docker-security

Optional security hardening for Docker containers that run Hermit. It adds network controls, resource limits, kernel-related safeguards, and a startup log for plugin installation.

In plain words
What is it for?
Use it to restrict container network access, limit resource use, add selected kernel settings, and record plugin installations through a reversible Docker Compose overlay.
Why use it?
It reduces some risks from compromised or careless plugins, while making clear that plugins still run with the agent's authority and are not fully isolated from the project.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/gtapps/claude-code-hermit/docker-security
Any agent
npx skills add gtapps/claude-code-hermit --skill docker-security
Clone the repo
git clone --depth 1 https://github.com/gtapps/claude-code-hermit

Made for: Claude Code, Codex.

Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 6,031 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00080 $0.06031
Opus 5 $0.00040 $0.03016
Sonnet 5 $0.00016 $0.01206
Haiku 4.5 $0.00008 $0.00603

Measured today against content hash 41feebc791a2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

docker-security scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

Stream the static verification script into the live container. It is placeholder-free (hardcoded probe values) and uses only tools the hermit base image ships — `bun`, `jq`, `curl`, glibc `getent` (no `python3`, `nc`, or
plugins/claude-code-hermit/skills/docker-security/SKILL.md · 391 lines

How it starts

The opening of the file, as written. The whole thing — 391 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Docker Security

Advanced hardening for already-deployed hermit containers. Each toggle is opt-in, presented with honest cost/benefit framing, and applied as a docker-compose.security.yml overlay that the hermit-docker wrapper auto-detects. Reversal: re-run and answer No to every prompt, or delete docker-compose.security.yml directly.

Tone: Honest about tradeoffs. Tell operators what each toggle does AND does not protect. Do not oversell.

Important: Run all checks and commands sequentially — do not use parallel tool calls.

Templates live in ${CLAUDE_SKILL_DIR}/../../state-templates/docker/security/.

Trust model framing (read to operator at the start of step 2)

Installing a plugin runs that plugin's hooks and skills with the same authority as hermit. The container hardening here reduces what a compromised plugin can do to the host kernel and your local network — it does not vet the plugin's intent, sandbox its file access within the project, or prevent it from acting on your behalf via the agent. A malicious or careless plugin still runs as you.

Honest limitation: DNS policy below blocks domain-based exfil/C2 but cannot stop direct-IP egress to a hardcoded public address. A future release may add nftset-driven IP allowlisting.

Plan

0. Refuse to run inside the hermit container

This skill is host-only — it writes a docker-compose.security.yml overlay on the host and recreates the container with stronger isolation.

Run: [ -f /.dockerenv ] || [ -f /run/.containerenv ] && echo container || echo host

If the output is container, stop immediately — do not proceed to step 1. Print:

This skill writes a docker-compose.security.yml overlay on the host and recreates the container with stronger isolation. Run it from your host shell in the project root. To inspect the live security posture inside the running container, run /claude-code-hermit:hermit-doctor — it includes a docker-security check.

1. Prerequisites

Read the full file on GitHub · 391 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. today Changed · +1 lines 41feebc791a2
  2. 2d ago First seen · 390 lines · 80 tokens per session scan A bf5df5e692a0

Subscribe to this mod's changes

docker-security is a skill published in the GitHub repository gtapps/claude-code-hermit (73 stars, last pushed today), licensed MIT. It adds 80 tokens to every session and 6,031 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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