<?php
/**
* Zend Framework (http://framework.zend.com/)
*
* @link http://github.com/zendframework/zf2 for the canonical source repository
* @copyright Copyright (c) 2005-2014 Zend Technologies USA Inc. (http://www.zend.com)
* @license http://framework.zend.com/license/new-bsd New BSD License
*/
namespace Zend\Crypt\PublicKey;
use Zend\Crypt\Exception;
use Zend\Math;
/**
* 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.
*/
class DiffieHellman
{
const DEFAULT_KEY_SIZE = 2048;
/**
* Key formats
*/
const FORMAT_BINARY = 'binary';
const FORMAT_NUMBER = 'number';
const FORMAT_BTWOC = 'btwoc';
/**
* Static flag to select whether to use PHP5.3's openssl extension
* if available.
*
* @var bool
*/
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\Math
*
* @var \Zend\Math\BigInteger\Adapter\AdapterInterface
*/
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;
/**
* @var resource
*/
protected $opensslKeyResource = null;
/**
* 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 $privateKeyFormat
*/
public function __construct($prime, $generator, $privateKey = null, $privateKeyFormat = self::FORMAT_NUMBER)
{
$this->setPrime($prime);
$this->setGenerator($generator);
if ($privateKey !== null) {
$this->setPrivateKey($privateKey, $privateKeyFormat);
}
// set up BigInteger adapter
$this->math = Math\BigInteger\BigInteger::factory();
}
/**
* Set whether to use openssl extension
*
* @static
* @param bool $flag
*/
public static function useOpensslExtension($flag = true)
{
static::$useOpenssl = (bool) $flag;
}
/**
* Generate own public key. If a private number has not already been set,
* one will be generated at this stage.
*
* @return DiffieHellman
* @throws \Zend\Crypt\Exception\RuntimeException
*/
public function generateKeys()
{
if (function_exists('openssl_dh_compute_key') && static::$useOpenssl !== false) {
$details = array(
'p' => $this->convert($this->getPrime(), self::FORMAT_NUMBER, self::FORMAT_BINARY),
'g' => $this->convert($this->getGenerator(), self::FORMAT_NUMBER, self::FORMAT_BINARY)
);
if ($this->hasPrivateKey()) {
$details['priv_key'] = $this->convert(
$this->privateKey, self::FORMAT_NUMBER, self::FORMAT_BINARY
);
$opensslKeyResource = openssl_pkey_new(array('dh' => $details));
} else {
$opensslKeyResource = openssl_pkey_new(array(
'dh' => $details,
'private_key_bits' => self::DEFAULT_KEY_SIZE,
'private_key_type' => OPENSSL_KEYTYPE_DH
));
}
if (false === $opensslKeyResource) {
throw new Exception\RuntimeException(
'Can not generate new key; openssl ' . openssl_error_string()
);
}
$data = openssl_pkey_get_details($opensslKeyResource);
$this->setPrivateKey($data['dh']['priv_key'], self::FORMAT_BINARY);
$this->setPublicKey($data['dh']['pub_key'], self::FORMAT_BINARY);
$this->opensslKeyResource = $opensslKeyResource;
} else {
// Private key is lazy generated in the absence of 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 $format
* @return DiffieHellman
* @throws \Zend\Crypt\Exception\InvalidArgumentException
*/
public function setPublicKey($number, $format = self::FORMAT_NUMBER)
{
$number = $this->convert($number, $format, self::FORMAT_NUMBER);
if (!preg_match('/^\d+$/', $number)) {
throw new Exception\InvalidArgumentException('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 $format
* @return string
* @throws \Zend\Crypt\Exception\InvalidArgumentException
*/
public function getPublicKey($format = self::FORMAT_NUMBER)
{
if ($this->publicKey === null) {
throw new Exception\InvalidArgumentException(
'A public key has not yet been generated using a prior call to generateKeys()'
);
}
return $this->convert($this->publicKey, self::FORMAT_NUMBER, $format);
}
/**
* 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 $publicKeyFormat
* @param string $secretKeyFormat
* @return string
* @throws \Zend\Crypt\Exception\InvalidArgumentException
* @throws \Zend\Crypt\Exception\RuntimeException
*/
public function computeSecretKey($publicKey, $publicKeyFormat = self::FORMAT_NUMBER,
$secretKeyFormat = self::FORMAT_NUMBER)
{
if (function_exists('openssl_dh_compute_key') && static::$useOpenssl !== false) {
$publicKey = $this->convert($publicKey, $publicKeyFormat, self::FORMAT_BINARY);
$secretKey = openssl_dh_compute_key($publicKey, $this->opensslKeyResource);
if (false === $secretKey) {
throw new Exception\RuntimeException(
'Can not compute key; openssl ' . openssl_error_string()
);
}
$this->secretKey = $this->convert($secretKey, self::FORMAT_BINARY, self::FORMAT_NUMBER);
} else {
$publicKey = $this->convert($publicKey, $publicKeyFormat, self::FORMAT_NUMBER);
