How can individual download files be securely provided for each user in a PHP-based system?

To securely provide individual download files for each user in a PHP-based system, you can generate unique download links with limited access and expiration times. This can be achieved by storing the file paths in a database along with user-specific information, generating a unique token for each user, and verifying the token and user information before allowing the download. 

// Generate a unique token for the user
$token = md5(uniqid(rand(), true));

// Store the token along with the file path and user information in a database
// This is just an example, make sure to properly sanitize and validate user input
$filePath = 'path/to/file.pdf';
$userID = 123;
$expiryTime = time() + 3600; // Link expires in 1 hour

// Insert data into database
$query = "INSERT INTO download_links (token, file_path, user_id, expiry_time) VALUES ('$token', '$filePath', $userID, $expiryTime)";
// Execute the query

// Provide the download link to the user with the token as a query parameter
$downloadLink = "http://example.com/download.php?token=$token";

// Verify the token and user information before allowing the download
// In download.php
$token = $_GET['token'];
$query = "SELECT * FROM download_links WHERE token = '$token' AND user_id = $userID AND expiry_time >= " . time();
// Execute the query and check if the token is valid

// If the token is valid, serve the file for download
// Make sure to set appropriate headers for file download
if ($validToken) {
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="' . basename($filePath) . '"');
    readfile($filePath);
} else {
    echo "Invalid token or link has expired.";
}

Keywords

file download user authentication session management access control encryption

Related Questions