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xlnt/source/detail/xlsx_crypto.cpp

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// Copyright (c) 2014-2016 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, WRISING 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 <array>
#include <xlnt/utils/exceptions.hpp>
#include <xlnt/workbook/workbook.hpp>
#include <detail/constants.hpp>
#include <detail/include_cryptopp.hpp>
#include <detail/include_libstudxml.hpp>
#include <detail/pole.hpp>
#include <detail/vector_streambuf.hpp>
#include <detail/xlsx_consumer.hpp>
#include <detail/xlsx_producer.hpp>
namespace xlnt {
namespace detail {
enum class hash_algorithm
{
sha1,
sha256,
sha384,
sha512,
md5,
md4,
md2,
ripemd128,
ripemd160,
whirlpool
};
} // namespace detail
} // namespace xlnt
namespace xml {
template <>
struct value_traits<xlnt::detail::hash_algorithm>
{
static xlnt::detail::hash_algorithm parse(std::string hash_algorithm_string, const parser &)
{
if (hash_algorithm_string == "SHA1")
return xlnt::detail::hash_algorithm::sha1;
else if (hash_algorithm_string == "SHA256")
return xlnt::detail::hash_algorithm::sha256;
else if (hash_algorithm_string == "SHA384")
return xlnt::detail::hash_algorithm::sha384;
else if (hash_algorithm_string == "SHA512")
return xlnt::detail::hash_algorithm::sha512;
else if (hash_algorithm_string == "MD5")
return xlnt::detail::hash_algorithm::md5;
else if (hash_algorithm_string == "MD4")
return xlnt::detail::hash_algorithm::md4;
else if (hash_algorithm_string == "MD2")
return xlnt::detail::hash_algorithm::md2;
else if (hash_algorithm_string == "Ripemd128")
return xlnt::detail::hash_algorithm::ripemd128;
else if (hash_algorithm_string == "Ripemd160")
return xlnt::detail::hash_algorithm::ripemd160;
else if (hash_algorithm_string == "Whirlpool")
return xlnt::detail::hash_algorithm::whirlpool;
throw xlnt::exception(hash_algorithm_string);
}
static std::string serialize(xlnt::detail::hash_algorithm algorithm, const serializer &)
{
switch (algorithm)
{
case xlnt::detail::hash_algorithm::sha1:
return "SHA1";
case xlnt::detail::hash_algorithm::sha256:
return "SHA256";
case xlnt::detail::hash_algorithm::sha384:
return "SHA384";
case xlnt::detail::hash_algorithm::sha512:
return "SHA512";
case xlnt::detail::hash_algorithm::md5:
return "MD5";
case xlnt::detail::hash_algorithm::md4:
return "MD4";
case xlnt::detail::hash_algorithm::md2:
return "MD2";
case xlnt::detail::hash_algorithm::ripemd128:
return "Ripemd128";
case xlnt::detail::hash_algorithm::ripemd160:
return "Ripemd160";
case xlnt::detail::hash_algorithm::whirlpool:
return "Whirlpool";
}
}
}; // struct value_traits<>
} // namespace xml
namespace xlnt {
namespace detail {
struct crypto_helper
{
static const std::size_t segment_length;
enum class cipher_algorithm
{
aes,
rc2,
rc4,
des,
desx,
triple_des,
triple_des_112
};
enum class cipher_chaining
{
ecb, // electronic code book
cbc, // cipher block chaining
cfb // cipher feedback chaining
};
enum class cipher_direction
{
encryption,
decryption
};
static std::vector<std::uint8_t> aes(const std::vector<std::uint8_t> &key, const std::vector<std::uint8_t> &iv,
const std::vector<std::uint8_t> &source, cipher_chaining chaining, cipher_direction direction)
{
std::vector<std::uint8_t> destination(source.size(), 0);
if (direction == cipher_direction::encryption && chaining == cipher_chaining::cbc)
{
