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<?php
namespace Aws\Crypto;
abstract class MaterialsProvider implements MaterialsProviderInterface
{
private static $supportedKeySizes = [
128 => true,
192 => true,
256 => true,
];
/**
* Returns if the requested size is supported by AES.
*
* @param int $keySize Size of the requested key in bits.
*
* @return bool
*/
public static function isSupportedKeySize($keySize)
{
return isset(self::$supportedKeySizes[$keySize]);
}
/**
* Performs further initialization of the MaterialsProvider based on the
* data inside the MetadataEnvelope.
*
* @param MetadataEnvelope $envelope A storage envelope for encryption
* metadata to be read from.
*
* @return MaterialsProvider
*
* @throws \RuntimeException Thrown when there is an empty or improperly
* formed materials description in the envelope.
*
* @internal
*/
abstract public function fromDecryptionEnvelope(MetadataEnvelope $envelope);
/**
* Returns the material description for this Provider so it can be verified
* by encryption mechanisms.
*
* @return string
*/
abstract public function getMaterialsDescription();
/**
* Returns the wrap algorithm name for this Provider.
*
* @return string
*/
abstract public function getWrapAlgorithmName();
/**
* Takes a content encryption key (CEK) and description to return an
* encrypted key according to the Provider's specifications.
*
* @param string $unencryptedCek Key for use in encrypting other data
* that itself needs to be encrypted by the
* Provider.
* @param string $materialDescription Material Description for use in
* encrypting the $cek.
*
* @return string
*/
abstract public function encryptCek($unencryptedCek, $materialDescription);
/**
* Takes an encrypted content encryption key (CEK) and material description
* for use decrypting the key according to the Provider's specifications.
*
* @param string $encryptedCek Encrypted key to be decrypted by the Provider
* for use decrypting other data.
* @param string $materialDescription Material Description for use in
* encrypting the $cek.
*
* @return string
*/
abstract public function decryptCek($encryptedCek, $materialDescription);
/**
* @param string $keySize Length of a cipher key in bits for generating a
* random content encryption key (CEK).
*
* @return string
*/
public function generateCek($keySize)
{
return openssl_random_pseudo_bytes($keySize / 8);
}
/**
* @param string $openSslName Cipher OpenSSL name to use for generating
* an initialization vector.
*
* @return string
*/
public function generateIv($openSslName)
{
return openssl_random_pseudo_bytes(
openssl_cipher_iv_length($openSslName)
);
}
}
|
