How to stop a file named filename.php.jpg from uploading - php

Question

so i have this script to upload files, and yes i know it's not secure. Howe ever, My problem right now is that i can upload files named filename.php.jpg. So how can i prevent files like theese to upload? I have used other stuff to stop php files from being executed.
<?php
$maindir = "../alla_bilder/images/";
$maindir_th = "../alla_bilder/images/thumbs/";
$uploaddir = "images/";
$uploaddir_th = "images/thumbs/";
$allowed = array('jpg','jpeg','png');
$notallowed = array('php');
$uploadOk = 1;
$max_size = 5048 * 1024;
while (list ($key, $val) = each ($_FILES))
{
if ($_FILES[$key]['size'] <= $max_size)
{
$file_ext = pathinfo($_FILES[$key]['name'],PATHINFO_EXTENSION);
$file_name = basename($_FILES[$key]['name'],'.'.$file_ext);
if (in_array(strtolower($file_ext),$allowed))
{
$name = $_FILES[$key]['name'];
$x = 1;
while (file_exists($uploaddir.'/'.$name))
{
$name = $file_name.'['.$x.'].'.$file_ext;
$x++;
}
$name = substr(str_shuffle(str_repeat("0123456789abcdefghijklmnopqrstuvwxyz", 22)), 0, 22). '.' .mb_strtolower ($file_ext);
if (move_uploaded_file($_FILES[$key]['tmp_name'],$uploaddir.'/'.$name))
{
chmod($uploaddir.'/'.$name, 0644);
}
else
{
die(error_get_last());
}
}
else
{
die("Invalid file type");
}
}
else
{
die("File size too big");
}
copy($uploaddir.'/'.$name, $maindir.'/'.$name);
$images = glob("images/thumbs/*.*");
foreach($images as $image)
{
$output .= '<div class="col-md-2" align="center" ><img src="' . $image .'" width="200px" height="140px" style="border:1px solid #ccc;" /></div>';
}
//thumbnail image making part
$modwidth = 200;
$modheight = 140;
list($width, $height) = getimagesize($uploaddir.'/'.$name);
$ratio_orig = $width/$height;
if ($width/$height > $ratio_orig)
{
$width = $height*$ratio_orig;
} else {
$height = $width/$ratio_orig;
}
$tn = imagecreatetruecolor($modwidth, $modheight);
//$image = imagecreatefromjpeg($uploaddir.'/'.$name);
$image = imagecreatefromstring(file_get_contents($uploaddir.'/'.$name));
imagecopyresampled($tn, $image, 0, 0, 0, 0, $modwidth, $modheight, $width, $height);
imagejpeg($tn, $uploaddir_th.'/'.$name);
imagejpeg($tn, $maindir_th.'/'.$name);
}
echo "STOP!";
?>

Answer 1

Take a look at the finfo extension, this allows you to determine the true file type as it sniffs the file type at the OS level.
http://php.net/manual/en/function.finfo-file.php
As finfo is an extension it will need to be installed and enabled.
http://php.net/manual/en/fileinfo.installation.php
Example
$path = $_FILES[$key]['tmp_name'],$uploaddir.'/'.$name;
$finfo = finfo_open(FILEINFO_MIME_TYPE);
$whitelist = array('image/jpg');
if (in_array(finfo_file($finfo, $path), $whitelist) && move_uploaded_file($path))
{
chmod($uploaddir.'/'.$name, 0644);
}