17 · Security Hardening Guide — Stella Ops

(v2.0 — 12 Jul 2025)

Audience — Site‑reliability and platform teams deploying the open‑source Core in production or restricted networks.

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0 Table of Contents

1. Threat model (summary)
2. Host‑OS baseline
3. Container & runtime hardening
4. Network‑plane guidance
5. Secrets & key management
6. Image, SBOM & plug‑in supply‑chain controls
7. Logging, monitoring & audit
8. Update & patch strategy
9. Incident‑response workflow
10. Pen‑testing & continuous assurance
11. Contacts & vulnerability disclosure
12. Change log

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1 Threat model (summary)

Asset	Threats	Mitigations
SBOMs & scan results	Disclosure, tamper	TLS‑in‑transit, read‑only Redis volume, RBAC, Cosign‑verified plug‑ins
Backend container	RCE, code‑injection	Distroless image, non‑root UID, read‑only FS, seccomp + CAP_DROP:ALL
Update artefacts	Supply‑chain attack	Cosign‑signed images & SBOMs, enforced by admission controller
Admin credentials	Phishing, brute force	OAuth 2.0 with 12‑h token TTL, optional mTLS

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2 Host‑OS baseline checklist

Item	Recommended setting
OS	Ubuntu 22.04 LTS (kernel ≥ 5.15) or Alma 9
Patches	unattended‑upgrades or vendor‑equivalent enabled
Filesystem	noexec,nosuid on /tmp, /var/tmp
Docker Engine	v24.*, API socket root‑owned (0660)
Auditd	Watch /etc/docker, /usr/bin/docker* and Compose files
Time sync	chrony or systemd‑timesyncd

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3 Container & runtime hardening

3.1 Docker Compose reference (compose-core.yml)

services:
  backend:
    image: registry.stella-ops.org/stella-ops/stella-ops:<PINNED_TAG_OR_DIGEST>
    user: "101:101"              # non‑root
    read_only: true
    security_opt:
      - "no-new-privileges:true"
      - "seccomp:./seccomp-backend.json"
    cap_drop: [ALL]
    tmpfs:
      - /tmp:size=64m,exec,nosymlink
    environment:
      - ASPNETCORE_URLS=https://+:8080
      - TLSPROVIDER=OpenSslGost
    depends_on: [redis]
    networks: [core-net]
    healthcheck:
      test: ["CMD", "wget", "-qO-", "https://localhost:8080/health"]
      interval: 30s
      timeout: 5s
      retries: 5

  redis:
    image: redis:7.2-alpine
    command: ["redis-server", "--requirepass", "${REDIS_PASS}", "--rename-command", "FLUSHALL", ""]
    user: "redis"
    read_only: true
    cap_drop: [ALL]
    tmpfs:
      - /data
    networks: [core-net]

networks:
  core-net:
    driver: bridge

No dedicated “Redis” or “Mongo” sub‑nets are declared; the single bridge network suffices for the default stack.

3.2 Kubernetes deployment highlights

Use a separate NetworkPolicy that only allows egress from backend to Redis :6379. securityContext: runAsNonRoot, readOnlyRootFilesystem, allowPrivilegeEscalation: false, drop all capabilities. PodDisruptionBudget of minAvailable: 1. Optionally add CosignVerified=true label enforced by an admission controller (e.g. Kyverno or Connaisseur).

4 Network‑plane guidance

Plane	Recommendation
North‑south	Terminate TLS 1.2+ (OpenSSL‑GOST default). Use LetsEncrypt or internal CA.
East‑west	Compose bridge or K8s ClusterIP only; no public Redis/Mongo ports.
Ingress controller	Limit methods to GET, POST, PATCH (no TRACE).
Rate‑limits	40 rps default; tune ScannerPool.Workers and ingress limit‑req to match.

5 Secrets & key management

Secret	Storage	Rotation
Client‑JWT (offline)	/var/lib/stella/tokens/client.jwt (root : 600)	30 days – provided by each OUK
REDIS_PASS	Docker/K8s secret	90 days
OAuth signing key	/keys/jwt.pem (read‑only mount)	180 days
Cosign public key	/keys/cosign.pub baked into image;	change on every major release
Trivy DB mirror token (if remote)	Secret + read‑only	30 days

Never bake secrets into images; always inject at runtime.

Operational tip: schedule a cron reminding ops 5 days before client.jwt expiry. The backend also emits a Prometheus metric stella_quota_token_days_remaining.

6 Image, SBOM & plug‑in supply‑chain controls

• Images — Pull by digest not latest; verify:

cosign verify ghcr.io/stellaops/backend@sha256:<DIGEST> \
  --key https://stella-ops.org/keys/cosign.pub

• SBOM — Each release ships an SPDX file; store alongside images for audit.
• Third‑party plug‑ins — Place in /plugins/; backend will:
• Validate Cosign signature.
• Check [StellaPluginVersion(“major.minor”)].
• Refuse to start if Security.DisablePluginUnsigned=false (default).

7 Logging, monitoring & audit

Control	Implementation
Log format	Serilog JSON; ship via Fluent‑Bit to ELK or Loki
Metrics	Prometheus /metrics endpoint; default Grafana dashboard in infra/
Audit events	Redis stream audit; export daily to SIEM
Alert rules	Feed age ≥ 48 h, P95 wall‑time > 5 s, Redis used memory > 75 %

8 Update & patch strategy

Layer	Cadence	Method
Backend & CLI images	Monthly or CVE‑driven docker pull + docker compose up -d
Trivy DB	24 h cron via FeedMerge Service	configurable (FeedMerge.Cron)
Docker Engine	vendor LTS	distro package manager
Host OS	security repos enabled	unattended‑upgrades

9 Incident‑response workflow

• Detect — PagerDuty alert from Prometheus or SIEM.
• Contain — Stop affected Backend container; isolate Redis RDB snapshot.
• Eradicate — Pull verified images, redeploy, rotate secrets.
• Recover — Restore RDB, replay SBOMs if history lost.
• Review — Post‑mortem within 72 h; create follow‑up issues.
• Escalate P1 incidents to <security@stella‑ops.org> (24 × 7).

10 Pen‑testing & continuous assurance

Control	Frequency	Tool/Runner
OWASP ZAP baseline	Each merge to main	GitHub Action zap-baseline-scan
Dependency scanning	Per pull request	Trivy FS + Dependabot
External red‑team	Annual or pre‑GA	CREST‑accredited third‑party

11 Vulnerability disclosure & contact

• Preferred channel: security@stella‑ops.org (GPG key on website).
• Coordinated disclosure reward: public credit and swag (no monetary bounty at this time).

12 Change log

Version	Date	Notes
v2.0	2025‑07‑12	Full overhaul: host‑OS baseline, supply‑chain signing, removal of unnecessary sub‑nets, role‑based contact e‑mail, K8s guidance.
v1.1	2025‑07‑09	Minor fence fixes.
v1.0	2025‑07‑09	Original draft.