ext/arc4random/explicit_bzero.c

   1 /* OPENBSD ORIGINAL: lib/libc/string/explicit_bzero.c */
   2 /*      $OpenBSD: explicit_bzero.c,v 1.1 2014/01/22 21:06:45 tedu Exp $ */
   3 /*
   4  * Public domain.
   5  * Written by Ted Unangst
   6  */
   7
   8 #include "includes.h"
   9
  10 #include <string.h>
  11
  12 /*
  13  * explicit_bzero - don't let the compiler optimize away bzero
  14  */
  15
  16 #ifndef HAVE_EXPLICIT_BZERO
  17
  18 #ifdef HAVE_EXPLICIT_MEMSET
  19
  20 void
  21 explicit_bzero(void *p, size_t n)
  22 {
  23         (void)explicit_memset(p, 0, n);
  24 }
  25
  26 #elif defined(HAVE_MEMSET_S)
  27
  28 void
  29 explicit_bzero(void *p, size_t n)
  30 {
  31         if (n == 0)
  32                 return;
  33         (void)memset_s(p, n, 0, n);
  34 }
  35
  36 #else /* HAVE_MEMSET_S */
  37
  38 /*
  39  * Indirect bzero through a volatile pointer to hopefully avoid
  40  * dead-store optimisation eliminating the call.
  41  */
  42 static void (* volatile ssh_bzero)(void *, size_t) = bzero;
  43
  44 void
  45 explicit_bzero(void *p, size_t n)
  46 {
  47         if (n == 0)
  48                 return;
  49         /*
  50          * clang -fsanitize=memory needs to intercept memset-like functions
  51          * to correctly detect memory initialisation. Make sure one is called
  52          * directly since our indirection trick above successfully confuses it.
  53          */
  54 #if defined(__has_feature)
  55 # if __has_feature(memory_sanitizer)
  56         memset(p, 0, n);
  57 # endif
  58 #endif
  59
  60         ssh_bzero(p, n);
  61 }
  62
  63 #endif /* HAVE_MEMSET_S */
  64
  65 #endif /* HAVE_EXPLICIT_BZERO */