io.github.leakferrethq/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.

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=AKIAIOSFODNN7EXAMPLE                  # 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 AKIAIOSFODNN7EXAMPLE 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.

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.

... View full README on GitHub