Segmenting Kubernetes Cluster Traffic with Istio AuthorizationPolicy

Question

Pulumi · Accepted Answer

To segment traffic in a Kubernetes cluster with Istio, you can use an AuthorizationPolicy resource. Istio's AuthorizationPolicy enables you to define access control policies for your services in the mesh. An Istio AuthorizationPolicy can be configured for a particular workload to control ingress and egress traffic to and from the workload based on the specified rules.

Let's go through the steps we'll take to segment the traffic:

Install Istio: Ensure that you have Istio installed on your Kubernetes cluster. Istio is installed using a set of CustomResourceDefinitions (CRDs), and this is usually done via an Istio-specific command-line tool or by applying the YAML files provided by Istio directly onto your Kubernetes cluster.
Define Workloads: Identify the workloads (by labels on pods) to which you want to apply the AuthorizationPolicy. Workload selectors in AuthorizationPolicy objects target services based on their Kubernetes labels.
Create an AuthorizationPolicy: Define an AuthorizationPolicy with specific rules allowing or denying traffic to the targeted workloads. You can specify detailed rules, including which users can access the workload, which HTTP paths are allowed, and which methods (GET, POST, etc.) are allowed.

Below is a program that describes how you could implement an AuthorizationPolicy using Pulumi's Kubernetes package. This example assumes that you have already labeled your Kubernetes deployments with app: my-app.

Here's the program:

import pulumi
import pulumi_kubernetes as k8s


# Initialize a Kubernetes provider with the context of your existing cluster.
k8s_provider = k8s.Provider('k8s-provider', kubeconfig='<YOUR_KUBECONFIG_CONTENT>')

# Define an Istio AuthorizationPolicy to allow/deny traffic to a service.
authorization_policy = k8s.apiextensions.CustomResource(
    "my-authorization-policy",
    api_version="security.istio.io/v1beta1",
    kind="AuthorizationPolicy",
    metadata={
        "name": "my-authorization-policy",
        "namespace": "default"  # Change this to the namespace of your service
    },
    spec={
        # Target the workload with label `app: my-app` (Change this to match your workload label)
        "selector": {
            "matchLabels": {
                "app": "my-app"
            }
        },
        # Define the rules for the policy, below allows all traffic.
        # Change this to reflect the specific rules for your use case.
        "rules": [
            {
                "from": [{"source": {"ipBlocks": ["192.168.0.1"]}}],
                "to": [{"operation": {"methods": ["GET", "POST"]}}],
            }
        ],
        # The action for the rule, can be ALLOW or DENY
        "action": "ALLOW"  
    },
    opts=pulumi.ResourceOptions(provider=k8s_provider)
)

pulumi.export('authorization_policy_name', authorization_policy.metadata["name"])

In this program, you'd replace <YOUR_KUBECONFIG_CONTENT> with the content of your kubeconfig file or another way of authenticating with your Kubernetes cluster. Modify the namespace and the matchLabels to target the desired workload in your environment. You also need to fine-tune the rules based on the source (from), operations (to), and the action (ALLOW or DENY) to match your requirements for traffic segmentation.

The pulumi.export() line at the end will output the name of the AuthorizationPolicy after the program is executed, which can be useful if you're integrating this into a larger automation system or need to reference it in future Pulumi stacks.