Fix broken unserialize in Magento SUPEE-8788 patch

fix-broken-unserialize.diff

diff --git a/lib/Unserialize/Parser.php b/lib/Unserialize/Parser.php
index 20a6a3c..88c6555 100644
--- a/lib/Unserialize/Parser.php
+++ b/lib/Unserialize/Parser.php
@@ -34,6 +34,7 @@ class Unserialize_Parser
     const TYPE_DOUBLE = 'd';
     const TYPE_ARRAY = 'a';
     const TYPE_BOOL = 'b';
+    const TYPE_NULL = 'N';
 
     const SYMBOL_QUOTE = '"';
     const SYMBOL_SEMICOLON = ';';
diff --git a/lib/Unserialize/Reader/Arr.php b/lib/Unserialize/Reader/Arr.php
index cf039f7..9526017 100644
--- a/lib/Unserialize/Reader/Arr.php
+++ b/lib/Unserialize/Reader/Arr.php
@@ -101,7 +101,10 @@ class Unserialize_Reader_Arr
         if ($this->_status == self::READING_VALUE) {
             $value = $this->_reader->read($char, $prevChar);
             if (!is_null($value)) {
-                $this->_result[$this->_reader->key] = $value;
+                $this->_result[$this->_reader->key] =
+                    ($value == Unserialize_Reader_Null::NULL_VALUE && $prevChar == Unserialize_Parser::TYPE_NULL)
+                        ? null
+                        : $value;
                 if (count($this->_result) < $this->_length) {
                     $this->_reader = new Unserialize_Reader_ArrKey();
                     $this->_status = self::READING_KEY;
diff --git a/lib/Unserialize/Reader/ArrValue.php b/lib/Unserialize/Reader/ArrValue.php
index 620e52b..e392d81 100644
--- a/lib/Unserialize/Reader/ArrValue.php
+++ b/lib/Unserialize/Reader/ArrValue.php
@@ -84,6 +84,10 @@ class Unserialize_Reader_ArrValue
                     $this->_reader = new Unserialize_Reader_Dbl();
                     $this->_status = self::READING_VALUE;
                     break;
+                case Unserialize_Parser::TYPE_NULL:
+                    $this->_reader = new Unserialize_Reader_Null();
+                    $this->_status = self::READING_VALUE;
+                    break;
                 default:
                     throw new Exception('Unsupported data type ' . $char);
             }
diff --git a/lib/Unserialize/Reader/Null.php b/lib/Unserialize/Reader/Null.php
new file mode 100644
index 0000000..ead7f77
--- /dev/null
+++ b/lib/Unserialize/Reader/Null.php
@@ -0,0 +1,64 @@
+<?php
+/**
+ * Magento
+ *
+ * NOTICE OF LICENSE
+ *
+ * This source file is subject to the Open Software License (OSL 3.0)
+ * that is bundled with this package in the file LICENSE.txt.
+ * It is also available through the world-wide-web at this URL:
+ * http://opensource.org/licenses/osl-3.0.php
+ * If you did not receive a copy of the license and are unable to
+ * obtain it through the world-wide-web, please send an email
+ * to license@magento.com so we can send you a copy immediately.
+ *
+ * DISCLAIMER
+ *
+ * Do not edit or add to this file if you wish to upgrade Magento to newer
+ * versions in the future. If you wish to customize Magento for your
+ * needs please refer to http://www.magento.com for more information.
+ *
+ * @category    Unserialize
+ * @package     Unserialize_Reader
+ * @copyright  Copyright (c) 2006-2016 X.commerce, Inc. and affiliates (http://www.magento.com)
+ * @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
+ */
+
+/**
+ * Class Unserialize_Reader_Null
+ */
+class Unserialize_Reader_Null
+{
+    /**
+     * @var int
+     */
+    protected $_status;
+
+    /**
+     * @var string
+     */
+    protected $_value;
+
+    const NULL_VALUE = 'null';
+
+    const READING_VALUE = 1;
+
+    /**
+     * @param string $char
+     * @param string $prevChar
+     * @return string|null
+     */
+    public function read($char, $prevChar)
+    {
+        if ($prevChar == Unserialize_Parser::SYMBOL_SEMICOLON) {
+            $this->_value = self::NULL_VALUE;
+            $this->_status = self::READING_VALUE;
+            return null;
+        }
+
+        if ($this->_status == self::READING_VALUE && $char == Unserialize_Parser::SYMBOL_SEMICOLON) {
+            return $this->_value;
+        }
+        return null;
+    }
+}