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<?php |
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namespace Psr7Middlewares\Utils; |
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use RuntimeException; |
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/** |
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* Trait used by all middlewares that needs encrypt/decrypt functions. |
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*/ |
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trait CryptTrait |
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{ |
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private $key; |
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private $authentication; |
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/** |
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* Set the keys to encrypt and authenticate. |
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* |
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* @param string $key The binary key |
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* |
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* @return self |
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*/ |
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public function key($key) |
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{ |
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$this->key = self::hkdf($key, 'KeyForEncryption'); |
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$this->authentication = self::hkdf($key, 'KeyForAuthentication'); |
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return $this; |
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} |
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/** |
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* Encrypt the given value. |
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* |
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* @param string $value |
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* |
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* @return string |
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*/ |
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private function encrypt($value) |
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{ |
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$this->checkKey(); |
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$iv = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM); |
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$cipher = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $this->key, json_encode($value), 'ctr', $iv); |
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$hmac = hash_hmac('sha256', $iv.$cipher, $this->authentication, true); |
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return base64_encode($hmac.$iv.$cipher); |
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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 string $value |
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* |
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* @return string |
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*/ |
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private function decrypt($value) |
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{ |
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$this->checkKey(); |
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$decoded = base64_decode($value); |
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$hmac = mb_substr($decoded, 0, 32, '8bit'); |
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$iv = mb_substr($decoded, 32, 16, '8bit'); |
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$cipher = mb_substr($decoded, 48, null, '8bit'); |
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$calculated = hash_hmac('sha256', $iv.$cipher, $this->authentication, true); |
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if (Helpers::hashEquals($hmac, $calculated)) { |
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$value = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $this->key, $cipher, 'ctr', $iv), "\0"); |
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return json_decode($value, true); |
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} |
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} |
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/** |
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* Check whether the key exists or not. |
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* |
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* @throws RuntimeException |
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*/ |
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private function checkKey() |
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{ |
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if (empty($this->key) || empty($this->authentication)) { |
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$key = $this->secureRandomKey(); |
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$message = 'No binary key provided to encrypt/decrypt data.'; |
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if ($key !== null) { |
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$message .= sprintf(" For example: base64_decode('%s')", base64_encode($key)); |
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} |
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throw new RuntimeException($message); |
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} |
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} |
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/** |
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* Generate a secure random key. |
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* |
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* @return string|null |
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*/ |
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private static function secureRandomKey() |
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{ |
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if (!function_exists('openssl_random_pseudo_bytes')) { |
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return; |
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} |
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$secure = false; |
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$random = openssl_random_pseudo_bytes(16, $secure); |
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if ($secure) { |
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return $random; |
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} |
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} |
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/** |
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* Get derived key |
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* http://tools.ietf.org/html/rfc5869. |
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* |
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* @param string $ikm Initial Keying Material |
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* @param string $info What sort of key are we deriving? |
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* |
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* @return string |
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*/ |
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private static function hkdf($ikm, $info = '') |
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{ |
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$salt = str_repeat("\x00", 32); |
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$prk = hash_hmac('sha256', $ikm, $salt, true); |
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$t = $last_block = ''; |
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$length = 0; |
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for ($block_index = 1; $length < 16; ++$block_index) { |
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$last_block = hash_hmac('sha256', $last_block.$info.chr($block_index), $prk, true); |
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$t .= $last_block; |
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$length = mb_strlen($t, '8bit'); |
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} |
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return mb_substr($t, 0, 16, '8bit'); |
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} |
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} |
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oscarotero /
psr7-middlewares
