claude-code-supply-chain-harden

Harden your dev environment against supply chain attacks, from inside Claude Code.

A one-time /harden command for Claude Code that detects your installed package managers, proposes security configurations, and writes them. Covers npm, pip, uv, bun, pnpm, yum, dnf, go, and cargo. Protects against dependency confusion, typosquatting, compromised maintainer accounts, and malicious install scripts.

Works on macOS, Linux, and Windows.

Install

mkdir -p ~/.claude/commands
curl -o ~/.claude/commands/harden.md \
  https://raw.githubusercontent.com/yonatan-genai/claude-code-supply-chain-harden/main/commands/harden.md

Then type /harden in any Claude Code session. No restart needed, even if you're mid-session. It runs once, writes your configs, and you're done. No ongoing hooks, no background processes.

What it does

1. Detects your OS and installed package managers (npm, pnpm, bun, uv, pip, yum, dnf, go, cargo, brew)
2. Checks for existing configs, CI pipelines, and lockfiles
3. Shows you a numbered list of proposed changes with explanations
4. You pick which ones to apply (all, some, or skip)
5. Writes user-level configs (merges with existing, never overwrites)
6. If CI is detected with unpinned deps, proposes project-level configs too
7. Appends rules to ~/.claude/CLAUDE.md so Claude itself follows the same guardrails

What it protects against

• Package age attacks — compromised account publishes malicious version, yanks it within hours. Blocked by requiring packages to be at least 7 days old before install (npm min-release-age, uv exclude-newer).
• Malicious install scripts — postinstall/preinstall running arbitrary code. Blocked by ignore-scripts=true in npm. Python has no equivalent, but most packages ship as wheels (no setup.py execution), and age filtering is the main defense.
• Dependency confusion — --extra-index-url checks all indexes and picks highest version. Blocked by CLAUDE.md rules and uv's safe first-index default.
• Unsigned packages — yum/dnf repos with gpgcheck disabled. Fixed by setting gpgcheck=1 globally.
• Claude using pip instead of uv — pip has no age filtering, no dependency confusion protection, almost nothing configurable for security. CLAUDE.md rules enforce uv usage.
• Insecure CI pipelines — npm install instead of npm ci, unpinned pip deps in workflows. Detected and fixed with project-level configs or workflow changes.

Configs it writes

User-level (always)

Manager	Config file	What it sets
npm	~/.npmrc	min-release-age=7d, ignore-scripts=true, package-lock=true
uv	~/.config/uv/uv.toml	exclude-newer = "7 days"
bun	bunfig.toml	minimumReleaseAge = 604800 (direct deps only)
pip	~/.config/pip/pip.conf	require-virtualenv = true (or install uv)
yum	/etc/yum.conf	gpgcheck=1, sslverify=1 (requires sudo)
dnf	/etc/dnf/dnf.conf	gpgcheck=1, sslverify=1 (requires sudo)
go	(none)	Secure by default. Checks for GONOSUMCHECK overrides.

Windows paths differ (%APPDATA%\uv\uv.toml, %APPDATA%\pip\pip.ini, etc.) and are handled automatically.

Project-level (only when CI detected with unpinned deps)

Situation	Change
CI uses npm install instead of npm ci	Recommend switching to npm ci, add project .npmrc
CI uses pip install with unpinned versions	Recommend uv with --exclude-newer, or pin versions

CLAUDE.md rules

Appended to ~/.claude/CLAUDE.md so Claude follows the same rules:

• Use uv instead of pip/pip3 (or use venvs if uv not available)
• Never use --extra-index-url (dependency confusion)
• Never use --trusted-host (disables TLS)
• Never re-enable ignore-scripts globally
• Never use --nogpgcheck or --setopt=gpgcheck=0
• Never pipe curl/wget to shell

Known limitations

• bun minimumReleaseAge only covers direct deps, not transitive.
• npm min-release-age requires npm >= 11.10.0 (Feb 2026). Older versions are told to upgrade.
• yum/dnf changes require sudo. The skill shows the exact command and asks the user to run it.
• pip has almost no security features. The skill recommends uv. If declined, it sets require-virtualenv=true as a minimal safety net.
• Python install scripts (setup.py) can't be disabled in pip or uv. Age filtering is the main defense.

License

MIT