<?php

/**

 * Zend Framework

 *

 * LICENSE

 *

 * This source file is subject to the new BSD license that is bundled

 * with this package in the file LICENSE.txt.

 * It is also available through the world-wide-web at this URL:

 * http://framework.zend.com/license/new-bsd

 * 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@zend.com so we can send you a copy immediately.

 *

 * @category   Zend

 * @package    Zend_Crypt

 * @subpackage DiffieHellman

 * @copyright  Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 * @version    $Id: DiffieHellman.php 24593 2012-01-05 20:35:02Z matthew $

 */

/**

 * PHP implementation of the Diffie-Hellman public key encryption algorithm.

 * Allows two unassociated parties to establish a joint shared secret key

 * to be used in encrypting subsequent communications.

 *

 * @category   Zend

 * @package    Zend_Crypt

 * @copyright  Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 */

class Zend_Crypt_DiffieHellman

{

    /**

     * Static flag to select whether to use PHP5.3's openssl extension

     * if available.

     *

     * @var boolean

     */

    public static $useOpenssl = true;

    /**

     * Default large prime number; required by the algorithm.

     *

     * @var string

     */

    private $_prime = null;

    /**

     * The default generator number. This number must be greater than 0 but

     * less than the prime number set.

     *

     * @var string

     */

    private $_generator = null;

    /**

     * A private number set by the local user. It's optional and will

     * be generated if not set.

     *

     * @var string

     */

    private $_privateKey = null;

    /**

     * BigInteger support object courtesy of Zend_Crypt_Math

     *

     * @var Zend_Crypt_Math_BigInteger

     */

    private $_math = null;

    /**

     * The public key generated by this instance after calling generateKeys().

     *

     * @var string

     */

    private $_publicKey = null;

    /**

     * The shared secret key resulting from a completed Diffie Hellman

     * exchange

     *

     * @var string

     */

    private $_secretKey = null;

    /**

     * Constants

     */

    const BINARY = 'binary';

    const NUMBER = 'number';

    const BTWOC  = 'btwoc';

    /**

     * Constructor; if set construct the object using the parameter array to

     * set values for Prime, Generator and Private.

     * If a Private Key is not set, one will be generated at random.

     *

     * @param string $prime

     * @param string $generator

     * @param string $privateKey

     * @param string $privateKeyType

     * @return void

     */

    public function __construct($prime, $generator, $privateKey = null, $privateKeyType = self::NUMBER)

    {

        $this->setPrime($prime);

        $this->setGenerator($generator);

        if ($privateKey !== null) {

            $this->setPrivateKey($privateKey, $privateKeyType);

        }

        $this->setBigIntegerMath();

    }

    /**

     * Generate own public key. If a private number has not already been

     * set, one will be generated at this stage.

     *

     * @return Zend_Crypt_DiffieHellman

     */

    public function generateKeys()

    {

        if (function_exists('openssl_dh_compute_key') && self::$useOpenssl !== false) {

            $details = array();

            $details['p'] = $this->getPrime();

            $details['g'] = $this->getGenerator();

            if ($this->hasPrivateKey()) {

                $details['priv_key'] = $this->getPrivateKey();

            }

            $opensslKeyResource = openssl_pkey_new( array('dh' => $details) );

            $data = openssl_pkey_get_details($opensslKeyResource);

            $this->setPrivateKey($data['dh']['priv_key'], self::BINARY);

            $this->setPublicKey($data['dh']['pub_key'], self::BINARY);

        } else {

            // Private key is lazy generated in the absence of PHP 5.3's ext/openssl

            $publicKey = $this->_math->powmod($this->getGenerator(), $this->getPrivateKey(), $this->getPrime());

            $this->setPublicKey($publicKey);

        }

        return $this;

    }

    /**

     * Setter for the value of the public number

     *

     * @param string $number

     * @param string $type

     * @return Zend_Crypt_DiffieHellman

     */

    public function setPublicKey($number, $type = self::NUMBER)

    {

        if ($type == self::BINARY) {

            $number = $this->_math->fromBinary($number);

        }

        if (!preg_match("/^\d+$/", $number)) {

            require_once('Zend/Crypt/DiffieHellman/Exception.php');

            throw new Zend_Crypt_DiffieHellman_Exception('invalid parameter; not a positive natural number');

        }

        $this->_publicKey = (string) $number;

        return $this;

    }

    /**

     * Returns own public key for communication to the second party to this

     * transaction.

     *

     * @param string $type

     * @return string

     */

    public function getPublicKey($type = self::NUMBER)

    {

        if ($this->_publicKey === null) {

            require_once 'Zend/Crypt/DiffieHellman/Exception.php';

            throw new Zend_Crypt_DiffieHellman_Exception('A public key has not yet been generated using a prior call to generateKeys()');

        }

        if ($type == self::BINARY) {

            return $this->_math->toBinary($this->_publicKey);

        } elseif ($type == self::BTWOC) {

            return $this->_math->btwoc($this->_math->toBinary($this->_publicKey));

        }

        return $this->_publicKey;

    }

    /**

     * Compute the shared secret key based on the public key received from the

     * the second party to this transaction. This should agree to the secret

     * key the second party computes on our own public key.

     * Once in agreement, the key is known to only to both parties.

     * By default, the function expects the public key to be in binary form

     * which is the typical format when being transmitted.

     *

     * If you need the binary form of the shared secret key, call

     * getSharedSecretKey() with the optional parameter for Binary output.