CryptoPP::AES::Encryption aesEncryption(key.data(), key.size());
CryptoPP::CBC_Mode_ExternalCipher::Encryption cbcEncryption(aesEncryption, iv.data());
CryptoPP::ArraySource as(
source.data(), source.size(), true, new CryptoPP::StreamTransformationFilter(cbcEncryption,
new CryptoPP::ArraySink(destination.data(), destination.size()),
CryptoPP::BlockPaddingSchemeDef::NO_PADDING));
}
else if (direction == cipher_direction::decryption && chaining == cipher_chaining::cbc)
{
CryptoPP::AES::Decryption aesDecryption(key.data(), key.size());
CryptoPP::CBC_Mode_ExternalCipher::Decryption cbcDecryption(aesDecryption, iv.data());
CryptoPP::ArraySource as(
source.data(), source.size(), true, new CryptoPP::StreamTransformationFilter(cbcDecryption,
new CryptoPP::ArraySink(destination.data(), destination.size()),
CryptoPP::BlockPaddingSchemeDef::NO_PADDING));
}
else if (direction == cipher_direction::encryption && chaining == cipher_chaining::ecb)
{
CryptoPP::AES::Encryption aesEncryption(key.data(), key.size());
CryptoPP::ECB_Mode_ExternalCipher::Encryption cbcEncryption(aesEncryption, iv.data());
CryptoPP::ArraySource as(
source.data(), source.size(), true, new CryptoPP::StreamTransformationFilter(cbcEncryption,
new CryptoPP::ArraySink(destination.data(), destination.size()),
CryptoPP::BlockPaddingSchemeDef::NO_PADDING));
}
else if (direction == cipher_direction::decryption && chaining == cipher_chaining::ecb)
{
CryptoPP::AES::Decryption aesDecryption(key.data(), key.size());
CryptoPP::ECB_Mode_ExternalCipher::Decryption cbcDecryption(aesDecryption, iv.data());
CryptoPP::ArraySource as(
source.data(), source.size(), true, new CryptoPP::StreamTransformationFilter(cbcDecryption,
new CryptoPP::ArraySink(destination.data(), destination.size()),
CryptoPP::BlockPaddingSchemeDef::NO_PADDING));
}
return destination;
}
static std::vector<std::uint8_t> decode_base64(const std::string &encoded)
{
CryptoPP::Base64Decoder decoder;
decoder.Put(reinterpret_cast<const std::uint8_t *>(encoded.data()), encoded.size());
decoder.MessageEnd();
std::vector<std::uint8_t> decoded(decoder.MaxRetrievable(), 0);
decoder.Get(decoded.data(), decoded.size());
return decoded;
}
static std::string encode_base64(const std::vector<std::uint8_t> &decoded)
{
CryptoPP::Base64Decoder encoder;
encoder.Put(reinterpret_cast<const std::uint8_t *>(decoded.data()), decoded.size());
encoder.MessageEnd();
std::vector<std::uint8_t> encoded(encoder.MaxRetrievable(), 0);
encoder.Get(encoded.data(), encoded.size());
return std::string(encoded.begin(), encoded.end());
}
static std::vector<std::uint8_t> hash(hash_algorithm algorithm, const std::vector<std::uint8_t> &input)
{
std::vector<std::uint8_t> digest;
if (algorithm == hash_algorithm::sha512)
{
CryptoPP::SHA512 sha512;
digest.resize(CryptoPP::SHA512::DIGESTSIZE, 0);
sha512.CalculateDigest(digest.data(), input.data(), input.size());
}
else if (algorithm == hash_algorithm::sha1)
{
CryptoPP::SHA1 sha1;
digest.resize(CryptoPP::SHA1::DIGESTSIZE, 0);
sha1.CalculateDigest(digest.data(), input.data(), input.size());
}
return digest;
}
static std::vector<std::uint8_t> file(POLE::Storage &storage, const std::string &name)
{
POLE::Stream stream(&storage, name.c_str());
if (stream.fail()) return {};
std::vector<std::uint8_t> bytes(stream.size(), 0);
stream.read(bytes.data(), static_cast<unsigned long>(bytes.size()));
return bytes;
}
