# Security Documentation

## Overview
This document outlines the security measures implemented in the Simple File Upload Server and provides guidelines for secure deployment and operation.

## Security Features

### Authentication
1. **API Key Authentication**
   - Required for all upload endpoints
   - Configured via CLIENT_KEY environment variable
   - Transmitted via X-Client-Key HTTP header
   - No default keys allowed in production

2. **Download Security**
   - 6-digit alphanumeric codes
   - One-time use downloads (configurable)
   - Automatic expiration
   - No directory listing

### File Security

1. **Upload Security**
   - Secure filename sanitization
   - No executable permissions
   - Temporary storage with cleanup
   - Chunked upload verification

2. **Storage Security**
   - Files stored outside web root
   - Metadata separation from files
   - Automatic cleanup of expired files
   - Abandoned upload detection

3. **Download Controls**
   - Maximum download limits
   - Expiry time enforcement
   - Force download headers
   - Content-Type verification

### Network Security

1. **SSL/TLS**
   - Required for production
   - Modern cipher configuration
   - Perfect forward secrecy
   - SSL certificate validation

2. **Headers**
   - Secure response headers
   - No version disclosure
   - XSS protection
   - Content security policy

## Secure Deployment

### Production Requirements

1. **SSL Configuration**
```nginx
ssl_protocols TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers on;
ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384;
```

2. **Environment Setup**
```bash
# Required settings
export CLIENT_KEY="strong-random-key"
export UPLOAD_FOLDER="/secure/path/uploads"

# SSL settings
export SSL_CERT="/path/to/cert.pem"
export SSL_KEY="/path/to/key.pem"
```

3. **File Permissions**
```bash
# Storage directory
chmod 750 /secure/path/uploads
chown www-data:www-data /secure/path/uploads

# SSL files
chmod 600 /path/to/key.pem
chmod 644 /path/to/cert.pem
```

### Docker Security

1. **Container Configuration**
   - Non-root user
   - Read-only root filesystem
   - Limited capabilities
   - Resource limits

2. **Volume Management**
   - Separate volumes for uploads
   - Proper permissions
   - Regular cleanup
   - Backup strategy

## Security Monitoring

### Logging

1. **Access Logs**
   - Upload attempts
   - Download tracking
   - Error logging
   - Authentication failures

2. **Audit Trail**
   - File operations
   - Configuration changes
   - System events
   - Cleanup activities

### Monitoring Requirements

1. **System Monitoring**
   - Disk usage
   - Memory utilization
   - Network traffic
   - Error rates

2. **Security Alerts**
   - Authentication failures
   - Unusual activity
   - Storage warnings
   - SSL certificate expiry

## Security Best Practices

### Server Configuration

1. **Firewall Rules**
   - Allow only required ports
   - Rate limit connections
   - Block suspicious IPs
   - Monitor access patterns

2. **Process Isolation**
   - Run as dedicated user
   - Minimal permissions
   - Resource limits
   - Process supervision

### Data Protection

1. **File Handling**
   - Validate file types
   - Scan for malware
   - Enforce size limits
   - Secure deletion

2. **Metadata Protection**
   - Regular backups
   - Access controls
   - Data validation
   - Secure storage

## Future Security Enhancements

### Planned Features

1. **Rate Limiting**
   - Per-IP limits
   - Token bucket algorithm
   - Configurable thresholds
   - Automatic blocking

2. **Advanced Authentication**
   - API key rotation
   - IP whitelisting
   - Two-factor auth option
   - Access tokens

3. **Enhanced Monitoring**
   - Real-time alerts
   - Usage analytics
   - Threat detection
   - Performance tracking

### Security Roadmap

1. **Short Term**
   - Implement rate limiting
   - Add file type restrictions
   - Enhance logging
   - Add health checks

2. **Long Term**
   - Access audit system
   - Advanced monitoring
   - Automated backups
   - High availability

## Incident Response

### Response Plan

1. **Detection**
   - Monitor logs
   - Track metrics
   - Alert on anomalies
   - User reports

2. **Response**
   - Assess impact
   - Contain threat
   - Notify stakeholders
   - Document incident

3. **Recovery**
   - Restore service
   - Update security
   - Review procedures
   - Implement fixes

### Security Contacts

For security issues or vulnerabilities:
1. Create a GitHub issue with [SECURITY] prefix
2. For critical issues, contact maintainers directly
3. Follow responsible disclosure guidelines
4. Allow time for patches before public disclosure