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/back-end-file.hpp b/src/security/tpm/back-end-file.hpp
new file mode 100644
index 0000000..02b575f
--- /dev/null
+++ b/src/security/tpm/back-end-file.hpp
@@ -0,0 +1,137 @@
+/* -*- 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_BACK_END_FILE_HPP
+#define NDN_SECURITY_TPM_BACK_END_FILE_HPP
+
+#include "back-end.hpp"
+
+namespace ndn {
+namespace security {
+namespace transform {
+class PrivateKey;
+} // namespace transform
+
+namespace tpm {
+
+/**
+ * @brief The back-end implementation of file-based TPM.
+ *
+ * In this TPM, each private key is stored in a separate file with permission 0400, i.e.,
+ * owner read-only.  The key is stored in PKCS #1 format in base64 encoding.
+ */
+class BackEndFile : public BackEnd
+{
+public:
+  class Error : public BackEnd::Error
+  {
+  public:
+    explicit
+    Error(const std::string& what)
+      : BackEnd::Error(what)
+    {
+    }
+  };
+
+public:
+  explicit
+  BackEndFile(const std::string& location = "");
+
+  ~BackEndFile() override;
+
+private: // inherited from tpm::BackEnd
+  /**
+   * @return True if a key with name @p keyName exists in TPM.
+   */
+  bool
+  doHasKey(const Name& keyName) const final;
+
+  /**
+   * @return The handle of a key with name @p keyName, or nullptr if the key does not exist
+   */
+  unique_ptr<KeyHandle>
+  doGetKeyHandle(const Name& keyName) const final;
+
+  /**
+   * @brief Create key for @p identityName according to @p params.
+   *
+   * The created key is named as: /<identityName>/[keyId]/KEY
+   * The key name is set in the returned KeyHandle.
+   *
+   * If the key with the same name exists, the old key will be overwritten.
+   * The behavior of using KeyHandler of removed key is undefined.
+   *
+   * @return The handle of the created key.
+   */
+  unique_ptr<KeyHandle>
+  doCreateKey(const Name& identityName, const KeyParams& params) final;
+
+  /**
+   * @brief Delete a key with name @p keyName.
+   *
+   * @throws Error if the deletion fails.
+   */
+  void
+  doDeleteKey(const Name& keyName) final;
+
+  /**
+   * @return A private key with name @p keyName in encrypted PKCS #8 format using password @p pw
+   * @throws Error if the key cannot be exported, e.g., not enough privilege
+   */
+  ConstBufferPtr
+  doExportKey(const Name& keyName, const char* pw, size_t pwLen) final;
+
+  /**
+   * @brief Import a private key in encrypted PKCS #8 format
+   *
+   * @param keyName The name of imported private key
+   * @param buf Pointer to the key in encrypted PKCS #8 format
+   * @param size The size of the key in encrypted PKCS #8 format
+   * @param pw The password to decrypt the key
+   * @param pwLen The length of the password
+   * @throws Error if import fails.
+   */
+  void
+  doImportKey(const Name& keyName, const uint8_t* buf, size_t size, const char* pw, size_t pwLen) final;
+
+private:
+  /**
+   * @brief Load a private key with name @p keyName from the key file directory
+   */
+  shared_ptr<transform::PrivateKey>
+  loadKey(const Name& keyName) const;
+
+  /**
+   * @brief Save a private key with name @p keyName into the key file directory
+   */
+  void
+  saveKey(const Name& keyName, shared_ptr<transform::PrivateKey> key);
+
+private:
+  class Impl;
+  unique_ptr<Impl> m_impl;
+};
+
+} // namespace tpm
+} // namespace security
+} // namespace ndn
+
+#endif // NDN_SECURITY_TPM_BACK_END_FILE_HPP