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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/>.
*/
#if defined(_WIN32) || defined(__MINGW64__)
#include "desktopdatabase.ih"
#include "../base64/base64.h"
#include <dpapi.h>
#include <openssl/core_names.h>
bool DesktopDatabase::getKeyFromEncrypted_win()
{
// 1. get the encrypted key from config.json
std::string keystr = readEncryptedKey();
if (keystr.empty())
return false;
unsigned long encryptedkey_data_length = keystr.size() / 2;
std::unique_ptr<unsigned char[]> encryptedkey_data(new unsigned char[encryptedkey_data_length]);
bepaald::hexStringToBytes(keystr, encryptedkey_data.get(), encryptedkey_data_length);
// 2. get the key to decrypt the encrypted key
//***** 2a. get the base64 encoded encrypted key to decrypt the encrypted key ******//
std::fstream localstate(d_configdir + "/Local State", std::ios_base::in | std::ios_base::binary);
if (!localstate.is_open())
{
Logger::error("Failed to open input: ", d_configdir, "/Local State");
return false;
}
std::string line;
std::regex keyregex(".*\"encrypted_key\":\\s*\"([^\"]*)\".*");
std::smatch m;
bool found = false;
while (std::getline(localstate, line))
{
//std::cout << "Line: " << line << std::endl;
if (std::regex_match(line, m, keyregex))
if (m.size() == 2) // m[0] is full match, m[1] is first submatch (which we want)
{
found = true;
break;
}
}
if (!found)
{
Logger::error("Failed to read key from Local State");
return false;
}
std::string encrypted_encryptedkey_keyb64 = m[1].str();
//std::cout << encrypted_encryptedkey_keyb64 << std::endl;
//***** 2b. decrypt it ******//
std::pair<unsigned char *, size_t> encrypted_encryptedkey_key = Base64::base64StringToBytes(encrypted_encryptedkey_keyb64);
//std::cout << "enc Key size: " << encrypted_encryptedkey_key.second << std::endl;
//std::cout << "enc Key: " << bepaald::bytesToHexString(encrypted_encryptedkey_key.first, encrypted_encryptedkey_key.second) << std::endl;
// the encrypted key starts with 'D' 'P' 'A' 'P' 'I' {0x44, 0x50, 0x41, 0x50, 0x41}, skip this...
DATA_BLOB encrypted_encryptedkey_key_blob{static_cast<unsigned long>(encrypted_encryptedkey_key.second - STRLEN("DPAPI")), encrypted_encryptedkey_key.first + STRLEN("DPAPI")};
DATA_BLOB encryptedkey_key_blob;
if (!CryptUnprotectData(&encrypted_encryptedkey_key_blob, nullptr, nullptr, nullptr, nullptr, 0, &encryptedkey_key_blob)) [[unlikely]]
{
Logger::error("Failed to decrypt key (1)");
bepaald::destroyPtr(&encrypted_encryptedkey_key.first, &encrypted_encryptedkey_key.second);
return false;
}
bepaald::destroyPtr(&encrypted_encryptedkey_key.first, &encrypted_encryptedkey_key.second);
uint64_t encryptedkey_key_length = encryptedkey_key_blob.cbData;
std::unique_ptr<unsigned char[]> encryptedkey_key(new unsigned char[encryptedkey_key_length]);
std::memcpy(encryptedkey_key.get(), encryptedkey_key_blob.pbData, encryptedkey_key_length);
LocalFree(encryptedkey_key_blob.pbData);
//std::cout << "Decrypted key to decrypt encrypted key: " << bepaald::bytesToHexString(encryptedkey_key.get(), encryptedkey_key_length) << std::endl << std::endl;
// 3. Now decrypt the encrypted_key using the decrypted key from local state
// the encrypted key (from step 1) is made up of
// - a 3 byte header ('v', '1', '0')
// - a 12 byte nonce
// - 64 bytes of encrypted data
// - 16 bytes mac
uint64_t constexpr header_length = 3;
unsigned char *header = encryptedkey_data.get();
uint64_t constexpr nonce_length = 12;
unsigned char *nonce = encryptedkey_data.get() + header_length;
uint64_t constexpr mac_length = 16;
unsigned char *mac = encryptedkey_data.get() + (encryptedkey_data_length - mac_length);
uint64_t encdata_length = encryptedkey_data_length - mac_length - header_length - nonce_length;
unsigned char *encdata = nonce + nonce_length;
//std::cout << bepaald::bytesToHexString(header, header_length) << std::endl;
//std::cout << bepaald::bytesToHexString(nonce, nonce_length) << std::endl;
//std::cout << bepaald::bytesToHexString(encdata, encdata_length) << std::endl;
//std::cout << bepaald::bytesToHexString(mac, mac_length) << std::endl;
unsigned char const v10header[3] = {'v', '1', '0'};
if (std::memcmp(header, v10header, header_length) != 0) [[unlikely]]
Logger::warning("Unexpected header value: ", bepaald::bytesToHexString(header, header_length));
// Create and initialize the decryption context & cipher
std::unique_ptr<EVP_CIPHER_CTX, decltype(&::EVP_CIPHER_CTX_free)> ctx(EVP_CIPHER_CTX_new(), &::EVP_CIPHER_CTX_free);
std::unique_ptr<EVP_CIPHER, decltype(&::EVP_CIPHER_free)> cipher(EVP_CIPHER_fetch(NULL, "AES-256-GCM", NULL), &::EVP_CIPHER_free);
if (!ctx || !cipher)
{
Logger::error("Failed to create decryption context or cipher");
return false;
}
// set parameters (to set and check MAC)
OSSL_PARAM params[2];
params[0] = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_AEAD_TAG, mac, mac_length);
params[1] = OSSL_PARAM_construct_end();
if (!EVP_DecryptInit_ex2(ctx.get(), cipher.get(), encryptedkey_key.get(), nonce, params)) [[unlikely]]
{
Logger::error("Failed to initialize decryption operation");
return false;
}
int len = 0;
uint64_t key_hexstr_length = 64;
std::unique_ptr<unsigned char[]> key_hexstr(new unsigned char[key_hexstr_length]);
if (!EVP_DecryptUpdate(ctx.get(), key_hexstr.get(), &len, encdata, encdata_length)) [[unlikely]]
{
Logger::error("Failed to decrypt key (2)");
return false;
}
if (EVP_DecryptFinal_ex(ctx.get(), key_hexstr.get() + len, &len) > 0) [[likely]]
{
// the decrypted data is not the actual key, but the key as hex in ascii for some reason...
d_hexkey = std::string(reinterpret_cast<char const *>(key_hexstr.get()), key_hexstr_length);
//std::cout << "KEY !! : " << d_hexkey << std::endl;
return true;
}
else [[unlikely]]
{
Logger::error("Failed to finalize decryption (possibly MAC failed)");
return false;
}
}
#endif
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