php mcrypt CBC

<?php
/**
 * 加密解密类  
 * 
 * @author zhenghua
 * @time   2015/4/29
 */
// include_once "errorCode.php";
class App_encrypt{

	public static $block_size = 32;   //块大小
	public $key;
	
	/**
	 * 对明文进行加密
	 * @param string $text 需要加密的明文
	 * @return string 加密后的密文
	 */
	public function encrypt($k, $text, $appid){
		$this->key = base64_decode($k . "=");		//微信的拼装 base64
		try {
			//获得16位随机字符串，填充到明文之前
			$random = $this->getRandomStr();
			$text = $random . pack("N", strlen($text)) . $text . $appid;
			
			// 网络字节序
			$size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
			$module = mcrypt_module_open(MCRYPT_RIJNDAEL_128, "", MCRYPT_MODE_CBC, "");
				
			$iv = substr($this->key, 0, 16);
			//使用自定义的填充方式对明文进行补位填充
			
			$text = $this->cover_position($text);
			mcrypt_generic_init($module, $this->key, $iv);
			//加密
			$encrypted = mcrypt_generic($module, $text);
			mcrypt_generic_deinit($module);
			mcrypt_module_close($module);
	
			return array(ErrorCode::$OK, urlencode(base64_encode($encrypted)));
		} catch (Exception $e) {
			return array(ErrorCode::$EncryptAESError, null);
		}
	}
	
	/**
	 * 对密文进行解密
	 * @param string $encrypted 需要解密的密文
	 * @return string 解密得到的明文
	 */
	public function decrypt($k, $encrypted, $appid){
		$this->key = base64_decode($k . "=");		//微信的拼装 base64
		try {
			$encrypted = urldecode($encrypted);
			$encrypted = str_replace(" ","+",$encrypted);	//加号补全
			$ciphertext_dec = base64_decode($encrypted);
			$module = mcrypt_module_open(MCRYPT_RIJNDAEL_128, "", MCRYPT_MODE_CBC, "");
			$iv = substr($this->key, 0, 16);
			mcrypt_generic_init($module, $this->key, $iv);
	
			//解密
			$decrypted = mdecrypt_generic($module, $ciphertext_dec);
			mcrypt_generic_deinit($module);
			mcrypt_module_close($module);
		} catch (Exception $e) {
			return array(ErrorCode::$DecryptAESError, null);
		}
		try {
			//去除补位字符
			$result = $this->remove_cover($decrypted);
			//去除16位随机字符串,网络字节序和AppId
			if (strlen($result) < 16)
				throw new Exception("null") ;
			$content = substr($result, 16, strlen($result));
			$len_list = unpack("N", substr($content, 0, 4));
			$xml_len = $len_list[1];
			$xml_content = substr($content, 4, $xml_len);
			$from_appid = substr($content, $xml_len + 4);	
		} catch (Exception $e) {
			return array(ErrorCode::$IllegalBuffer, null);
		}
		if ($from_appid != $appid)
			return array(ErrorCode::$ValidateAppidError, null);
		return array(0, $xml_content);
	
	}
	
	/**
	 * 随机生成16位字符串
	 * @return string 生成的字符串
	 */
	function getRandomStr(){
		
		$str = "";
		$str_pol = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz";
		$max = strlen($str_pol) - 1;
		for ($i = 0; $i < 16; $i++) {
			$str .= $str_pol[mt_rand(0, $max)];
		}
		return $str;
	}
	
	/**
	 * 对需要加密的明文进行填充补位
	 * @param $text 需要进行填充补位操作的明文
	 * @return 补齐明文字符串
	 */
	function cover_position($text){
		
		$block_size = App_encrypt::$block_size;
		$text_length = strlen($text);
		//计算需要填充的位数
		$amount_to_pad = App_encrypt::$block_size - ($text_length % App_encrypt::$block_size);
		if ($amount_to_pad == 0) {
			$amount_to_pad = App_encrypt::block_size;
		}
		//获得补位所用的字符
		$pad_chr = chr($amount_to_pad);
		$tmp = "";
		for ($index = 0; $index < $amount_to_pad; $index++) {
			$tmp .= $pad_chr;
		}
		return $text . $tmp;
	}
	
	/**
	 * 对解密后的明文进行补位删除
	 * @param decrypted 解密后的明文
	 * @return 删除填充补位后的明文
	 */
	function remove_cover($text){
		
		$pad = ord(substr($text, -1));
		if ($pad < 1 || $pad > 32) {
			$pad = 0;
		}
		return substr($text, 0, (strlen($text) - $pad));
	}
	
	/**
	 * 用SHA1算法生成安全签名
	 * @param array  string 加密数据
	 */
	public static function getSHA1($string)
	{
		//排序
		try {
			$str = $string;
			return array(ErrorCode::$OK, sha1($str));
		} catch (Exception $e) {
			return array(ErrorCode::$ComputeSignatureError, null);
		}
	}
	
}

class ErrorCode
{
	public static $OK = 0;
	public static $ValidateSignatureError = -40001;
	public static $ParseXmlError = -40002;
	public static $ComputeSignatureError = -40003;
	public static $IllegalAesKey = -40004;
	public static $ValidateAppidError = -40005;
	public static $EncryptAESError = -40006;
	public static $DecryptAESError = -40007;
	public static $IllegalBuffer = -40008;
	public static $EncodeBase64Error = -40009;
	public static $DecodeBase64Error = -40010;
	public static $GenReturnXmlError = -40011;
}