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<?php |
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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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* |
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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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* |
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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\InvalidKeyEncodingException; |
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use Dcrypt\Exceptions\InvalidKeyLengthException; |
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use Exception; |
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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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* |
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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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* |
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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 $_iv; |
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/** |
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* Name of cipher. |
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* |
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* @var string |
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*/ |
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private $_cipher; |
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/** |
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* OpensslKey constructor. |
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* |
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* @param string $key Key to use for encryption |
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* @param string $algo Algo to use for HKDF |
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* @param string $cipher Name of cipher |
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* @param string $iv Initialization vector |
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* |
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* @throws InvalidKeyLengthException |
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* @throws InvalidKeyEncodingException |
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*/ |
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public function __construct( |
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string $key, |
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string $algo, |
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string $cipher = '', |
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string $iv = '' |
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) { |
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// Store the key as what was supplied |
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$this->_key = self::decode($key); |
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// If key was not proper base64, bail out |
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if ($this->_key === false) { |
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throw new InvalidKeyEncodingException(); |
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} |
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// If key was too short, bail out |
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if (Str::strlen($this->_key) < 32) { |
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throw new InvalidKeyLengthException(); |
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} |
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// Store algo in object |
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$this->_algo = $algo; |
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// Store init vector in object |
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$this->_iv = $iv; |
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// Store the cipher name |
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$this->_cipher = $cipher; |
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} |
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/** |
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* Decode key and test validity. |
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* |
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* @param string $key Encoded key to unpack |
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* |
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* @throws InvalidKeyLengthException |
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* @throws InvalidKeyEncodingException |
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* |
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* @return string |
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*/ |
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private static function decode(string $key): string |
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{ |
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// Store the key as what was supplied |
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$key = base64_decode($key, true); |
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// If key was not proper base64, bail out |
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if ($key === false) { |
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throw new InvalidKeyEncodingException(); |
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} |
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// If key was too short, bail out |
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if (Str::strlen($key) < 32) { |
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throw new InvalidKeyLengthException(); |
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} |
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return $key; |
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} |
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/** |
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* Generate the authentication key. |
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* |
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* @return string |
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*/ |
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public function authenticationKey(): string |
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{ |
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return $this->deriveKey(__FUNCTION__ . '|' . $this->_cipher); |
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} |
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/** |
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* Generate the encryption key. |
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* |
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* @return string |
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*/ |
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public function encryptionKey(): string |
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{ |
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return $this->deriveKey(__FUNCTION__ . '|' . $this->_cipher); |
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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->_iv); |
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} |
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/** |
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* Calculates a given message HMAC. |
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* |
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* @param string $message |
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* |
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* @return string |
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*/ |
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public function messageChecksum(string $message): string |
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{ |
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return hash_hmac($this->_algo, $message, $this->authenticationKey(), true); |
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} |
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/** |
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* Allows read only access to the internal variables needed by the openssl wrapper. |
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* |
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* @return array |
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*/ |
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public function wrapperVariables(): array |
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{ |
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return [ |
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$this->_iv, |
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$this->encryptionKey(), |
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$this->_cipher, |
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]; |
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} |
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/** |
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* Generate a new key. |
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* |
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* @param int $bytes Size of key in bytes |
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* |
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* @throws Exception |
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* @throws InvalidKeyLengthException |
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* |
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* @return string |
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*/ |
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public static function create(int $bytes = 32): string |
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{ |
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if ($bytes < 32) { |
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throw new InvalidKeyLengthException(); |
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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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