template <typename T>
static auto read_int(std::size_t &index, const std::vector<std::uint8_t> &raw_data)
{
auto result = *reinterpret_cast<const T *>(&raw_data[index]);
index += sizeof(T);
return result;
}
struct standard_encryption_info
{
const std::size_t spin_count = 50000;
std::size_t block_size;
std::size_t key_bits;
std::size_t key_bytes;
std::size_t hash_size;
cipher_algorithm cipher;
cipher_chaining chaining;
const hash_algorithm hash = hash_algorithm::sha1;
std::vector<std::uint8_t> salt_value;
std::vector<std::uint8_t> verifier_hash_input;
std::vector<std::uint8_t> verifier_hash_value;
std::vector<std::uint8_t> encrypted_key_value;
};
static std::vector<std::uint8_t> decrypt_xlsx_standard(const std::vector<std::uint8_t> &encryption_info,
const std::string &password, const std::vector<std::uint8_t> &encrypted_package)
{
std::size_t offset = 0;
standard_encryption_info info;
auto header_length = read_int<std::uint32_t>(offset, encryption_info);
auto index_at_start = offset;
/*auto skip_flags = */ read_int<std::uint32_t>(offset, encryption_info);
/*auto size_extra = */ read_int<std::uint32_t>(offset, encryption_info);
auto alg_id = read_int<std::uint32_t>(offset, encryption_info);
if (alg_id == 0 || alg_id == 0x0000660E || alg_id == 0x0000660F || alg_id == 0x00006610)
{
info.cipher = cipher_algorithm::aes;
}
else
{
throw xlnt::exception("invalid cipher algorithm");
}
auto alg_id_hash = read_int<std::uint32_t>(offset, encryption_info);
if (alg_id_hash != 0x00008004 && alg_id_hash == 0)
{
throw xlnt::exception("invalid hash algorithm");
}
info.key_bits = read_int<std::uint32_t>(offset, encryption_info);
info.key_bytes = info.key_bits / 8;
auto provider_type = read_int<std::uint32_t>(offset, encryption_info);
if (provider_type != 0 && provider_type != 0x00000018)
{
throw xlnt::exception("invalid provider type");
}
read_int<std::uint32_t>(offset, encryption_info); // reserved 1
if (read_int<std::uint32_t>(offset, encryption_info) != 0) // reserved 2
{
throw xlnt::exception("invalid header");
}
const auto csp_name_length = header_length - (offset - index_at_start);
std::vector<std::uint16_t> csp_name_wide(
reinterpret_cast<const std::uint16_t *>(&*(encryption_info.begin() + static_cast<std::ptrdiff_t>(offset))),
reinterpret_cast<const std::uint16_t *>(
&*(encryption_info.begin() + static_cast<std::ptrdiff_t>(offset + csp_name_length))));
std::string csp_name(csp_name_wide.begin(), csp_name_wide.end() - 1); // without trailing null
if (csp_name != "Microsoft Enhanced RSA and AES Cryptographic Provider (Prototype)"
&& csp_name != "Microsoft Enhanced RSA and AES Cryptographic Provider")
{
throw xlnt::exception("invalid cryptographic provider");
}
offset += csp_name_length;
const auto salt_size = read_int<std::uint32_t>(offset, encryption_info);
std::vector<std::uint8_t> salt(encryption_info.begin() + static_cast<std::ptrdiff_t>(offset),
encryption_info.begin() + static_cast<std::ptrdiff_t>(offset + salt_size));
offset += salt_size;
static const auto verifier_size = std::size_t(16);
std::vector<std::uint8_t> verifier_hash_input(encryption_info.begin() + static_cast<std::ptrdiff_t>(offset),
encryption_info.begin() + static_cast<std::ptrdiff_t>(offset + verifier_size));
offset += verifier_size;
const auto verifier_hash_size = read_int<std::uint32_t>(offset, encryption_info);
std::vector<std::uint8_t> verifier_hash_value(encryption_info.begin() + static_cast<std::ptrdiff_t>(offset),
