# External Secrets - Usage Guide

This guide explains how to use External Secrets Operator (ESO) to manage secrets across your Kubernetes cluster and sync them from various secret backends (Vault, Kubernetes secrets, etc.) into your applications.

## Table of Contents

- [Overview](#overview)
- [Architecture](#architecture)
- [Getting Started](#getting-started)
- [Using External Secrets in Your Repository](#using-external-secrets-in-your-repository)
- [SecretStore Configuration](#secretstore-configuration)
- [Creating External Secrets](#creating-external-secrets)
- [Examples](#examples)
- [Troubleshooting](#troubleshooting)

## Overview

External Secrets Operator allows you to use external secret management systems (Vault, AWS Secrets Manager, Azure Key Vault, etc.) as a source of truth for secrets in your Kubernetes cluster. It automatically syncs secrets from these backends into native Kubernetes Secrets.

**Key Benefits:**
- Centralized secret management
- Automatic synchronization
- No need to store secrets in Git
- Support for multiple secret backends
- Templating and transformation capabilities

## Architecture

```
┌─────────────────────────────────────────────────────────┐
│         External Secret Operator (ESO)                   │
│         (installed in external-secrets namespace)        │
└─────────────────────────────────────────────────────────┘
                            ↓
        ┌───────────────────┼───────────────────┐
        ↓                   ↓                   ↓
   ┌─────────┐         ┌─────────┐        ┌──────────┐
   │  Vault  │         │   AWS   │        │ Kubernetes
   │ Secrets │         │ SecretsM│        │ Secrets
   └─────────┘         └─────────┘        └──────────┘
        ↑                   ↑                   ↑
        └───────────────────┼───────────────────┘
                            ↓
        ┌───────────────────────────────────┐
        │   SecretStore (or ClusterStore)   │
        │   (defines backend connection)    │
        └───────────────────────────────────┘
                            ↓
        ┌───────────────────────────────────┐
        │       ExternalSecret              │
        │  (defines what to sync & where)   │
        └───────────────────────────────────┘
                            ↓
        ┌───────────────────────────────────┐
        │     Kubernetes Secret             │
        │  (synced and kept in sync)        │
        └───────────────────────────────────┘
                            ↓
        ┌───────────────────────────────────┐
        │    Your Application Pods          │
        │   (consumes the secrets)          │
        └───────────────────────────────────┘
```

## Getting Started

### Installation

External Secrets Operator is already installed in your cluster via the Helm chart in this repo. Verify the installation:

```bash
kubectl get deployments -n external-secrets
kubectl get crd | grep external-secrets
```

You should see:
- Deployment: `external-secrets`
- Deployment: `external-secrets-webhook`
- CRDs: `secretstores.external-secrets.io`, `externalsecrets.external-secrets.io`, etc.

## Using External Secrets in Your Repository

### Directory Structure

For each repository that needs to manage secrets with External Secrets, create a `secrets-reponame` folder in your Kubernetes manifests:

```
my-app-repo/
├── src/
├── k8s/
│   ├── base/
│   ├── overlays/
│   └── secrets-my-app/          ← Create this folder
│       ├── secretstore.yaml
│       ├── externalsecret.yaml
│       └── values.yaml          (optional, for kustomize/helm values)
└── README.md
```

### Folder Contents

The `secrets-reponame` folder should contain:

1. **secretstore.yaml** - Defines how to connect to your secret backend (Vault, AWS, etc.)
2. **externalsecret.yaml** - Defines which secrets to sync from the backend into Kubernetes

## SecretStore Configuration

A `SecretStore` is a namespaced resource that defines the connection to your secret backend. Create `secretstore.yaml` in your `secrets-reponame` folder:

### Example: Vault Backend

```yaml
apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: vault-secretstore
  namespace: default  # Change to your app's namespace
spec:
  provider:
    vault:
      server: "https://vault.example.com:8200"
      path: "secret"
      auth:
        kubernetes:
          mountPath: "kubernetes"
          role: "my-app-role"  # Define this in Vault
```

### Example: Kubernetes Secrets Backend

If you want to sync secrets from another namespace or use Kubernetes as the backend:

```yaml
apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: k8s-secretstore
  namespace: default
spec:
  provider:
    kubernetes:
      remoteNamespace: "secrets-management"
      auth:
        serviceAccount:
          name: external-secrets-reader
```

### ClusterSecretStore (Cluster-Wide)

If you want the SecretStore to be available cluster-wide, use `ClusterSecretStore` instead:

```yaml
apiVersion: external-secrets.io/v1beta1
kind: ClusterSecretStore
metadata:
  name: vault-cluster-store
spec:
  provider:
    vault:
      server: "https://vault.example.com:8200"
      path: "secret"
      auth:
        kubernetes:
          mountPath: "kubernetes"
          role: "my-app-role"
```

## Creating External Secrets

An `ExternalSecret` is a Kubernetes custom resource that defines:
- Which `SecretStore` to use
- Which secrets to fetch from the backend
- How to transform them
- Where to create the resulting Kubernetes Secret

### Basic Example

```yaml
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: app-secrets
  namespace: default
spec:
  refreshInterval: 1h  # Sync every hour
  secretStoreRef:
    name: vault-secretstore
    kind: SecretStore
  target:
    name: app-secrets  # Name of the Kubernetes Secret to create
    creationPolicy: Owner
    template:
      engineVersion: v2
      data:
        DATABASE_URL: "{{ .db_url }}"
        API_KEY: "{{ .api_key }}"
  data:
    - secretKey: db_url
      remoteRef:
        key: my-app/database  # Key in Vault
        property: url         # Property within that key
    - secretKey: api_key
      remoteRef:
        key: my-app/api       # Key in Vault
        property: token
```

