Method doDecompressData

src/Compression/CompressionCodecEncrypted.cpp:542–573

}

UInt32 CompressionCodecEncrypted::doDecompressData(const char * source, UInt32 source_size, char * dest, UInt32 uncompressed_size) const
{
    /// The key is needed for decrypting. That's why it is read at the beginning of process.
    UInt64 key_id = 0;
    const char * ciphertext_with_nonce = readVarUInt(key_id, source, source_size);

    /// Size of text should be decreased by key_size, because key_size bytes were not participating in encryption process.
    size_t keyid_size = ciphertext_with_nonce - source;
    String nonce;
    String key = Configuration::instance().getKey(encryption_method, key_id);

    /// try to read nonce from file (if it was set while encrypting)
    const char * ciphertext = readNonce(nonce, ciphertext_with_nonce);

    /// Size of text should be decreased by nonce_size, because nonce_size bytes were not participating in encryption process.
    UInt64 nonce_size = ciphertext - ciphertext_with_nonce;

    /// Count text size (nonce and key_id was read from source)
    size_t ciphertext_size = source_size - keyid_size - nonce_size;
    if (ciphertext_size != uncompressed_size + tag_size)
        throw Exception(ErrorCodes::LOGICAL_ERROR, "Can't decrypt data, uncompressed_size {} is wrong, expected {}",
                        uncompressed_size, ciphertext_size - tag_size);


    size_t out_len = decrypt({ciphertext, ciphertext_size}, dest, encryption_method, key, nonce);
    if (out_len != ciphertext_size - tag_size)
        throw Exception(ErrorCodes::LOGICAL_ERROR,
                        "Can't decrypt data, out length after decryption {} is wrong, expected {}",
                        out_len, ciphertext_size - tag_size);

    return static_cast<UInt32>(out_len);
}

}