encryption_info.begin() + static_cast<std::ptrdiff_t>(offset + verifier_hash_size));
offset += verifier_hash_size;
// begin key generation algorithm
// H_0 = H(salt + password)
auto salt_plus_password = salt;
std::vector<std::uint16_t> password_wide(password.begin(), password.end());
std::for_each(password_wide.begin(), password_wide.end(), [&salt_plus_password](std::uint16_t c) {
salt_plus_password.insert(salt_plus_password.end(), reinterpret_cast<char *>(&c),
reinterpret_cast<char *>(&c) + sizeof(std::uint16_t));
});
std::vector<std::uint8_t> h_0 = hash(info.hash, salt_plus_password);
// H_n = H(iterator + H_n-1)
std::vector<std::uint8_t> iterator_plus_h_n(4, 0);
iterator_plus_h_n.insert(iterator_plus_h_n.end(), h_0.begin(), h_0.end());
std::uint32_t &iterator = *reinterpret_cast<std::uint32_t *>(iterator_plus_h_n.data());
std::vector<std::uint8_t> h_n;
for (iterator = 0; iterator < info.spin_count; ++iterator)
{
h_n = hash(info.hash, iterator_plus_h_n);
std::copy(h_n.begin(), h_n.end(), iterator_plus_h_n.begin() + 4);
}
// H_final = H(H_n + block)
auto h_n_plus_block = h_n;
const std::uint32_t block_number = 0;
h_n_plus_block.insert(h_n_plus_block.end(), reinterpret_cast<const std::uint8_t *>(&block_number),
reinterpret_cast<const std::uint8_t *>(&block_number) + sizeof(std::uint32_t));
auto h_final = hash(info.hash, h_n_plus_block);
// X1 = H(h_final ^ 0x36)
std::vector<std::uint8_t> buffer(64, 0x36);
for (std::size_t i = 0; i < h_final.size(); ++i)
{
buffer[i] = static_cast<std::uint8_t>(0x36 ^ h_final[i]);
}
auto X1 = hash(info.hash, buffer);
// X2 = H(h_final ^ 0x5C)
buffer.assign(64, 0x5c);
for (std::size_t i = 0; i < h_final.size(); ++i)
{
buffer[i] = static_cast<std::uint8_t>(0x5c ^ h_final[i]);
}
auto X2 = hash(info.hash, buffer);
auto X3 = X1;
X3.insert(X3.end(), X2.begin(), X2.end());
auto key_derived =
std::vector<std::uint8_t>(X3.begin(), X3.begin() + static_cast<std::ptrdiff_t>(info.key_bytes));
// todo: verify here
std::size_t package_offset = 0;
auto decrypted_size = static_cast<std::size_t>(read_int<std::uint64_t>(package_offset, encrypted_package));
auto decrypted =
aes(key_derived, {}, std::vector<std::uint8_t>(encrypted_package.begin() + 8, encrypted_package.end()),
cipher_chaining::ecb, cipher_direction::decryption);
decrypted.resize(decrypted_size);
return decrypted;
}
struct agile_encryption_info
{
// key data
struct
{
std::size_t salt_size;
std::size_t block_size;
std::size_t key_bits;
std::size_t hash_size;
std::string cipher_algorithm;
std::string cipher_chaining;
std::string hash_algorithm;
std::vector<std::uint8_t> salt_value;
} key_data;
struct
{
std::vector<std::uint8_t> hmac_key;
std::vector<std::uint8_t> hmac_value;
} data_integrity;
struct
{
std::size_t spin_count;
std::size_t salt_size;
std::size_t block_size;
std::size_t key_bits;
std::size_t hash_size;
std::string cipher_algorithm;
std::string cipher_chaining;
hash_algorithm hash;
std::vector<std::uint8_t> salt_value;
std::vector<std::uint8_t> verifier_hash_input;
std::vector<std::uint8_t> verifier_hash_value;
std::vector<std::uint8_t> encrypted_key_value;
} key_encryptor;
};
static agile_encryption_info generate_agile_encryption_info(const std::string &password)
{
agile_encryption_info result;
result.key_data.salt_value.assign(password.begin(), password.end());
return result;
}
