Implement custom authorization by using the gRPC protocol to improve service security - Alibaba Cloud Service Mesh

The custom authorization feature allows you to perform fine-grained Resource Access Management (RAM) on services that use the gRPC protocol. With this feature, you can customize authorization mechanisms based on your business requirements. Authentication is required when services communicate with each other. This ensures that only authenticated and authorized requests can access specific service resources and improves the security of service-to-service communication. This topic uses the httpbin application and the sleep application in the following example to describe how to implement custom authorization by using the gRPC protocol.

Prerequisites

A Container Service for Kubernetes (ACK) cluster is added to your ASM instance. For more information, see The cluster is added to the ASM instance..

Step 1: Deploy a custom authorization service

Deploy a custom authorization service in the ACK cluster. This service must comply with the API specifications of Istio for custom authorization services and support the HTTP and gRPC protocols. This service is used to implement custom authorization. The sample authorization service provided in this topic specifies that only requests with the x-ext-authz: allow header can pass the authentication.

Note

You can use the following sample authorization service or create a custom authorization service based on the code of the sample authorization service. For more information, visit the GitHub website.

Create an ext-authz.yaml file that contains the following content:

Show the ext-authz.yaml file

# Copyright Istio Authors
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.

# Example configurations for deploying ext-authz server separately in the mesh.

apiVersion: v1
kind: Service
metadata:
  name: ext-authz
  labels:
    app: ext-authz
spec:
  ports:
  - name: http
    port: 8000
    targetPort: 8000
  - name: grpc
    port: 9000
    targetPort: 9000
  selector:
    app: ext-authz
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: ext-authz
spec:
  replicas: 1
  selector:
    matchLabels:
      app: ext-authz
  template:
    metadata:
      labels:
        app: ext-authz
    spec:
      containers:
      - image: istio/ext-authz:0.6
        imagePullPolicy: IfNotPresent
        name: ext-authz
        ports:
        - containerPort: 8000
        - containerPort: 9000
---

Use kubectl to connect to the cluster and run the following command to deploy the custom authorization service in the cluster.
For more information, see Obtain the kubeconfig file of a cluster and use kubectl to connect to the cluster.
```
kubectl apply -f ext-authz.yaml
```
Expected output:
```
service/ext-authz created
deployment.apps/ext-authz created
```

Run the following command to check whether the ext-authz service works as expected:

kubectl logs "$(kubectl get pod -l app=ext-authz -n default -o jsonpath={.items..metadata.name})" -n default -c ext-authz

Expected output:

2023/12/20 08:15:39 Starting gRPC server at [::]:9000
2023/12/20 08:15:39 Starting HTTP server at [::]:8000

If the preceding result is returned, the custom authorization service is deployed.

Obtain the gRPC port that is used by the ext-authz service.
1. Log on to the ACK console. In the left-side navigation pane, click Clusters.
2. On the Clusters page, find the cluster that you want to manage and click its name. In the left-side pane, choose Network > Services.
3. On the Services page, click ext-authz.
  In the Endpoint section of the service details page, you can view the gRPC port. In this example, the port is 9000.

Step 2: Deploy sample applications

Create an httpbin.yaml file that contains the following content:

Show the httpbin.yaml file

# Copyright Istio Authors
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.

##################################################################################################
# httpbin service
##################################################################################################
apiVersion: v1
kind: ServiceAccount
metadata:
  name: httpbin
---
apiVersion: v1
kind: Service
metadata:
  name: httpbin
  labels:
    app: httpbin
    service: httpbin
spec:
  ports:
  - name: http
    port: 8000
    targetPort: 80
  selector:
    app: httpbin
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpbin
spec:
  replicas: 1
  selector:
    matchLabels:
      app: httpbin
      version: v1
  template:
    metadata:
      labels:
        app: httpbin
        version: v1
    spec:
      serviceAccountName: httpbin
      containers:
      - image: docker.io/kennethreitz/httpbin
        imagePullPolicy: IfNotPresent
        name: httpbin
        ports:
        - containerPort: 80

Run the following command to deploy the httpbin application in the cluster:
```
kubectl apply -f httpbin.yaml
```

Create a sleep.yaml file that contains the following content:

Show the sleep.yaml file

# Copyright Istio Authors
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.

##################################################################################################
# Sleep service
##################################################################################################
apiVersion: v1
kind: ServiceAccount
metadata:
  name: sleep
---
apiVersion: v1
kind: Service
metadata:
  name: sleep
  labels:
    app: sleep
    service: sleep
spec:
  ports:
  - port: 80
    name: http
  selector:
    app: sleep
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: sleep
spec:
  replicas: 1
  selector:
    matchLabels:
      app: sleep
  template:
    metadata:
      labels:
        app: sleep
    spec:
      terminationGracePeriodSeconds: 0
      serviceAccountName: sleep
      containers:
      - name: sleep
        image: curlimages/curl
        command: ["/bin/sleep", "3650d"]
        imagePullPolicy: IfNotPresent
        volumeMounts:
        - mountPath: /etc/sleep/tls
          name: secret-volume
      volumes:
      - name: secret-volume
        secret:
          secretName: sleep-secret
          optional: true
---

Run the following command to deploy the sleep application in the cluster:
```
kubectl apply -f sleep.yaml
```

Step 3: Use the gRPC protocol to connect to the custom authorization service

Declare the custom authorization service that you deployed in Step 1 in the ASM instance. This way, the ASM instance can use the service to authenticate requests.

Log on to the ASM console. In the left-side navigation pane, choose Service Mesh > Mesh Management.
On the Mesh Management page, click the name of the ASM instance. In the left-side navigation pane, choose Mesh Security Center > Custom Authorization Service. On the page that appears, click Define Custom Authorization Service.

