Security Scrubbing Knowledge

LLM Provider API Keys

Key Patterns by Provider

Secure API Key Usage

Never do this:

# BAD - hardcoded key
client = OpenAI(api_key="sk-abc123...")

Do this instead:

# GOOD - environment variable
import os
client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])

Or use dotenv:

from dotenv import load_dotenv
load_dotenv()  # Loads from .env file
client = OpenAI()  # Auto-reads OPENAI_API_KEY

Other Common Secret Patterns

Credential Guard

The scrub plugin includes a PreToolUse hook that blocks Claude from reading files containing credentials.

How It Works

1. Hook intercepts Read operations
2. Scans target file for 40+ credential patterns
3. Blocks read if secrets detected
4. Allows if file is in allowlist

Allowlist

Add trusted files to ~/.claude/plugins/scrub/.guard-allowlist:

# Allow test fixtures
tests/fixtures/
*.test.js
.env.example

Commands

/scrub:guard status      # Check if enabled
/scrub:guard on          # Enable guard
/scrub:guard off         # Disable guard
/scrub:guard allowlist   # Manage allowlist

Where Secrets Hide

1. Configuration files: .env, config.js, settings.py
2. Test files: Hardcoded test credentials
3. Git history: Removed from HEAD but still in commits
4. Logs: Accidentally logged tokens
5. Comments: "Temporary" credentials
6. CI/CD files: .github/workflows/, Jenkinsfile
7. Notebooks: Jupyter notebooks with inline keys
8. Docker files: Dockerfile, docker-compose.yml

PII Categories

Identifiable Data

• Direct identifiers: Name, SSN, passport number
• Contact info: Email, phone, address
• Network info: IP address, MAC address
• Financial: Credit card, bank account
• Biometric: Fingerprints, face data

Log Sanitization

Before sharing logs:

1. Remove IP addresses
2. Redact email addresses
3. Mask user IDs
4. Strip session tokens
5. Remove query parameters with PII

Git History Security

When to Scrub History

• Accidentally committed credentials
• Pushed .env file
• Included private keys
• Added database dumps with PII

Tools

• git-filter-repo (recommended): Fast, safe, feature-rich
• git filter-branch: Built-in but slower
• BFG Repo Cleaner: Java-based, good for large repos

Post-Scrub Checklist

1. Force push all branches
2. Delete all tags and recreate
3. Notify all collaborators
4. Rotate ALL exposed credentials
5. Clear CI/CD caches
6. GitHub: Contact support to clear caches

File Permissions

Secure Defaults

Dangerous Permissions

• World-writable (o+w): Anyone can modify
• World-readable keys: Credentials exposed
• SetUID on scripts: Privilege escalation risk

.gitignore Security

Must-Have Entries

# Environment
.env
.env.*
.env.local

# Keys and certificates
*.pem
*.key
*.p12
*.pfx
*.keystore
id_rsa
id_ed25519

# Credentials
credentials.json
secrets.json
*secret*
*credential*

# Logs
*.log
logs/

Best Practices

1. Never commit secrets - Use environment variables
2. Use credential guard - Block secrets from reaching AI
3. Pre-commit hooks - Scan before commit
4. Least privilege - Minimal file permissions
5. Rotate regularly - Even if not leaked
6. Audit trails - Know who accessed what
7. Defense in depth - Multiple protection layers
8. .env.example - Document required vars without values