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/*
Copyright (C) 2024-2025 Selwin van Dijk
This file is part of signalbackup-tools.
signalbackup-tools is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
signalbackup-tools is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with signalbackup-tools. If not, see <https://www.gnu.org/licenses/>.
*/
#include "desktopattachmentreader.h"
#include "../common_filesystem.h"
int DesktopAttachmentReader::getAttachmentData(unsigned char **rawdata, bool verbose [[maybe_unused]])
{
// set AES+MAC key
auto [tmpdata, key_data_length] = Base64::base64StringToBytes(d_key);
std::unique_ptr<unsigned char[]> key_data(tmpdata);
//uint64_t aeskey_length = 32;
unsigned char *aeskey = key_data.get();
uint64_t mackey_length = 32;
unsigned char *mackey = key_data.get() + 32;
// open file
std::ifstream file(std::filesystem::path(d_path), std::ios_base::in | std::ios_base::binary);
if (!file.is_open())
{
Logger::error("Failed to open file '", d_path, "'");
return 1;
}
// set iv/data length.
int64_t iv_length = 16;
//file.seekg(0, std::ios_base::end);
//int64_t data_length = file.tellg() - static_cast<int64_t>(iv_length + mackey_length);
//file.seekg(0, std::ios_base::beg);
int64_t data_length = bepaald::fileSize(d_path) - static_cast<int64_t>(iv_length + mackey_length);
// set iv
std::unique_ptr<unsigned char[]> iv(new unsigned char[iv_length]);
if (!file.read(reinterpret_cast<char *>(iv.get()), iv_length) ||
file.gcount() != iv_length)
{
Logger::error("Failed to read iv");
return 1;
}
// set data to decrypt
std::unique_ptr<unsigned char[]> data(new unsigned char[data_length]);
if (!file.read(reinterpret_cast<char *>(data.get()), data_length) ||
file.gcount() != data_length)
{
Logger::error("Failed to read in file data");
return 1;
}
// set theirMAC
int64_t theirmac_length = 32;
std::unique_ptr<unsigned char[]> theirmac(new unsigned char[32]);
if (!file.read(reinterpret_cast<char *>(theirmac.get()), theirmac_length) ||
file.gcount() != theirmac_length)
{
Logger::error("Failed to read theirmac");
return 1;
}
// calculate MAC
evp_md_st const *digest = EVP_sha256();
#if OPENSSL_VERSION_NUMBER >= 0x30000000L
char digestname[] = "SHA256";
std::unique_ptr<EVP_MAC, decltype(&::EVP_MAC_free)> mac(EVP_MAC_fetch(nullptr, "hmac", nullptr), &::EVP_MAC_free);
std::unique_ptr<EVP_MAC_CTX, decltype(&::EVP_MAC_CTX_free)> hctx(EVP_MAC_CTX_new(mac.get()), &::EVP_MAC_CTX_free);
OSSL_PARAM params[] = {OSSL_PARAM_construct_utf8_string("digest", digestname, 0), OSSL_PARAM_construct_end()};
if (EVP_MAC_init(hctx.get(), mackey, mackey_length, params) != 1)
{
Logger::error("Failed to initialize HMAC context");
return false;
}
std::unique_ptr<unsigned char[]> calculatedmac(new unsigned char[EVP_MD_size(digest)]);
if (EVP_MAC_update(hctx.get(), iv.get(), iv_length) != 1 ||
EVP_MAC_update(hctx.get(), data.get(), data_length) != 1 ||
EVP_MAC_final(hctx.get(), calculatedmac.get(), nullptr, EVP_MD_size(digest)) != 1)
{
Logger::error("Failed to update/finalize hmac");
return false;
}
#else
std::unique_ptr<HMAC_CTX, decltype(&::HMAC_CTX_free)> hctx(HMAC_CTX_new(), &::HMAC_CTX_free);
if (HMAC_Init_ex(hctx.get(), mackey, mackey_length, digest, nullptr) != 1)
{
Logger::error("Failed to initialize HMAC context");
return false;
}
std::unique_ptr<unsigned char[]> calculatedmac(new unsigned char[32]);
unsigned int finalsize = EVP_MD_size(digest);
if (HMAC_Update(hctx.get(), iv.get(), iv_length) != 1 ||
HMAC_Update(hctx.get(), data.get(), data_length) != 1 ||
HMAC_Final(hctx.get(), calculatedmac.get(), &finalsize) != 1)
{
Logger::error("Failed to update/finalize hmac");
return false;
}
#endif
if (std::memcmp(calculatedmac.get(), theirmac.get(), theirmac_length) != 0)
{
Logger::error("MAC failed! (theirMAC: ", bepaald::bytesToString(theirmac.get(), theirmac_length),
" ourMAC: ", bepaald::bytesToString(calculatedmac.get(), theirmac_length));
return -1;
}
// DECRYPT DATA:
// init decryption context
std::unique_ptr<EVP_CIPHER_CTX, decltype(&::EVP_CIPHER_CTX_free)> ctx(EVP_CIPHER_CTX_new(), &::EVP_CIPHER_CTX_free);
if (!ctx) [[unlikely]]
{
Logger::error("Failed to create decryption context");
return 1;
}
// init decrypt
if (!EVP_DecryptInit_ex(ctx.get(), EVP_aes_256_cbc(), nullptr, aeskey, iv.get())) [[unlikely]]
{
Logger::error("Failed to initialize decryption operation");
return 1;
}
// decrypt update
int out_len = 0;
int output_length = data_length;
std::unique_ptr<unsigned char[]> output(new unsigned char[output_length]);
if (EVP_DecryptUpdate(ctx.get(), output.get(), &out_len, data.get(), output_length) != 1) [[unlikely]]
{
Logger::error("Failed to update decryption");
return 1;
}
// decrypt final
int tail_len = 0;
if (EVP_DecryptFinal_ex(ctx.get(), output.get() + out_len, &tail_len) != 1) [[unlikely]]
{
Logger::error("Failed to finalize decryption");
return 1;
}
out_len += tail_len;
//std::cout << out_len << std::endl;
//std::cout << "Start of decrypted data: " << bepaald::bytesToHexString(output.get(), 64) << std::endl;
*rawdata = output.release();
return 0;
}
int DesktopAttachmentReader::getEncryptedAttachment(FrameWithAttachment *frame, bool verbose)
{
unsigned char *data = nullptr;
int ret = getAttachmentData(&data, verbose);
if (ret == 0) [[likely]]
frame->setAttachmentDataBacked(data, d_size);
return ret;
}
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