add a memwipe function

It's meant to avoid being optimized out

memory_cleanse lifted from bitcoin

3 files changed, 153 insertions, 0 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 50887e35c..7ad08ea83 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -35,6 +35,7 @@ set(common_sources
   download.cpp
   util.cpp
   i18n.cpp
+  memwipe.c
   password.cpp
   perf_timer.cpp
   threadpool.cpp
@@ -63,6 +64,7 @@ set(common_private_headers
   util.h
   varint.h
   i18n.h
+  memwipe.h
   password.h
   perf_timer.h
   stack_trace.h
@@ -90,5 +92,9 @@ target_link_libraries(common
     ${OPENSSL_LIBRARIES}
     ${EXTRA_LIBRARIES})
 
+if(HAVE_C11)
+SET_PROPERTY(SOURCE memwipe.c PROPERTY COMPILE_FLAGS -std=c11)
+endif()
+
 #monero_install_headers(common
 #  ${common_headers})
diff --git a/src/common/memwipe.c b/src/common/memwipe.c
new file mode 100644
index 000000000..da7e9f346
--- /dev/null
+++ b/src/common/memwipe.c
@@ -0,0 +1,106 @@
+// 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 Copyright (c) 2009-2015 The Bitcoin Core developers
+
+#define __STDC_WANT_LIB_EXT1__ 1
+#include <string.h>
+#include <stdlib.h>
+#ifdef HAVE_EXPLICIT_BZERO
+#include <strings.h>
+#endif
+#include "memwipe.h"
+
+#if defined(_MSC_VER)
+#define SCARECROW \
+    __asm;
+#else
+#define SCARECROW \
+    __asm__ __volatile__("" : : "r"(ptr) : "memory");
+#endif
+
+#ifdef HAVE_MEMSET_S
+
+void *memwipe(void *ptr, size_t n)
+{
+  if (memset_s(ptr, n, 0, n))
+  {
+    abort();
+  }
+  SCARECROW // might as well...
+  return ptr;
+}
+
+#elif defined HAVE_EXPLICIT_BZERO
+
+void *memwipe(void *ptr, size_t n)
+{
+  explicit_bzero(ptr, n);
+  SCARECROW
+  return ptr;
+}
+
+#else
+
+/* The memory_cleanse implementation is taken from Bitcoin */
+
+/* Compilers have a bad habit of removing "superfluous" memset calls that
+ * are trying to zero memory. For example, when memset()ing a buffer and
+ * then free()ing it, the compiler might decide that the memset is
+ * unobservable and thus can be removed.
+ *
+ * Previously we used OpenSSL which tried to stop this by a) implementing
+ * memset in assembly on x86 and b) putting the function in its own file
+ * for other platforms.
+ *
+ * This change removes those tricks in favour of using asm directives to
+ * scare the compiler away. As best as our compiler folks can tell, this is
+ * sufficient and will continue to be so.
+ *
+ * Adam Langley <agl@google.com>
+ * Commit: ad1907fe73334d6c696c8539646c21b11178f20f
+ * BoringSSL (LICENSE: ISC)
+ */
+static void memory_cleanse(void *ptr, size_t len)
+{
+    memset(ptr, 0, len);
+
+    /* As best as we can tell, this is sufficient to break any optimisations that
+       might try to eliminate "superfluous" memsets. If there's an easy way to
+       detect memset_s, it would be better to use that. */
+    SCARECROW
+}
+
+void *memwipe(void *ptr, size_t n)
+{
+  memory_cleanse(ptr, n);
+  SCARECROW
+  return ptr;
+}
+
+#endif
diff --git a/src/common/memwipe.h b/src/common/memwipe.h
new file mode 100644
index 000000000..e9a3fba7b
--- /dev/null
+++ b/src/common/memwipe.h
@@ -0,0 +1,41 @@
+// 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
+extern "C" {
+#endif
+
+void *memwipe(void *src, size_t n);
+
+#ifdef __cplusplus
+}
+#endif