static std::vector<std::uint8_t> write_agile_encryption_info(const std::string &password)
{
static const auto &xmlns = xlnt::constants::namespace_("encryption");
static const auto &xmlns_p = xlnt::constants::namespace_("encryption-password");
std::vector<std::uint8_t> encryption_info;
xlnt::detail::vector_ostreambuf encryption_info_buffer(encryption_info);
std::ostream encryption_info_stream(&encryption_info_buffer);
xml::serializer serializer(encryption_info_stream, "EncryptionInfo");
agile_encryption_info result = generate_agile_encryption_info(password);
serializer.start_element(xmlns, "encryption");
serializer.start_element(xmlns, "keyData");
serializer.attribute("saltSize", result.key_data.salt_size);
serializer.attribute("blockSize", result.key_data.block_size);
serializer.attribute("keyBits", result.key_data.key_bits);
serializer.attribute("hashSize", result.key_data.hash_size);
serializer.attribute("cipherAlgorithm", result.key_data.cipher_algorithm);
serializer.attribute("cipherChaining", result.key_data.cipher_chaining);
serializer.attribute("hashAlgorithm", result.key_data.hash_algorithm);
serializer.attribute("saltValue", encode_base64(result.key_data.salt_value));
serializer.end_element(xmlns, "keyData");
serializer.start_element(xmlns, "dataIntegrity");
serializer.attribute("encryptedHmacKey", encode_base64(result.data_integrity.hmac_key));
serializer.attribute("encryptedHmacValue", encode_base64(result.data_integrity.hmac_value));
serializer.end_element(xmlns, "dataIntegrity");
serializer.start_element(xmlns, "keyEncryptors");
serializer.start_element(xmlns, "keyEncryptor");
serializer.attribute("uri", "");
serializer.start_element(xmlns_p, "encryptedKey");
serializer.attribute("spinCount", result.key_encryptor.spin_count);
serializer.attribute("saltSize", result.key_encryptor.salt_size);
serializer.attribute("blockSize", result.key_encryptor.block_size);
serializer.attribute("keyBits", result.key_encryptor.key_bits);
serializer.attribute("hashSize", result.key_encryptor.hash_size);
serializer.attribute("cipherAlgorithm", result.key_encryptor.cipher_algorithm);
serializer.attribute("cipherChaining", result.key_encryptor.cipher_chaining);
serializer.attribute("hashAlgorithm", result.key_encryptor.hash);
serializer.attribute("saltValue", encode_base64(result.key_encryptor.salt_value));
serializer.attribute("encryptedVerifierHashInput", encode_base64(result.key_encryptor.verifier_hash_input));
serializer.attribute("encryptedVerifierHashValue", encode_base64(result.key_encryptor.verifier_hash_value));
serializer.attribute("encryptedKeyValue", encode_base64(result.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");
return encryption_info;
}
static std::vector<std::uint8_t> decrypt_xlsx_agile(const std::vector<std::uint8_t> &encryption_info,
const std::string &password, const std::vector<std::uint8_t> &encrypted_package)
{
static const auto &xmlns = xlnt::constants::namespace_("encryption");
static const auto &xmlns_p = xlnt::constants::namespace_("encryption-password");
// static const auto &xmlns_c = xlnt::constants::namespace_("encryption-certificate");
agile_encryption_info result;
xml::parser parser(encryption_info.data(), encryption_info.size(), "EncryptionInfo");
parser.next_expect(xml::parser::event_type::start_element, xmlns, "encryption");
parser.next_expect(xml::parser::event_type::start_element, xmlns, "keyData");
