xlnt/source/detail/cryptography/xlsx_crypto_producer.cpp

// Copyright (c) 2014-2021 Thomas Fussell
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE
//
// @license: http://www.opensource.org/licenses/mit-license.php
// @author: see AUTHORS file

#include <xlnt/utils/exceptions.hpp>
#include <detail/constants.hpp>
#include <detail/cryptography/aes.hpp>
#include <detail/cryptography/base64.hpp>
#include <detail/cryptography/compound_document.hpp>
#include <detail/cryptography/encryption_info.hpp>
#include <detail/cryptography/value_traits.hpp>
#include <detail/cryptography/xlsx_crypto_producer.hpp>
#include <detail/external/include_libstudxml.hpp>
#include <detail/serialization/vector_streambuf.hpp>
#include <detail/serialization/xlsx_producer.hpp>
#include <detail/serialization/zstream.hpp>
#include <detail/unicode.hpp>

namespace {

using xlnt::detail::encryption_info;

encryption_info generate_encryption_info(const std::u16string & /*password*/)
{
    encryption_info result;

    result.is_agile = true;

    result.agile = encryption_info::agile_encryption_info();

    result.agile.key_data.block_size = 16;
    result.agile.key_data.cipher_algorithm = "AES";
    result.agile.key_data.cipher_chaining = "ChainingModeCBC";
    result.agile.key_data.hash_algorithm = "SHA512";
    result.agile.key_data.hash_size = 64;
    result.agile.key_data.key_bits = 256;
    result.agile.key_data.salt_size = 16;
    result.agile.key_data.salt_value =
        {
            {40, 183, 193, 64, 115, 97, 10, 177, 122, 50, 243, 123, 229, 145, 162, 247}};

    result.agile.data_integrity.hmac_key =
        {
            {90, 206, 203, 147, 102, 81, 82, 14, 118, 94, 168, 38, 200, 79, 13, 147, 60,
                123, 167, 220, 17, 165, 124, 188, 206, 74, 98, 33, 156, 63, 220, 152, 180, 201,
                167, 183, 141, 252, 182, 55, 90, 189, 187, 167, 230, 186, 61, 239, 80, 49, 54,
                208, 52, 133, 232, 187, 117, 136, 213, 48, 133, 15, 7, 126}};
    result.agile.data_integrity.hmac_value =
        {
            {49, 128, 174, 178, 161, 48, 1, 82, 241, 103, 72, 223, 103, 111, 204, 73,
                210, 70, 254, 43, 12, 134, 180, 201, 124, 153, 214, 115, 82, 184, 78, 2,
                166, 106, 69, 18, 173, 177, 40, 238, 243, 240, 3, 86, 145, 218, 223, 177,
                36, 34, 44, 159, 104, 163, 217, 42, 203, 135, 173, 14, 218, 172, 72, 224}};

    result.agile.key_encryptor.spin_count = 100000;
    result.agile.key_encryptor.block_size = 16;
    result.agile.key_encryptor.cipher_algorithm = "AES";
    result.agile.key_encryptor.cipher_chaining = "ChainingModeCBC";
    result.agile.key_encryptor.hash = xlnt::detail::hash_algorithm::sha512;
    result.agile.key_encryptor.hash_size = 64;
    result.agile.key_encryptor.key_bits = 256;
    result.agile.key_encryptor.salt_size = 16;
    result.agile.key_encryptor.salt_value =
        {
            {98, 169, 85, 224, 173, 253, 2, 52, 199, 108, 195, 73, 116, 112, 72, 165}};
    result.agile.key_encryptor.verifier_hash_input =
        {
            {179, 105, 118, 193, 217, 180, 248, 7, 174, 45, 186, 17, 202, 101, 178, 12}};
    result.agile.key_encryptor.verifier_hash_value =
        {
            {82, 190, 235, 102, 30, 33, 103, 191, 3, 160, 153, 30, 127, 117, 8, 195, 65,
                245, 77, 219, 85, 28, 206, 236, 55, 86, 243, 49, 104, 128, 243, 138, 227, 113,
                82, 88, 88, 73, 243, 108, 193, 11, 84, 162, 235, 189, 9, 137, 151, 97, 43,
                137, 197, 72, 164, 192, 65, 252, 253, 227, 236, 242, 252, 179}};
    result.agile.key_encryptor.encrypted_key_value =
        {
            {220, 6, 106, 218, 31, 210, 9, 75, 28, 154, 173, 232, 190, 109, 112, 203, 25,
                5, 45, 152, 75, 131, 122, 17, 166, 95, 117, 124, 121, 123, 32, 133}};

