secrets

name	secrets
description	Secret management patterns for the Kubernetes homelab platform. Covers secret-generator, ExternalSecret, app-secrets Terragrunt module, and cross-namespace replication via kubernetes-replicator. Use when: (1) Adding secrets for a new application, (2) Deciding between secret-generator and ExternalSecret, (3) Configuring cross-namespace secret replication, (4) Creating persistent secrets via the app-secrets Terragrunt module, (5) Debugging secret sync failures. Triggers: "secret", "ExternalSecret", "secret-generator", "aws ssm", "parameter store", "kubernetes-replicator", "replicate secret", "app-secrets", "persistent secret", "cross-namespace secret", "secret not syncing", "ClusterSecretStore"
user-invocable	false

Secrets Management

Four mechanisms exist for provisioning secrets. See reference.md for the mechanism comparison table and annotation reference.

Decision Tree

App needs a secret?
│
├─ Can it be randomly generated? (password, API key, token)
│   │
│   ├─ Does it need to survive cluster rebuilds?
│   │   ├─ YES (e.g., encryption key seed, LDAP key)
│   │   │   └─ Use app-secrets Terragrunt module + ExternalSecret
│   │   └─ NO (e.g., session secret, internal API key)
│   │       └─ Use secret-generator annotation
│   │
│   └─ Is it a database credential?
│       └─ Use secret-generator with type: kubernetes.io/basic-auth
│
├─ Must match an external value? (OAuth, cloud API, webhook URL)
│   └─ Use ExternalSecret → AWS SSM
│
├─ Shared across namespaces? (DB superuser, Dragonfly password)
│   └─ Use kubernetes-replicator annotations
│
└─ Unclear?
    └─ AskUserQuestion: "Can this secret be randomly generated,
       or must it match a specific external value?"

---

Mechanism 1: secret-generator (Ephemeral, In-Cluster)

The mittwald/kubernetes-secret-generator controller watches for annotated Secrets and auto-populates them with random values. Preferred for secrets that do not need to persist across cluster rebuilds.

Template: see reference.md

---

Mechanism 2: ExternalSecret (Persistent, from AWS SSM)

ESO pulls values from AWS SSM Parameter Store via the aws-ssm ClusterSecretStore at kubernetes/platform/config/secrets/cluster-secret-store.yaml (region: us-east-2).

SSM path convention: /homelab/kubernetes/${cluster_name}/<app-or-secret-name>

Template: see reference.md

---

Mechanism 3: app-secrets Terragrunt Module (Generated + Persistent)

For secrets that must be randomly generated AND survive cluster rebuilds. OpenTofu generates random values and stores them as a JSON SecureString in AWS SSM. An ExternalSecret then pulls individual keys.

lifecycle.prevent_destroy = true protects the SSM parameter. lifecycle.ignore_changes = [value] prevents re-generating on subsequent applies. Local backup written to ~/.secrets/homelab/<app>-secrets.json.

Workflow: create unit → add to stack → apply → create ExternalSecret using the multi-key JSON pattern from Mechanism 2. Real example: infrastructure/units/lldap-secrets/terragrunt.hcl.

Template: see reference.md

---

Mechanism 4: kubernetes-replicator (Cross-Namespace)

Copies Secrets from one namespace to another. Used when a shared resource generates a secret that consumer namespaces need. Add replication annotations to the source Secret, then create an empty consumer Secret referencing it. Add both files to their respective kustomization.yaml.

Template: see reference.md

---

Three-Tier Pattern (Exemplar: Authelia)

kubernetes/clusters/live/config/authelia-prereqs/ demonstrates all three types together:

File	Mechanism	Purpose
lldap-secrets.yaml	ExternalSecret (app-secrets module)	Persistent LLDAP encryption keys
authelia-db-credentials.yaml	secret-generator	Ephemeral DB password
cnpg-superuser-replica.yaml	kubernetes-replicator	Replicated from database namespace
dragonfly-secret-replication.yaml	kubernetes-replicator	Replicated from database namespace

---

Debugging

Run scripts/check-secret-sync.sh <name> <namespace> for the full status check sequence.

To verify an SSM parameter exists:

aws ssm get-parameter --name "/homelab/kubernetes/<cluster>/<secret>" --with-decryption

See reference.md for common failure causes and alert definitions.

---

Cross-References

Document	Relevance
kubernetes/platform/CLAUDE.md	Secrets management overview, SSM parameters for bootstrap
deploy-app skill	Secrets decision tree for new deployments
cnpg-database skill	Database credential chain
terragrunt skill	Infrastructure operations for app-secrets module