---
name: mtls-configuration
description: Configure mutual TLS (mTLS) for zero-trust service-to-service communication. Use when implementing zero-trust networking, certificate management, or securing internal service communication.
---

# mTLS Configuration

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

## When to Use This Skill

- 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 and detailed worked examples

Full template library and detailed worked examples live in `references/details.md`. Read that file when you need the concrete templates.

## Best Practices

### Do's

- **Start with PERMISSIVE** - Migrate gradually to STRICT
- **Monitor certificate expiry** - Set up alerts
- **Use short-lived certs** - 24h or less for workloads
- **Rotate CA periodically** - Plan for CA rotation
- **Log TLS errors** - For debugging and audit

### Don'ts

- **Don't disable mTLS** - For convenience in production
- **Don't ignore cert expiry** - Automate rotation
- **Don't use self-signed certs** - Use proper CA hierarchy
- **Don't skip verification** - Verify the full chain