Charon/docs/SECURITY_PRACTICES.md

Security Best Practices

This document outlines security best practices for developing and maintaining Charon. These guidelines help prevent common vulnerabilities and ensure compliance with industry standards.

Table of Contents

• Secret Management
• Logging Security
• Input Validation
• File System Security
• Database Security
• API Security
• Compliance
• Security Testing

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Secret Management

Principles

1. Never commit secrets to version control
2. Use environment variables for production
3. Rotate secrets regularly
4. Mask secrets in logs
5. Encrypt secrets at rest

API Keys and Tokens

Storage

• Development: Store in .env file (gitignored)
• Production: Use environment variables or secret management service
• File storage: Use 0600 permissions (owner read/write only)

# Example: Secure key file creation
echo "api-key-here" > /data/crowdsec/bouncer.key
chmod 0600 /data/crowdsec/bouncer.key
chown charon:charon /data/crowdsec/bouncer.key

Masking

Always mask secrets before logging:

// ✅ GOOD: Masked secret
logger.Infof("API Key: %s", maskAPIKey(apiKey))

// ❌ BAD: Full secret exposed
logger.Infof("API Key: %s", apiKey)

Charon's masking rules:

• Empty: [empty]
• Short (< 16 chars): [REDACTED]
• Normal (≥ 16 chars): abcd...xyz9 (first 4 + last 4)

Validation

Validate secret format before use:

if !validateAPIKeyFormat(apiKey) {
    return fmt.Errorf("invalid API key format")
}

Requirements:

• Length: 16-128 characters
• Charset: Alphanumeric + underscore + hyphen
• No spaces or special characters

Rotation

Rotate secrets regularly:

1. Schedule: Every 90 days (recommended)
2. Triggers: After suspected compromise, employee offboarding, security incidents
3. Process:
   • Generate new secret
   • Update configuration
   • Test with new secret
   • Revoke old secret
   • Update documentation

Passwords and Credentials

• Storage: Hash with bcrypt (cost factor ≥ 12) or Argon2
• Transmission: HTTPS only
• Never log: Full passwords or password hashes
• Requirements: Enforce minimum complexity and length

---

Logging Security

What to Log

✅ Safe to log:

• Timestamps
• User IDs (not usernames if PII)
• IP addresses (consider GDPR implications)
• Request paths (sanitize query parameters)
• Response status codes
• Error types (generic messages)
• Performance metrics

❌ Never log:

• Passwords or password hashes
• API keys or tokens (use masking)
• Session IDs (full values)
• Credit card numbers
• Social security numbers
• Personal health information (PHI)
• Any Personally Identifiable Information (PII)

Log Sanitization

Before logging user input, sanitize:

// ✅ GOOD: Sanitized logging
logger.Infof("Login attempt from IP: %s", sanitizeIP(ip))

// ❌ BAD: Direct user input
logger.Infof("Login attempt: username=%s password=%s", username, password)

Log Retention

• Development: 7 days
• Production: 30-90 days (depends on compliance requirements)
• Audit logs: 1-7 years (depends on regulations)

Important: Shorter retention reduces exposure risk if logs are compromised.

Log Aggregation

If using external log services (CloudWatch, Splunk, Datadog):

• Ensure logs are encrypted in transit (TLS)
• Ensure logs are encrypted at rest
• Redact sensitive data before shipping
• Apply same retention policies
• Audit access controls regularly

---

Input Validation

Principles

1. Validate all inputs (user-provided, file uploads, API requests)
2. Whitelist approach: Define what's allowed, reject everything else
3. Fail securely: Reject invalid input with generic error messages
4. Sanitize before use: Escape/encode for target context

File Uploads

// ✅ GOOD: Comprehensive validation
func validateUpload(file multipart.File, header *multipart.FileHeader) error {
    // 1. Check file size
    if header.Size > maxFileSize {
        return fmt.Errorf("file too large")
    }

    // 2. Validate file type (magic bytes, not extension)
    buf := make([]byte, 512)
    file.Read(buf)
    mimeType := http.DetectContentType(buf)
    if !isAllowedMimeType(mimeType) {
        return fmt.Errorf("invalid file type")
    }

    // 3. Sanitize filename
    safeName := sanitizeFilename(header.Filename)

    // 4. Check for path traversal
    if containsPathTraversal(safeName) {
        return fmt.Errorf("invalid filename")
    }

    return nil
}

Path Traversal Prevention

// ✅ GOOD: Secure path handling
func securePath(baseDir, userPath string) (string, error) {
    // Clean and resolve path
    fullPath := filepath.Join(baseDir, filepath.Clean(userPath))

    // Ensure result is within baseDir
    if !strings.HasPrefix(fullPath, baseDir) {
        return "", fmt.Errorf("path traversal detected")
    }

    return fullPath, nil
}

// ❌ BAD: Direct path join (vulnerable)
fullPath := baseDir + "/" + userPath

SQL Injection Prevention

// ✅ GOOD: Parameterized query
db.Where("email = ?", email).First(&user)

