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efrain |
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<?php
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namespace Aws\Crypto;
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use Aws\Exception\CryptoException;
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use Aws\Kms\KmsClient;
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/**
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* Uses KMS to supply materials for encrypting and decrypting data. This
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* V2 implementation should be used with the V2 encryption clients (i.e.
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* S3EncryptionClientV2).
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*/
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class KmsMaterialsProviderV2 extends MaterialsProviderV2 implements MaterialsProviderInterfaceV2
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{
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const WRAP_ALGORITHM_NAME = 'kms+context';
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private $kmsClient;
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private $kmsKeyId;
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/**
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* @param KmsClient $kmsClient A KMS Client for use encrypting and
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* decrypting keys.
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* @param string $kmsKeyId The private KMS key id to be used for encrypting
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* and decrypting keys.
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*/
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public function __construct(
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KmsClient $kmsClient,
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$kmsKeyId = null
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) {
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$this->kmsClient = $kmsClient;
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$this->kmsKeyId = $kmsKeyId;
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}
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/**
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* @inheritDoc
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*/
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public function getWrapAlgorithmName()
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{
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return self::WRAP_ALGORITHM_NAME;
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}
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/**
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* @inheritDoc
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*/
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public function decryptCek($encryptedCek, $materialDescription, $options)
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{
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$params = [
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'CiphertextBlob' => $encryptedCek,
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'EncryptionContext' => $materialDescription
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];
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if (empty($options['@KmsAllowDecryptWithAnyCmk'])) {
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if (empty($this->kmsKeyId)) {
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throw new CryptoException('KMS CMK ID was not specified and the'
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. ' operation is not opted-in to attempting to use any valid'
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. ' CMK it discovers. Please specify a CMK ID, or explicitly'
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. ' enable attempts to use any valid KMS CMK with the'
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. ' @KmsAllowDecryptWithAnyCmk option.');
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}
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$params['KeyId'] = $this->kmsKeyId;
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}
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$result = $this->kmsClient->decrypt($params);
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return $result['Plaintext'];
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}
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/**
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* @inheritDoc
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*/
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public function generateCek($keySize, $context, $options)
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{
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if (empty($this->kmsKeyId)) {
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throw new CryptoException('A KMS key id is required for encryption'
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. ' with KMS keywrap. Use a KmsMaterialsProviderV2 that has been'
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. ' instantiated with a KMS key id.');
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}
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$options = array_change_key_case($options);
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if (!isset($options['@kmsencryptioncontext'])
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|| !is_array($options['@kmsencryptioncontext'])
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) {
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throw new CryptoException("'@KmsEncryptionContext' is a"
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. " required argument when using KmsMaterialsProviderV2, and"
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. " must be an associative array (or empty array).");
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}
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if (isset($options['@kmsencryptioncontext']['aws:x-amz-cek-alg'])) {
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throw new CryptoException("Conflict in reserved @KmsEncryptionContext"
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. " key aws:x-amz-cek-alg. This value is reserved for the S3"
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. " Encryption Client and cannot be set by the user.");
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}
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$context = array_merge($options['@kmsencryptioncontext'], $context);
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$result = $this->kmsClient->generateDataKey([
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'KeyId' => $this->kmsKeyId,
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'KeySpec' => "AES_{$keySize}",
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'EncryptionContext' => $context
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]);
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return [
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'Plaintext' => $result['Plaintext'],
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'Ciphertext' => base64_encode($result['CiphertextBlob']),
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'UpdatedContext' => $context
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];
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}
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}
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