common: add a class to safely wrap mlock/munlock

This class will allow mlocking small objects, of which there
may be several per page. It adds refcounting so pages are only
munlocked when the last object on that page munlocks.

2 files changed, 94 insertions, 0 deletions

diff --git a/contrib/epee/include/mlocker.h b/contrib/epee/include/mlocker.h
new file mode 100644
index 000000000..d2fc2ed58
--- /dev/null
+++ b/contrib/epee/include/mlocker.h
@@ -0,0 +1,87 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once 
+
+#include <map>
+#include <boost/thread/mutex.hpp>
+
+namespace epee
+{
+  class mlocker
+  {
+  public:
+    mlocker(void *ptr, size_t len);
+    ~mlocker();
+
+    static size_t get_page_size();
+    static size_t get_num_locked_pages();
+    static size_t get_num_locked_objects();
+
+    static void lock(void *ptr, size_t len);
+    static void unlock(void *ptr, size_t len);
+
+  private:
+    static size_t page_size;
+    static size_t num_locked_objects;
+
+    static boost::mutex &mutex();
+    static std::map<size_t, unsigned int> &map();
+    static void lock_page(size_t page);
+    static void unlock_page(size_t page);
+
+    void *ptr;
+    size_t len;
+  };
+
+  /// Locks memory while in scope
+  ///
+  /// Primarily useful for making sure that private keys don't get swapped out
+  //  to disk
+  template <class T>
+  struct mlocked : public T {
+    using type = T;
+
+    mlocked(): T() { mlocker::lock(this, sizeof(T)); }
+    mlocked(const T &t): T(t) { mlocker::lock(this, sizeof(T)); }
+    mlocked(const mlocked<T> &mt): T(mt) { mlocker::lock(this, sizeof(T)); }
+    mlocked(const T &&t): T(t) { mlocker::lock(this, sizeof(T)); }
+    mlocked(const mlocked<T> &&mt): T(mt) { mlocker::lock(this, sizeof(T)); }
+    mlocked<T> &operator=(const mlocked<T> &mt) { T::operator=(mt); return *this; }
+    ~mlocked() { mlocker::unlock(this, sizeof(T)); }
+  };
+
+  template<typename T>
+  T& unwrap(mlocked<T>& src) { return src; }
+
+  template<typename T>
+  const T& unwrap(mlocked<T> const& src) { return src; }
+
+  template <class T, size_t N>
+  using mlocked_arr = mlocked<std::array<T, N>>;
+}
diff --git a/contrib/epee/include/string_tools.h b/contrib/epee/include/string_tools.h
index 8d8603076..aba065cc7 100644
--- a/contrib/epee/include/string_tools.h
+++ b/contrib/epee/include/string_tools.h
@@ -46,6 +46,7 @@
 #include <boost/algorithm/string/predicate.hpp>
 #include "hex.h"
 #include "memwipe.h"
+#include "mlocker.h"
 #include "span.h"
 #include "warnings.h"
 
@@ -358,6 +359,12 @@ POP_WARNINGS
     return hex_to_pod(hex_str, unwrap(s));
   }
   //----------------------------------------------------------------------------
+  template<class t_pod_type>
+  bool hex_to_pod(const std::string& hex_str, epee::mlocked<t_pod_type>& s)
+  {
+    return hex_to_pod(hex_str, unwrap(s));
+  }
+  //----------------------------------------------------------------------------
   bool validate_hex(uint64_t length, const std::string& str);
   //----------------------------------------------------------------------------
 	inline std::string get_extension(const std::string& str)