docker-compose-security

name	docker-compose-security
description	Review and harden docker-compose files for privileged mode, host port publishing, secrets, volume mounts, networks, and capability grants. Use when docker-compose.yml security, privileged containers, docker.sock mounts, Compose secrets, host network mode, or authorized Compose misconfig review.

Docker Compose Security

Assess and harden Docker Compose so stacks do not grant host-equivalent power, publish unintended services, or embed secrets in plain files. Defensive and authorized work only.

Scope And Authorization

• In scope: Compose files/overrides/stacks you own or are contracted to harden; local lab/CTF; read-only customer Compose under written engagement.
• Out of scope: Attacking third-party hosts via docker.sock; escalating misconfig on shared prod without approval; publishing real credentials.
• Prefer static review and docker compose config first. Gate privileged or escape experiments behind ownership and a lab host.
• Redact passwords, tokens, keys, and customer hostnames from reports.
• Deep breakout research → container-escape-techniques (lab). Image build → dockerfile-best-practices. App/YAML quality → code-quality-standards.

Use When

• Reviewing docker-compose.yml / compose.yaml / overrides
• privileged: true, pid/ipc/uts: host, network_mode: host, broad cap_add
• Host publishes DB/admin ports as bare PORT:PORT / all interfaces
• Secrets in environment:, committed .env, or build args
• Mounts of /var/run/docker.sock, /, /etc, or other sensitive host paths
• Mentions: Compose security, privileged compose, docker.sock, Compose secrets

Do not use as primary for:

Need	Skill instead
Dockerfile multi-stage / non-root image	dockerfile-best-practices
Lab container breakout / cgroup escape	container-escape-techniques
Kubernetes NetworkPolicy	k8s-network-policy
Full K8s RBAC / cluster pentest	kubernetes-pentesting
App reliability inside the container	code-quality-standards

Workflow

1. Inventory

1. Render effective config: docker compose -f … config (authorized env only).
2. List services, images (tag/digest), networks, volumes, profiles.
3. Note rootful vs rootless Docker; map internet-facing vs internal services.

2. Privilege and isolation

Setting	Prefer
privileged: true	Off; minimal cap_add only
cap_add: [ALL] / unconfined seccomp/apparmor	Defaults + least caps
pid/ipc/uts: host, network_mode: host	Avoid; use bridge/custom nets
Root user / omitted USER	Non-root matching image
Host devices:	Narrow and justified

Privileged + sensitive mounts → note impact; validate escape only via container-escape-techniques on lab hosts.

3. Ports and networks

1. Prefer 127.0.0.1:PORT:PORT for admin/debug; avoid bare publishes for DB/MQ.
2. Do not publish backends; use user-defined networks; internal: true when fit.
3. Drop leftover debug ports; confirm each publish matches product intent.

4. Secrets

1. No passwords/tokens in committed environment:, .env, or build.args.
2. Prefer Compose secrets: (file/external) mounted read-only when available.
3. Ship .env.example placeholders only; rotate anything that was committed.
4. Do not bake secrets into images (dockerfile-best-practices).

5. Volume and socket mounts

Mount	Guidance
docker.sock	Root-equivalent — avoid on app services
Host /, /etc, Docker root	Deny by default
Config/static binds	Prefer :ro
Secret files on host	ro + host mode 0600

6. Images and verify

1. Pin tags/digests; avoid prod latest.
2. Align Compose user: with hardened image (dockerfile-best-practices).
3. Apply code-quality-standards when editing Compose/scripts/tests.
4. Re-render config; confirm ports/flags; document exceptions with owner/expiry.
5. Prove exposure from config — do not demo host compromise on shared prod.

Routing

Situation	Primary	Helper
Compose privileged, ports, secrets, mounts, nets	This skill	—
Dockerfile / non-root / secrets-in-layers	dockerfile-best-practices	this skill for runtime
Lab breakout (sock/privileged/cgroup)	container-escape-techniques	this skill for evidence
K8s workloads / cluster pentest	kubernetes-pentesting	—
Pod NetworkPolicy design/review	k8s-network-policy	—
Compose/app structure and tests	code-quality-standards	this skill for intent

• dockerfile-best-practices: image side; Compose can undo non-root via user:, mounts, or privileged.
• container-escape-techniques: authorized lab host-boundary validation only.
• kubernetes-pentesting: cluster runtime, not Compose files.
• code-quality-standards: baseline when implementing fixes.

Checklist

• Scope/authorization clear; no out-of-scope host abuse
• Effective Compose inventoried (services, nets, volumes)
• No unjustified privileged / host namespaces / unconfined profiles
• Caps minimized; non-root user where supported
• Publishes intentional; admin/DB not on all interfaces without exception
• Backends internal; secrets not in VCS; safe secret mounts
• No docker.sock / sensitive host mounts on untrusted services
• Images pinned; aligned with dockerfile-best-practices
• Fixes follow code-quality-standards; residuals documented
• Escape claims only via container-escape-techniques in lab

Rules

• docker.sock and privileged are critical, not style nits.
• Least publish, least privilege, secrets out of VCS, read-only where possible.
• Authorized org/lab only; evidence from config, not destructive demos.
• Review image and Compose — neither alone is sufficient.