PHP File Type Validation - php

Question

I wrote the following php function to upload files but I'm having a hard time with the array of allowed file types. If I assign just one file type i.e. image/png, it works fine. If I assign more than one, its not working. I use the in_array() function to determine the allowed file types but I can't figure out how to use it properly.
Thank you!
function mcSingleFileUpload($mcUpFileName, $mcAllowedFileTypes, $mcFileSizeMax){
if(!empty($mcUpFileName)){
$mcIsValidUpload = true;
// upload directory
$mcUploadDir = UPLOAD_DIRECTORY;
// current file properties
$mcFileName = $_FILES[$mcUpFileName]['name'];
$mcFileType = $_FILES[$mcUpFileName]['type'];
$mcFileSize = $_FILES[$mcUpFileName]['size'];
$mcTempFileName = $_FILES[$mcUpFileName]['tmp_name'];
$mcFileError = $_FILES[$mcUpFileName]['error'];
// file size limit
$mcFileSizeLimit = $mcFileSizeMax;
// convert bytes to kilobytes
$mcBytesInKb = 1024;
$mcFileSizeKb = round($mcFileSize / $mcBytesInKb, 2);
// create array for allowed file types
$mcAllowedFTypes = array($mcAllowedFileTypes);
// create unique file name
$mcUniqueFileName = date('m-d-Y').'-'.time().'-'.$mcFileName;
// if file error
if($mcFileError > 0)
{
$mcIsValidUpload = false;
mcResponseMessage(true, 'File error!');
}
// if no file error
if($mcFileError == 0)
{
// check file type
if( !in_array($mcFileType, $mcAllowedFTypes) ){
$mcIsValidUpload = false;
mcResponseMessage(true, 'Invalid file type!');
}
// check file size
if( $mcFileSize > $mcFileSizeLimit ){
$mcIsValidUpload = false;
mcResponseMessage(true, 'File exceeds maximum limit of '.$mcFileSizeKb.'kB');
}
// move uploaded file to assigned directory
if($mcIsValidUpload == true){
if(move_uploaded_file($mcTempFileName, $mcUploadDir.$mcUniqueFileName)){
mcResponseMessage(false, 'File uploaded successfully!');
}
else{
mcResponseMessage(true, 'File could not be uploaded!');
}
}
}
}
}
//mcRequiredFile('mcFileUpSingle','please select a file to upload!');
mcSingleFileUpload('mcFileUpSingle', 'image/png,image/jpg', 2097152);

Answer 1

Change this line:
$mcAllowedFTypes = array($mcAllowedFileTypes);
To this:
$mcAllowedFTypes = explode(',',$mcAllowedFileTypes);

Answer 2

Don't rely on the clent file type from $_FILES which is unsafe, get it from the file content.
Then define your allowed file types, check if the upload file type in your white list.
if(in_array(mime_type($file_path),$allowed_mime_types)){
// save the file
}
$allowed_mime_types = array(
'image/jpeg',
'image/jpg',
'image/png',
'image/gif',
'video/mp4'
);
/*
For PHP>=5.3.0, you can use php's `finfo_file`([finfo_file](https://www.php.net/manual/en/function.finfo-file.php)) function to get the file infomation about the file.
For PHP<5.3.0, you can use your's system's `file` command to get the file information.
*/
function mime_type($file_path)
{
if (function_exists('finfo_open')) {
$finfo = new finfo(FILEINFO_MIME_TYPE, null);
$mime_type = $finfo->file($file_path);
}
if (!$mime_type && function_exists('passthru') && function_exists('escapeshellarg')) {
ob_start();
passthru(sprintf('file -b --mime %s 2>/dev/null', escapeshellarg($file_path)), $return);
if ($return > 0) {
ob_end_clean();
$mime_type = null;
}
$type = trim(ob_get_clean());
if (!preg_match('#^([a-z0-9\-]+/[a-z0-9\-\.]+)#i', $type, $match)) {
$mime_type = null;
}
$mime_type = $match[1];
}
return $mime_type;
}