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:

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:

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.