# SSL/TLS Security Enhancement Documentation
## Overview
This document describes the enhanced SSL/TLS verification features implemented to address security issue [#24](https://github.com/aywengo/kafka-schema-reg-mcp/issues/24). These enhancements ensure secure communications with Schema Registry servers and OAuth providers by implementing explicit SSL certificate verification, custom CA bundle support, and certificate pinning framework.
## 🔒 Security Features
### 1. Explicit SSL/TLS Verification
All HTTP requests now use explicit SSL verification instead of relying on library defaults. This includes:
- **Schema Registry Communications**: All requests to Schema Registry instances
- **OAuth Provider Communications**: JWKS fetching, OAuth discovery, token validation
- **Secure Session Management**: Persistent sessions with proper SSL configuration
### 2. Custom CA Bundle Support
Support for custom Certificate Authority bundles for enterprise environments:
- Load custom CA certificates for internal/corporate environments
- Validate against both system and custom CA stores
- Automatic fallback to system CA bundle if custom bundle fails
### 3. Enhanced SSL Context Configuration
- **TLS Version**: Minimum TLS 1.2 enforced
- **Cipher Suites**: Strong cipher suites only (ECDHE+AESGCM, ECDHE+CHACHA20, etc.)
- **Certificate Validation**: Full certificate chain validation
- **Hostname Verification**: Strict hostname verification enabled
### 4. Certificate Pinning Framework
Framework for certificate pinning (future enhancement):
- Environment variable configuration
- Extensible architecture for known Schema Registry providers
- Comprehensive logging for pinning events
## 📝 Environment Variables
### Core SSL/TLS Configuration
| Variable | Default | Description |
|----------|---------|-------------|
| `ENFORCE_SSL_TLS_VERIFICATION` | `true` | Enable/disable SSL certificate verification |
| `CUSTOM_CA_BUNDLE_PATH` | `""` | Path to custom CA certificate bundle file |
| `SSL_CERT_PINNING_ENABLED` | `false` | Enable certificate pinning (future enhancement) |
### Example Configuration
```bash
# Basic configuration (recommended for production)
ENFORCE_SSL_TLS_VERIFICATION=true
# Enterprise environment with custom CA
ENFORCE_SSL_TLS_VERIFICATION=true
CUSTOM_CA_BUNDLE_PATH=/etc/ssl/certs/corporate-ca-bundle.pem
# Development environment (not recommended for production)
ENFORCE_SSL_TLS_VERIFICATION=false
```
## 🚀 Implementation Details
### Registry Client Enhancements
The `RegistryClient` class now includes:
```python
class RegistryClient:
def __init__(self, config: RegistryConfig):
# ... existing code ...
# Create secure session with SSL/TLS configuration
self.session = self._create_secure_session()
def _create_secure_session(self) -> requests.Session:
"""Create a secure requests session with proper SSL/TLS configuration."""
session = requests.Session()
# Configure SSL verification
if ENFORCE_SSL_TLS_VERIFICATION:
session.verify = True
# Use custom CA bundle if specified
if CUSTOM_CA_BUNDLE_PATH and os.path.exists(CUSTOM_CA_BUNDLE_PATH):
session.verify = CUSTOM_CA_BUNDLE_PATH
# Mount secure adapter for HTTPS connections
session.mount('https://', SecureHTTPAdapter())
return session
```
### OAuth Provider Enhancements
OAuth communications now use secure SSL contexts:
```python
def create_secure_ssl_context() -> ssl.SSLContext:
"""Create a secure SSL context for OAuth HTTP requests."""
