Sending parameters to ckfinder with the config options

I have set up CKEditor and CKFinder and integrated both, uploading files with a s3 backend works well.

I now need to send the S3 bucket name where the file should be uploaded as a parameter so that files from different organisations (schools in this case) end up in different buckets.

For testing I am modifying the config.js file in ckfinder folder. Once it works I will move configuration options in the setupCKEditor() method.

CKFinder.setupCKEditor(null, {pass:"bucket", token:"nameofbucket"});

Here is what I have in the config.js file for now :

var config = {};

config.pass = 'bucket';
config.token = 'nameofbucket';

CKFinder.define( config );

Here is what's in the config.php file to get the parameter :

if (isset($_GET['bucket'])) {
    $bucketname = $_GET['bucket'];
} else {
    $bucketname = "buckethasnoname";

No matter what I try I cant get the value of the parameter and end up with buckethasnoname in my URL. I have tried using connectorInfo as well but to the same results.

How can I send extra parameters to ckfinder ?