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<?php declare(strict_types=1); |
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/** |
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* OpensslKey.php |
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* |
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* PHP version 7 |
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* |
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* @category Dcrypt |
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* @package Dcrypt |
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* @author Michael Meyer (mmeyer2k) <[email protected]> |
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* @license http://opensource.org/licenses/MIT The MIT License (MIT) |
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* @link https://github.com/mmeyer2k/dcrypt |
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*/ |
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namespace Dcrypt; |
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use Dcrypt\Exceptions\InvalidKeyException; |
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/** |
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* Provides key derivation functions |
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* |
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* @category Dcrypt |
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* @package Dcrypt |
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* @author Michael Meyer (mmeyer2k) <[email protected]> |
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* @license http://opensource.org/licenses/MIT The MIT License (MIT) |
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* @link https://github.com/mmeyer2k/dcrypt |
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*/ |
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final class OpensslKey |
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{ |
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/** |
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* High entropy key |
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* |
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* @var string |
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*/ |
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private $_key; |
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/** |
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* Algo string |
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* |
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* @var string |
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*/ |
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private $_algo; |
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/** |
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* High entropy salt |
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* |
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* @var string |
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*/ |
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private $_ivr; |
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/** |
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* OpensslKey constructor. |
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* |
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* @param string $algo Algo to use for HKDF |
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* @param string $key Key |
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* @param string $ivr Initialization vector |
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* @param bool $testKey Validate the key |
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* |
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* @throws InvalidKeyException |
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*/ |
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public function __construct( |
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string $algo, |
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string $key, |
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string $ivr = '', |
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bool $testKey = true |
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) { |
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// Store the key as what was supplied |
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$this->_key = \base64_decode($key); |
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if ($testKey) { |
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// Make sure key was properly decoded and meets minimum required length |
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if (!is_string($this->_key) || Str::strlen($this->_key) < 2048) { |
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throw new InvalidKeyException(InvalidKeyException::KEYLENGTH); |
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} |
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// Make sure key meets minimum entropy requirement |
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if (self::_testKeyEntropy($this->_key) === false) { |
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throw new InvalidKeyException(InvalidKeyException::KEYRANDOM); |
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} |
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} |
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// Store algo in object |
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$this->_algo = $algo; |
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// Store init vector in object |
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$this->_ivr = $ivr; |
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} |
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/** |
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* Generate the authentication key |
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* |
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* @param string $info The extra info parameter for hash_hkdf |
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* |
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* @return string |
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*/ |
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public function authenticationKey(string $info): string |
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{ |
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return $this->deriveKey(__FUNCTION__ . '|' . $info); |
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} |
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/** |
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* Generate the encryption key |
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* |
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* @param string $info The extra info parameter for hash_hkdf |
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* |
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* @return string |
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*/ |
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public function encryptionKey(string $info): string |
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{ |
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return $this->deriveKey(__FUNCTION__ . '|' . $info); |
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} |
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/** |
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* Derive a key with differing info string parameters |
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* |
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* @param string $info Info parameter to provide to hash_hkdf |
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* |
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* @return string |
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*/ |
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public function deriveKey(string $info): string |
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{ |
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return \hash_hkdf($this->_algo, $this->_key, 0, $info, $this->_ivr); |
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} |
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/** |
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* Generate a new key that meets requirements for dcrypt |
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* |
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* @param int $bytes Size of key in bytes |
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* |
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* @return string |
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* @throws InvalidKeyException |
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*/ |
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public static function create(int $bytes = 2048): string |
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{ |
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if ($bytes < 2048) { |
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throw new InvalidKeyException(InvalidKeyException::KEYLENGTH); |
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} |
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return \base64_encode(\random_bytes($bytes)); |
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} |
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/** |
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* Returns true if key has enough entropy |
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* |
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* @param string $key Key string to test |
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* |
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* @return bool |
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*/ |
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private static function _testKeyEntropy(string $key): bool |
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{ |
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return \count(\array_unique(\str_split($key))) > 250; |
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} |
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} |