Decode CGSS packets (USER_ID, UDID, viewer_id, Response)

DecodeCGSS.php

<?php
# Decode USER_ID, UDID
echo decode("USER_ID, UDID");

# Decode Response
echo decrypt("Response", decode("UDID"));

# Decode viewer_id
echo deviewer_id("viewer_id");

function decrypt($data, $IV){
	
	$dbase64 = base64_decode($data);
	$key = substr($dbase64, -32);
	$dbase64 = substr($dbase64, 0, -32);
	$rtn = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $dbase64, MCRYPT_MODE_CBC, $IV);
	$rtn = base64_decode($rtn);
	return msgpack_unpack($rtn);
	
}

function decode($str){
	
	if($str == null || mb_strlen($str) < 4){
		return $str;
	}
	
	$s = substr($str, 0, 4);
	$n = hexdec($s);
	$text = "";
	$n2 = 2;
	$text2 = substr($str, 4, mb_strlen($str) - 4);
	
	for($i = 0; $i < mb_strlen($text2); $i++){
		$value = $text2[$i];
		if($n2 % 4 == 0){
			$text .= chr(ord($value) - 10);
		}
		$n2++;
		if(mb_strlen($text) >= $n){
			break;
		}
	}
	return str_replace("-", "", $text);
	
}

function decryptRJ256($key, $iv, $string_to_decrypt)
{
	$string_to_decrypt = base64_decode($string_to_decrypt);
	$rtn = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $string_to_decrypt, MCRYPT_MODE_CBC, $iv);
	$rtn = rtrim($rtn, "");
	return($rtn);
}

function deviewer_id($data){
	$key = "s%5VNQ(H$&Bqb6#3+78h29!Ft4wSg)ex";
	$IV = substr($data, 0, 32);
	$data = substr($data, 32);
	return decryptRJ256($key, $IV, $data);
}