xamxam/formulaire/SECURITY.md

# Security Improvements

## Changes Made

### 1. Critical Vulnerability Fixes

#### Path Traversal in thanks.php (CRITICAL)
- **Before**: User could access ANY file on the system via `?file=../../../../etc/passwd`
- **After**:
  - Validates file path using `realpath()` to resolve symlinks
  - Ensures file is within allowed `data/yaml/` directory
  - Verifies file extension is `.yaml`
  - Proper error handling without exposing system paths

#### CSRF Protection
- **Before**: Form could be submitted from any website
- **After**:
  - Session-based CSRF tokens generated for each form load
  - Token validated on submission using timing-safe comparison (`hash_equals()`)
  - Token cleared after successful submission

### 2. Input Validation & Sanitization

#### Deprecated Functions Replaced
- **Before**: Used `FILTER_SANITIZE_STRING` (deprecated in PHP 8.1+)
- **After**: Custom `sanitize_string()` function using `htmlspecialchars()` and `strip_tags()`

#### Enhanced Validation
- Required fields properly validated with custom `validate_required()` function
- Email validation using `FILTER_VALIDATE_EMAIL`
- URL validation using `FILTER_VALIDATE_URL`
- Year validation with reasonable range checking (2000 to current year + 1)
- Comprehensive error messages for validation failures

### 3. File Upload Security

#### Random Filenames
- **Before**: Used original or predictable filenames (author + timestamp)
- **After**:
  - Generates cryptographically secure random filenames using `random_bytes()`
  - Prevents file overwrites
  - Prevents path traversal attacks via malicious filenames
  - Stores mapping to original filename for reference

#### Enhanced File Validation
- MIME type checking using `finfo`
- File extension whitelist
- File size limits (50MB max)
- Proper error handling for upload errors
- Cover image restricted to JPEG/PNG only

### 4. Bug Fixes

- Fixed undefined variable `$memoireFolder` (used before definition)
- Fixed undefined variable `$resume` (should be `$description`)
- Fixed variable ordering (generate `$uniqueId` before using it)
- Added proper `__DIR__` prefix for absolute paths

### 5. Error Handling

- Try-catch block wraps entire form processing
- Detailed error logging (not exposed to users)
- User-friendly error messages
- Proper exit after redirect
- No system path exposure in error messages

## Nginx Configuration Notes

Since this form is behind nginx password authentication, additional security layers:

### Recommended nginx config:
```nginx
location /formulaire {
    auth_basic "Restricted Access";
    auth_basic_user_file /etc/nginx/.htpasswd;

    # Rate limiting
    limit_req zone=form_limit burst=5 nodelay;

    # File upload size
    client_max_body_size 100M;

    # Timeout settings
    client_body_timeout 60s;

    # Prevent access to sensitive files
    location ~ /\. {
        deny all;
    }

    location ~ /(vendor|composer\.(json|lock)|error\.log)$ {
        deny all;
    }
}
```

## Additional Recommendations

### 1. Database Migration (In Progress)
Moving to SQLite will provide:
- Structured data storage
- Better query capabilities
- Easier data management
- Prepared statements for SQL injection prevention

### 2. File Storage
- Consider moving uploaded files outside web root
- Serve files through PHP script with access control
- Implement file scanning for malware if possible

### 3. Monitoring
- Regularly review `error.log` for suspicious activity
- Monitor file upload patterns
- Set up alerts for failed CSRF validations

### 4. Backup Strategy
- Regular backups of `data/` directory
- Version control for code changes
- Test restore procedures

### 5. PHP Configuration
Ensure these settings in php.ini:
```ini
file_uploads = On
upload_max_filesize = 100M
post_max_size = 100M
max_execution_time = 60
max_input_time = 60
memory_limit = 256M

# Security
expose_php = Off
allow_url_fopen = Off
allow_url_include = Off
display_errors = Off
log_errors = On
```

## Testing Checklist

- [ ] Form submission with all fields
- [ ] Form submission with minimal required fields
- [ ] Invalid email format
- [ ] Invalid URL format
- [ ] Invalid year
- [ ] File upload (various formats)
- [ ] Large file upload (>50MB, should fail)
- [ ] Invalid file types
- [ ] Multiple file uploads
- [ ] Cover image upload
- [ ] CSRF token validation (try submitting with wrong token)
- [ ] Path traversal attempt in thanks.php
- [ ] Error handling for missing directories

## Known Limitations

1. **No atomic transactions**: File operations and YAML save not atomic
2. **No rollback**: Failed submissions may leave partial files
3. **Session storage**: CSRF tokens in default PHP session (consider database sessions)
4. **No upload progress**: Large files have no progress indicator
5. **No duplicate detection**: Same submission can be made multiple times

These limitations will be addressed in the SQLite migration.