On the Register Custom Authorization Service page, click the Custom authorization service (HTTP or gRPC protocol) implemented based on envoy.ext_authz tab, configure the related parameters, and then click Create.

Type	Parameter	Description
Required parameters	Protocol	The protocol that is used by the custom authorization service. In this example, GRPC is selected.
	Name	The name of the custom authorization service. In this example, the value is set to `test`.
	Service Address	The endpoint of the custom authorization service in the format of `<Service name>.<Namespace>.svc.<Domain name of the cluster>`. In this example, the value is set to `ext-authz.default.svc.cluster.local`.
	Port(1 - 65535)	The service port of the custom authorization service. In this example, the value is set to `9000`.
	Timeout(second)	The period of time during which the authentication result must be returned. Unit: seconds. If the custom authorization service fails to respond within this period of time, the service is considered unavailable. In this example, the value is set to `10`.
Optional parameters	Skip authentication while authorization service is unavailable	Specifies whether to allow requests when the custom authorization service is unavailable. If you turn on this switch, requests are allowed when the custom authorization service is unavailable.
	Error code returned by asm proxy while Auth-Service is not available	The error code to return when the custom authorization service is unavailable. This parameter is available only if you turn off Skip authentication while authorization service is unavailable. If you turn on Error code returned by asm proxy while Auth-Service is not available, you must specify an error code. This way, ASM returns this error code to the caller when the custom authorization service is unavailable.
	Carry origin request body within auth request	Specifies whether to add the body of the request to be authenticated to the authentication request to be sent to the custom authorization service. If you turn on this switch, you must specify the maximum length of the request body. If you also turn on Allow send incomplete message to Auth-Service, ASM truncates the request body if the length of the request body exceeds the maximum length. Then, ASM sends the authentication request with the truncated request body to the custom authorization service.

Step 4: Create an authorization policy

Create an authorization policy to configure the request operation that requires authentication.

Log on to the ASM console. In the left-side navigation pane, choose Service Mesh > Mesh Management.
On the Mesh Management page, click the name of the ASM instance. In the left-side navigation pane, choose Mesh Security Center > AuthorizationPolicy. On the page that appears, click Create.

On the Create page, configure the related parameters and click Create.

Parameter	Description
Name	The name of the custom authorization policy. In this example, the value is set to `test1`.
Policy Type	The type of the custom authorization policy. In this example, the value is set to Custom Authorization Service.
Custom Authorization Service	In this example, grpcextauth-test(GRPC) is selected.
Namespace	The namespace in which you want to create the authorization policy. In this example, the Namespace parameter on the Workload Scope tab is set to default.
Effective Scope	The effective scope of the authorization policy. In this example, the value is set to Service.
Workload	The workload on which the authorization policy takes effect. In this example, the value is set to httpbin.
Request Matching Rules	In this example, Paths is turned on in the Add Request Target section and the value is set to `/headers`.

Step 5: Verify that custom authorization is implemented as expected

Run the following command to access httpbin.default:8000/ip:

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

The status code 200 is returned, which indicates that custom authorization is not triggered.

Run the following command to use a request with the x-ext-authz: deny request header to access httpbin.default:8000/headers:

kubectl exec "$(kubectl get pod -l app=sleep -n default -o jsonpath={.items..metadata.name})" -c sleep -ndefault -- curl "http://httpbin.default:8000/headers" -H "x-ext-authz: deny" -s

Expected output:

denied by ext_authz for not found header `x-ext-authz: allow` in the request

The preceding result indicates that custom authorization is triggered but the authentication fails.

Run the following command to use a request with the x-ext-authz: allow request header to access httpbin.default:8000/headers:

kubectl exec "$(kubectl get pod -l app=sleep -n default -o jsonpath={.items..metadata.name})" -c sleep -n default -- curl "http://httpbin.default:8000/headers" -H "x-ext-authz: allow" -s

Expected output:

{
  "headers": {
    "Accept": "*/*",
    "Host": "httpbin.default:8000",
    "User-Agent": "curl/8.5.0",
    "X-Envoy-Attempt-Count": "1",
    "X-Ext-Authz": "allow",
    "X-Ext-Authz-Check-Result": "allowed",
    "X-Forwarded-Client-Cert": "By=spiffe://cluster.local/ns/default/sa/httpbin;Hash=c3e5364e87add0f4f69e6b0d029f5961b404c8f209bf9004b3d21a82cf67****;Subject=\"\";URI=spiffe://cluster.local/ns/default/sa/sleep"
  }
}

The preceding result indicates that custom authorization is triggered and the authentication is successful. The verification results show that only requests with the x-ext-authz: allow header are allowed to access httpbin.default:8000/headers. This indicates that custom authorization is implemented as expected.

References

For more information about how to develop an HTTP-based custom authorization service, see Develop an HTTP-based custom authorization service.
For more information about how to develop a gRPC-based custom authorization service, see Develop a gRPC-based custom authorization service.
For more information about how to perform fine-grained RAM for HTTP requests, see Implement custom authorization by using the HTTP protocol.
For more information about how to control access traffic from services in an ASM instance to external services, see Use an authorization policy to control access traffic from services in an ASM instance to an external website and Use an authorization policy to control access traffic from services in an ASM instance to an external database.
You can enable the mesh audit feature to record or trace the daily operations of different users. You can also configure audit alerts for operations on ASM resources and send alert notifications to alert contacts in a timely manner when important resources change. For more information, see Use the KubeAPI operation audit feature in ASM and Configure audit alerts for operations on ASM resources.