mtls-configuration

mTLS Configuration

Comprehensive guide to implementing mutual TLS for zero-trust service mesh communication.

Do not use this skill when

• The task is unrelated to mtls configuration
• You need a different domain or tool outside this scope

Instructions

• Clarify goals, constraints, and required inputs.
• Apply relevant best practices and validate outcomes.
• Provide actionable steps and verification.

Use this skill when

• Implementing zero-trust networking
• Securing service-to-service communication
• Certificate rotation and management
• Debugging TLS handshake issues
• Compliance requirements (PCI-DSS, HIPAA)
• Multi-cluster secure communication

Core Concepts

1. mTLS Flow

┌─────────┐                              ┌─────────┐
│ Service │                              │ Service │
│    A    │                              │    B    │
└────┬────┘                              └────┬────┘
     │                                        │
┌────┴────┐      TLS Handshake          ┌────┴────┐
│  Proxy  │◄───────────────────────────►│  Proxy  │
│(Sidecar)│  1. ClientHello             │(Sidecar)│
│         │  2. ServerHello + Cert      │         │
│         │  3. Client Cert             │         │
│         │  4. Verify Both Certs       │         │
│         │  5. Encrypted Channel       │         │
└─────────┘                              └─────────┘

2. Certificate Hierarchy

Root CA (Self-signed, long-lived)
    │
    ├── Intermediate CA (Cluster-level)
    │       │
    │       ├── Workload Cert (Service A)
    │       └── Workload Cert (Service B)
    │
    └── Intermediate CA (Multi-cluster)
            │
            └── Cross-cluster certs

Templates

Template 1: Istio mTLS (Strict Mode)

# Enable strict mTLS mesh-wide
apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
metadata:
  name: default
  namespace: istio-system
spec:
  mtls:
    mode: STRICT
---
# Namespace-level override (permissive for migration)
apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
metadata:
  name: default
  namespace: legacy-namespace
spec:
  mtls:
    mode: PERMISSIVE
---
# Workload-specific policy
apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
metadata:
  name: payment-service
  namespace: production
spec:
  selector:
    matchLabels:
      app: payment-service
  mtls:
    mode: STRICT
  portLevelMtls:
    8080:
      mode: STRICT
    9090:
      mode: DISABLE  # Metrics port, no mTLS