Leakferret

MCP-native secret scanner — verified findings, agent-applied rewrites.

leakferret is one fast Rust binary that is engine, CLI, and MCP server. It finds hardcoded secrets in your code, calls the provider to confirm which ones are actually live, and rewrites the leak in place to read from an environment variable. It runs in your terminal, in CI, and as a tool your coding agent calls before it commits — and the raw secret never leaves your machine.

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What it looks like

Say you accidentally commit a real key, plus the usual noise:

# .env  — every key below is fabricated for this example

STRIPE_SECRET_KEY=sk_live_FAKE_example_not_a_real_key # fabricated GITHUB_TOKEN=ghp_FAKE_example_not_a_real_token # fabricated SENDGRID_API_KEY=${SENDGRID_API_KEY} # a reference — not a leak ADMIN_PASSWORD=changeme # a placeholder — not a leak AWS_ACCESS_KEY_ID=[PopNx MCP ตัดค่าที่หน้าตาเหมือนกุญแจออก] # AWS's public docs example

leakferret verify calls each provider and tells you what is real and live — and stays quiet on the rest:

$ leakferret verify .

.env L2 UNKNOWN CRITICAL stripe_secret sk_l..._key L3 VERIFIED CRITICAL github_token ghp_...oken ← live, rotate it now

2 findings · 1 verified · 1 unknown

The keys above are fabricated, so the VERIFIED line illustrates what a genuinely live key reports — on these examples both would be UNKNOWN.

The ${SENDGRID_API_KEY} reference, the changeme placeholder, and the well-known [PopNx MCP ตัดค่าที่หน้าตาเหมือนกุญแจออก] example are recognized and left out — that precision is the point. Then leakferret rewrite --apply rewrites the hardcoded key in your code (it leaves .env files alone — there's nothing sensible to rewrite a secret *to* there):

  # app/billing.rb  (fabricated example)

• Stripe.api_key = "sk_live_FAKE_example_not_a_real_key" # fabricated
• Stripe.api_key = ENV.fetch("STRIPE_API_KEY")

…and appends STRIPE_API_KEY= to .env.example with a seed command for your secret manager. Find → confirm live → fix, with almost no false alarms.

The full secret value never leaves your machine. Only a redacted

AKIA...4XYZ preview is ever written to a report, log, or network message.

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Quick start

Install however you like — every package ships the same prebuilt binary.

# Ruby gem

gem install leakferret

npm (CLI)

npm i -g @leakferret/cli

Go

go install github.com/leakferrethq/leakferret-go/cmd/leakferret@latest

Native binary — download from GitHub Releases, unpack, and put it on $PATH:

https://github.com/leakferrethq/leakferret/releases

Rust, from source

cargo install leakferret-cli

Then scan the current directory:

leakferret scan .

scan respects .gitignore and also reads dotfiles such as .env. Add --git to walk commit history instead of the working tree.

Every wrapper honors a LEAKFERRET_BIN environment variable pointing at a

local binary, for offline or development use.

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How it works

leakferret runs findings through a five-station pipeline. Each station only sees what it needs, and the raw secret never advances past disk.

1. Scan — a fast regex pre-filter over your files, across 60+ secret types. Respects .gitignore, reads dotfiles like .env, and (with --git) walks history.
2. Catalog — every candidate is checked against a signed database of *known-public* example credentials: Stripe test keys, [PopNx MCP ตัดค่าที่หน้าตาเหมือนกุญแจออก], jwt.io samples, RFC examples. Matches are marked FIXTURE so documented examples never raise a false alarm. The catalog is bundled with the binary and can be refreshed and signature-verified.
3. Classify — each remaining candidate gets a verdict: REAL, FIXTURE, or UNKNOWN. This runs offline by default (path rules plus dummy-marker heuristics), or asks the host editor or agent's own language model — no extra API key, no added cost.
4. Verify — makes a single harmless API call to the provider to confirm a key is LIVE. Around 25 providers are covered natively (AWS SigV4, GitHub, GitLab, Stripe, OpenAI, Anthropic, Slack, Twilio, SendGrid, Mailgun, Datadog, Heroku, npm, PyPI, DigitalOcean, Hugging Face, Groq, Replicate, Notion, Postman, Figma, Linear, Square, Shopify, Databricks), with a trufflehog binary fallback for the rest. The call goes straight from your machine to the provider — leakferret has no servers.
5. Rewrite — swaps a hardcoded literal for an environment-variable lookup (ENV.fetch / os.environ / process.env), appends a line to .env.example, and prints seed commands for your secret manager (env, Vault, Doppler, AWS Secrets Manager, or Infisical).