// ❌ BAD: String concatenation (vulnerable)
db.Raw("SELECT * FROM users WHERE email = '" + email + "'").Scan(&user)

Command Injection Prevention

// ✅ GOOD: Use exec.Command with separate arguments
cmd := exec.Command("cscli", "bouncers", "list")

// ❌ BAD: Shell with user input (vulnerable)
cmd := exec.Command("sh", "-c", "cscli bouncers list " + userInput)

---

File System Security

File Permissions

File Type	Permissions	Owner	Rationale
Secret files (keys, tokens)	0600	charon:charon	Owner read/write only
Configuration files	0640	charon:charon	Owner read/write, group read
Log files	0640	charon:charon	Owner read/write, group read
Executables	0750	root:charon	Owner read/write/execute, group read/execute
Data directories	0750	charon:charon	Owner full access, group read/execute

Directory Structure

/data/charon/
├── config/          (0750 charon:charon)
│   ├── config.yaml  (0640 charon:charon)
│   └── secrets/     (0700 charon:charon) - Secret storage
│       └── api.key  (0600 charon:charon)
├── logs/            (0750 charon:charon)
│   └── app.log      (0640 charon:charon)
└── data/            (0750 charon:charon)

Temporary Files

// ✅ GOOD: Secure temp file creation
f, err := os.CreateTemp("", "charon-*.tmp")
if err != nil {
    return err
}
defer os.Remove(f.Name())  // Clean up

// Set secure permissions
if err := os.Chmod(f.Name(), 0600); err != nil {
    return err
}

---

Database Security

Query Security

1. Always use parameterized queries (GORM Where with ? placeholders)
2. Validate all inputs before database operations
3. Use transactions for multi-step operations
4. Limit query results (avoid SELECT *)
5. Index sensitive columns sparingly (balance security vs performance)

Sensitive Data

Data Type	Storage Method	Example
Passwords	bcrypt hash	bcrypt.GenerateFromPassword([]byte(password), 12)
API Keys	Environment variable or encrypted field	os.Getenv("API_KEY")
Tokens	Hashed with random salt	sha256(token + salt)
PII	Encrypted at rest	AES-256-GCM

Migrations

// ✅ GOOD: Add sensitive field with proper constraints
migrator.AutoMigrate(&User{})

// ❌ BAD: Store sensitive data in plaintext
// (Don't add columns like `password_plaintext`)

---

API Security

Authentication

• Use JWT tokens or session cookies with secure flags
• Implement rate limiting (prevent brute force)
• Enforce HTTPS in production
• Validate all tokens before processing requests

Authorization

// ✅ GOOD: Check user permissions
if !user.HasPermission("crowdsec:manage") {
    return c.JSON(403, gin.H{"error": "forbidden"})
}

// ❌ BAD: Assume user has access
// (No permission check)

Rate Limiting

Protect endpoints from abuse:

// Example: 100 requests per hour per IP
limiter := rate.NewLimiter(rate.Every(36*time.Second), 100)

Critical endpoints (require stricter limits):

• Login: 5 attempts per 15 minutes
• Password reset: 3 attempts per hour
• API key generation: 5 per day

Input Validation

// ✅ GOOD: Validate request body
type CreateBouncerRequest struct {
    Name string `json:"name" binding:"required,min=3,max=64,alphanum"`
}

if err := c.ShouldBindJSON(&req); err != nil {
    return c.JSON(400, gin.H{"error": "invalid request"})
}

Error Handling

// ✅ GOOD: Generic error message
return c.JSON(401, gin.H{"error": "authentication failed"})

// ❌ BAD: Reveals authentication details
return c.JSON(401, gin.H{"error": "invalid API key: abc123"})

---

Compliance

GDPR (General Data Protection Regulation)

Applicable if: Processing data of EU residents

Requirements:

1. Data minimization: Collect only necessary data
2. Purpose limitation: Use data only for stated purposes
3. Storage limitation: Delete data when no longer needed
4. Security: Implement appropriate technical measures (encryption, masking)
5. Breach notification: Report breaches within 72 hours

Implementation:

• ✅ Charon masks API keys in logs (prevents exposure of personal data)
• ✅ Secure file permissions (0600) protect sensitive data
• ✅ Log retention policies prevent indefinite storage
• ⚠️ Ensure API keys don't contain personal identifiers

Reference: GDPR Article 32 - Security of processing

---

PCI-DSS (Payment Card Industry Data Security Standard)

Applicable if: Processing, storing, or transmitting credit card data

Requirements:

1. Requirement 3.4: Render PAN unreadable (encryption, masking)
2. Requirement 8.2: Strong authentication
3. Requirement 10.2: Audit trails
4. Requirement 10.7: Retain audit logs for 1 year

