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<?php |
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namespace SGP\IronBox\Encryption; |
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use SGP\IronBox\Exceptions\DecryptException; |
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use SGP\IronBox\Exceptions\EncryptException; |
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use RuntimeException; |
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class Encrypter |
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{ |
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/** |
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* The encryption key. |
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* |
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* @var string |
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*/ |
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protected $key; |
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/** |
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* The algorithm used for encryption. |
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* |
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* @var string |
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*/ |
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protected $cipher; |
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/** |
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* The initialization vector to use. |
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* |
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* @var string |
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*/ |
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protected $iv; |
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/** |
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* Create a new encrypter instance. |
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* |
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* @param string $key |
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* @param string $cipher |
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* @param string $iv |
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* |
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* @return void |
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* |
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* @throws \RuntimeException |
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*/ |
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public function __construct($key, $cipher = 'AES-128-CBC', $iv = null) |
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{ |
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$key = (string) $key; |
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if (static::supported($key, $cipher)) { |
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$this->key = $key; |
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$this->cipher = $cipher; |
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$this->iv = $iv; |
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} else { |
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throw new RuntimeException('The only supported ciphers are AES-128-CBC and AES-256-CBC'); |
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} |
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} |
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/** |
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* Determine if the given key and cipher combination is valid. |
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* |
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* @param string $key |
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* @param string $cipher |
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* |
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* @return bool |
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*/ |
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public static function supported($key, $cipher) |
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{ |
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$length = mb_strlen($key, '8bit'); |
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return ($cipher === 'AES-128-CBC' && $length === 16) || |
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($cipher === 'AES-256-CBC' && $length === 32); |
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} |
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/** |
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* Create a new encryption key for the given cipher. |
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* |
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* @param string $cipher |
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* |
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* @return string |
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* @throws \Exception |
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*/ |
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public static function generateKey($cipher) |
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{ |
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return random_bytes($cipher === 'AES-128-CBC' ? 16 : 32); |
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} |
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/** |
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* @param $value |
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* @param bool $serialize |
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* |
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* @return string |
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* |
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* @throws \SGP\IronBox\Exceptions\EncryptException |
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*/ |
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public function encrypt($value, $serialize = true) |
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{ |
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$iv = $this->iv ?? random_bytes(openssl_cipher_iv_length($this->cipher)); |
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// First we will encrypt the value using OpenSSL. After this is encrypted we |
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// will proceed to calculating a MAC for the encrypted value so that this |
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// value can be verified later as not having been changed by the users. |
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$value = \openssl_encrypt( |
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$serialize ? serialize($value) : $value, |
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$this->cipher, |
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$this->key, |
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0, |
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$iv |
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); |
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if ($value === false) { |
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throw new EncryptException('Could not encrypt the data.'); |
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} |
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// Once we get the encrypted value we'll go ahead and base64_encode the input |
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// vector and create the MAC for the encrypted value so we can then verify |
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// its authenticity. Then, we'll JSON the data into the "payload" array. |
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$mac = $this->hash($iv = base64_encode($iv), $value); |
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$json = json_encode(compact('iv', 'value', 'mac')); |
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if (json_last_error() !== JSON_ERROR_NONE) { |
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throw new EncryptException('Could not encrypt the data.'); |
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} |
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return base64_encode($json); |
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} |
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/** |
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* Encrypt a string without serialization. |
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* |
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* @param string $value |
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* |
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* @return string |
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* |
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* @throws \SGP\IronBox\Exceptions\EncryptException |
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*/ |
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public function encryptString($value) |
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{ |
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return $this->encrypt($value, false); |
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} |
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/** |
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* Decrypt the given value. |
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* |
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* @param mixed $payload |
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* @param bool $unserialize |
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* |
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* @return mixed |
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* |
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* @throws \SGP\IronBox\Exceptions\DecryptException |
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*/ |
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public function decrypt($payload, $unserialize = true) |
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{ |
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$payload = $this->getJsonPayload($payload); |
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$iv = base64_decode($payload['iv']); |
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// Here we will decrypt the value. If we are able to successfully decrypt it |
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// we will then unserialize it and return it out to the caller. If we are |
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// unable to decrypt this value we will throw out an exception message. |
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$decrypted = \openssl_decrypt( |
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$payload['value'], |
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$this->cipher, |
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$this->key, |
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0, |
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$iv |
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); |
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if ($decrypted === false) { |
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throw new DecryptException('Could not decrypt the data.'); |
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} |
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return $unserialize ? unserialize($decrypted) : $decrypted; |
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} |
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/** |
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* Decrypt the given string without unserialization. |
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* |
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* @param string $payload |
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* |
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* @return string |
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* |
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* @throws \SGP\IronBox\Exceptions\DecryptException |
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*/ |
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public function decryptString($payload) |
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{ |
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return $this->decrypt($payload, false); |
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} |
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/** |
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* Get the encryption key. |
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* |
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* @return string |
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*/ |
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public function getKey() |
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{ |
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return $this->key; |
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} |
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/** |
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* Create a MAC for the given value. |
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* |
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* @param string $iv |
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* @param mixed $value |
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* |
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* @return string |
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*/ |
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protected function hash($iv, $value) |
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{ |
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return hash_hmac('sha256', $iv . $value, $this->key); |
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} |
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/** |
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* Get the JSON array from the given payload. |
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* |
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* @param string $payload |
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* |
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* @return array |
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* |
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* @throws \SGP\IronBox\Exceptions\DecryptException |
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*/ |
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protected function getJsonPayload($payload) |
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{ |
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$payload = json_decode(base64_decode($payload), true); |
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// If the payload is not valid JSON or does not have the proper keys set we will |
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// assume it is invalid and bail out of the routine since we will not be able |
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// to decrypt the given value. We'll also check the MAC for this encryption. |
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if (! $this->validPayload($payload)) { |
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throw new DecryptException('The payload is invalid.'); |
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} |
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if (! $this->validMac($payload)) { |
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throw new DecryptException('The MAC is invalid.'); |
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} |
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return $payload; |
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} |
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/** |
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* Verify that the encryption payload is valid. |
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* |
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* @param mixed $payload |
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* |
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* @return bool |
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*/ |
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protected function validPayload($payload) |
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{ |
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return is_array($payload) && |
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isset($payload['iv'], $payload['value'], $payload['mac']) && |
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strlen(base64_decode($payload['iv'], true)) === openssl_cipher_iv_length($this->cipher); |
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} |
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/** |
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* Determine if the MAC for the given payload is valid. |
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* |
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* @param array $payload |
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* |
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* @return bool |
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* @throws \Exception |
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*/ |
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protected function validMac(array $payload) |
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{ |
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$calculated = $this->calculateMac($payload, $bytes = random_bytes(16)); |
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return hash_equals( |
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hash_hmac('sha256', $payload['mac'], $bytes, true), |
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$calculated |
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); |
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} |
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/** |
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* Calculate the hash of the given payload. |
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* |
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* @param array $payload |
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* @param string $bytes |
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* |
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* @return string |
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*/ |
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protected function calculateMac($payload, $bytes) |
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{ |
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return hash_hmac( |
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'sha256', |
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$this->hash($payload['iv'], $payload['value']), |
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$bytes, |
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true |
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); |
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} |
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} |
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