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/* Test of explicit_bzero() function.
Copyright (C) 2020-2021 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2020. */
#include <config.h>
/* Specification. */
#include <string.h>
#include "signature.h"
SIGNATURE_CHECK (explicit_bzero, void, (void *, size_t));
#include <stdbool.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include "vma-iter.h"
#include "macros.h"
#define SECRET "xyzzy1729"
#define SECRET_SIZE 9
static char zero[SECRET_SIZE] = { 0 };
/* Enable this to verify that the test is effective. */
#if 0
# define explicit_bzero(a, n) memset (a, '\0', n)
#endif
/* =================== Verify operation on static memory =================== */
static char stbuf[SECRET_SIZE];
static void
test_static (void)
{
memcpy (stbuf, SECRET, SECRET_SIZE);
explicit_bzero (stbuf, SECRET_SIZE);
ASSERT (memcmp (zero, stbuf, SECRET_SIZE) == 0);
}
/* =============== Verify operation on heap-allocated memory =============== */
/* Test whether an address range is mapped in memory. */
#if VMA_ITERATE_SUPPORTED
struct locals
{
uintptr_t range_start;
uintptr_t range_end;
};
static int
vma_iterate_callback (void *data, uintptr_t start, uintptr_t end,
unsigned int flags)
{
struct locals *lp = (struct locals *) data;
/* Remove from [range_start, range_end) the part at the beginning or at the
end that is covered by [start, end). */
if (start <= lp->range_start && end > lp->range_start)
lp->range_start = (end < lp->range_end ? end : lp->range_end);
if (start < lp->range_end && end >= lp->range_end)
lp->range_end = (start > lp->range_start ? start : lp->range_start);
return 0;
}
static bool
is_range_mapped (uintptr_t range_start, uintptr_t range_end)
{
struct locals l;
l.range_start = range_start;
l.range_end = range_end;
vma_iterate (vma_iterate_callback, &l);
return l.range_start == l.range_end;
}
#else
static bool
is_range_mapped (uintptr_t range_start, uintptr_t range_end)
{
return true;
}
#endif
static void
test_heap (void)
{
char *heapbuf = (char *) malloc (SECRET_SIZE);
uintptr_t addr = (uintptr_t) heapbuf;
memcpy (heapbuf, SECRET, SECRET_SIZE);
explicit_bzero (heapbuf, SECRET_SIZE);
free (heapbuf);
if (is_range_mapped (addr, addr + SECRET_SIZE))
{
/* some implementation could override freed memory by canaries so
compare against secret */
ASSERT (memcmp (heapbuf, SECRET, SECRET_SIZE) != 0);
printf ("test_heap: address range is still mapped after free().\n");
}
else
printf ("test_heap: address range is unmapped after free().\n");
}
/* =============== Verify operation on stack-allocated memory =============== */
/* There are two passes:
1. Put a secret in memory and invoke explicit_bzero on it.
2. Verify that the memory has been erased.
Implement them in the same function, so that they access the same memory
range on the stack. */
static int _GL_ATTRIBUTE_NOINLINE
do_secret_stuff (volatile int pass)
{
char stackbuf[SECRET_SIZE];
if (pass == 1)
{
memcpy (stackbuf, SECRET, SECRET_SIZE);
explicit_bzero (stackbuf, SECRET_SIZE);
return 0;
}
else /* pass == 2 */
{
return memcmp (zero, stackbuf, SECRET_SIZE) != 0;
}
}
static void
test_stack (void)
{
int count = 0;
int repeat;
for (repeat = 1000; repeat > 0; repeat--)
{
do_secret_stuff (1);
count += do_secret_stuff (2);
}
/* If explicit_bzero works, count is near 0. (It may be > 0 if there were
some asynchronous signal invocations between the two calls of
do_secret_stuff.)
If explicit_bzero is optimized away by the compiler, count comes out as
approximately 1000. */
printf ("test_stack: count = %d\n", count);
ASSERT (count < 50);
}
/* ========================================================================== */
int
main ()
{
test_static ();
test_heap ();
test_stack ();
return 0;
}
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