Verify hash of Python installer

PR #21877.

src/gui/mainwindow.cpp

@@ -56,6 +56,11 @@
 #include <QString>
 #include <QTimer>
 
+#ifdef Q_OS_WIN
+#include <QCryptographicHash>
+#include <QScopeGuard>
+#endif
+
 #include "base/bittorrent/session.h"
 #include "base/bittorrent/sessionstatus.h"
 #include "base/global.h"
@@ -113,7 +118,11 @@ namespace
 
     const std::chrono::seconds PREVENT_SUSPEND_INTERVAL {60};
 
+#ifdef Q_OS_WIN
     const QString PYTHON_INSTALLER_URL = u"https://www.python.org/ftp/python/3.13.0/python-3.13.0-amd64.exe"_s;
+    const QByteArray PYTHON_INSTALLER_MD5 = QByteArrayLiteral("f5e5d48ba86586d4bef67bcb3790d339");
+    const QByteArray PYTHON_INSTALLER_SHA3_512 = QByteArrayLiteral("28ed23b82451efa5ec87e5dd18d7dacb9bc4d0a3643047091e5a687439f7e03a1c6e60ec64ee1210a0acaf2e5012504ff342ff27e5db108db05407e62aeff2f1");
+#endif
 }
 
 MainWindow::MainWindow(IGUIApplication *app, const WindowState initialState, const QString &titleSuffix)
@@ -1899,33 +1908,79 @@ void MainWindow::installPython()
             , this, &MainWindow::pythonDownloadFinished);
 }
 
+bool MainWindow::verifyPythonInstaller(const Path &installerPath) const
+{
+    // Verify installer hash
+    // Python.org only provides MD5 hash but MD5 is already broken and doesn't guarantee file is not tampered.
+    // Therefore, MD5 is only included to prove that the hash is still the same with upstream and we rely on
+    // SHA3-512 for the main check.
+
+    QFile file {installerPath.data()};
+    if (!file.open(QIODevice::ReadOnly))
+    {
+        LogMsg((tr("Failed to open Python installer. File: \"%1\".").arg(installerPath.toString())), Log::WARNING);
+        return false;
+    }
+
+    QCryptographicHash md5Hash {QCryptographicHash::Md5};
+    md5Hash.addData(&file);
+    if (const QByteArray hashHex = md5Hash.result().toHex(); hashHex != PYTHON_INSTALLER_MD5)
+    {
+        LogMsg((tr("Failed MD5 hash check for Python installer. File: \"%1\". Result hash: \"%2\". Expected hash: \"%3\".")
+                .arg(installerPath.toString(), QString::fromLatin1(hashHex), QString::fromLatin1(PYTHON_INSTALLER_MD5)))
+            , Log::WARNING);
+        return false;
+    }
+
+    file.seek(0);
+
+    QCryptographicHash sha3Hash {QCryptographicHash::Sha3_512};
+    sha3Hash.addData(&file);
+    if (const QByteArray hashHex = sha3Hash.result().toHex(); hashHex != PYTHON_INSTALLER_SHA3_512)
+    {
+        LogMsg((tr("Failed SHA3-512 hash check for Python installer. File: \"%1\". Result hash: \"%2\". Expected hash: \"%3\".")
+                .arg(installerPath.toString(), QString::fromLatin1(hashHex), QString::fromLatin1(PYTHON_INSTALLER_SHA3_512)))
+            , Log::WARNING);
+        return false;
+    }
+
+    return true;
+}
+
 void MainWindow::pythonDownloadFinished(const Net::DownloadResult &result)
 {
-    const auto restoreWidgetsState = [this]
+    auto restoreWidgetsGuard = qScopeGuard([this]
     {
         m_ui->actionSearchWidget->setEnabled(true);
         m_ui->actionSearchWidget->setToolTip({});
         setCursor(Qt::ArrowCursor);
-    };
+    });
 
     if (result.status != Net::DownloadStatus::Success)
     {
-        restoreWidgetsState();
         QMessageBox::warning(
                     this, tr("Download error")
-                    , tr("Python setup could not be downloaded, reason: %1.\nPlease install it manually.")
+                    , tr("Python installer could not be downloaded. Error: %1.\nPlease install it manually.")
                     .arg(result.errorString));
         return;
     }
 
     const Path exePath = result.filePath + u".exe";
-    Utils::Fs::renameFile(result.filePath, exePath);
+    if (!Utils::Fs::renameFile(result.filePath, exePath))
+    {
+        LogMsg(tr("Rename Python installer failed. Source: \"%1\". Destination: \"%2\".")
+                .arg(result.filePath.toString(), exePath.toString())
+            , Log::WARNING);
+        return;
+    }
+
+    if (!verifyPythonInstaller(exePath))
+        return;
 
     // launch installer
     auto *installer = new QProcess(this);
-    installer->connect(installer, &QProcess::finished, this, [this, exePath, installer, restoreWidgetsState](const int exitCode, const QProcess::ExitStatus exitStatus)
+    installer->connect(installer, &QProcess::finished, this, [this, exePath, installer, restoreWidgetsGuard = std::move(restoreWidgetsGuard)](const int exitCode, const QProcess::ExitStatus exitStatus)
     {
-        restoreWidgetsState();
         installer->deleteLater();
 
         if ((exitStatus == QProcess::NormalExit) && (exitCode == 0))

src/gui/mainwindow.h

@@ -133,9 +133,6 @@ private slots:
     void optionsSaved();
     void toggleAlternativeSpeeds();
 
-#ifdef Q_OS_WIN
-    void pythonDownloadFinished(const Net::DownloadResult &result);
-#endif
     void addToolbarContextMenu();
     void manageCookies();
 
@@ -184,12 +181,12 @@ private slots:
 #else
     void toggleVisibility();
 #endif
+#ifdef Q_OS_WIN
+    void pythonDownloadFinished(const Net::DownloadResult &result);
+#endif
 
 private:
     void populateDesktopIntegrationMenu();
-#ifdef Q_OS_WIN
-    void installPython();
-#endif
 
     void closeEvent(QCloseEvent *) override;
     void showEvent(QShowEvent *) override;
@@ -204,6 +201,11 @@ private:
     void refreshWindowTitle();
     void refreshTrayIconTooltip();
 
+#ifdef Q_OS_WIN
+    void installPython();
+    bool verifyPythonInstaller(const Path &installerPath) const;
+#endif
+
     Ui::MainWindow *m_ui = nullptr;
 
     QString m_windowTitle;