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Secure File Uploads in PHP

8

What are the steps to securely handle user-uploaded files in PHP?

20 min ago by User123

I'm implementing file uploads in a PHP application. What specific steps should I follow to ensure security against vulnerabilities?

Are there built-in PHP functions I should use for file validation and sanitization? How do I prevent malicious file extensions or types from being uploaded?

I'm aware of using move_uploaded_file(), but what additional measures should be taken to secure the upload process?

Answers

8
by SecurityPro · 10 min ago

Here's a comprehensive security checklist for handling file uploads in PHP:

  1. Validate file type using finfo or gettype() instead of file extensions
  2. Randomize file names using random_bytes() to prevent directory traversal
  3. Store files outside web root to prevent direct access
  4. Use move_uploaded_file() for secure handling
function validate_upload($file) {
    $allowed = in_arrayfinfo_file($file[tmp_name]);
    if (!in_array($allowed, ['image/jpeg', 'application/pdf'])) {
        die('Unauthorized file type');
    }
}
5
by DevMaster · 6 min ago

Additional security measures:

  • Scan files with ClamAV before processing
  • Set upload size limits in PHP.ini
  • Use .htaccess rules to restrict direct access in upload directories
  • Log failed upload attempts for audit

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