security: Add CommandInterestSigner

v2::KeyChain::sign(Interest) does not add timestamp and nonce
components, required by CommandInterest specification
(https://redmine.named-data.net/projects/ndn-cxx/wiki/CommandInterest).
Whenever command interests are needed, CommandInterestSigner should be
used.

Change-Id: I3d573e6dd1bc686e42b0564add54173b7edf40f2
Refs: #3912
diff --git a/src/security/command-interest-signer.cpp b/src/security/command-interest-signer.cpp
new file mode 100644
index 0000000..1dfe1ce
--- /dev/null
+++ b/src/security/command-interest-signer.cpp
@@ -0,0 +1,59 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2017 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.
+ */
+
+#include "command-interest-signer.hpp"
+#include "../util/random.hpp"
+
+namespace ndn {
+namespace security {
+
+Name
+CommandInterestPreparer::prepareCommandInterestName(Name name)
+{
+  time::milliseconds timestamp = time::toUnixTimestamp(time::system_clock::now());
+  if (timestamp <= m_lastUsedTimestamp) {
+    timestamp = m_lastUsedTimestamp + time::milliseconds(1);
+  }
+  m_lastUsedTimestamp = timestamp;
+
+  name
+    .append(name::Component::fromNumber(timestamp.count()))
+    .append(name::Component::fromNumber(random::generateWord64())) // nonce
+    ;
+
+  return name;
+}
+
+CommandInterestSigner::CommandInterestSigner(v2::KeyChain& keyChain)
+  : m_keyChain(keyChain)
+{
+}
+
+Interest
+CommandInterestSigner::makeCommandInterest(const Name& name, const SigningInfo& params)
+{
+  Interest commandInterest(prepareCommandInterestName(name));
+  m_keyChain.sign(commandInterest, params);
+  return commandInterest;
+}
+
+} // namespace security
+} // namespace ndn