result.key_data.salt_size = parser.attribute<std::size_t>("saltSize");
result.key_data.block_size = parser.attribute<std::size_t>("blockSize");
result.key_data.key_bits = parser.attribute<std::size_t>("keyBits");
result.key_data.hash_size = parser.attribute<std::size_t>("hashSize");
result.key_data.cipher_algorithm = parser.attribute("cipherAlgorithm");
result.key_data.cipher_chaining = parser.attribute("cipherChaining");
result.key_data.hash_algorithm = parser.attribute("hashAlgorithm");
result.key_data.salt_value = decode_base64(parser.attribute("saltValue"));
parser.next_expect(xml::parser::event_type::end_element, xmlns, "keyData");
parser.next_expect(xml::parser::event_type::start_element, xmlns, "dataIntegrity");
result.data_integrity.hmac_key = decode_base64(parser.attribute("encryptedHmacKey"));
result.data_integrity.hmac_value = decode_base64(parser.attribute("encryptedHmacValue"));
parser.next_expect(xml::parser::event_type::end_element, xmlns, "dataIntegrity");
parser.next_expect(xml::parser::event_type::start_element, xmlns, "keyEncryptors");
parser.next_expect(xml::parser::event_type::start_element, xmlns, "keyEncryptor");
parser.attribute("uri");
bool any_password_key = false;
while (parser.peek() != xml::parser::event_type::end_element)
{
parser.next_expect(xml::parser::event_type::start_element);
if (parser.namespace_() == xmlns_p && parser.name() == "encryptedKey")
{
any_password_key = true;
result.key_encryptor.spin_count = parser.attribute<std::size_t>("spinCount");
result.key_encryptor.salt_size = parser.attribute<std::size_t>("saltSize");
result.key_encryptor.block_size = parser.attribute<std::size_t>("blockSize");
result.key_encryptor.key_bits = parser.attribute<std::size_t>("keyBits");
result.key_encryptor.hash_size = parser.attribute<std::size_t>("hashSize");
result.key_encryptor.cipher_algorithm = parser.attribute("cipherAlgorithm");
result.key_encryptor.cipher_chaining = parser.attribute("cipherChaining");
auto hash_algorithm_string = parser.attribute("hashAlgorithm");
if (hash_algorithm_string == "SHA512")
{
result.key_encryptor.hash = hash_algorithm::sha512;
}
else if (hash_algorithm_string == "SHA1")
{
result.key_encryptor.hash = hash_algorithm::sha1;
}
else if (hash_algorithm_string == "SHA256")
{
result.key_encryptor.hash = hash_algorithm::sha256;
}
else if (hash_algorithm_string == "SHA384")
{
result.key_encryptor.hash = hash_algorithm::sha384;
}
result.key_encryptor.salt_value = decode_base64(parser.attribute("saltValue"));
result.key_encryptor.verifier_hash_input =
decode_base64(parser.attribute("encryptedVerifierHashInput"));
result.key_encryptor.verifier_hash_value =
decode_base64(parser.attribute("encryptedVerifierHashValue"));
result.key_encryptor.encrypted_key_value = decode_base64(parser.attribute("encryptedKeyValue"));
}
else
{
throw xlnt::unsupported("other encryption key types not supported");
}
parser.next_expect(xml::parser::event_type::end_element);
}
if (!any_password_key)
{
throw "no password key in keyEncryptors";
}
parser.next_expect(xml::parser::event_type::end_element, xmlns, "keyEncryptor");
parser.next_expect(xml::parser::event_type::end_element, xmlns, "keyEncryptors");
parser.next_expect(xml::parser::event_type::end_element, xmlns, "encryption");
// begin key generation algorithm
// H_0 = H(salt + password)
auto salt_plus_password = result.key_encryptor.salt_value;