if (!preg_match('/^\d+$/', $publicKey)) {
throw new Exception\InvalidArgumentException(
'Invalid parameter; not a positive natural number'
);
}
$this->secretKey = $this->math->powmod($publicKey, $this->getPrivateKey(), $this->getPrime());
}
return $this->getSharedSecretKey($secretKeyFormat);
}
/**
* Return the computed shared secret key from the DiffieHellman transaction
*
* @param string $format
* @return string
* @throws \Zend\Crypt\Exception\InvalidArgumentException
*/
public function getSharedSecretKey($format = self::FORMAT_NUMBER)
{
if (!isset($this->secretKey)) {
throw new Exception\InvalidArgumentException(
'A secret key has not yet been computed; call computeSecretKey() first'
);
}
return $this->convert($this->secretKey, self::FORMAT_NUMBER, $format);
}
/**
* Setter for the value of the prime number
*
* @param string $number
* @return DiffieHellman
* @throws \Zend\Crypt\Exception\InvalidArgumentException
*/
public function setPrime($number)
{
if (!preg_match('/^\d+$/', $number) || $number < 11) {
throw new Exception\InvalidArgumentException(
'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
*
* @param string $format
* @return string
* @throws \Zend\Crypt\Exception\InvalidArgumentException
*/
public function getPrime($format = self::FORMAT_NUMBER)
{
if (!isset($this->prime)) {
throw new Exception\InvalidArgumentException('No prime number has been set');
}
return $this->convert($this->prime, self::FORMAT_NUMBER, $format);
}
/**
* Setter for the value of the generator number
*
* @param string $number
* @return DiffieHellman
* @throws \Zend\Crypt\Exception\InvalidArgumentException
*/
public function setGenerator($number)
{
if (!preg_match('/^\d+$/', $number) || $number < 2) {
throw new Exception\InvalidArgumentException(
'Invalid parameter; not a positive natural number greater than 1'
);
}
$this->generator = (string) $number;
return $this;
}
/**
* Getter for the value of the generator number
*
* @param string $format
* @return string
* @throws \Zend\Crypt\Exception\InvalidArgumentException
*/
public function getGenerator($format = self::FORMAT_NUMBER)
{
if (!isset($this->generator)) {
throw new Exception\InvalidArgumentException('No generator number has been set');
}
return $this->convert($this->generator, self::FORMAT_NUMBER, $format);
}
/**
* Setter for the value of the private number
*
* @param string $number
* @param string $format
* @return DiffieHellman
* @throws \Zend\Crypt\Exception\InvalidArgumentException
*/
public function setPrivateKey($number, $format = self::FORMAT_NUMBER)
{
$number = $this->convert($number, $format, self::FORMAT_NUMBER);
if (!preg_match('/^\d+$/', $number)) {
throw new Exception\InvalidArgumentException('Invalid parameter; not a positive natural number');
}
$this->privateKey = (string) $number;
return $this;
}
/**
* Getter for the value of the private number
*
* @param string $format
* @return string
*/
public function getPrivateKey($format = self::FORMAT_NUMBER)
{
if (!$this->hasPrivateKey()) {
$this->setPrivateKey($this->generatePrivateKey(), self::FORMAT_BINARY);
}
return $this->convert($this->privateKey, self::FORMAT_NUMBER, $format);
}
/**
* Check whether a private key currently exists.
*
* @return bool
*/
public function hasPrivateKey()
{
return isset($this->privateKey);
}
/**
* Convert number between formats
*
* @param $number
* @param string $inputFormat
* @param string $outputFormat
* @return string
*/
protected function convert($number, $inputFormat = self::FORMAT_NUMBER,
$outputFormat = self::FORMAT_BINARY)
{
if ($inputFormat == $outputFormat) {
return $number;
}
// convert to number
switch ($inputFormat) {
case self::FORMAT_BINARY:
case self::FORMAT_BTWOC:
$number = $this->math->binToInt($number);
break;
case self::FORMAT_NUMBER:
default:
// do nothing
break;
}
// convert to output format
switch ($outputFormat) {
case self::FORMAT_BINARY:
return $this->math->intToBin($number);
break;
case self::FORMAT_BTWOC:
return $this->math->intToBin($number, true);
break;
case self::FORMAT_NUMBER:
default:
return $number;
break;
}
}
/**
* In the event a private number/key has not been set by the user,
* or generated by ext/openssl, a best attempt will be made to
* generate a random key. Having a random number generator installed
* on linux/bsd is highly recommended! The alternative is not recommended
* for production unless without any other option.
*
* @return string
*/
protected function generatePrivateKey()
{
return Math\Rand::getBytes(strlen($this->getPrime()), true);
}
}