### Advanced: Multiple Secrets

```yaml
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: multi-secrets
  namespace: default
spec:
  refreshInterval: 30m
  secretStoreRef:
    name: vault-secretstore
    kind: SecretStore
  target:
    name: multi-secrets
    creationPolicy: Owner
  dataFrom:
    - extract:
        key: my-app/all-secrets  # Fetch entire secret object
```

## Examples

### Example 1: Django Application

**Directory:** `my-django-app/k8s/secrets-django/`

**secretstore.yaml:**
```yaml
apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: django-vault
  namespace: django
spec:
  provider:
    vault:
      server: "https://vault.example.com:8200"
      path: "secret"
      auth:
        kubernetes:
          mountPath: "kubernetes"
          role: "django-app"
```

**externalsecret.yaml:**
```yaml
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: django-env
  namespace: django
spec:
  refreshInterval: 1h
  secretStoreRef:
    name: django-vault
    kind: SecretStore
  target:
    name: django-env
    creationPolicy: Owner
    template:
      engineVersion: v2
      data:
        SECRET_KEY: "{{ .secret_key }}"
        DATABASE_URL: "{{ .database_url }}"
        ALLOWED_HOSTS: "{{ .allowed_hosts }}"
  data:
    - secretKey: secret_key
      remoteRef:
        key: django/prod
        property: secret_key
    - secretKey: database_url
      remoteRef:
        key: django/prod
        property: database_url
    - secretKey: allowed_hosts
      remoteRef:
        key: django/prod
        property: allowed_hosts
```

**Deployment usage:**
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: django-app
  namespace: django
spec:
  template:
    spec:
      containers:
      - name: django
        envFrom:
        - secretRef:
            name: django-env  # Reference the synced secret
```

### Example 2: PostgreSQL Database Credentials

**secretstore.yaml:**
```yaml
apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: postgres-vault
  namespace: databases
spec:
  provider:
    vault:
      server: "https://vault.example.com:8200"
      path: "secret"
      auth:
        kubernetes:
          mountPath: "kubernetes"
          role: "postgres"
```

**externalsecret.yaml:**
```yaml
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: postgres-credentials
  namespace: databases
spec:
  refreshInterval: 24h
  secretStoreRef:
    name: postgres-vault
    kind: SecretStore
  target:
    name: postgres-credentials
    creationPolicy: Owner
  data:
    - secretKey: username
      remoteRef:
        key: postgres/primary
        property: username
    - secretKey: password
      remoteRef:
        key: postgres/primary
        property: password
```

### Example 3: TLS Certificates

```yaml
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: tls-certs
  namespace: ingress-nginx
spec:
  refreshInterval: 720h  # 30 days
  secretStoreRef:
    name: vault-cluster-store
    kind: ClusterSecretStore
  target:
    name: app-tls
    creationPolicy: Owner
    template:
      engineVersion: v2
      data:
        tls.crt: "{{ .cert }}"
        tls.key: "{{ .key }}"
  data:
    - secretKey: cert
      remoteRef:
        key: tls/app
        property: certificate
    - secretKey: key
      remoteRef:
        key: tls/app
        property: key
```

## Troubleshooting

### Check ExternalSecret Status

```bash
# Get ExternalSecret status
kubectl get externalsecret -n <namespace>
kubectl describe externalsecret <name> -n <namespace>

# Check if the synced Kubernetes Secret exists
kubectl get secret <target-name> -n <namespace>
```

### View Operator Logs

```bash
# Check External Secrets Operator logs
kubectl logs -n external-secrets deployment/external-secrets

# Check webhook logs (if using webhook)
kubectl logs -n external-secrets deployment/external-secrets-webhook
```

### Common Issues

#### 1. ExternalSecret shows "Error" status
- Check SecretStore connection details (URL, path, role)
- Verify Vault authentication is configured correctly
- Check role exists in Vault and has proper permissions
- Review operator logs for detailed error messages

#### 2. Secret is not being created
- Ensure `refreshInterval` has passed or manually trigger a sync
- Verify the target name is correct
- Check RBAC permissions for the operator

#### 3. Secret content is empty
- Verify the remote key path is correct in Vault
- Ensure the property name exists in the secret
- Check that the ExternalSecret template is valid

#### 4. Authentication failures
- Verify the ServiceAccount has the `external-secrets` name or matches the configured account
- Check Vault auth method configuration
- Ensure Kubernetes auth role is properly configured in Vault

### Force Refresh

To trigger an immediate refresh of an ExternalSecret:

```bash
kubectl annotate externalsecret <name> \
  -n <namespace> \
  force-sync="$(date +%s)" \
  --overwrite
```

## Best Practices

1. **Use ClusterSecretStore** for widely-shared secrets (databases, certs)
2. **Use namespaced SecretStore** for app-specific secrets
3. **Set appropriate refreshInterval** - shorter for sensitive data, longer for stable secrets
4. **Use templating** for complex secret transformations
5. **Enable RBAC** to restrict which services can access which secrets
6. **Monitor** ExternalSecret status regularly
7. **Version control** the SecretStore and ExternalSecret manifests (not the actual secrets)
8. **Rotate secrets** in your backend independently of the operator

## Resources

- [Official External Secrets Documentation](https://external-secrets.io/)
- [Supported Secret Backends](https://external-secrets.io/latest/introduction/overview/#features)
- [API Reference](https://external-secrets.io/latest/api/secretstore/)
- [Vault Integration](https://external-secrets.io/latest/provider/vault/)

## Support

For issues specific to this cluster's External Secrets setup, check the main README or contact the infrastructure team.