context = ssl.create_default_context()
# Configure SSL context for maximum security
context.check_hostname = True
context.verify_mode = ssl.CERT_REQUIRED
# Disable weak protocols and ciphers
context.minimum_version = ssl.TLSVersion.TLSv1_2
context.set_ciphers('ECDHE+AESGCM:ECDHE+CHACHA20:DHE+AESGCM:DHE+CHACHA20:!aNULL:!MD5:!DSS')
return context
```
### Enhanced Error Handling
Improved error handling for SSL-related failures:
- **SSL Certificate Errors**: Clear error messages for certificate validation failures
- **CA Bundle Issues**: Warnings for missing or invalid CA bundle files
- **Connection Timeouts**: Proper timeout handling for SSL handshakes
- **Security Logging**: Comprehensive logging of SSL configuration and errors
## 🔧 Migration Guide
### From Previous Versions
1. **No Breaking Changes**: All existing configurations continue to work
2. **Default Security**: SSL verification is enabled by default
3. **Gradual Migration**: Can disable SSL verification temporarily during migration
### Recommended Steps
1. **Review Current Setup**:
```bash
# Check current SSL configuration
echo "ENFORCE_SSL_TLS_VERIFICATION=${ENFORCE_SSL_TLS_VERIFICATION:-true}"
echo "CUSTOM_CA_BUNDLE_PATH=${CUSTOM_CA_BUNDLE_PATH:-none}"
```
2. **Test SSL Connectivity**:
```bash
# Test connection to your Schema Registry
curl -v https://your-schema-registry.com/subjects
```
3. **Configure Custom CA (if needed)**:
```bash
# For enterprise environments
export CUSTOM_CA_BUNDLE_PATH=/path/to/corporate-ca-bundle.pem
```
## 🛡️ Security Best Practices
### Production Deployments
1. **Always Enable SSL Verification**:
```bash
ENFORCE_SSL_TLS_VERIFICATION=true
```
2. **Use Valid Certificates**: Ensure Schema Registry servers have valid SSL certificates
3. **Monitor SSL Logs**: Review SSL-related log messages for security events
4. **Regular Certificate Updates**: Keep CA bundles updated
### Enterprise Environments
1. **Custom CA Bundles**: Use corporate CA certificates when required
2. **Certificate Pinning**: Plan for certificate pinning implementation (future enhancement)
3. **Network Security**: Combine with network-level security measures
4. **Audit Logging**: Enable comprehensive SSL audit logging
### Development Environments
1. **Use Valid Certificates**: Even in development, use proper SSL certificates when possible
2. **Temporary Bypass**: Only disable SSL verification if absolutely necessary
3. **Clear Documentation**: Document any SSL verification bypasses
## 📊 Monitoring and Troubleshooting
### SSL Configuration Logging
The system logs SSL configuration on startup:
```
INFO: SSL/TLS Verification: ENABLED
INFO: Custom CA Bundle: /etc/ssl/certs/ca-bundle.pem (exists)
INFO: Certificate Pinning: DISABLED
INFO: Created secure session for registry 'production' at https://registry.company.com
```
### Common Issues and Solutions
#### Certificate Verification Failures
**Issue**: SSL verification failed
```
ERROR: SSL verification failed: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed
```
**Solutions**:
1. Check certificate validity: `openssl s_client -connect registry.company.com:443`
2. Verify CA bundle path: `ls -la /path/to/ca-bundle.pem`
3. Test with curl: `curl -v --cacert /path/to/ca-bundle.pem https://registry.company.com`
#### Custom CA Bundle Issues
**Issue**: Custom CA bundle not found
```
WARNING: Custom CA Bundle: /path/to/ca-bundle.pem (FILE NOT FOUND)
```
**Solutions**:
1. Verify file path and permissions
2. Check file format (PEM format required)
3. Validate CA bundle content
#### Connection Timeouts
**Issue**: SSL handshake timeouts
```
ERROR: SSL handshake timeout
```
**Solutions**:
1. Check network connectivity
2. Verify SSL/TLS version support
3. Review firewall configurations
## 🔮 Future Enhancements
### Certificate Pinning
Planned enhancements for certificate pinning:
1. **Known Provider Support**: Pre-configured pins for major Schema Registry providers
2. **Dynamic Pin Management**: Runtime pin updates and validation
3. **Pin Rotation**: Automated certificate pin rotation
4. **Comprehensive Logging**: Detailed pinning event logs
### Additional Security Features
1. **OCSP Stapling**: Online Certificate Status Protocol support
2. **Certificate Transparency**: CT log validation
3. **HPKP Support**: HTTP Public Key Pinning
4. **Security Headers**: Additional HTTP security headers
## 📚 References
- [RFC 5280](https://tools.ietf.org/html/rfc5280) - Internet X.509 Public Key Infrastructure
- [RFC 6125](https://tools.ietf.org/html/rfc6125) - Representation and Verification of Domain-Based Application Service Identity
- [RFC 7469](https://tools.ietf.org/html/rfc7469) - Public Key Pinning Extension for HTTP
- [OWASP Transport Layer Protection](https://owasp.org/www-project-cheat-sheets/cheatsheets/Transport_Layer_Protection_Cheat_Sheet.html)
## 🤝 Contributing
When contributing SSL/TLS related features:
1. **Follow Security Principles**: Implement defense in depth
2. **Test Thoroughly**: Test with various certificate configurations
3. **Document Changes**: Update this documentation for any SSL/TLS changes
4. **Security Review**: Request security review for SSL/TLS modifications
## 📞 Support
For SSL/TLS related issues:
1. **Review Logs**: Check application logs for SSL configuration and errors
2. **Verify Certificates**: Validate certificate chains and CA bundles
3. **Test Connectivity**: Use standard tools (curl, openssl) to test SSL connectivity
4. **Create Issues**: Report SSL/TLS issues with detailed error messages and configuration
