Returns 'Access Denied'

I have file nodes created by File Framework module with taxonomy enabled. So each file node has one term from a certain vocabulary.

My client wants to provide access to only the files defined for certain role(s). So here is my setup:

Roles:
client A
client B
...
client Z

Vocabulary terms for node-type File:
Term 1
Term 2
Term 3
Term 4

I configured tac_lite settings at http://www.example.com/admin/user/access/tac_lite/scheme_1 and gave view access to certain roles for certain terms.

It works like a charm when all the request are made "normally".

The problem occurs on the following step. Some of these files are PDFs and I need to stamp those PDFs with user name and role, etc. For this, I use a custom page and SetaPDF APIs.

Before I integrated tac_lite PDF stamper was working without any problem. But after I set up tac_lite it started giving "access denied" errors:

The code i am using:
(Note; the code below works if the file is a stream not controlled by tac_lite, or a local file on file system. But chokes on streams controlled by tac_lite.)

require_once './includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

global $user;

/**
 * set the includepath for SetaPDF APIs
 * You have to point to the root directory "SetaPDF"
 */
set_include_path(get_include_path() . PATH_SEPARATOR . realpath(dirname(__FILE__).'/Download'));

// Watermark text
$watermark = "Downloaded by $user->name on date('M j, Y g:ia') from $user->hostname";

// Get file
$download_path = 'http://www.example.com/file/213/view/471';
$varInAnyScope = file_get_contents($download_path);

$newVarInAnyScope = '';

require_once("Tools/StreamWrapper/Php5/VarStream.php");
require_once("Stamper/SetaPDF_Stamper.php");
define('SetaPDF_STAMPER_FONTPATH', 'Stamper/font/');
$stamper =& SetaPDF_Stamper::factory('I');

$stamper->addFile(array(
//    'in'  => 'Any_file_on_the_filesystem.pdf',
      'in'  => VarStream::createReference($varInAnyScope),
      'out' => 'stamped_version.pdf'
));
require_once("Stamper/SetaPDF_Stamp/SetaPDF_TextStamp.php");
$textstamp =& new SetaPDF_TextStamp();
$textstamp->setText($watermark);
$textstamp->setFontFamily('Arial');
$textstamp->setFontSize(-1);
$textstamp->setTextWidth(650);
$textstamp->setAlign('C');
$textstamp->setAlpha(1);
$textstamp->setFontColor(153,153,153);
$textstamp->setRenderingMode(0);
$stamper->setStamp($textstamp,"CM", "all", 0, 0, 60, true);
$stamper->stampit();

Frankly, it took a while for me to figure what was the problem. Because there was only white blank page, no error message, nothing. After trying out several methods like cURL and drupal_http_request I got the error message(s), different errors but all are 403...

Error message from the logs:

Type	php
Date	Thursday, January 7, 2010 - 10:53
User	superadmin
Location	http://www.example.com/demo13.php
Referrer	
Message	file_get_contents(http://www.example.com/file/213/view/471) [<a href='function.file-get-contents'>function.file-get-contents</a>]: failed to open stream: HTTP request failed! HTTP/1.1 403 Forbidden in /var/www/httpdocs/demo13.php on line 26.
Severity	error
Operations	

or

Type	access denied
Date	Thursday, January 7, 2010 - 00:10
User	Visitor
Location	http://www.example.com/file/249/view/533
Referrer	
Message	file/249/view/533
Severity	warning
Operations	

So, I guess tac_lite cannot authenticate user if the call is made by a stream. Is there a way I can accomplish my goal, but still use tac_lite?

p.s. I also tried stream context to add headers for the call but it didn't work either:

  $download_path = 'http://www.example.com/file/213/view/471';

  $uri  = parse_url($download_path);
  $port = isset($uri['port']) ? $uri['port'] : 80;
  $host = $uri['host'] . ($port != 80 ? ':'. $port : '');
  $opts = array(
    'http'=>array(
      'method'=>"GET",
      'header'=>"Host: " . $host . "\r\n" .
                "User-Agent: Drupal (+http://drupal.org/)\r\n" .
                "Content-type: application/pdf"
    )
  );

  $context = stream_context_create($opts);
  
  $varInAnyScope = file_get_contents($download_path, 0, $context);