Role-Based Access Rules in Service Mesh with Istio

Question

Pulumi · Accepted Answer

Role-Based Access Control (RBAC) is a method of regulating access to computer or network resources based on the roles of individual users within an organization. Istio, a service mesh solution, provides fine-grained access control to ensure that services in a mesh communicate with each other based on predefined permissions.

To implement role-based access rules in a service mesh using Istio, you will need to define `ServiceRoles` and `ServiceRoleBindings`. The `ServiceRole` custom resource specifies a group of permissions to access services in the mesh, while `ServiceRoleBinding` grants these permissions to particular subjects (like a user or group).

Pulumi does not provide direct resources corresponding to Istio's `ServiceRole` and `ServiceRoleBinding` at the time of my last update. However, you can manage Kubernetes resources directly with Pulumi's Kubernetes provider to accomplish this task.

Here is a program that creates an example of Istio RBAC on a Kubernetes cluster using Pulumi. We'll use Pulumi's Kubernetes provider to create these resources:

1. A `ServiceRole` named `details-viewer`, which allows read access (HTTP GET) to the `details` service.
2. A `ServiceRoleBinding` named `bind-details-viewer`, which binds the `details-viewer` role to a user named `alice`.

Make sure you have Istio installed in your Kubernetes cluster and have a namespace labeled with `istio-injection=enabled` to enable automatic sidecar injection by Istio.

```python
import pulumi
import pulumi_kubernetes as kubernetes

# Create a ServiceRole to allow read access to a specific service.
service_role = kubernetes.rbac.v1alpha1.ClusterRole(
    "details-viewer",
    metadata=kubernetes.meta.v1.ObjectMetaArgs(
        name="details-viewer",
        namespace="default",  # Replace with the namespace where your services are located.
    ),
    # The rules defining the access permissions for the role.
    rules=[kubernetes.rbac.v1alpha1.PolicyRuleArgs(
        services=["details.default.svc.cluster.local"],  # Change accordingly with your service FQDN.
        paths=["/details/*"],
        methods=["GET"],
    )],
    __opts__=pulumi.ResourceOptions(provider=istio_provider)  # Use the Istio provider if separate from the default K8s provider.
)

# Create a ServiceRoleBinding to assign the role to a user.
service_role_binding = kubernetes.rbac.v1alpha1.ClusterRoleBinding(
    "bind-details-viewer",
    metadata=kubernetes.meta.v1.ObjectMetaArgs(
        name="bind-details-viewer",
        namespace="default",  # Replace with the namespace where your ServiceRole was created.
    ),
    role_ref=kubernetes.rbac.v1alpha1.RoleRefArgs(
        kind="ServiceRole",
        name="details-viewer",
        api_group="rbac.istio.io",  # Istio's API group for RBAC
    ),
    subjects=[kubernetes.rbac.v1alpha1.SubjectArgs(
        kind="User",
        name="alice",  # Specify the user you want to grant the role to.
    )],
    __opts__=pulumi.ResourceOptions(provider=istio_provider)  # Use the Istio provider if separate from the default K8s provider.
)

# Export the names of the resources we've created.
pulumi.export('service_role_name', service_role.metadata.apply(lambda metadata: metadata.name))
pulumi.export('service_role_binding_name', service_role_binding.metadata.apply(lambda metadata: metadata.name))
```

In the code above, we'r using Pulumi's Kubernetes provider to create two Istio RBAC resources. We define the service we want to connect (`details`), and we set up rules for allowing a GET method on it. We then bind this role to the user `alice`. Note you will need to customize the `namespace` and `services` fields to match your setup.

Istio RBAC is included in the `rbac.istio.io` API group, which is a custom resource definition provided by Istio, and is managed just like standard Kubernetes resources using Pulumi.

For real-world usage, you'll need to tailor the service names, namespaces, paths, and user names to the specific services and organizational structure in your environment. Also, it's essential to note that starting from Istio 1.4, they introduced a new Authorization Policy which deprecates `ServiceRole` and `ServiceRoleBinding`. You might want to look into the `AuthorizationPolicy` resource if you are using a newer version of Istio.

Remember, before running this code, you need a configured Kubernetes cluster with Istio installed and the `istio-injection=enabled` label in your namespace. You should have the Pulumi CLI installed and configured to communicate with your Kubernetes cluster.