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✏️ Editing: JWEDecrypter.php

<?php

declare (strict_types=1);
namespace Platform360\Jose\Component\Encryption;

use InvalidArgumentException;
use Platform360\Jose\Component\Core\Algorithm;
use Platform360\Jose\Component\Core\AlgorithmManager;
use Platform360\Jose\Component\Core\JWK;
use Platform360\Jose\Component\Core\JWKSet;
use Platform360\Jose\Component\Core\Util\KeyChecker;
use Platform360\Jose\Component\Encryption\Algorithm\ContentEncryptionAlgorithm;
use Platform360\Jose\Component\Encryption\Algorithm\KeyEncryption\DirectEncryption;
use Platform360\Jose\Component\Encryption\Algorithm\KeyEncryption\KeyAgreement;
use Platform360\Jose\Component\Encryption\Algorithm\KeyEncryption\KeyAgreementWithKeyWrapping;
use Platform360\Jose\Component\Encryption\Algorithm\KeyEncryption\KeyEncryption;
use Platform360\Jose\Component\Encryption\Algorithm\KeyEncryption\KeyWrapping;
use Platform360\Jose\Component\Encryption\Algorithm\KeyEncryptionAlgorithm;
use Throwable;
use function is_string;
use function sprintf;
use function strlen;
class JWEDecrypter
{
    private readonly AlgorithmManager $keyEncryptionAlgorithmManager;
    private readonly AlgorithmManager $contentEncryptionAlgorithmManager;
    public function __construct(AlgorithmManager $algorithmManager)
    {
        $keyEncryptionAlgorithms = [];
        $contentEncryptionAlgorithms = [];
        foreach ($algorithmManager->all() as $key => $algorithm) {
            if ($algorithm instanceof KeyEncryptionAlgorithm) {
                $keyEncryptionAlgorithms[$key] = $algorithm;
            }
            if ($algorithm instanceof ContentEncryptionAlgorithm) {
                $contentEncryptionAlgorithms[$key] = $algorithm;
            }
        }
        $this->keyEncryptionAlgorithmManager = new AlgorithmManager($keyEncryptionAlgorithms);
        $this->contentEncryptionAlgorithmManager = new AlgorithmManager($contentEncryptionAlgorithms);
    }
    /**
     * Returns the key encryption algorithm manager.
     */
    public function getKeyEncryptionAlgorithmManager() : AlgorithmManager
    {
        return $this->keyEncryptionAlgorithmManager;
    }
    /**
     * Returns the content encryption algorithm manager.
     */
    public function getContentEncryptionAlgorithmManager() : AlgorithmManager
    {
        return $this->contentEncryptionAlgorithmManager;
    }
    /**
     * This method will try to decrypt the given JWE and recipient using a JWK.
     *
     * @param JWE $jwe A JWE object to decrypt
     * @param JWK $jwk The key used to decrypt the input
     * @param int $recipient The recipient used to decrypt the token
     */
    public function decryptUsingKey(JWE &$jwe, JWK $jwk, int $recipient, ?JWK $senderKey = null) : bool
    {
        $jwkset = new JWKSet([$jwk]);
        return $this->decryptUsingKeySet($jwe, $jwkset, $recipient, $senderKey);
    }
    /**
     * This method will try to decrypt the given JWE and recipient using a JWKSet.
     *
     * @param JWE $jwe A JWE object to decrypt
     * @param JWKSet $jwkset The key set used to decrypt the input
     * @param JWK $jwk The key used to decrypt the token in case of success
     * @param int $recipient The recipient used to decrypt the token in case of success
     */
    public function decryptUsingKeySet(JWE &$jwe, JWKSet $jwkset, int $recipient, ?JWK &$jwk = null, ?JWK $senderKey = null) : bool
    {
        if ($jwkset->count() === 0) {
            throw new InvalidArgumentException('No key in the key set.');
        }
        if ($jwe->getPayload() !== null) {
            return \true;
        }
        if ($jwe->countRecipients() === 0) {
            throw new InvalidArgumentException('The JWE does not contain any recipient.');
        }
        $plaintext = $this->decryptRecipientKey($jwe, $jwkset, $recipient, $jwk, $senderKey);
        if ($plaintext !== null) {
            $jwe = $jwe->withPayload($plaintext);
            return \true;
        }
        return \false;
    }
    private function decryptRecipientKey(JWE $jwe, JWKSet $jwkset, int $i, ?JWK &$successJwk = null, ?JWK $senderKey = null) : ?string
    {
        $recipient = $jwe->getRecipient($i);
        $completeHeader = \array_merge($jwe->getSharedProtectedHeader(), $jwe->getSharedHeader(), $recipient->getHeader());
        $this->checkCompleteHeader($completeHeader);
        $key_encryption_algorithm = $this->getKeyEncryptionAlgorithm($completeHeader);
        $content_encryption_algorithm = $this->getContentEncryptionAlgorithm($completeHeader);
        $this->checkIvSize($jwe->getIV(), $content_encryption_algorithm->getIVSize());
        foreach ($jwkset as $recipientKey) {
            try {
                KeyChecker::checkKeyUsage($recipientKey, 'decryption');
                if ($key_encryption_algorithm->name() !== 'dir') {
