<?php
/**
 * A helper class for cryptographical things like hashing passwords and so on
 *
 * @author		Roland Haeder <webmaster@ship-simu.org>
 * @version		0.0.0
 * @copyright	Copyright (c) 2007, 2008 Roland Haeder, 2009 Core Developer Team
 * @license		GNU GPL 3.0 or any newer version
 * @link		http://www.ship-simu.org
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
class CryptoHelper extends BaseFrameworkSystem implements Cryptable {
	// Exception constants
	const EXCEPTION_ENCRYPT_MISSING = 0x1f0;
	const EXCEPTION_ENCRYPT_INVALID = 0x1f1;

	/**
	 * An instance of this own clas
	 */
	private static $selfInstance = null;

	/**
	 * Instance of the random number generator
	 */
	private $rngInstance = null;

	/**
	 * Instance of the crypto stream
	 */
	private $cryptoStreamInstance = null;

	/**
	 * Salt for hashing operations
	 */
	private $salt = '';

	/**
	 * Protected constructor
	 *
	 * @return	void
	 */
	protected function __construct () {
		// Call parent constructor
		parent::__construct(__CLASS__);
	}

	/**
	 * Creates an instance of this class
	 *
	 * @return	$cryptoInstance		An instance of this crypto helper class
	 */
	public final static function createCryptoHelper () {
		// Get a new instance
		$cryptoInstance = new CryptoHelper();

		// Initialize the hasher
		$cryptoInstance->initHasher();

		// Attach a crypto stream
		$cryptoInstance->attachCryptoStream();

		// Return the instance
		return $cryptoInstance;
	}

	/**
	 * Get a singleton instance of this class
	 *
	 * @return	$selfInstance	An instance of this crypto helper class
	 */
	public final static function getInstance () {
		// Is no instance there?
		if (is_null(self::$selfInstance)) {
			// Then get a new one
			self::$selfInstance = self::createCryptoHelper();
		} // END - if

		// Return the instance
		return self::$selfInstance;
	}

	/**
	 * Attaches a crypto stream to this crypto helper by detecting loaded
	 * modules.
	 *
	 * @return	void
	 */
	protected function attachCryptoStream () {
		// Do we have mcrypt loaded?
		if ($this->isPhpExtensionLoaded('mcrypt')) {
			// Then use it
			$this->cryptoStreamInstance = ObjectFactory::createObjectByName('McryptStream', array($this->getRngInstance()));
		} else {
			// If nothing works ...
			$this->cryptoStreamInstance = ObjectFactory::createObjectByName('NullCryptoStream');
		}
	}

	/**
	 * Initializes the hasher for different purposes.
	 *
	 * @return	void
	 */
	protected function initHasher () {
		// Initialize the random number generator which is required by some crypto methods
		$this->setRngInstance(ObjectFactory::createObjectByConfiguredName('rng_class'));

		// Generate a salt for the hasher
		$this->generateSalt();
	}

	/**
	 * Generates the salt based on configured length
	 *
	 * @return	void
	 */
	private function generateSalt () {
		// Get a random string from the RNG
		$randomString = $this->getRngInstance()->randomString();

		// Get config entry for salt length
		$length = $this->getConfigInstance()->getConfigEntry('salt_length');

		// Keep only defined number of characters
		$this->salt = substr(sha1($randomString), -$length, $length);
	}

	/**
	 * Hashes a string with salt and returns the hash. If an old previous hash
	 * is supplied the method will use the first X chars of that hash for hashing
	 * the password. This is useful if you want to check if password is identical
	 * for authorization purposes.
	 *
	 * @param	$str		Unhashed string
	 * @param	$oldHash	A hash from previous hashed string
	 * @return	$hashed		The hashed and salted string
	 */
	public function hashString ($str, $oldHash = '') {
		// Cast the string
		$str = (string) $str;

		// Default is the default salt ;-)
		$salt = $this->salt;

		// Is the old password set?
		if (!empty($oldHash)) {
			// Use the salt from hash, first get length
			$length = $this->getConfigInstance()->getConfigEntry('salt_length');

			// Then extract the X first characters from the hash as our salt
			$salt = substr($oldHash, 0, $length);
		} // END - if

		// Hash the password with salt
		//* DEBUG: */ echo "salt=".$salt."/plain=".$str."<br />\n";
		$hashed = $salt . md5(sprintf($this->getConfigInstance()->getConfigEntry('hash_mask'),
			$salt,
			$this->getRngInstance()->getFixedSalt(),
			$str
		));

		// And return it
		return $hashed;
	}

	/**
	 * Encrypt the string with fixed salt
	 *
	 * @param	$str		The unencrypted string
	 * @return	$encrypted	Encrypted string
	 */
	public function encryptString ($str) {
		// Encrypt the string through the stream
		$encrypted = $this->cryptoStreamInstance->encryptStream($str);

		// Return the string
		return $encrypted;
	}

	/**
	 * Decrypt the string with fixed salt
	 *
	 * @param	$encrypted	Encrypted string
	 * @return	$str		The unencrypted string
	 */
	public function decryptString ($encrypted) {
		// Encrypt the string through the stream
		$str = $this->cryptoStreamInstance->decryptStream($encrypted);

		// Return the string
		return $str;
	}
}

// [EOF]
?>