move memwipe to epee to avoid common<->crypto circular dependencies

contrib/epee/include/memwipe.h

@@ -0,0 +1,84 @@
+// Copyright (c) 2017, 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.
+// 
+// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
+
+#pragma once
+
+#ifdef __cplusplus
+#include <array>
+
+extern "C" {
+#endif
+
+void *memwipe(void *src, size_t n);
+
+#ifdef __cplusplus
+}
+#endif
+
+#ifdef __cplusplus
+namespace tools {
+
+  /// Scrubs data in the contained type upon destruction.
+  ///
+  /// Primarily useful for making sure that private keys don't stick around in
+  /// memory after the objects that held them have gone out of scope.
+  template <class T>
+  struct scrubbed : public T {
+    using type = T;
+
+    ~scrubbed() {
+      scrub();
+    }
+
+    /// Destroy the contents of the contained type.
+    void scrub() {
+      static_assert(std::is_pod<T>::value,
+                    "T cannot be auto-scrubbed. T must be POD.");
+      static_assert(std::is_trivially_destructible<T>::value,
+                    "T cannot be auto-scrubbed. T must be trivially destructable.");
+      memwipe(this, sizeof(T));
+    }
+  };
+
+  template <class T, size_t N>
+  using scrubbed_arr = scrubbed<std::array<T, N>>;
+} // namespace tools
+
+// Partial specialization for std::is_pod<tools::scrubbed<T>> so that it can
+// pretend to be the containted type in those contexts.
+namespace std
+{
+  template<class t_scrubbee>
+  struct is_pod<tools::scrubbed<t_scrubbee>> {
+    static const bool value = is_pod<t_scrubbee>::value;
+  };
+}
+
+#endif // __cplusplus