jakman85andClaude Opus 4.8
70a98675ac
- docs/07: correct plaintext-secret enforcement — CI-time ciphertext check vs
admission SOPS-provenance (Flux decrypts before the API server, so an admitted
Secret carries no ciphertext; a 'reject plaintext' admission rule is impossible).
- docs/13: add Contract clarifications (v1.1) — source exactly-one-of; longhorn⇒size
(L0 policy); backup is a {policy} ref; update.channel free-string/stable default;
auth.groups required for oidc|forward-auth; public⇒auth.mode≠none (schema);
irreplaceable⇒off-cluster-backup (L0 policy).
- docs/02: Cilium install ownership — Ansible bootstraps, Flux adopts config, value-parity contract.
- docs/03: platform label-key convention (homelab.keithjackson.dev/{egress-class,auth-mode,...}).
- docs/14: ServiceDefinition validation is two complementary L0 gates (JSON Schema shape + Kyverno invariants).
Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
96 lines
5.9 KiB
Markdown
96 lines
5.9 KiB
Markdown
# 07 — Security & Secrets
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Serves: **R-SEC-01/02/03**, supports all `R-NET-*` and `R-TLS-*`. Related:
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[ADR-0007 (SOPS+age)](../decisions/adr-0007-secrets-sops-age.md).
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## Security posture
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Defense in depth with declarative, auditable controls:
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- **Network**: default-deny east-west, explicit port-level allow, egress-class routing, VPN kill-
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switch ([03](03-networking-isolation-and-egress.md)). This is the primary isolation control.
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- **Identity/least privilege**: each workload runs with a minimal ServiceAccount and only the RBAC
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it needs; no workload gets cluster-admin. VMs and containers alike get least network reach
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(R-SEC-02).
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- **Secrets**: encrypted at rest in git; decrypted only in-cluster (R-SEC-01).
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- **TLS**: trusted, auto-managed certificates end to end ([08](08-tls-and-certificates.md), R-TLS-*).
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- **Supply chain**: pin images by digest where automation allows; prefer known-good upstreams;
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updates flow through policy, not ad-hoc pulls ([11](11-automated-updates.md)).
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- **Identity / SSO**: a central IdP (**Keycloak**) provides single sign-on, one user directory,
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group-based authorization, and MFA; services authenticate via native OIDC or an oauth2-proxy
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forward-auth layer so no management UI is unauthenticated ([15](15-identity-and-access.md),
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[ADR-0014](../decisions/adr-0014-idp-keycloak.md), R-IDP-*). This is the primary *authentication*
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control, complementing network default-deny (the primary *isolation* control).
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- **Policy enforcement (admission)**: **Kyverno** runs in-cluster as an admission controller and
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rejects non-conforming resources at reconcile time — e.g. a namespace missing its default-deny
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baseline, or a workload without a required egress-class/auth-mode label. The *same* policies
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gate CI ([14](14-testing-and-conformance.md), [ADR-0011](../decisions/adr-0011-test-tooling-kyverno-chainsaw.md)),
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so invariants are enforced both before merge and at admission (defense in depth). Enforcement
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complements — never replaces — the runtime behavior tests.
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- **Plaintext-secret enforcement is split by layer (do not conflate):** the "no plaintext Secret"
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invariant is a **CI-time** check (the committed Secret must carry SOPS ciphertext). It **cannot**
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be an admission rule, because Flux **decrypts SOPS before** the object reaches the API server —
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an admitted Secret never carries ciphertext, so an admission "reject plaintext" rule would reject
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*every* real Secret. Admission instead enforces **SOPS provenance** (the Secret was reconciled
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through the Flux/SOPS path), not ciphertext presence.
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- **Auditability**: isolation, egress path, cert validity, and backup integrity are all
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demonstrable (R-SEC-03) via Hubble, cert status, and DR drills.
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## Secrets management (R-SEC-01)
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**SOPS + age**, native to Flux:
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- Secrets are committed to git **encrypted** with `age` recipients; Flux decrypts them at
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reconciliation using an in-cluster age key. Plaintext never enters git.
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- The age private key is bootstrapped into the cluster out-of-band (documented bootstrap step, one
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of the few sanctioned non-GitOps actions) and stored as a Kubernetes Secret Flux can read.
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- **Never** print decrypted secret material into logs, PR text, or agent output (see
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[AGENTS.md §5](../AGENTS.md)).
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### Secret categories to manage
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- VPN credentials (PIA username/password; WireGuard) for the egress model (ADR-0013).
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- Keycloak admin credential and per-service **OIDC client secrets** ([15](15-identity-and-access.md)).
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- DNS provider API token (Cloudflare) for ACME DNS-01 + ExternalDNS.
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- SMTP credentials for Alertmanager email.
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- Service credentials (Nextcloud, Gitea admin, UniFi, Semaphore, Kasm, DB passwords).
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- Off-cluster backup target credentials (S3/NFS) for Velero/Longhorn.
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- Grafana admin, and any API tokens the C2 UI needs.
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### Rotation
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- Rotating a secret = re-encrypting with SOPS and committing; Flux rolls it out. Where a secret
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change requires a workload restart, that is triggered by the reconcile (e.g. checksum annotation).
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- VPN keys, DNS tokens, and SMTP creds SHOULD have a documented rotation procedure.
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## Alternatives considered (see ADR-0007)
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- **Sealed Secrets** — viable; SOPS chosen for Flux-native decryption and multi-recipient/age
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simplicity and readable diffs.
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- **External Secrets Operator + external vault** — heavier; deferred until a real external secret
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store exists. May be revisited via ADR.
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## RBAC & tenancy
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- Single operator + platform automation; no multi-tenant RBAC now (out of scope, [00](00-vision-and-scope.md)).
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- Platform controllers (Flux, cert-manager, ExternalDNS, Velero, KubeVirt) get scoped permissions;
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application workloads get near-zero cluster permissions.
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- The C2 UI's operational actions run through a constrained, audited path — not a shared admin
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kubeconfig handed to a browser.
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## Node & host security
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- Nodes baselined via cloud-init/Ansible ([02](02-environments-and-provisioning.md)); SSH key-only,
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minimal packages, required sysctls only.
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- Host-level changes are IaC, not hand edits (drift + auditability).
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## Auditability requirements (R-SEC-03) — what an operator must be able to prove
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- **Isolation**: "service X cannot reach service Y" — via Hubble flow logs + a denied-probe test.
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- **Egress path**: "service X's public IP is the VPN's" — via an egress IP check.
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- **Kill-switch**: "with VPN down, X leaks nothing" — via a fault-injection test.
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- **TLS**: "every endpoint serves a valid, non-self-signed, unexpired cert" — via cert status +
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external check.
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- **Backups**: "irreplaceable data is restorable" — via a DR drill.
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These proofs are part of the platform acceptance suite, not one-time checks.
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## Acceptance gates
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- No plaintext secret exists anywhere in git history (scanned).
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- Flux decrypts SOPS secrets and workloads consume them without manual steps.
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- Least-privilege RBAC verified (no workload has broad cluster rights).
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- The five auditability proofs above can be produced on demand.
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