std::vector<std::uint16_t> password_wide(password.begin(), password.end());
std::for_each(password_wide.begin(), password_wide.end(), [&salt_plus_password](std::uint16_t c) {
salt_plus_password.insert(salt_plus_password.end(), reinterpret_cast<char *>(&c),
reinterpret_cast<char *>(&c) + sizeof(std::uint16_t));
});
auto h_0 = hash(result.key_encryptor.hash, salt_plus_password);
// H_n = H(iterator + H_n-1)
std::vector<std::uint8_t> iterator_plus_h_n(4, 0);
iterator_plus_h_n.insert(iterator_plus_h_n.end(), h_0.begin(), h_0.end());
std::uint32_t &iterator = *reinterpret_cast<std::uint32_t *>(iterator_plus_h_n.data());
std::vector<std::uint8_t> h_n;
for (iterator = 0; iterator < result.key_encryptor.spin_count; ++iterator)
{
h_n = hash(result.key_encryptor.hash, iterator_plus_h_n);
std::copy(h_n.begin(), h_n.end(), iterator_plus_h_n.begin() + 4);
}
static const std::size_t block_size = 8;
auto calculate_block = [&result](const std::vector<std::uint8_t> &raw_key,
const std::array<std::uint8_t, block_size> &block, const std::vector<std::uint8_t> &encrypted) {
auto combined = raw_key;
combined.insert(combined.end(), block.begin(), block.end());
auto key = hash(result.key_encryptor.hash, combined);
key.resize(result.key_encryptor.key_bits / 8);
return aes(
key, result.key_encryptor.salt_value, encrypted, cipher_chaining::cbc, cipher_direction::decryption);
};
const std::array<std::uint8_t, block_size> input_block_key = {{0xfe, 0xa7, 0xd2, 0x76, 0x3b, 0x4b, 0x9e, 0x79}};
auto hash_input = calculate_block(h_n, input_block_key, result.key_encryptor.verifier_hash_input);
auto calculated_verifier = hash(result.key_encryptor.hash, hash_input);
const std::array<std::uint8_t, block_size> verifier_block_key = {
{0xd7, 0xaa, 0x0f, 0x6d, 0x30, 0x61, 0x34, 0x4e}};
auto expected_verifier = calculate_block(h_n, verifier_block_key, result.key_encryptor.verifier_hash_value);
expected_verifier.resize(calculated_verifier.size());
if (calculated_verifier.size() != expected_verifier.size()
|| std::mismatch(calculated_verifier.begin(), calculated_verifier.end(), expected_verifier.begin(),
expected_verifier.end())
!= std::make_pair(calculated_verifier.end(), expected_verifier.end()))
{
throw xlnt::exception("bad password");
}
const std::array<std::uint8_t, block_size> key_value_block_key = {
{0x14, 0x6e, 0x0b, 0xe7, 0xab, 0xac, 0xd0, 0xd6}};
auto key = calculate_block(h_n, key_value_block_key, result.key_encryptor.encrypted_key_value);
auto salt_size = result.key_data.salt_size;
auto salt_with_block_key = result.key_data.salt_value;
salt_with_block_key.resize(salt_size + sizeof(std::uint32_t), 0);
auto &segment = *reinterpret_cast<std::uint32_t *>(salt_with_block_key.data() + salt_size);
auto total_size = static_cast<std::size_t>(*reinterpret_cast<const std::uint64_t *>(encrypted_package.data()));
std::vector<std::uint8_t> encrypted_segment(segment_length, 0);
std::vector<std::uint8_t> decrypted_package;
decrypted_package.reserve(encrypted_package.size() - 8);
for (std::size_t i = 8; i < encrypted_package.size(); i += segment_length)
{
auto iv = hash(result.key_encryptor.hash, salt_with_block_key);
iv.resize(16);
auto segment_begin = encrypted_package.begin() + static_cast<std::ptrdiff_t>(i);
auto current_segment_length = std::min(segment_length, encrypted_package.size() - i);
auto segment_end = encrypted_package.begin() + static_cast<std::ptrdiff_t>(i + current_segment_length);
