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<?php |
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/* |
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* The MIT License (MIT) |
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* |
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* Copyright (c) 2014-2016 Spomky-Labs |
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* |
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* This software may be modified and distributed under the terms |
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* of the MIT license. See the LICENSE file for details. |
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*/ |
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namespace Jose\Algorithm\KeyEncryption; |
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use Assert\Assertion; |
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use Base64Url\Base64Url; |
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use Jose\Object\JWKInterface; |
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/** |
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* Class AESGCMKW. |
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*/ |
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abstract class AESGCMKW implements KeyWrappingInterface |
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{ |
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/** |
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* {@inheritdoc} |
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*/ |
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public function wrapKey(JWKInterface $key, string $cek, array $complete_headers, array &$additional_headers): string |
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{ |
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$this->checkKey($key); |
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$kek = Base64Url::decode($key->get('k')); |
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$iv = random_bytes(96 / 8); |
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$additional_headers['iv'] = Base64Url::encode($iv); |
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$mode = $this->getMode($kek); |
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$tag = null; |
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$tag_length = 128; |
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$encrypted_cek = openssl_encrypt($cek, $mode, $kek, OPENSSL_RAW_DATA, $iv, $tag, null, $tag_length / 8); |
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Assertion::true(false !== $encrypted_cek, 'Unable to encrypt the data.'); |
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$additional_headers['tag'] = Base64Url::encode($tag); |
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return $encrypted_cek; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function unwrapKey(JWKInterface $key, string $encrypted_cek, array $header): string |
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{ |
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$this->checkKey($key); |
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$this->checkAdditionalParameters($header); |
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$kek = Base64Url::decode($key->get('k')); |
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$tag = Base64Url::decode($header['tag']); |
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$iv = Base64Url::decode($header['iv']); |
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$mode = $this->getMode($kek); |
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return openssl_decrypt($encrypted_cek, $mode, $kek, OPENSSL_RAW_DATA, $iv, $tag, null); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function getKeyManagementMode(): string |
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{ |
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return self::MODE_WRAP; |
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} |
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/** |
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* @param JWKInterface $key |
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*/ |
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protected function checkKey(JWKInterface $key) |
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{ |
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Assertion::eq($key->get('kty'), 'oct', 'Wrong key type.'); |
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Assertion::true($key->has('k'), 'The key parameter "k" is missing.'); |
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} |
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/** |
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* @param array $header |
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*/ |
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protected function checkAdditionalParameters(array $header) |
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{ |
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Assertion::keyExists($header, 'iv', 'Parameter "iv" is missing.'); |
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Assertion::keyExists($header, 'tag', 'Parameter "tag" is missing.'); |
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} |
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/** |
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* @return int |
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*/ |
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abstract protected function getKeySize(): int; |
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/** |
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* @param string $kek |
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* |
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* @return string |
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*/ |
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private function getMode(string $kek): string |
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{ |
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$key_length = mb_strlen($kek, '8bit') * 8; |
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return 'aes-'.($key_length).'-gcm'; |
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} |
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} |
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Spomky-Labs /
jose
