upload.php

<?php
/*
Copyright 2017 Ziadin Givan

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

https://github.com/givanz/VvvebJs
*/

/*
This script is used by image upload input to save the image on the server and return the image url to be set as image src attribute.
*/ 

$uploadDenyExtensions  = ['php'];
$uploadAllowExtensions = ['ico','jpg','jpeg','png','gif','webp','svg'];

function showError($error) {
	header($_SERVER['SERVER_PROTOCOL'] . ' 500 Internal Server Error', true, 500);
	die($error);
}

function sanitizeFileName($file)
{
	$disallow = ['.htaccess', 'passwd'];
	$file = str_replace($disallow, '', $file);
	
	//sanitize, remove double dot .. and remove get parameters if any
	$file = preg_replace('@\?.*$@' , '', preg_replace('@\.{2,}@' , '', preg_replace('@[^\/\\a-zA-Z0-9\-\._]@', '', $file)));
	
	return $file;
}

define('UPLOAD_FOLDER', __DIR__ . DIRECTORY_SEPARATOR);
if (isset($_POST['mediaPath'])) {
	define('UPLOAD_PATH', sanitizeFileName($_POST['mediaPath']) . DIRECTORY_SEPARATOR);
} else {
	define('UPLOAD_PATH', DIRECTORY_SEPARATOR);
}

$fileName  = sanitizeFileName($_FILES['file']['name']);
if (!$fileName) {
	showError('Invalid filename!');
}

$extension = strtolower(substr($fileName, strrpos($fileName, '.') + 1));

//check if extension is on deny list
if (in_array($extension, $uploadDenyExtensions)) {
	showError("File type $extension not allowed!");
}

//comment deny code above and uncomment this code to change to a more restrictive allowed list
// check if extension is on allow list
if (!in_array($extension, $uploadAllowExtensions)) {
	showError("File type $extension not allowed!");
}

$destination = UPLOAD_FOLDER . UPLOAD_PATH . DIRECTORY_SEPARATOR . $fileName;
move_uploaded_file($_FILES['file']['tmp_name'], $destination);

if (isset($_POST['onlyFilename'])) {
	echo $fileName;
} else {
	echo UPLOAD_PATH . $fileName;
}