security: Add new TPM framework

The TPM framework is separated into two parts:
1) The front end class Tpm provides the interface to KeyChain. The public
   interface of Tpm is read-only.
2) The back end classes represent concrete implementations, such as
   tpm::BackEndFile and tpm::BackEndOsx which may also provide
   implementation-specific management interfaces.

New TPM supports different key id type when generating new key.  The
default type is changed to 64-bit random number.

Change-Id: I41154c2ded4b65fb0bef2f4a0d2c5b77843be05d
Refs: #2948
diff --git a/src/security/tpm/helper-osx.hpp b/src/security/tpm/helper-osx.hpp
new file mode 100644
index 0000000..2e7d827
--- /dev/null
+++ b/src/security/tpm/helper-osx.hpp
@@ -0,0 +1,154 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2016 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library 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 Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#ifndef NDN_SECURITY_TPM_HELPER_OSX_HPP
+#define NDN_SECURITY_TPM_HELPER_OSX_HPP
+
+#include "../../common.hpp"
+
+#ifndef NDN_CXX_HAVE_OSX_SECURITY
+#error "This file should not be included ..."
+#endif
+
+#include <CoreFoundation/CoreFoundation.h>
+#include <Security/Security.h>
+
+namespace ndn {
+namespace security {
+namespace tpm {
+
+/**
+ * @brief Helper class to wrap CoreFoundation object pointers
+ *
+ * The class is similar in spirit to shared_ptr, but uses CoreFoundation
+ * mechanisms to retain/release object.
+ *
+ * Original implementation by Christopher Hunt and it was borrowed from
+ * http://www.cocoabuilder.com/archive/cocoa/130776-auto-cfrelease-and.html
+ */
+template<class T>
+class CFReleaser
+{
+public: // Construction/destruction
+  CFReleaser()
+    : m_typeRef(nullptr)
+  {
+  }
+
+  CFReleaser(const T& typeRef)
+    : m_typeRef(typeRef)
+  {
+  }
+
+  CFReleaser(const CFReleaser& inReleaser)
+    : m_typeRef(nullptr)
+  {
+    retain(inReleaser.m_typeRef);
+  }
+
+  CFReleaser&
+  operator=(const T& typeRef)
+  {
+    if (typeRef != m_typeRef) {
+      release();
+      m_typeRef = typeRef;
+    }
+    return *this;
+  }
+
+  CFReleaser&
+  operator=(const CFReleaser& inReleaser)
+  {
+    retain(inReleaser.m_typeRef);
+    return *this;
+  }
+
+  ~CFReleaser()
+  {
+    release();
+  }
+
+public: // Access
+  const T&
+  get() const
+  {
+    return m_typeRef;
+  }
+
+  T&
+  get()
+  {
+    return m_typeRef;
+  }
+
+  bool
+  operator==(const std::nullptr_t&)
+  {
+    return m_typeRef == nullptr;
+  }
+
+  bool
+  operator!=(const std::nullptr_t&)
+  {
+    return m_typeRef != nullptr;
+  }
+
+  ///////////////////
+  // Miscellaneous //
+
+  void
+  retain(const T& typeRef)
+  {
+    if (typeRef != nullptr) {
+      CFRetain(typeRef);
+    }
+    release();
+    m_typeRef = typeRef;
+  }
+
+  void
+  retain()
+  {
+    T typeRef = m_typeRef;
+    m_typeRef = nullptr;
+    retain(typeRef);
+  }
+
+  void
+  release()
+  {
+    if (m_typeRef != nullptr) {
+      CFRelease(m_typeRef);
+      m_typeRef = nullptr;
+    }
+  };
+
+private:
+  T m_typeRef;
+};
+
+typedef CFReleaser<SecKeyRef> KeyRefOsx;
+
+} // namespace tpm
+} // namespace security
+} // namespace ndn
+
+#endif // NDN_SECURITY_TPM_HELPER_OSX_HPP