Securing service-to-service communication with Ambassador's mTLS

Question

Pulumi · Accepted Answer

Mutual TLS (mTLS) is an authentication protocol that helps in securing communications between services. It ensures that both parties in a communication are authenticated, which in the context of service-to-service communication means that both the client and the server verify each other's identities via TLS certificates before establishing a trusted connection.

Let's walk through setting up mTLS for service-to-service communication within a Kubernetes cluster using Ambassador, a popular open-source Kubernetes-native API Gateway built on the Envoy Proxy. Although we don't have a direct Pulumi resource for Ambassador, we can utilize the Pulumi Kubernetes provider to set up the necessary Kubernetes resources and configure Ambassador for mTLS.

Here's a high-level outline of what we need to do to enable mTLS with Ambassador:

Install the Ambassador API Gateway in your Kubernetes cluster.
Generate a Certificate Authority (CA) certificate and a private key.
Create server certificates for your services signed by the CA.
Enable mTLS in Ambassador's configuration.
Deploy your services and configure them to use TLS certificates for communication.

The following Pulumi TypeScript program accomplishes these tasks using fictitious data. Please ensure you replace the placeholders with actual values relevant to your setup:

import * as k8s from "@pulumi/kubernetes";

// Step 1: Install the Ambassador API Gateway in your Kubernetes cluster.
// Note: We assume that the Ambassador installation manifests are available and have been tested.
const ambassadorNamespace = new k8s.core.v1.Namespace("ambassador-namespace", {
    metadata: {
        name: "ambassador",
    },
});

const ambassadorManifests = new k8s.yaml.ConfigFile("ambassador-manifests", {
    file: "path/to/ambassador/installation/manifests.yaml",
    namespace: ambassadorNamespace.metadata.name,
});

// Step 2: Generate a Certificate Authority (CA) certificate and a private key.
// You will usually use an existing CA or a service like cert-manager for this in a real-world scenario.
const caCert = new k8s.core.v1.Secret("ca-cert", {
    metadata: {
        name: "ca-cert",
        namespace: ambassadorNamespace.metadata.name,
    },
    stringData: {
        "tls.crt": "<PLACE_YOUR_CA_CERTIFICATE_HERE>",
        "tls.key": "<PLACE_YOUR_CA_PRIVATE_KEY_HERE>",
    },
});

// Step 3: Create server certificates for your services signed by the CA.
// This example uses self-signed certificates, but you should use your CA to sign service certificates.
const serviceCert = new k8s.core.v1.Secret("service-cert", {
    metadata: {
        name: "service-cert",
        namespace: ambassadorNamespace.metadata.name,
    },
    stringData: {
        "tls.crt": "<PLACE_YOUR_SERVICE_CERTIFICATE_HERE>",
        "tls.key": "<PLACE_YOUR_SERVICE_PRIVATE_KEY_HERE>",
    },
});

// Step 4: Enable mTLS in Ambassador's configuration with a TLSContext.
// This configuration instructs Ambassador to use the provided certificates for mTLS.
const tlsContext = new k8s.core.v1.ConfigMap("ambassador-tls-context", {
    metadata: {
        name: "ambassador-tls-context",
        namespace: ambassadorNamespace.metadata.name,
    },
    data: {
        "ambassador.yaml": `
apiVersion: getambassador.io/v2
kind: TLSContext
metadata:
  name: ambassador-mtls-context
spec:
  hosts: []
  secret: service-cert
  ca_secret: ca-cert
  redirect_cleartext_from: 8080
        `,
    },
});

// Step 5: Deploy your services and configure them to use TLS certificates for communication.
// Here, we are deploying a placeholder service. Replace this with your actual service deployment.
const myService = new k8s.core.v1.Service("my-service", {
    metadata: {
        name: "my-service",
    },
    spec: {
        selector: {"app": "my-service"},
        ports: [{protocol: "TCP", port: 80, targetPort: 8080}],
    },
});

// Make sure to label your service pods with `app: my-service` or the actual label selector.

The code above walks through a high-level simulation of setting up mTLS in an Ambassador-managed Kubernetes cluster. It doesn't cover all the intricate details involved in managing certificates within a real-world production scenario, such as certificate rotation and revocation.

A few important things to note:

In a production environment, you would likely use cert-manager for certificate management.
You need to replace placeholder path "path/to/ambassador/installation/manifests.yaml" with the actual path to your Ambassador YAML manifests file.
Replace the <PLACE_YOUR_CA_CERTIFICATE_HERE> and other placeholder strings with actual certificate and key material.
Assigning empty hosts: [] under the TLSContext spec in Ambassador configures it to terminate TLS for all hosts. You should specify your service's hosts if you only want it to termiate TLS for particular domains.

Furthermore, remember that Ambassador will perform TLS termination, so the traffic within your cluster (from Ambassador to the service) will be internal and can use regular HTTP, unless you enable end-to-end encryption within your cluster which is an advanced setup.

In real-world applications, you would automate the certificate generation process and integrate a full certificate management lifecycle, including automatic renewal and revocation. Pulumi does not natively manage TLS certificates, so you would use an external tool or service for this purpose, and leverage Pulumi to orchestrate the actual deployment of your services and Ambassador configuration.