Security issues. PHP window.location - php

Question

i have created this application which creates a csv file from given list from DB and than allows user to download it! When i finished the job i came to realise that there is a security issues!
Here is the ajas i am using to make a request:
$.ajax({
type: "POST",
url:HTTPS + '/lib/model/data/ctlRates.php?export=1',
data: {
ext: ext,
filter: filter,
fileName: fileName
},
dataType: 'json',
success: function(data){
if(data['results'] == "success"){
console.log(data['results']);
var filename = data['filename'];
var extension = data['ext'];
window.location = HTTPS + '/lib/model/data/ctlRates.php download=1&filename='+filename+'&ext='+extension;
} else {
console.log(data['results']);
}
}
});
} else {
alert("Error: File name and extension must be provided");
}
});
And i imagine that most of you already sees the problem!
but here is the controller to which window.location is pointing:
if(isset($_GET['download']) && $_GET['download'] == 1){
$filePath = "/path/to/file/dir";
$name = $_GET['filename'];
$extension = $_GET['ext'];
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: private",false);
header('Content-Description: File Transfer');
header('Content-type: text/'.$extension.'');
header('Content-Disposition: attachment; filename="'.$name.".".$extension.'');
header("Content-Transfer-Encoding: binary");
header("Pragma: public");
ob_clean();
flush();
readfile($filePath.$name.".".$extension);
}
Started testing and came to realize that everyone can ender filename and extension they pleases and get files from that directory....Any ideas how to burry this hole?

Answer 1

And i imagine that most of you already sees the problem!
Not really - there are very few security issues i javascript - and this does not exhibit any of them - the problem is how you are procesing your data server-side. Do not attempt to server security holes with javascript changes.
If you want to restrict access to a specific directory tree...
if(isset($_GET['download']) && $_GET['download'] == 1){
$filePath = "/path/to/file/dir";
$fetchfrom = realpath($filepath . '/'
. /* basename( */ $name /* ) */
. "." . $extension);
if (substr($fetchfrom, 0, strlen($filepath))!=$filepath) {
header("HTTP/1.0 404 Not Found");
print "Directory traversal not allowed";
exit;
}