Implementation:

• ✅ Charon uses masking for sensitive credentials (same principle for PAN)
• ✅ Secure file permissions align with access control requirements
• ⚠️ Charon doesn't handle payment cards directly (delegated to payment processors)

Reference: PCI-DSS Quick Reference Guide

---

SOC 2 (System and Organization Controls)

Applicable if: SaaS providers, cloud services

Trust Service Criteria:

1. CC6.1: Logical access controls (authentication, authorization)
2. CC6.6: Encryption of data in transit
3. CC6.7: Encryption of data at rest
4. CC7.2: Monitoring and detection (logging, alerting)

Implementation:

• ✅ API key validation ensures strong credentials (CC6.1)
• ✅ File permissions (0600) protect data at rest (CC6.7)
• ✅ Masked logging enables monitoring without exposing secrets (CC7.2)
• ⚠️ Ensure HTTPS enforcement for data in transit (CC6.6)

Reference: SOC 2 Trust Services Criteria

---

ISO 27001 (Information Security Management)

Applicable to: Any organization implementing ISMS

Key Controls:

1. A.9.4.3: Password management systems
2. A.10.1.1: Cryptographic controls
3. A.12.4.1: Event logging
4. A.18.1.5: Protection of personal data

Implementation:

• ✅ API key format validation (minimum 16 chars, charset restrictions)
• ✅ Key rotation procedures documented
• ✅ Secure storage with file permissions (0600)
• ✅ Masked logging protects sensitive data

Reference: ISO 27001:2013 Controls

---

Compliance Summary Table

Framework	Key Requirement	Charon Implementation	Status
GDPR	Data protection (Art. 32)	API key masking, secure storage	✅ Compliant
PCI-DSS	Render PAN unreadable (Req. 3.4)	Masking utility (same principle)	✅ Aligned
SOC 2	Logical access controls (CC6.1)	Key validation, file permissions	✅ Compliant
ISO 27001	Password management (A.9.4.3)	Key rotation, validation	✅ Compliant

---

Security Testing

Static Analysis

# Run CodeQL security scan
.github/skills/scripts/skill-runner.sh security-codeql-scan

# Expected: 0 CWE-312/315/359 findings

Unit Tests

# Run security-focused unit tests
go test ./backend/internal/api/handlers -run TestMaskAPIKey -v
go test ./backend/internal/api/handlers -run TestValidateAPIKeyFormat -v
go test ./backend/internal/api/handlers -run TestSaveKeyToFile_SecurePermissions -v

Integration Tests

# Run Playwright E2E tests
.github/skills/scripts/skill-runner.sh test-e2e-playwright

# Check for exposed secrets in test logs
grep -i "api[_-]key\|token\|password" playwright-report/index.html
# Expected: Only masked values (abcd...xyz9) or no matches

Penetration Testing

Recommended schedule: Annual or after major releases

Focus areas:

1. Authentication bypass
2. Authorization vulnerabilities
3. SQL injection
4. Path traversal
5. Information disclosure (logs, errors)
6. Rate limiting effectiveness

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Security Checklist

Before Every Release

• Run CodeQL scan (0 critical findings)
• Run unit tests (100% pass)
• Run integration tests (100% pass)
• Check for hardcoded secrets (TruffleHog, Semgrep)
• Review log output for sensitive data exposure
• Verify file permissions (secrets: 0600, configs: 0640)
• Update dependencies (no known CVEs)
• Review security documentation updates
• Test secret rotation procedure
• Verify HTTPS enforcement in production

During Code Review

• No secrets in environment variables (use .env)
• All secrets are masked in logs
• Input validation on all user-provided data
• Parameterized queries (no string concatenation)
• Secure file permissions (0600 for secrets)
• Error messages don't reveal sensitive info
• No commented-out secrets or debugging code
• Security tests added for new features

After Security Incident

• Rotate all affected secrets immediately
• Audit access logs for unauthorized use
• Purge logs containing exposed secrets
• Notify affected users (if PII exposed)
• Update incident response procedures
• Document lessons learned
• Implement additional controls to prevent recurrence

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Resources

Internal Documentation

• API Key Handling Guide
• ARCHITECTURE.md
• CONTRIBUTING.md

External References

• OWASP Top 10
• OWASP Cheat Sheet Series
• CWE Top 25
• NIST Cybersecurity Framework
• SANS Top 25 Software Errors

Security Standards

• GDPR Official Text
• PCI-DSS Standards
• SOC 2 Trust Services
• ISO 27001

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Updates

Date	Change	Author
2026-02-03	Initial security practices documentation	GitHub Copilot

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Last Updated: 2026-02-03 Next Review: 2026-05-03 (Quarterly) Owner: Security Team / Lead Developer