<?php

/**
 * @package Am_Crypt 
 */
class Am_Exception_Crypt extends Am_Exception_InternalError {}

/**
 * @package Am_Crypt 
 */
abstract class Am_Crypt
{
    protected $key;
    function __construct($key = null) 
    {
        $this->key = $key;
    }
    abstract function encrypt($s);
    abstract function decrypt($s);
    
    abstract function getKeySignature();
    
    public function checkKeyChanged()
    {
        if ( $this->compareKeySignatures() != 0)
            throw new Am_Exception_Crypt('The encryption key has been changed, you have to re-encode database with new key - please visit upgrade script');
    }

    /**
     * @return 0 if the same, 1 if different signatures
     */
    public function compareKeySignatures()
    {
        if ($this->loadKeySignature() == '') {
            $this->saveKeySigunature();
            return 0;
        }
        $loadedSig = $this->loadKeySignature();
        if (preg_match('/^strong:/', $loadedSig))
        {
            $ret = strcmp($loadedSig, $this->getKeySignatureCompat());
            if ($ret === 0)
                $this->saveKeySigunature();
            return $ret;
        } else {
            return strcmp($loadedSig, $this->getKeySignature());
        }
    }
    public function saveKeySigunature()
    {
        $sign = $this->getKeySignature($this->key);
        Am_Di::getInstance()->config->saveValue('crypt_key_signature', $sign);
        Am_Di::getInstance()->config->set('crypt_key_signature', $sign);
    }
    public function loadKeySignature()
    {
        return Am_Di::getInstance()->config->get('crypt_key_signature');
    }
}

/**
 * Old encryption method used in v3
 * @package Am_Crypt 
 */
class Am_Crypt_Compat extends Am_Crypt
{
    const DEFAULT_KEY = 'Xjk23cbnmk28;ajandb4b300zxchB&!@^#$DOFCNCccc334ff,masd';
    function  __construct($key=null)
    {
        if ($key === null)
            $key = self::DEFAULT_KEY;
        parent::__construct($key);
    }
    function encrypt($s) 
    {
        return rawurlencode($this->__internal_crypt($s, $this->key));
    }
    function decrypt($s) 
    {
        return rawurldecode(rawurlencode($this->__internal_crypt(rawurldecode($s), $this->key)));
    }
    function getKeySignature()
    {
        return 'compat:'.crc32(substr($this->key, 0, 2) . sha1($this->key) . substr($this->key, -2, 2));
    }
    function __internal_crypt($data, $pwd) 
    {
        $cb='';
        settype($cb,'array');
        settype($tt, 'string');
        $kk='';
        settype($kk,'array');
        for ($i=0,$pl=strlen($pwd);$i<256;$i++) {
            $kk[$i]=ord(substr($pwd, ($i % $pl), 1));
            $cb[$i]=$i;
        }
        for ($i=0,$j=0;$i<256;$i++) {
            $j = ($j + $cb[$i] + $kk[$i]) % 256;
            $tt = $cb[$i];
            $cb[$i] = $cb[$j];
            $cb[$j] = $tt;
        }
        $tttt = $k = $news = $newss = '';
        $a = 0;
        $j = 0;
        for ($i = 0; $i < strlen($data); $i++) {
            $a +=       1;
            $a %= 256;
            $j += $cb[$a];
            $j %= 256;
            $tttt = $cb[$a];
            $cb[$a] = $cb[$j];
            $cb[$j] = $tttt;
            $k = $cb[(($cb[$a] + $cb[$j]) % 256)];
            $newss .= chr(ord(substr($data, $i, 1)) ^ $k);
        }
        return $newss;
    }
}

/**
 * New encryption based on mcrypt 3des
 * @package Am_Crypt 
 */
class Am_Crypt_Strong extends Am_Crypt
{
    protected $ch;
    protected $chKey;
    
    protected static $instance;

    function __construct($key=null)
    {
        if (!function_exists('mcrypt_module_open'))
            throw new Am_Exception_Crypt("mcrypt module is not enabled");
        if ($key === null)
            $key = $this->openKeyFile();
        $this->ch = mcrypt_module_open(MCRYPT_3DES, '', MCRYPT_MODE_ECB, '');
        if ($this->ch===false) 
            throw new Am_Exception_Crypt('Internal error: could not init mcrypt library');
        parent::__construct($key);
    }
    protected function init()
    {
        $keySize = mcrypt_enc_get_key_size($this->ch);
        $this->chKey = substr(pack("H*", md5($this->key)), 0, $keySize);
        $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($this->ch), MCRYPT_RAND);
        if (($err=mcrypt_generic_init($this->ch, $this->chKey, $iv)) < 0) 
            throw new Am_Exception_Crypt('Error initializing mcrypt library : '.$err);
    }
    public function openKeyFile()
    {
        $path = defined('AM_KEYFILE') ? 
            AM_KEYFILE :
            APPLICATION_PATH . '/configs/key.php';
        if (!file_exists($path))
            throw new Am_Exception_Crypt('Key file does not exists'); // @todo comment
        $key = include $path;
        if (!strlen($key))
            throw new Am_Exception_Crypt('Key file has incorrect format or the key is empty'); // @todo comment
        if ($key == 'REPLACE THIS STRING TO YOUR KEYSTRING')
            throw new Am_Exception_Crypt('You must define a valid key in the file [$path] instead of default');
        return $key;
    }
    function encrypt($s)
    {
        if ($s == '') return $s;
        $this->init();
        return base64_encode(trim(mcrypt_generic($this->ch, $s), chr(0)));
    }
    function decrypt($s)
    {
        if ($s == '') return $s;
        $this->init();
        return trim(mdecrypt_generic($this->ch, base64_decode($s)), chr(0));
    }
    function getKeySignature()
    {
        return 'strong2:'. substr(sha1($this->key), 4, -4);
    }
    function getKeySignatureCompat()
    {
        return 'strong:'.crc32(substr($this->key, 0, 2) . sha1($this->key) . substr($this->key, -2, 2));
    }
}