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<?php
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namespace Aws\Crypto\Cipher;
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use Aws\Exception\CryptoException;
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trait CipherBuilderTrait
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{
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    /**
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     * Returns an identifier recognizable by `openssl_*` functions, such as
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     * `aes-256-cbc` or `aes-128-ctr`.
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     *
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     * @param string $cipherName Name of the cipher being used for encrypting
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     *                           or decrypting.
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     * @param int $keySize Size of the encryption key, in bits, that will be
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     *                     used.
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     *
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     * @return string
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     */
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    protected function getCipherOpenSslName($cipherName, $keySize)
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    {
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        return "aes-{$keySize}-{$cipherName}";
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    }
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    /**
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     * Constructs a CipherMethod for the given name, initialized with the other
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     * data passed for use in encrypting or decrypting.
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     *
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     * @param string $cipherName Name of the cipher to generate for encrypting.
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     * @param string $iv Base Initialization Vector for the cipher.
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     * @param int $keySize Size of the encryption key, in bits, that will be
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     *                     used.
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     *
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     * @return CipherMethod
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     *
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     * @internal
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     */
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    protected function buildCipherMethod($cipherName, $iv, $keySize)
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    {
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        switch ($cipherName) {
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            case 'cbc':
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                return new Cbc(
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                    $iv,
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                    $keySize
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                );
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            default:
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                return null;
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        }
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    }
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    /**
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     * Performs a reverse lookup to get the openssl_* cipher name from the
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     * AESName passed in from the MetadataEnvelope.
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     *
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     * @param $aesName
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     *
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     * @return string
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     *
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     * @internal
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     */
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    protected function getCipherFromAesName($aesName)
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    {
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        switch ($aesName) {
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            case 'AES/GCM/NoPadding':
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                return 'gcm';
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            case 'AES/CBC/PKCS5Padding':
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                return 'cbc';
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            default:
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                throw new CryptoException('Unrecognized or unsupported'
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                    . ' AESName for reverse lookup.');
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        }
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    }
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}