     *

     * @param string $publicKey

     * @param string $type

     * @return mixed

     */

    public function computeSecretKey($publicKey, $type = self::NUMBER, $output = self::NUMBER)

    {

        if ($type == self::BINARY) {

            $publicKey = $this->_math->fromBinary($publicKey);

        }

        if (!preg_match("/^\d+$/", $publicKey)) {

            require_once('Zend/Crypt/DiffieHellman/Exception.php');

            throw new Zend_Crypt_DiffieHellman_Exception('invalid parameter; not a positive natural number');

        }

        if (function_exists('openssl_dh_compute_key') && self::$useOpenssl !== false) {

            $this->_secretKey = openssl_dh_compute_key($publicKey, $this->getPublicKey());

        } else {

            $this->_secretKey = $this->_math->powmod($publicKey, $this->getPrivateKey(), $this->getPrime());

        }

        return $this->getSharedSecretKey($output);

    }

    /**

     * Return the computed shared secret key from the DiffieHellman transaction

     *

     * @param string $type

     * @return string

     */

    public function getSharedSecretKey($type = self::NUMBER)

    {

        if (!isset($this->_secretKey)) {

            require_once('Zend/Crypt/DiffieHellman/Exception.php');

            throw new Zend_Crypt_DiffieHellman_Exception('A secret key has not yet been computed; call computeSecretKey()');

        }

        if ($type == self::BINARY) {

            return $this->_math->toBinary($this->_secretKey);

        } elseif ($type == self::BTWOC) {

            return $this->_math->btwoc($this->_math->toBinary($this->_secretKey));

        }

        return $this->_secretKey;

    }

    /**

     * Setter for the value of the prime number

     *

     * @param string $number

     * @return Zend_Crypt_DiffieHellman

     */

    public function setPrime($number)

    {

        if (!preg_match("/^\d+$/", $number) || $number < 11) {

            require_once('Zend/Crypt/DiffieHellman/Exception.php');

            throw new Zend_Crypt_DiffieHellman_Exception('invalid parameter; not a positive natural number or too small: should be a large natural number prime');

        }

        $this->_prime = (string) $number;

        return $this;

    }

    /**

     * Getter for the value of the prime number

     *

     * @return string

     */

    public function getPrime()

    {

        if (!isset($this->_prime)) {

            require_once('Zend/Crypt/DiffieHellman/Exception.php');

            throw new Zend_Crypt_DiffieHellman_Exception('No prime number has been set');

        }

        return $this->_prime;

    }

    /**

     * Setter for the value of the generator number

     *

     * @param string $number

     * @return Zend_Crypt_DiffieHellman

     */

    public function setGenerator($number)

    {

        if (!preg_match("/^\d+$/", $number) || $number < 2) {

            require_once('Zend/Crypt/DiffieHellman/Exception.php');

            throw new Zend_Crypt_DiffieHellman_Exception('invalid parameter; not a positive natural number greater than 1');

        }

        $this->_generator = (string) $number;

        return $this;

    }

    /**

     * Getter for the value of the generator number

     *

     * @return string

     */

    public function getGenerator()

    {

        if (!isset($this->_generator)) {

            require_once('Zend/Crypt/DiffieHellman/Exception.php');

            throw new Zend_Crypt_DiffieHellman_Exception('No generator number has been set');

        }

        return $this->_generator;

    }

    /**

     * Setter for the value of the private number

     *

     * @param string $number

     * @param string $type

     * @return Zend_Crypt_DiffieHellman

     */

    public function setPrivateKey($number, $type = self::NUMBER)

    {

        if ($type == self::BINARY) {

            $number = $this->_math->fromBinary($number);

        }

        if (!preg_match("/^\d+$/", $number)) {

            require_once('Zend/Crypt/DiffieHellman/Exception.php');

            throw new Zend_Crypt_DiffieHellman_Exception('invalid parameter; not a positive natural number');

        }

        $this->_privateKey = (string) $number;

        return $this;

    }

    /**

     * Getter for the value of the private number

     *

     * @param string $type

     * @return string

     */

    public function getPrivateKey($type = self::NUMBER)

    {

        if (!$this->hasPrivateKey()) {

            $this->setPrivateKey($this->_generatePrivateKey(), self::BINARY);

        }

        if ($type == self::BINARY) {

            return $this->_math->toBinary($this->_privateKey);

        } elseif ($type == self::BTWOC) {

            return $this->_math->btwoc($this->_math->toBinary($this->_privateKey));

        }

        return $this->_privateKey;

    }

    /**

     * Check whether a private key currently exists.

     *

     * @return boolean

     */

    public function hasPrivateKey()

    {

        return isset($this->_privateKey);

    }

    /**

     * Setter to pass an extension parameter which is used to create

     * a specific BigInteger instance for a specific extension type.

     * Allows manual setting of the class in case of an extension

     * problem or bug.

     *

     * @param string $extension

     * @return void

     */

    public function setBigIntegerMath($extension = null)

    {

        /**

         * @see Zend_Crypt_Math

         */

        require_once 'Zend/Crypt/Math.php';

        $this->_math = new Zend_Crypt_Math($extension);

    }

    /**

     * In the event a private number/key has not been set by the user,

     * or generated by ext/openssl, a best attempt will be made to

     * generate a random key. Having a random number generator installed

     * on linux/bsd is highly recommended! The alternative is not recommended

     * for production unless without any other option.

     *

     * @return string

     */

    protected function _generatePrivateKey()

    {

        $rand = $this->_math->rand($this->getGenerator(), $this->getPrime());

        return $rand;

    }

}