/*

* (C) 2025 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/mem_ops.h>

#include <botan/internal/target_info.h>

#include <cstring>

#if defined(BOTAN_TARGET_OS_HAS_EXPLICIT_BZERO)

   #include <string.h>

#endif

#if defined(BOTAN_TARGET_OS_HAS_RTLSECUREZEROMEMORY)

   #define NOMINMAX 1

   #define _WINSOCKAPI_  // stop windows.h including winsock.h

   #include <windows.h>

#endif

namespace Botan {

void secure_scrub_memory(void* ptr, size_t n) {

#if defined(BOTAN_TARGET_OS_HAS_RTLSECUREZEROMEMORY)

   ::RtlSecureZeroMemory(ptr, n);

#elif defined(BOTAN_TARGET_OS_HAS_EXPLICIT_BZERO)

   ::explicit_bzero(ptr, n);

#elif defined(BOTAN_TARGET_OS_HAS_EXPLICIT_MEMSET)

   (void)::explicit_memset(ptr, 0, n);

#else

   /*

   * Call memset through a static volatile pointer, which the compiler should

   * not elide. This construct should be safe in conforming compilers, but who

   * knows. This has been checked to generate the expected code, which saves the

   * memset address in the data segment and unconditionally loads and jumps to

   * that address, with the following targets:

   *

   * x86-64: Clang 19, GCC 6, 11, 13, 14

   * riscv64: GCC 14

   * aarch64: GCC 14

   * armv7: GCC 14

   *

   * Actually all of them generated the expected jump even without marking the

   * function pointer as volatile. However this seems worth including as an

   * additional precaution.

   */

   static void* (*const volatile memset_ptr)(void*, int, size_t) = std::memset;

   (memset_ptr)(ptr, 0, n);

#endif

}

}  // namespace Botan