securitycheck

Block API keys, tokens, .env files, and private keys from leaking into git. Ships as a Claude Code skill and a standalone CLI / git hook.

After the GitHub OAuth-token compromise in early 2026, "my repo is private" stopped being a credible secrets-management strategy. Any secret committed to a repo — public or private — should be considered compromised the moment it enters .git/objects. securitycheck runs before commits land so it never gets that far.

What it does

Three phases, always run all three:

1. .gitignore audit — verifies the file exists and covers .env, *.pem, *.key, SSH keys, .aws/, service-account JSON. Flags any sensitive file that's already tracked (a .gitignore rule does not retroactively untrack).
2. Staged-file check — refuses to commit a .env, private key, or credential file, regardless of content.
3. Diff content scan — applies ~30 provider-specific regexes to the staged diff. Catches AWS, GitHub, OpenAI, Anthropic, Google, Slack, Stripe, npm, DigitalOcean, HuggingFace, Azure, MongoDB/Postgres URIs, PEM private key blocks, JWT, and generic password=... assignments (under --strict).

Findings come back as BLOCK (exit 1, refuse commit) or WARN (looks like a placeholder or public sample — human verifies).

Install

As a Claude Code skill

npx @404labs/securitycheck install

This copies the skill to ~/.claude/skills/securitycheck/. Restart Claude Code so the skill index picks it up. Claude will then run securitycheck scan automatically before any commit, push, or PR — and will fall back to a manual review if the CLI isn't on PATH.

As a one-off CLI

npx @404labs/securitycheck scan          # scan the staged diff
npx @404labs/securitycheck scan --strict # also generic password=... heuristics
npx @404labs/securitycheck scan --all    # scan working tree, not just staged
npx @404labs/securitycheck scan --json   # machine-readable output

After a global install (npm i -g @404labs/securitycheck) the securitycheck binary is on your $PATH, so you can drop the npx @error404/ prefix.

As a git pre-commit hook (no dependencies)

npx @404labs/securitycheck hook > .git/hooks/pre-commit
chmod +x .git/hooks/pre-commit

With Husky

npm install -D husky @404labs/securitycheck
npx husky init
echo 'npx securitycheck scan' > .husky/pre-commit

With lefthook

# lefthook.yml
pre-commit:
  commands:
    securitycheck:
      run: npx securitycheck scan

Output

securitycheck — pre-commit scan

  .gitignore:      present
  BLOCK findings:  2
  WARN findings:   1

  BLOCK — do not commit:
    • src/config.ts:14 — Anthropic API key [anthropic-key]
      const key = "sk-ant-api03-AbCdEf...";
    • .env — staged sensitive file
      Fix: git restore --staged ".env" && add to .gitignore

  WARN — verify these manually:
    • tests/fixtures/token.js:3 — JWT-shaped token [jwt]
      const t = "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjM...";

  ✗ 2 blocking finding(s). Refusing to commit.
    Bypass (NOT recommended): SECURITYCHECK_SKIP=1 git commit ...

JSON mode (--json) emits the same data as a single JSON object — see test/scan.test.js for the shape.

Exit codes

| Code | Meaning | |---|---| | 0 | Clean, or WARN-only | | 1 | One or more BLOCK findings | | 2 | Usage error or not a git repository |

What it catches

Full catalogue in skill/references/secret-patterns.md. Highlights:

| Provider | Token shape | |---|---| | AWS | AKIA…, ASIA…, aws_secret_access_key="…" | | GitHub | ghp_…, github_pat_…, gho_…, ghs_…, ghu_…, ghr_… | | Anthropic | sk-ant-api03-…, sk-ant-admin01-… | | OpenAI | sk-…, sk-proj-… | | Google | AIza…, GOCSPX-…, "type": "service_account" | | Slack | xoxb-…, xoxp-…, hooks.slack.com/services/… | | Stripe | sk_live_…, rk_live_…, sk_test_… (WARN) | | npm / HF / DO | npm_…, hf_…, dop_v1_… | | Azure | DefaultEndpointsProtocol=…;AccountKey=… | | Databases | mongodb://user:pass@…, postgres://user:pass@… | | Private keys | -----BEGIN (RSA\|EC\|OPENSSH\|PGP) PRIVATE KEY----- | | Generic | password=, secret=, api_key= (--strict only) |

Placeholder-like strings (YOUR_API_KEY, xxx, changeme, <API_KEY>) are auto-downgraded to WARN.

When a real secret is found

If the secret has ever been committed (not just staged), unstaging is not enough. In order:

1. Rotate at the provider immediately. Assume it's already compromised.
2. Remove from history — git filter-repo --path <file> --invert-paths or BFG. Squashing in a PR does not remove the blob.
3. Force-push. Coordinate with collaborators; this rewrites shared history.
4. Add the path to .gitignore so it can't come back.

Order matters. Cleaning a still-valid key buys nothing — the attacker already has it cached.

Configuration

No config file. Behaviour is controlled by CLI flags:

--all         Scan working tree, not just staged diff
--strict      Enable lower-confidence heuristics (more false positives)
--json        Machine-readable output
--no-color    Disable ANSI colors
--no-ignore   Skip the .gitignore audit
--no-files    Skip the sensitive-file presence check
--no-content  Skip the diff content scan

Environment:

• SECURITYCHECK_SKIP=1 — bypass entirely. Intended for emergencies only; the output makes the bypass visible in CI logs.

FAQ

Why not use gitleaks / trufflehog? Use them too if you can — they're battle-tested. securitycheck is zero-config, has no Go/Python dependency, and ships as a Claude Code skill so the agent inside your editor checks before you do. If a repo already runs gitleaks in CI, this is a strictly local belt-and-suspenders.

False positives? Three guards: provider-specific prefixes (we don't match sk- generically; we require sk-proj- / sk-ant- / 32+ chars and not a Stripe prefix); a placeholder heuristic that downgrades YOUR_API_KEY/xxx/changeme; and a --strict opt-in for the lossy generic password= rule.

False negatives? Yes, by design. We don't do entropy scanning in v0.1 — it has too many false positives without per-language tuning. Add provider-specific patterns via PR; see skill/references/secret-patterns.md.

Why ship a Claude Code skill at all? Because the agent writing your code is also the one most likely to paste a secret into it. Wiring securitycheck into the agent's pre-commit workflow closes that loop before the commit reaches your git index.

Roadmap

• [ ] Entropy-based detection (opt-in, per-file-type tuned)
• [ ] gitleaks-compatible config file consumption
• [ ] Pre-push hook variant that scans the full pushed range
• [ ] GitHub Action wrapper
• [ ] Per-project pattern overrides via .securitycheck.json

License

MIT — see LICENSE.