A baseline stores one-way HMAC fingerprints of known findings — never the raw secret — so CI can fail only on *new* leaks.

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Use it with AI agents (MCP)

MCP (Model Context Protocol) is the open standard for giving coding agents tools. Agents hardcode secrets too, and nobody reviews their diffs line by line — leakferret lets the agent self-check before it commits.

Start the server over JSON-RPC on stdio:

npx @leakferret/mcp

Add it to your mcpServers config (Claude Desktop, Cursor, Continue, Claude Code):

{

"mcpServers": { "leakferret": { "command": "npx", "args": ["@leakferret/mcp"] } } }

For Claude Code, save that block as .mcp.json in your project root, or add it with one command:

claude mcp add leakferret -- npx -y @leakferret/mcp

If you installed the native binary, you can point at it directly instead:

{

"mcpServers": { "leakferret": { "command": "leakferret", "args": ["mcp"] } } }

leakferret is also listed in the MCP Registry as io.github.leakferrethq/leakferret, so registry-aware clients can discover it.

Tools exposed: scan_repository, classify_candidates, verify_finding, propose_rewrite, and baseline_diff. A classify prompt is also provided so an agent can classify candidates inline using the model it already has. Two read-only resources expose the engine's catalog as context: leakferret://secret-types (every detectable pattern) and leakferret://verifiers (the live-verification providers).

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How it compares

gitleaks is the fastest pre-commit regex blocker. trufflehog set the bar for live verification. detect-secrets owns the baseline-a-legacy-repo workflow. GitGuardian is the paid platform with the broadest detectors and a dashboard. leakferret does the regex pre-filter, verifies which keys are live, rewrites the leak to an env var, and runs as an MCP server so coding agents check their own diffs. Full writeup: leakferret.com/compare.

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CLI reference

leakferret scan      Regex pre-filter only (no classifier, no verifier)

leakferret verify Scan + classify + provider verification leakferret rewrite Scan + classify + propose/apply ENV-fetch rewrites leakferret org Scan every public repo owned by a GitHub user/org leakferret baseline Manage the per-repo fingerprint baseline leakferret catalog Load and inspect the fixture catalog leakferret mcp Start the MCP server on stdio

Scan a whole GitHub account or org in one go (handy for finding leaks across all your public repos before someone else does):

leakferret org leakferrethq            # all public repos for that owner

leakferret org myco --token "$GITHUB_TOKEN" --format sarif > leaks.sarif

Common flags:

# scan

leakferret scan . # working tree leakferret scan . --git # scan HEAD's commit history leakferret scan . --git --all # scan every branch / tag leakferret scan . --git --since HEAD~50 # bounded history window

verify

leakferret verify . # best-effort verification leakferret verify . --verify-mode none --fail-on any # offline gate: exit 1 on any finding leakferret verify . --only-verified # emit only confirmed-live keys leakferret verify . --verify-mode ever-verified # fail on historical leaks leakferret verify . --verifier-timeout-secs 10

rewrite

leakferret rewrite . --apply # write ENV.fetch in place leakferret rewrite . --dry-run-diff # show the diff, touch nothing leakferret rewrite . --check # CI mode: exit 1 if rewrites pending leakferret rewrite . --apply --include-unknown # also fix UNKNOWN (unconfirmed) candidates leakferret rewrite . --backend doppler # seed cmds for your manager

baseline (scan/verify are read-only — they never write to your repo)

leakferret baseline init # create .leakferret-baseline.json (gitignores the salt) leakferret verify . --update-baseline # record current findings into the baseline leakferret baseline show leakferret baseline ignore --fingerprint # acknowledge a finding

catalog

leakferret catalog info leakferret catalog test "sk_test_4eC39..." # deterministic FIXTURE verdict leakferret catalog refresh # fetch + signature-verify update

Shared flags on scan / verify / rewrite: --format, --show-fixtures, --exclude , --only , --only-verified, --fail-on . --backend accepts env, vault, doppler, aws-secrets-manager, infisical.

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Block commits locally (pre-commit hook)

Catch a secret before it is ever committed. From your repo root:

cat > .git/hooks/pre-commit <<'HOOK'

#!/bin/sh

Offline secret scan (no network). Blocks the commit on any finding.

leakferret verify . --verify-mode none --fail-on any || { echo "leakferret blocked this commit. Bypass: git commit --no-verify" exit 1 } HOOK chmod +x .git/hooks/pre-commit

--verify-mode none keeps it fully offline; --fail-on any exits non-zero on any non-fixture finding (documented examples like [PopNx MCP ตัดค่าที่หน้าตาเหมือนกุญแจออก] are still ignored). Pair it with `leakferret baseline