Zero-Trust Security Enforcement using Istio Policies

Question

Pulumi · Accepted Answer

To enforce a zero trust security model using Istio policies, you'll be creating policies and rules that enable strict control over the communication between services in a Kubernetes cluster. Istio leverages custom resources such as AuthorizationPolicy, PeerAuthentication and RequestAuthentication to define these strict communication policies.

Here’s how these resources work to enforce zero-trust security:

AuthorizationPolicy: This defines the access control policies, specifying which users or services can access which resources. It is applied to a subset of services within a namespace or the entire namespace.
PeerAuthentication: This defines the mutual TLS settings for a service or a group of services, specifying how the data in transit should be secured. It controls the mutual TLS settings at the namespace or mesh level.
RequestAuthentication: This determines how requests are authenticated, specifying which JWT tokens are valid, and how they should be validated.

Let's walk through the steps and corresponding Pulumi code needed to enforce zero trust security using Istio policies for a hypothetical application running in a Kubernetes cluster.

import pulumi
import pulumi_kubernetes as k8s

# This component assumes you have a Kubernetes cluster with Istio installed.
# Make sure your Pulumi environment is configured to access your Kubernetes cluster.

# Note: Replace `<your-namespace>` with the namespace in which your application is deployed.

# Define an AuthorizationPolicy to restrict access to a service.
authorization_policy = k8s.core.v1.Namespace("authorization-policy",
    metadata=k8s.meta.v1.ObjectMetaArgs(
        name="restrict-access",
        namespace="<your-namespace>",  # Replace with your service's namespace.
    ),
    spec=k8s.core.v1.NamespaceSpecArgs(
        # Apply the policy to the ingress gateway for example sake; this should be adjusted to fit your services.
        selector=k8s.meta.v1.LabelSelectorArgs(
            match_labels={
                "app": "istio-ingressgateway",
                "istio": "ingressgateway",
            },
        ),
        # Define access control rules.
        action="DENY",  # By default, deny all traffic.
        rules=[  # Define rules to allow specific traffic.
            k8s.types.input.IstioPolicyV1Beta1.RuleArgs(
                # For simplicity, we will allow read access to all services in the namespace for all authenticated users.
                # Adjust the following to match your application's requirements.
                from_=[
                    k8s.types.input.IstioPolicyV1Beta1.SourceArgs(
                        principals=["*"],  # Could be refined to specific principals.
                    ),
                ],
                to=[
                    k8s.types.input.IstioPolicyV1Beta1.OperationArgs(
                        methods=["GET"],  # Adjust HTTP methods as necessary.
                    ),
                ],
            ),
        ],
    ))

# Define a PeerAuthentication resource to enable mutual TLS for services in the namespace.
peer_authentication = k8s.core.v1.Namespace("peer-authentication",
    metadata=k8s.meta.v1.ObjectMetaArgs(
        name="default",
        namespace="<your-namespace>",  # Replace with your service's namespace.
    ),
    spec=k8s.types.input.IstioSecurityV1Beta1.PeerAuthenticationArgs(
        mtls=k8s.types.input.IstioSecurityV1Beta1.PeerAuthenticationMutualTLSArgs(
            mode="STRICT",  # Enforce mutual TLS, ensuring secure service-to-service communication.
        ),
    ))

# Define a RequestAuthentication resource to verify JWT tokens for services in the namespace.
request_authentication = k8s.core.v1.Namespace("request-authentication",
    metadata=k8s.meta.v1.ObjectMetaArgs(
        name="jwt-authentication",
        namespace="<your-namespace>",  # Replace with your service's namespace.
    ),
    spec=k8s.types.input.IstioSecurityV1Beta1.RequestAuthenticationArgs(
        jwt_rules=[  # Define JWT validation rules.
            k8s.types.input.IstioSecurityV1Beta1.JWTArgs(
                issuer="https://example.com",  # Replace with your JWT token issuer.
                jwks_uri="https://example.com/.well-known/jwks.json",  # Replace with the JWKS URI.
                # Additional JWT validation parameters can be set here.
            ),
        ],
    ))

# Export the names of the resources.
pulumi.export("authorization_policy_name", authorization_policy.metadata["name"])
pulumi.export("peer_authentication_name", peer_authentication.metadata["name"])
pulumi.export("request_authentication_name", request_authentication.metadata["name"])

Here's what each part of the code does:

authorization_policy creates an AuthorizationPolicy that denies all access by default and allows "GET" requests for authenticated users.
peer_authentication sets up mutual TLS on a service-by-service basis, ensuring that all communication is encrypted and authenticated.
request_authentication configures Istio to expect JWT tokens for requests and validates them based on provided issuer and JWKS URI.

Remember to replace placeholders such as <your-namespace>, https://example.com, and "https://example.com/.well-known/jwks.json" with your actual namespace and JWT configuration.

In a real-world scenario, you would have more complex and tailored rules for the specific services and traffic patterns in your environment. This code provides a starting framework to build upon.