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libraries/fof30/Encrypt/AesAdapter/AbstractAdapter.php

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+<?php
+/**
+ * @package   FOF
+ * @copyright Copyright (c)2010-2021 Nicholas K. Dionysopoulos / Akeeba Ltd
+ * @license   GNU General Public License version 2, or later
+ */
+
+namespace FOF30\Encrypt\AesAdapter;
+
+defined('_JEXEC') || die;
+
+/**
+ * Abstract AES encryption class
+ */
+abstract class AbstractAdapter
+{
+	/**
+	 * Trims or zero-pads a key / IV
+	 *
+	 * @param   string  $key   The key or IV to treat
+	 * @param   int     $size  The block size of the currently used algorithm
+	 *
+	 * @return  null|string  Null if $key is null, treated string of $size byte length otherwise
+	 */
+	public function resizeKey($key, $size)
+	{
+		if (empty($key))
+		{
+			return null;
+		}
+
+		$keyLength = strlen($key);
+
+		if (function_exists('mb_strlen'))
+		{
+			$keyLength = mb_strlen($key, 'ASCII');
+		}
+
+		if ($keyLength == $size)
+		{
+			return $key;
+		}
+
+		if ($keyLength > $size)
+		{
+			if (function_exists('mb_substr'))
+			{
+				return mb_substr($key, 0, $size, 'ASCII');
+			}
+
+			return substr($key, 0, $size);
+		}
+
+		return $key . str_repeat("\0", ($size - $keyLength));
+	}
+
+	/**
+	 * Returns null bytes to append to the string so that it's zero padded to the specified block size
+	 *
+	 * @param   string  $string     The binary string which will be zero padded
+	 * @param   int     $blockSize  The block size
+	 *
+	 * @return  string  The zero bytes to append to the string to zero pad it to $blockSize
+	 */
+	protected function getZeroPadding($string, $blockSize)
+	{
+		$stringSize = strlen($string);
+
+		if (function_exists('mb_strlen'))
+		{
+			$stringSize = mb_strlen($string, 'ASCII');
+		}
+
+		if ($stringSize == $blockSize)
+		{
+			return '';
+		}
+
+		if ($stringSize < $blockSize)
+		{
+			return str_repeat("\0", $blockSize - $stringSize);
+		}
+
+		$paddingBytes = $stringSize % $blockSize;
+
+		return str_repeat("\0", $blockSize - $paddingBytes);
+	}
+}