[libcalamares] Add umask helper functions

src/libcalamares/CMakeLists.txt

@@ -46,6 +46,7 @@ set( libSources
     utils/PluginFactory.cpp
     utils/Retranslator.cpp
     utils/String.cpp
+    utils/UMask.cpp
     utils/Variant.cpp
     utils/Yaml.cpp
 )

src/libcalamares/utils/UMask.cpp

@@ -0,0 +1,44 @@
+/* === This file is part of Calamares - <https://github.com/calamares> ===
+ *
+ *   Copyright 2019, Adriaan de Groot <groot@kde.org>
+ *
+ *   Calamares 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.
+ *
+ *   Calamares 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 Calamares. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "UMask.h"
+
+#include <sys/stat.h>
+#include <sys/types.h>
+
+namespace CalamaresUtils
+{
+mode_t
+setUMask( mode_t u )
+{
+    return umask( u );
+}
+
+UMask::UMask( mode_t u )
+    : m_mode( setUMask( u ) )
+{
+}
+
+UMask::~UMask()
+{
+    setUMask( m_mode );
+}
+
+static_assert( UMask::Safe == ( S_IRGRP | S_IWGRP | S_IXGRP | S_IROTH | S_IWOTH | S_IXOTH ), "Bad permissions." );
+
+}  // namespace CalamaresUtils

src/libcalamares/utils/UMask.h

@@ -0,0 +1,55 @@
+/* === This file is part of Calamares - <https://github.com/calamares> ===
+ *
+ *   Copyright 2019, Adriaan de Groot <groot@kde.org>
+ *
+ *   Calamares 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.
+ *
+ *   Calamares 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 Calamares. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef UTILS_UMASK_H
+#define UTILS_UMASK_H
+
+#include "DllMacro.h"
+
+#include <sys/types.h>
+
+namespace CalamaresUtils
+{
+/// @brief Wrapper for umask(2)
+DLLEXPORT mode_t setUMask( mode_t u );
+
+/** @brief RAII for setting and re-setting umask.
+ *
+ * Create an object of this class to set the umask,
+ * and the umask is reset to its original value when
+ * the object goes out of scope.
+ */
+class DLLEXPORT UMask
+{
+public:
+    UMask( mode_t u );
+    ~UMask();
+
+    /** @brief a "safe" umask
+     *
+     * This umask will switch off group- and other- permissions for
+     * files, so that the file cannot be read, written, or executed
+     * except by the owner.
+     */
+    static constexpr mode_t Safe = 077;  // octal!
+private:
+    mode_t m_mode;
+};
+}  // namespace CalamaresUtils
+
+#endif