Question

I have a site on which users can upload files to a subdirectory. I’m filtering the uploads check for potentially malicious code. I’m new to the security side of things, so does this look like a best-practice for securing uploads to the server? If not or if I’m missing anything, could you point me in the right direction?

//arrays with acceptable file extensions/types -- default validations set to false
$acceptable_ext = array('jpg', 'JPG', 'jpeg', 'JPEG', 'gif', 'GIF', 'png', 'PNG');
$acceptable_type = array('image/jpeg', 'image/gif', 'image/png');
$validated_ext = 0;
$validated_type = 0;

//validate file extension and type
if($_FILES && $_FILES['file']['name']) {

    $file_info = pathinfo($_FILES['file']['name']);

    //validate extension
    for ($x=0; $x < count($acceptable_ext); $x++) { 
        if($file_info['extension'] == $acceptable_ext[$x]) {
            $validated_ext = 1;
        }
    }
    //validate type
    for ($x=0; $x < count($acceptable_type); $x++) { 
        if($file_info['type'] == $acceptable_type[$x]) {
            $validated_type = 1;
        }
    }
}

if($validated_ext && $validated_type) {
   //upload file to the server blah blah
}

Answer 1

You can check out some security configurations here.

Checking MIME types, ini config, .htaccess etc will give you extra security or extra validation as per the link.