varlock

name	varlock
version	1.0.0
description	Secure environment variable management with Varlock. Use when handling secrets, API keys, credentials, or any sensitive configuration. Ensures secrets are never exposed in terminals, logs, traces, or Claude's context. Trigger phrases include "environment variables", "secrets", ".env", "API key", "credentials", "sensitive", "Varlock".
category	security
tags	["security","secrets","environment-variables","credentials","configuration"]
author	Smith Horn
repository	https://github.com/dmno-dev/varlock
compatibility	["claude-code","cursor","claude"]

Varlock Security Skill

Secure-by-default environment variable management for Claude Code sessions.

Repository: https://github.com/dmno-dev/varlock Documentation: https://varlock.dev

Core Principle: Secrets Never Exposed

When working with Claude, secrets must NEVER appear in:

• Terminal output
• Claude's input/output context
• Log files or traces
• Git commits or diffs
• Error messages

This skill ensures all sensitive data is properly protected.

---

CRITICAL: Security Rules for Claude

Rule 1: Never Echo Secrets

# ❌ NEVER DO THIS - exposes secret to Claude's context
echo $CLERK_SECRET_KEY
cat .env | grep SECRET
printenv | grep API

# ✅ DO THIS - validates without exposing
varlock load --quiet && echo "✓ Secrets validated"

Rule 2: Never Read .env Directly

# ❌ NEVER DO THIS - exposes all secrets
cat .env
less .env
Read tool on .env file

# ✅ DO THIS - read schema (safe) not values
cat .env.schema
varlock load  # Shows masked values

Rule 3: Use Varlock for Validation

# ❌ NEVER DO THIS - exposes secret in error
test -n "$API_KEY" && echo "Key: $API_KEY"

# ✅ DO THIS - Varlock validates and masks
varlock load
# Output shows: API_KEY 🔐sensitive └ ▒▒▒▒▒

Rule 4: Never Include Secrets in Commands

# ❌ NEVER DO THIS - secret in command history
curl -H "Authorization: Bearer sk_live_xxx" https://api.example.com

# ✅ DO THIS - use environment variable
curl -H "Authorization: Bearer $API_KEY" https://api.example.com
# Or better: varlock run -- curl ...

---

Quick Start

Installation

# Install Varlock CLI
curl -sSfL https://varlock.dev/install.sh | sh -s -- --force-no-brew

# Add to PATH (add to ~/.zshrc or ~/.bashrc)
export PATH="$HOME/.varlock/bin:$PATH"

# Verify
varlock --version

Initialize Project

# Create .env.schema from existing .env
varlock init

# Or create manually
touch .env.schema

---

Schema File: .env.schema

The schema defines types, validation, and sensitivity for each variable.

Basic Structure

# Global defaults
# @defaultSensitive=true @defaultRequired=infer

# Application
# @type=enum(development,staging,production) @sensitive=false
NODE_ENV=development

# @type=port @sensitive=false
PORT=3000

# Database - SENSITIVE
# @type=url @required
DATABASE_URL=

# @type=string @required @sensitive
DATABASE_PASSWORD=

# API Keys - SENSITIVE
# @type=string(startsWith=sk_) @required @sensitive
STRIPE_SECRET_KEY=

# @type=string(startsWith=pk_) @sensitive=false
STRIPE_PUBLISHABLE_KEY=

Security Annotations

Annotation	Effect	Use For
@sensitive	Redacted in all output	API keys, passwords, tokens
@sensitive=false	Shown in logs	Public keys, non-secret config
@defaultSensitive=true	All vars sensitive by default	High-security projects

Type Annotations

Type	Validates	Example
string	Any string	@type=string
string(startsWith=X)	Prefix validation	@type=string(startsWith=sk_)
string(contains=X)	Substring validation	@type=string(contains=+clerk_test)
url	Valid URL	@type=url
port	1-65535	@type=port
boolean	true/false	@type=boolean
enum(a,b,c)	One of values	@type=enum(dev,prod)

---

Safe Commands for Claude

Validating Environment

# Check all variables (safe - masks sensitive values)
varlock load

# Quiet mode (no output on success)
varlock load --quiet

# Check specific environment
varlock load --env=production

Running Commands with Secrets

# Inject validated env into command
varlock run -- npm start
varlock run -- node script.js
varlock run -- pytest

# Secrets are available to the command but never printed

Checking Schema (Safe)

