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/*
* Copyright (C) 2022 KeePassXC Team <team@keepassxc.org>
*
* This program 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 2 or (at your option)
* version 3 of the License.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "WindowsHello.h"
#include <Userconsentverifierinterop.h>
#include <winrt/base.h>
#include <winrt/windows.foundation.h>
#include <winrt/windows.security.credentials.h>
#include <winrt/windows.security.cryptography.h>
#include <winrt/windows.storage.streams.h>
#include "core/AsyncTask.h"
#include "crypto/CryptoHash.h"
#include "crypto/Random.h"
#include "crypto/SymmetricCipher.h"
#include <QTimer>
#include <QWindow>
using namespace winrt;
using namespace Windows::Foundation;
using namespace Windows::Security::Credentials;
using namespace Windows::Security::Cryptography;
using namespace Windows::Storage::Streams;
namespace
{
const std::wstring s_winHelloKeyName{L"keepassxc_winhello"};
int g_promptFocusCount = 0;
void queueSecurityPromptFocus(int delay = 500)
{
QTimer::singleShot(delay, [] {
auto hWnd = ::FindWindowA("Credential Dialog Xaml Host", nullptr);
if (hWnd) {
::SetForegroundWindow(hWnd);
} else if (++g_promptFocusCount <= 3) {
queueSecurityPromptFocus();
return;
}
g_promptFocusCount = 0;
});
}
bool deriveEncryptionKey(QByteArray& challenge, QByteArray& key, QString& error)
{
error.clear();
auto challengeBuffer = CryptographicBuffer::CreateFromByteArray(
array_view<uint8_t>(reinterpret_cast<uint8_t*>(challenge.data()), challenge.size()));
return AsyncTask::runAndWaitForFuture([&] {
// The first time this is used a key-pair will be generated using the common name
auto result =
KeyCredentialManager::RequestCreateAsync(s_winHelloKeyName, KeyCredentialCreationOption::FailIfExists)
.get();
if (result.Status() == KeyCredentialStatus::CredentialAlreadyExists) {
result = KeyCredentialManager::OpenAsync(s_winHelloKeyName).get();
} else if (result.Status() != KeyCredentialStatus::Success) {
error = QObject::tr("Failed to create Windows Hello credential.");
return false;
}
try {
const auto signature = result.Credential().RequestSignAsync(challengeBuffer).get();
if (signature.Status() != KeyCredentialStatus::Success) {
error = QObject::tr("Failed to sign challenge using Windows Hello.");
return false;
}
// Use the SHA-256 hash of the challenge signature as the encryption key
const auto response = signature.Result();
CryptoHash hasher(CryptoHash::Sha256);
hasher.addData({reinterpret_cast<const char*>(response.data()), static_cast<int>(response.Length())});
key = hasher.result();
return true;
} catch (winrt::hresult_error const& ex) {
error = QString::fromStdString(winrt::to_string(ex.message()));
return false;
}
});
}
} // namespace
WindowsHello* WindowsHello::m_instance{nullptr};
WindowsHello* WindowsHello::instance()
{
if (!m_instance) {
m_instance = new WindowsHello();
}
return m_instance;
}
WindowsHello::WindowsHello(QObject* parent)
: QObject(parent)
{
concurrency::create_task([this] {
bool state = KeyCredentialManager::IsSupportedAsync().get();
m_available = state;
emit availableChanged(m_available);
});
}
bool WindowsHello::isAvailable() const
{
return m_available;
}
QString WindowsHello::errorString() const
{
return m_error;
}
bool WindowsHello::storeKey(const QString& dbPath, const QByteArray& data)
{
queueSecurityPromptFocus();
// Generate a random challenge that will be signed by Windows Hello
// to create the key. The challenge is also used as the IV.
auto ivSize = SymmetricCipher::defaultIvSize(SymmetricCipher::Aes256_GCM);
auto challenge = Random::instance()->randomArray(ivSize);
QByteArray key;
if (!deriveEncryptionKey(challenge, key, m_error)) {
return false;
}
// Encrypt the data using AES-256-CBC
SymmetricCipher cipher;
if (!cipher.init(SymmetricCipher::Aes256_GCM, SymmetricCipher::Encrypt, key, challenge)) {
m_error = tr("Failed to init KeePassXC crypto.");
return false;
}
QByteArray encrypted = data;
if (!cipher.finish(encrypted)) {
m_error = tr("Failed to encrypt key data.");
return false;
}
// Prepend the challenge/IV to the encrypted data
encrypted.prepend(challenge);
m_encryptedKeys.insert(dbPath, encrypted);
return true;
}
bool WindowsHello::getKey(const QString& dbPath, QByteArray& data)
{
data.clear();
if (!hasKey(dbPath)) {
m_error = tr("Failed to get Windows Hello credential.");
return false;
}
queueSecurityPromptFocus();
// Read the previously used challenge and encrypted data
auto ivSize = SymmetricCipher::defaultIvSize(SymmetricCipher::Aes256_GCM);
const auto& keydata = m_encryptedKeys.value(dbPath);
auto challenge = keydata.left(ivSize);
auto encrypted = keydata.mid(ivSize);
QByteArray key;
if (!deriveEncryptionKey(challenge, key, m_error)) {
return false;
}
// Decrypt the data using the generated key and IV from above
SymmetricCipher cipher;
if (!cipher.init(SymmetricCipher::Aes256_GCM, SymmetricCipher::Decrypt, key, challenge)) {
m_error = tr("Failed to init KeePassXC crypto.");
return false;
}
// Store the decrypted data into the passed parameter
data = encrypted;
if (!cipher.finish(data)) {
data.clear();
m_error = tr("Failed to decrypt key data.");
return false;
}
return true;
}
void WindowsHello::reset(const QString& dbPath)
{
m_encryptedKeys.remove(dbPath);
}
bool WindowsHello::hasKey(const QString& dbPath) const
{
return m_encryptedKeys.contains(dbPath);
}
void WindowsHello::reset()
{
m_encryptedKeys.clear();
}
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