key:"x-request-id"  value:"9609691a-4e9b-9545-ac71-3889bc2dffb0"}  path:"/headers"  host:"httpbin.foo:8000"  protocol:"HTTP/1.1"}}  metadata_context:{}
    2021/01/08 03:25:06 [gRPCv3][allowed]: httpbin.foo:8000/headers, attributes: source:{address:{socket_address:{address:"10.44.0.22"  port_value:52184}}  principal:"spiffe://cluster.local/ns/foo/sa/curl"}  destination:{address:{socket_address:{address:"10.44.3.30"  port_value:80}}  principal:"spiffe://cluster.local/ns/foo/sa/httpbin"}  request:{time:{seconds:1610076300  nanos:925912000}  http:{id:"17995949296433813435"  method:"GET"  headers:{key:":authority"  value:"httpbin.foo:8000"}  headers:{key:":method"  value:"GET"}  headers:{key:":path"  value:"/headers"}  headers:{key:"accept"  value:"*/*"}  headers:{key:"content-length"  value:"0"}  headers:{key:"user-agent"  value:"curl/7.74.0-DEV"}  headers:{key:"x-b3-sampled"  value:"1"}  headers:{key:"x-b3-spanid"  value:"a66b5470e922fa80"}  headers:{key:"x-b3-traceid"  value:"300c2f2b90a618c8a66b5470e922fa80"}  headers:{key:"x-envoy-attempt-count"  value:"1"}  headers:{key:"x-ext-authz"  value:"allow"}  headers:{key:"x-forwarded-client-cert"  value:"By=spiffe://cluster.local/ns/foo/sa/httpbin;Hash=dd14782fa2f439724d271dbed846ef843ff40d3932b615da650d028db655fc8d;Subject=\"\";URI=spiffe://cluster.local/ns/foo/sa/curl"}  headers:{key:"x-forwarded-proto"  value:"http"}  headers:{key:"x-request-id"  value:"2b62daf1-00b9-97d9-91b8-ba6194ef58a4"}  path:"/headers"  host:"httpbin.foo:8000"  protocol:"HTTP/1.1"}}  metadata_context:{}
    {{< /text >}}

    You can also tell from the log that mTLS is enabled for the connection between the `ext-authz` filter and the
    sample `ext-authz` server because the source principal is populated with the value `spiffe://cluster.local/ns/foo/sa/curl`.

    You can now apply another authorization policy for the sample `ext-authz` server to control who is allowed to access it.

## Clean up

1. Remove the namespace `foo` from your configuration:

    {{< text bash >}}
    $ kubectl delete namespace foo
    {{< /text >}}

1. Remove the extension provider definition from the mesh config.

## Performance expectations

See [performance benchmarking](https://github.com/istio/tools/tree/master/perf/benchmark/configs/istio/ext_authz).