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<?php |
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declare(strict_types = 1); |
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namespace Sop\JWX\JWE\KeyAlgorithm; |
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use Sop\JWX\JWA\JWA; |
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use Sop\JWX\JWE\KeyManagementAlgorithm; |
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use Sop\JWX\JWK\JWK; |
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use Sop\JWX\JWK\Symmetric\SymmetricKeyJWK; |
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use Sop\JWX\JWT\Header\Header; |
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use Sop\JWX\JWT\Parameter\AlgorithmParameter; |
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/** |
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* Algorithm to carry CEK in plaintext. |
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* |
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* @see https://tools.ietf.org/html/rfc7518#section-4.5 |
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*/ |
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class DirectCEKAlgorithm extends KeyManagementAlgorithm |
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{ |
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/** |
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* Content encryption key. |
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* |
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* @var string |
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*/ |
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protected $_cek; |
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/** |
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* Constructor. |
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* |
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* @param string $cek Content encryption key |
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*/ |
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public function __construct(string $cek) |
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{ |
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$this->_cek = $cek; |
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} |
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/** |
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* Initialize from JWK. |
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* |
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* @throws \UnexpectedValueException |
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* |
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* @return self |
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*/ |
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public static function fromJWK(JWK $jwk, Header $header): KeyManagementAlgorithm |
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{ |
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$jwk = SymmetricKeyJWK::fromJWK($jwk); |
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$alg = JWA::deriveAlgorithmName($header); |
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if (JWA::ALGO_DIR !== $alg) { |
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throw new \UnexpectedValueException("Invalid algorithm '{$alg}'."); |
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} |
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return new self($jwk->key()); |
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} |
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/** |
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* Get content encryption key. |
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*/ |
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public function cek(): string |
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{ |
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return $this->_cek; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function cekForEncryption(int $length): string |
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{ |
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if (strlen($this->_cek) !== $length) { |
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throw new \UnexpectedValueException('Invalid key length.'); |
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} |
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return $this->_cek; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function algorithmParamValue(): string |
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{ |
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return JWA::ALGO_DIR; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function headerParameters(): array |
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{ |
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return array_merge(parent::headerParameters(), |
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[AlgorithmParameter::fromAlgorithm($this)]); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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protected function _encryptKey(string $key, Header &$header): string |
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{ |
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if ($key !== $this->_cek) { |
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throw new \LogicException("Content encryption key doesn't match."); |
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} |
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return ''; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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protected function _decryptKey(string $ciphertext, Header $header): string |
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{ |
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if ('' !== $ciphertext) { |
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throw new \UnexpectedValueException( |
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'Encrypted key must be an empty octet sequence.'); |
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} |
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return $this->_cek; |
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} |
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} |
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sop /
jwx