# Schema is safe to read - contains no values
cat .env.schema

# List expected variables
grep "^[A-Z]" .env.schema

---

Common Patterns

Pattern 1: Validate Before Operations

# Always validate environment first
varlock load --quiet || {
  echo "❌ Environment validation failed"
  exit 1
}

# Then proceed with operation
npm run build

Pattern 2: Safe Secret Rotation

# 1. Update secret in external source (1Password, AWS, etc.)
# 2. Update .env file manually (don't use Claude for this)
# 3. Validate new value works
varlock load

# 4. If using GitHub Secrets, sync (values not shown)
./scripts/update-github-secrets.sh

Pattern 3: CI/CD Integration

# GitHub Actions - secrets from GitHub Secrets
- name: Validate environment
  env:
    DATABASE_URL: ${{ secrets.DATABASE_URL }}
    API_KEY: ${{ secrets.API_KEY }}
  run: varlock load --quiet

Pattern 4: Docker Integration

# Install Varlock in container
RUN curl -sSfL https://varlock.dev/install.sh | sh -s -- --force-no-brew \
    && ln -s /root/.varlock/bin/varlock /usr/local/bin/varlock

# Validate at container start
CMD ["varlock", "run", "--", "npm", "start"]

---

Handling Secret-Related Tasks

When User Asks to "Check if API key is set"

# ✅ Safe approach
varlock load 2>&1 | grep "API_KEY"
# Shows: ✅ API_KEY 🔐sensitive └ ▒▒▒▒▒

# ❌ Never do
echo $API_KEY

When User Asks to "Debug authentication"

# ✅ Safe approach - check presence and format
varlock load  # Validates types and required fields

# Check if key has correct prefix (without showing value)
varlock load 2>&1 | grep -E "(CLERK|AUTH)"

# ❌ Never do
printenv | grep KEY

When User Asks to "Update a secret"

Claude should respond:
"I cannot directly modify secrets for security reasons. Please:
1. Update the value in your .env file manually
2. Or update in your secrets manager (1Password, AWS, etc.)
3. Then run `varlock load` to validate

I can help you update the .env.schema if you need to add new variables."

When User Asks to "Show me the .env file"

Claude should respond:
"I won't read .env files directly as they contain secrets. Instead:
- Run `varlock load` to see masked values
- Run `cat .env.schema` to see the schema (safe)
- I can help you modify .env.schema if needed"

---

External Secret Sources

1Password Integration

# In .env.schema
# @type=string @sensitive
API_KEY=exec('op read "op://vault/item/field"')

AWS Secrets Manager

# In .env.schema
# @type=string @sensitive
DB_PASSWORD=exec('aws secretsmanager get-secret-value --secret-id prod/db')

Environment-Specific Values

# In .env.schema
# @type=url
API_URL=env('API_URL_${NODE_ENV}', 'http://localhost:3000')

---

Troubleshooting

"varlock: command not found"

# Check installation
ls ~/.varlock/bin/varlock

# Add to PATH
export PATH="$HOME/.varlock/bin:$PATH"

# Or use full path
~/.varlock/bin/varlock load

"Schema validation failed"

# Check which variables are missing/invalid
varlock load  # Shows detailed errors

# Common fixes:
# - Add missing required variables to .env
# - Fix type mismatches (port must be number)
# - Check string prefixes match schema

"Sensitive value exposed in logs"

# 1. Rotate the exposed secret immediately
# 2. Check .env.schema has @sensitive annotation
# 3. Ensure using varlock commands, not echo/cat

# Add missing sensitivity:
# Before: API_KEY=
# After:  # @type=string @sensitive
#         API_KEY=

---

npm Scripts

Add these to your package.json:

{
  "scripts": {
    "env:validate": "varlock load",
    "env:check": "varlock load --quiet || echo 'Environment validation failed'",
    "prestart": "varlock load --quiet",
    "start": "varlock run -- node server.js"
  }
}

---

Security Checklist for New Projects

• Install Varlock CLI
• Create .env.schema with all variables defined
• Mark all secrets with @sensitive annotation
• Add @defaultSensitive=true to schema header
• Add .env to .gitignore
• Commit .env.schema to version control
• Add npm run env:validate to CI/CD
• Document secret rotation procedure
• Never use cat .env or echo $SECRET in Claude sessions

---

Quick Reference Card

Task	Safe Command
Validate all env vars	varlock load
Quiet validation	varlock load --quiet
Run with env	varlock run -- <cmd>
View schema	cat .env.schema
Check specific var	varlock load | grep VAR_NAME

Never Do	Why
cat .env	Exposes all secrets
echo $SECRET	Exposes to Claude context
printenv | grep	Exposes matching secrets
Read .env with tools	Secrets in Claude's context
Hardcode in commands	In shell history

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Last updated: December 22, 2025 Secure-by-default environment management for Claude Code