encrypted_segment.assign(segment_begin, segment_end);
auto decrypted_segment =
aes(key, iv, encrypted_segment, cipher_chaining::cbc, cipher_direction::decryption);
decrypted_segment.resize(current_segment_length);
decrypted_package.insert(decrypted_package.end(), decrypted_segment.begin(), decrypted_segment.end());
++segment;
}
decrypted_package.resize(total_size);
return decrypted_package;
}
static std::vector<std::uint8_t> decrypt_xlsx(const std::vector<std::uint8_t> &bytes, const std::string &password)
{
if (bytes.empty())
{
throw xlnt::exception("empty file");
}
std::vector<char> as_chars(bytes.begin(), bytes.end());
POLE::Storage storage(as_chars.data(), static_cast<unsigned long>(bytes.size()));
if (!storage.open())
{
throw xlnt::exception("not an ole compound file");
}
auto encrypted_package = file(storage, "EncryptedPackage");
auto encryption_info = file(storage, "EncryptionInfo");
std::size_t index = 0;
auto version_major = read_int<std::uint16_t>(index, encryption_info);
auto version_minor = read_int<std::uint16_t>(index, encryption_info);
auto encryption_flags = read_int<std::uint32_t>(index, encryption_info);
// get rid of header
encryption_info.erase(encryption_info.begin(), encryption_info.begin() + static_cast<std::ptrdiff_t>(index));
// version 4.4 is agile
if (version_major == 4 && version_minor == 4)
{
if (encryption_flags != 0x40)
{
throw xlnt::exception("bad header");
}
return decrypt_xlsx_agile(encryption_info, password, encrypted_package);
}
// not agile, only try to decrypt versions 3.2 and 4.2
if (version_minor != 2 || (version_major != 2 && version_major != 3 && version_major != 4))
{
throw xlnt::exception("unsupported encryption version");
}
if ((encryption_flags & 0b00000011) != 0) // Reserved1 and Reserved2, MUST be 0
{
throw xlnt::exception("bad header");
}
if ((encryption_flags & 0b00000100) == 0 // fCryptoAPI
|| (encryption_flags & 0b00010000) != 0) // fExternal
{
throw xlnt::exception("extensible encryption is not supported");
}
if ((encryption_flags & 0b00100000) == 0) // fAES
{
throw xlnt::exception("not an OOXML document");
}
return decrypt_xlsx_standard(encryption_info, password, encrypted_package);
}
static std::vector<std::uint8_t> encrypt_xlsx(const std::vector<std::uint8_t> &bytes, const std::string &password)
{
if (bytes.empty())
{
throw xlnt::exception("empty file");
}
generate_agile_encryption_info(password);
return {};
}
};
const std::size_t crypto_helper::segment_length = 4096;
void xlsx_consumer::read(std::istream &source, const std::string &password)
{
std::vector<std::uint8_t> data((std::istreambuf_iterator<char>(source)), (std::istreambuf_iterator<char>()));
const auto decrypted = crypto_helper::decrypt_xlsx(data, password);
vector_istreambuf decrypted_buffer(decrypted);
std::istream decrypted_stream(&decrypted_buffer);
read(decrypted_stream);
}
void xlsx_producer::write(std::ostream &destination, const std::string &password)
{
std::vector<std::uint8_t> decrypted;
{
vector_ostreambuf decrypted_buffer(decrypted);
std::ostream decrypted_stream(&decrypted_buffer);
write(decrypted_stream);
}
const auto encrypted = crypto_helper::encrypt_xlsx(decrypted, password);
vector_istreambuf encrypted_buffer(encrypted);
destination << &encrypted_buffer;
}
} // namespace detail
} // namespace xlnt
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