                    KeyChecker::checkKeyAlgorithm($recipientKey, $key_encryption_algorithm->name());
                } else {
                    KeyChecker::checkKeyAlgorithm($recipientKey, $content_encryption_algorithm->name());
                }
                $cek = $this->decryptCEK($key_encryption_algorithm, $content_encryption_algorithm, $recipientKey, $senderKey, $recipient, $completeHeader);
                $this->checkCekSize($cek, $key_encryption_algorithm, $content_encryption_algorithm);
                $payload = $this->decryptPayload($jwe, $cek, $content_encryption_algorithm);
                $successJwk = $recipientKey;
                return $payload;
            } catch (Throwable) {
                //We do nothing, we continue with other keys
                continue;
            }
        }
        return null;
    }
    private function checkCekSize(string $cek, KeyEncryptionAlgorithm $keyEncryptionAlgorithm, ContentEncryptionAlgorithm $algorithm) : void
    {
        if ($keyEncryptionAlgorithm instanceof DirectEncryption || $keyEncryptionAlgorithm instanceof KeyAgreement) {
            return;
        }
        if (strlen($cek) * 8 !== $algorithm->getCEKSize()) {
            throw new InvalidArgumentException('Invalid CEK size');
        }
    }
    private function checkIvSize(?string $iv, int $requiredIvSize) : void
    {
        if ($iv === null && $requiredIvSize !== 0) {
            throw new InvalidArgumentException('Invalid IV size');
        }
        if (is_string($iv) && strlen($iv) !== $requiredIvSize / 8) {
            throw new InvalidArgumentException('Invalid IV size');
        }
    }
    private function decryptCEK(Algorithm $key_encryption_algorithm, ContentEncryptionAlgorithm $content_encryption_algorithm, JWK $recipientKey, ?JWK $senderKey, Recipient $recipient, array $completeHeader) : string
    {
        if ($key_encryption_algorithm instanceof DirectEncryption) {
            return $key_encryption_algorithm->getCEK($recipientKey);
        }
        if ($key_encryption_algorithm instanceof KeyAgreement) {
            return $key_encryption_algorithm->getAgreementKey($content_encryption_algorithm->getCEKSize(), $content_encryption_algorithm->name(), $recipientKey, $senderKey, $completeHeader);
        }
        if ($key_encryption_algorithm instanceof KeyAgreementWithKeyWrapping) {
            return $key_encryption_algorithm->unwrapAgreementKey($recipientKey, $senderKey, $recipient->getEncryptedKey() ?? '', $content_encryption_algorithm->getCEKSize(), $completeHeader);
        }
        if ($key_encryption_algorithm instanceof KeyEncryption) {
            return $key_encryption_algorithm->decryptKey($recipientKey, $recipient->getEncryptedKey() ?? '', $completeHeader);
        }
        if ($key_encryption_algorithm instanceof KeyWrapping) {
            return $key_encryption_algorithm->unwrapKey($recipientKey, $recipient->getEncryptedKey() ?? '', $completeHeader);
        }
        throw new InvalidArgumentException('Unsupported CEK generation');
    }
    private function decryptPayload(JWE $jwe, string $cek, ContentEncryptionAlgorithm $content_encryption_algorithm) : string
    {
        return $content_encryption_algorithm->decryptContent($jwe->getCiphertext() ?? '', $cek, $jwe->getIV() ?? '', $jwe->getAAD(), $jwe->getEncodedSharedProtectedHeader(), $jwe->getTag() ?? '');
    }
    private function checkCompleteHeader(array $completeHeaders) : void
    {
        foreach (['enc', 'alg'] as $key) {
            if (!isset($completeHeaders[$key])) {
                throw new InvalidArgumentException(sprintf("Parameter '%s' is missing.", $key));
            }
        }
    }
    private function getKeyEncryptionAlgorithm(array $completeHeaders) : KeyEncryptionAlgorithm
    {
        $key_encryption_algorithm = $this->keyEncryptionAlgorithmManager->get($completeHeaders['alg']);
        if (!$key_encryption_algorithm instanceof KeyEncryptionAlgorithm) {
            throw new InvalidArgumentException(sprintf('The key encryption algorithm "%s" is not supported or does not implement KeyEncryptionAlgorithm interface.', $completeHeaders['alg']));
        }
        return $key_encryption_algorithm;
    }
    private function getContentEncryptionAlgorithm(array $completeHeader) : ContentEncryptionAlgorithm
    {
        $content_encryption_algorithm = $this->contentEncryptionAlgorithmManager->get($completeHeader['enc']);
        if (!$content_encryption_algorithm instanceof ContentEncryptionAlgorithm) {
            throw new InvalidArgumentException(sprintf('The key encryption algorithm "%s" is not supported or does not implement the ContentEncryption interface.', $completeHeader['enc']));
        }
        return $content_encryption_algorithm;
    }
}

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