    return result;
}

void write_agile_encryption_info(
    const encryption_info &info,
    std::ostream &info_stream)
{
    const auto version_major = std::uint16_t(4);
    const auto version_minor = std::uint16_t(4);
    const auto encryption_flags = std::uint32_t(0x40);

    info_stream.write(reinterpret_cast<const char *>(&version_major), sizeof(std::uint16_t));
    info_stream.write(reinterpret_cast<const char *>(&version_minor), sizeof(std::uint16_t));
    info_stream.write(reinterpret_cast<const char *>(&encryption_flags), sizeof(std::uint32_t));

    static const auto &xmlns = xlnt::constants::ns("encryption");
    static const auto &xmlns_p = xlnt::constants::ns("encryption-password");

    xml::serializer serializer(info_stream, "EncryptionInfo");

    serializer.start_element(xmlns, "encryption");

    const auto key_data = info.agile.key_data;
    serializer.start_element(xmlns, "keyData");
    serializer.attribute("saltSize", key_data.salt_size);
    serializer.attribute("blockSize", key_data.block_size);
    serializer.attribute("keyBits", key_data.key_bits);
    serializer.attribute("hashSize", key_data.hash_size);
    serializer.attribute("cipherAlgorithm", key_data.cipher_algorithm);
    serializer.attribute("cipherChaining", key_data.cipher_chaining);
    serializer.attribute("hashAlgorithm", key_data.hash_algorithm);
    serializer.attribute("saltValue",
        xlnt::detail::encode_base64(key_data.salt_value));
    serializer.end_element(xmlns, "keyData");

    const auto data_integrity = info.agile.data_integrity;
    serializer.start_element(xmlns, "dataIntegrity");
    serializer.attribute("encryptedHmacKey",
        xlnt::detail::encode_base64(data_integrity.hmac_key));
    serializer.attribute("encryptedHmacValue",
        xlnt::detail::encode_base64(data_integrity.hmac_value));
    serializer.end_element(xmlns, "dataIntegrity");

    const auto key_encryptor = info.agile.key_encryptor;
    serializer.start_element(xmlns, "keyEncryptors");
    serializer.start_element(xmlns, "keyEncryptor");
    serializer.attribute("uri", "");
    serializer.start_element(xmlns_p, "encryptedKey");
    serializer.attribute("spinCount", key_encryptor.spin_count);
    serializer.attribute("saltSize", key_encryptor.salt_size);
    serializer.attribute("blockSize", key_encryptor.block_size);
    serializer.attribute("keyBits", key_encryptor.key_bits);
    serializer.attribute("hashSize", key_encryptor.hash_size);
    serializer.attribute("cipherAlgorithm", key_encryptor.cipher_algorithm);
    serializer.attribute("cipherChaining", key_encryptor.cipher_chaining);
    serializer.attribute("hashAlgorithm", key_encryptor.hash);
    serializer.attribute("saltValue",
        xlnt::detail::encode_base64(key_encryptor.salt_value));
    serializer.attribute("encryptedVerifierHashInput",
        xlnt::detail::encode_base64(key_encryptor.verifier_hash_input));
    serializer.attribute("encryptedVerifierHashValue",
        xlnt::detail::encode_base64(key_encryptor.verifier_hash_value));
    serializer.attribute("encryptedKeyValue",
        xlnt::detail::encode_base64(key_encryptor.encrypted_key_value));
    serializer.end_element(xmlns_p, "encryptedKey");
    serializer.end_element(xmlns, "keyEncryptor");
    serializer.end_element(xmlns, "keyEncryptors");

    serializer.end_element(xmlns, "encryption");
}

void write_standard_encryption_info(const encryption_info &info, std::ostream &info_stream)
{
    auto result = std::vector<std::uint8_t>();
    auto writer = xlnt::detail::binary_writer<std::uint8_t>(result);

    const auto version_major = std::uint16_t(4);
    const auto version_minor = std::uint16_t(2);
    const auto encryption_flags = std::uint32_t(0x10 & 0x20);

    writer.write(version_major);
    writer.write(version_minor);
    writer.write(encryption_flags);

    const auto header_length = std::uint32_t(32); // calculate this!

