core: move nfd-specific files to daemon/

Refs: #4922
Change-Id: I2243dbb87c63f9cbaf7d7051d7a0d4bca2f9fdb5
diff --git a/daemon/common/privilege-helper.hpp b/daemon/common/privilege-helper.hpp
new file mode 100644
index 0000000..52daf84
--- /dev/null
+++ b/daemon/common/privilege-helper.hpp
@@ -0,0 +1,99 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2014-2019,  Regents of the University of California,
+ *                           Arizona Board of Regents,
+ *                           Colorado State University,
+ *                           University Pierre & Marie Curie, Sorbonne University,
+ *                           Washington University in St. Louis,
+ *                           Beijing Institute of Technology,
+ *                           The University of Memphis.
+ *
+ * This file is part of NFD (Named Data Networking Forwarding Daemon).
+ * See AUTHORS.md for complete list of NFD authors and contributors.
+ *
+ * NFD 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.
+ *
+ * NFD 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
+ * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef NFD_DAEMON_COMMON_PRIVILEGE_HELPER_HPP
+#define NFD_DAEMON_COMMON_PRIVILEGE_HELPER_HPP
+
+#include "core/common.hpp"
+
+#include <unistd.h>
+
+namespace nfd {
+
+class PrivilegeHelper
+{
+public:
+  /** \brief represents a serious seteuid/gid failure
+   *
+   *  This should only be caught by main as part of a graceful program termination.
+   *  \note This is not an std::exception and NDN_THROW should not be used.
+   */
+  class Error
+  {
+  public:
+    explicit
+    Error(const std::string& what)
+      : m_whatMessage(what)
+    {
+    }
+
+    const char*
+    what() const
+    {
+      return m_whatMessage.data();
+    }
+
+  private:
+    const std::string m_whatMessage;
+  };
+
+  static void
+  initialize(const std::string& userName, const std::string& groupName);
+
+  static void
+  drop();
+
+  template<class F>
+  static void
+  runElevated(F&& f)
+  {
+    raise();
+    try {
+      f();
+    }
+    catch (...) {
+      drop();
+      throw;
+    }
+    drop();
+  }
+
+PUBLIC_WITH_TESTS_ELSE_PRIVATE:
+  static void
+  raise();
+
+PUBLIC_WITH_TESTS_ELSE_PRIVATE:
+#ifdef HAVE_PRIVILEGE_DROP_AND_ELEVATE
+  static uid_t s_normalUid;
+  static gid_t s_normalGid;
+
+  static uid_t s_privilegedUid;
+  static gid_t s_privilegedGid;
+#endif // HAVE_PRIVILEGE_DROP_AND_ELEVATE
+};
+
+} // namespace nfd
+
+#endif // NFD_DAEMON_COMMON_PRIVILEGE_HELPER_HPP