Method doCompressData

src/Compression/CompressionCodecEncrypted.cpp:502–540

}

UInt32 CompressionCodecEncrypted::doCompressData(const char * source, UInt32 source_size, char * dest) const
{
    // Nonce, key and plaintext will be used to generate authentication tag
    // and message encryption key. AES-GCM-SIV authenticates the encoded additional data and plaintext.
    // For this purpose message_authentication_key is used.
    // Algorithm is completely deterministic, but does not leak any
    // information about the data block except for equivalence of
    // identical blocks (under the same key).

    const std::string_view plaintext = std::string_view(source, source_size);

    /// Get key and nonce for encryption
    UInt64 current_key_id = 0;
    String current_key;
    String nonce;
    Configuration::instance().getCurrentKeyAndNonce(encryption_method, current_key_id, current_key, nonce);

    /// Write current key id to support multiple keys.
    /// (key id in the beginning will help to decrypt data after changing current key)
    char* ciphertext_with_nonce = writeVarUInt(current_key_id, dest);
    size_t keyid_size = ciphertext_with_nonce - dest;

    /// write nonce in data. This will help to read data even after changing nonce in config
    /// If there were no nonce in data, one zero byte will be written
    char* ciphertext = writeNonce(nonce, ciphertext_with_nonce);
    UInt64 nonce_size = ciphertext - ciphertext_with_nonce;

    // The ciphertext and the authentication tag will be written directly in the dest buffer.
    size_t out_len = encrypt(plaintext, ciphertext, encryption_method, current_key, nonce);

    /// Length of encrypted text should be equal to text length plus tag_size (which was added by algorithm).
    if (out_len != source_size + tag_size)
        throw Exception(ErrorCodes::LOGICAL_ERROR,
                        "Can't encrypt data, length after encryption {} is wrong, expected {}",
                        out_len, source_size + tag_size);

    size_t out_size = out_len + keyid_size + nonce_size;
    return safe_cast<UInt32>(out_size);
}

UInt32 CompressionCodecEncrypted::doDecompressData(const char * source, UInt32 source_size, char * dest, UInt32 uncompressed_size) const
{