    writer.write(header_length);
    writer.write(std::uint32_t(0)); // skip_flags
    writer.write(std::uint32_t(0)); // size_extra
    writer.write(std::uint32_t(0x0000660E));
    writer.write(std::uint32_t(0x00008004));
    writer.write(std::uint32_t(info.standard.key_bits));
    writer.write(std::uint32_t(0x00000018));
    writer.write(std::uint32_t(0));
    writer.write(std::uint32_t(0));

    const auto provider = std::u16string(u"Microsoft Enhanced RSA and AES Cryptographic Provider");
    writer.append(xlnt::detail::string_to_bytes(provider));

    writer.write(std::uint32_t(info.standard.salt.size()));
    writer.append(info.standard.salt);

    writer.append(info.standard.encrypted_verifier);

    writer.write(std::uint32_t(20));
    writer.append(info.standard.encrypted_verifier_hash);

    info_stream.write(reinterpret_cast<char *>(result.data()),
        static_cast<std::streamsize>(result.size()));
}

void encrypt_xlsx_agile(
    const encryption_info &info,
    const std::vector<std::uint8_t> &plaintext,
    std::ostream &ciphertext_stream)
{
    const auto length = static_cast<std::uint64_t>(plaintext.size());
    ciphertext_stream.write(reinterpret_cast<const char *>(&length), sizeof(std::uint64_t));

    auto key = info.calculate_key();

    auto salt_size = info.agile.key_data.salt_size;
    auto salt_with_block_key = info.agile.key_data.salt_value;
    salt_with_block_key.resize(salt_size + sizeof(std::uint32_t), 0);
    auto &segment_index = *reinterpret_cast<std::uint32_t *>(salt_with_block_key.data() + salt_size);

    auto segment = std::vector<std::uint8_t>(4096, 0);

    for (auto i = std::size_t(0); i < length; i += 4096)
    {
        auto iv = hash(info.agile.key_encryptor.hash, salt_with_block_key);
        iv.resize(16);

        auto start = plaintext.begin() + static_cast<std::ptrdiff_t>(i);
        auto bytes = std::min(std::size_t(length - i), std::size_t(4096));
        std::copy(start, start + static_cast<std::ptrdiff_t>(bytes), segment.begin());
        auto encrypted_segment = xlnt::detail::aes_cbc_encrypt(segment, key, iv);
        ciphertext_stream.write(reinterpret_cast<char *>(encrypted_segment.data()),
            static_cast<std::streamsize>(bytes));

        ++segment_index;
    }
}

void encrypt_xlsx_standard(
    const encryption_info &info,
    const std::vector<std::uint8_t> &plaintext,
    std::ostream &ciphertext_stream)
{
    const auto length = static_cast<std::uint64_t>(plaintext.size());
    ciphertext_stream.write(reinterpret_cast<const char *>(&length), sizeof(std::uint64_t));

    auto key = info.calculate_key();
    auto segment = std::vector<std::uint8_t>(4096, 0);

    for (auto i = std::size_t(0); i < length; ++i)
    {
        auto start = plaintext.begin() + static_cast<std::ptrdiff_t>(i);
        auto bytes = std::min(std::size_t(length - i), std::size_t(4096));
        std::copy(start, start + static_cast<std::ptrdiff_t>(bytes), segment.begin());
        auto encrypted_segment = xlnt::detail::aes_ecb_encrypt(segment, key);
        ciphertext_stream.write(reinterpret_cast<char *>(encrypted_segment.data()),
            static_cast<std::streamsize>(bytes));
    }
}

std::vector<std::uint8_t> encrypt_xlsx(
    const std::vector<std::uint8_t> &plaintext,
    const std::u16string &password)
{
    auto encryption_info = generate_encryption_info(password);
    encryption_info.password = u"secret";

    auto ciphertext = std::vector<std::uint8_t>();

    xlnt::detail::vector_ostreambuf buffer(ciphertext);
    std::ostream stream(&buffer);
    xlnt::detail::compound_document document(stream);

    if (encryption_info.is_agile)
    {
        write_agile_encryption_info(encryption_info,
            document.open_write_stream("/EncryptionInfo"));
        encrypt_xlsx_agile(encryption_info, plaintext,
            document.open_write_stream("/EncryptedPackage"));
    }
    else
    {
        write_standard_encryption_info(encryption_info,
            document.open_write_stream("/EncryptionInfo"));
        encrypt_xlsx_standard(encryption_info, plaintext,
            document.open_write_stream("/EncryptedPackage"));
    }

    return ciphertext;
}

} // namespace

namespace xlnt {
namespace detail {

std::vector<std::uint8_t> XLNT_API encrypt_xlsx(
    const std::vector<std::uint8_t> &plaintext,
    const std::string &password)
{
    return ::encrypt_xlsx(plaintext, utf8_to_utf16(password));
}

void xlsx_producer::write(std::ostream &destination, const std::string &password)
{
    std::vector<std::uint8_t> plaintext;
    vector_ostreambuf plaintext_buffer(plaintext);
    std::ostream decrypted_stream(&plaintext_buffer);
    write(decrypted_stream);
    archive_.reset();

    const auto ciphertext = ::encrypt_xlsx(plaintext, utf8_to_utf16(password));
    vector_istreambuf encrypted_buffer(ciphertext);

    destination << &encrypted_buffer;
}

} // namespace detail
} // namespace xlnt