Wordpress login to download uploaded files

dl-file.php

<?php
/*
 * dl-file.php
 *
 * Protect uploaded files with login.
 * 
 * @link http://wordpress.stackexchange.com/questions/37144/protect-wordpress-uploads-if-user-is-not-logged-in
 * 
 * @author hakre <http://hakre.wordpress.com/>
 * @license GPL-3.0+
 * @registry SPDX
 * 
 * Modified per comments on original gist.
 *
 * Add below to .htaccess or Apache conf, above the filename RewriteCond in the normal WordPress rules:
 * 
 * RewriteCond %{REQUEST_FILENAME} -s
 * RewriteRule ^wp-content/uploads/(.*)$ dl-file.php?file=$1 [QSA,L]
 *
 */

// Fix to allow for large files without exhausting PHP memory: http://stackoverflow.com/questions/6627952/why-does-readfile-exhaust-php-memory/38986798#38986798
    if (ob_get_level()) {
        ob_end_clean();
    }
    
    ob_start();
    require_once('wp-load.php');
    require_once ABSPATH . WPINC . '/formatting.php';
    require_once ABSPATH . WPINC . '/capabilities.php';
    require_once ABSPATH . WPINC . '/user.php';
    require_once ABSPATH . WPINC . '/meta.php';
    require_once ABSPATH . WPINC . '/post.php';
    require_once ABSPATH . WPINC . '/pluggable.php';
    wp_cookie_constants();
    ob_end_clean();
    ob_end_flush();
    
    is_user_logged_in() ||  auth_redirect();
    
    list($basedir) = array_values(array_intersect_key(wp_upload_dir(), array('basedir' => 1)))+array(NULL);
    
    $file = $basedir.'/'.str_replace('..', '', isset($_GET[ 'file' ])?$_GET[ 'file' ]:'');
    if (!$basedir || !is_file($file)) {
        status_header(404);
        echo $file;
        die(' 404 &#8212; File not found.');
    }
    
    $mime = wp_check_filetype($file);
    if( false === $mime[ 'type' ] && function_exists( 'mime_content_type' ) )
        $mime[ 'type' ] = mime_content_type( $file );
    
    if( $mime[ 'type' ] )
        $mimetype = $mime[ 'type' ];
    else
        $mimetype = 'image/' . substr( $file, strrpos( $file, '.' ) + 1 );
    
    header( 'Content-Type: ' . $mimetype ); // always send this
    if ( false === strpos( $_SERVER['SERVER_SOFTWARE'], 'Microsoft-IIS' ) )
        header( 'Content-Length: ' . filesize( $file ) );

    // Optional support for X-Sendfile and X-Accel-Redirect
    if ( WPMU_ACCEL_REDIRECT ) {
        header( 'X-Accel-Redirect: ' . str_replace( WP_CONTENT_DIR, '', $file ) );
        exit;
    } elseif ( WPMU_SENDFILE ) {
        header( 'X-Sendfile: ' . $file );
        exit;
    }

    $last_modified = gmdate( 'D, d M Y H:i:s', filemtime( $file ) );
    $etag = '"' . md5( $last_modified ) . '"';
    header( "Last-Modified: $last_modified GMT" );
    header( 'ETag: ' . $etag );
    header( 'Expires: ' . gmdate( 'D, d M Y H:i:s', time() + 100000000 ) . ' GMT' );
    
    // Support for Conditional GET
    $client_etag = isset( $_SERVER['HTTP_IF_NONE_MATCH'] ) ? stripslashes( $_SERVER['HTTP_IF_NONE_MATCH'] ) : false;
    
    if( ! isset( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) )
        $_SERVER['HTTP_IF_MODIFIED_SINCE'] = false;
    
    $client_last_modified = trim( $_SERVER['HTTP_IF_MODIFIED_SINCE'] );
    // If string is empty, return 0. If not, attempt to parse into a timestamp
    $client_modified_timestamp = $client_last_modified ? strtotime( $client_last_modified ) : 0;
    
    // Make a timestamp for our most recent modification...
    $modified_timestamp = strtotime($last_modified);
    
    if ( ( $client_last_modified && $client_etag )
        ? ( ( $client_modified_timestamp >= $modified_timestamp) && ( $client_etag == $etag ) )
        : ( ( $client_modified_timestamp >= $modified_timestamp) || ( $client_etag == $etag ) )
        ) {
        status_header( 304 );
        exit;
    }
    
    // If we made it this far, just serve the file
    readfile( $file );
    flush();