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C: add mem/safe_mem.*

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パチュリー・ノーレッジ 2024-03-24 15:54:04 +03:00
parent df611cf964
commit eb0c6e0dd9
Signed by: 80486DX2-66
GPG Key ID: 83631EF27054609B
2 changed files with 128 additions and 0 deletions
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65
c-programming/mem/safe_mem.h Normal file
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/*
* safe_mem.h
*
* A header-only library (macro collection) for safer memory management.
*
* Author: Intel A80486DX2-66
* License: Creative Commons Zero 1.0 Universal
*/
#ifndef _SAFE_MEM_H
#define _SAFE_MEM_H
#include <stdlib.h>
#define SAFE_FREE_ERROR_HOOK /* user-defined */
#define safe_free(ptr) do { \
/* prevents NULL-freeing and double freeing */ \
if (ptr != NULL) { \
free(ptr); \
ptr = NULL; \
} else { SAFE_FREE_ERROR_HOOK; } \
} while (0)
#define precise_malloc(nmemb, size) \
/* prevents incorrect casting */ \
malloc((size_t) nmemb * (size_t) size)
/* secure_erase(dest, count): erases memory explicitly */
#if defined(__FreeBSD__)
# define NO_SECURE_ERASE_WARRANTY 0
# define SECURE_ERASE_WARRANTY "OpenBSD/FreeBSD: explicit_bzero"
# include <strings.h>
# define secure_erase explicit_bzero
#elif defined(_WIN32)
# define NO_SECURE_ERASE_WARRANTY 0
# define SECURE_ERASE_WARRANTY "Microsoft Windows: SecureZeroMemory"
# include <windows.h>
# define secure_erase SecureZeroMemory
#elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
# define NO_SECURE_ERASE_WARRANTY 0
# define SECURE_ERASE_WARRANTY "C11+: memset_s"
# define secure_erase(dest, count) memset_s(dest, count, 0, count)
#else
# define NO_SECURE_ERASE_WARRANTY 1
# define __observe__(ptr) do { \
if (*ptr == 0) { \
++(*ptr); \
fprintf(stderr, ""); \
} else \
--(*ptr); \
} while (0)
# define secure_erase(dest, count) do { \
memset(dest, 0, count); \
for (size_t i = 0; i < count; i++) \
__observe__(dest[i]); \
} while (0)
#endif
#endif /* _SAFE_MEM_H */

63
c-programming/mem/safe_mem.test.c Normal file
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/*
* safe_mem.c
*
* Author: Intel A80486DX2-66
* License: Creative Commons Zero 1.0 Universal
*/
#include <stdio.h>
#include <stdlib.h>
#include "safe_mem.h"
#undef SAFE_FREE_ERROR_HOOK
#define SAFE_FREE_ERROR_HOOK do { \
fprintf(stderr, "Double freeing detected!\n"); \
exit(EXIT_FAILURE); \
} while (0)
#define PRINT_POINTER(caption, ptr) \
printf(caption " = %p\n", (void*) ptr);
#define DUMP_INT_ARRAY(caption, ptr, count) do { \
printf("%s: [", caption); \
for (size_t i = 0; i < count; i++) { \
printf("%d", ptr[i]); \
if (i != (count - 1)) \
printf(", "); \
} \
printf("]\n"); \
} while (0)
int main(void) {
#define COUNT 4
int* integers = precise_malloc(COUNT, sizeof(int));
PRINT_POINTER("int* integers (before freeing)", integers);
integers[0] = 0;
integers[1] = EOF;
integers[2] = STDERR_FILENO;
integers[3] = 1;
DUMP_INT_ARRAY("int* integers (before secure erasure)", integers, COUNT);
printf("Secure erasure is "
#if NO_SECURE_ERASE_WARRANTY
"not guaranteed!"
#else
"guaranteed: %s"
#endif
"\n"
#if !NO_SECURE_ERASE_WARRANTY
, SECURE_ERASE_WARRANTY
#endif
);
secure_erase(integers, COUNT * sizeof(int));
DUMP_INT_ARRAY("int* integers (after secure erasure)", integers, COUNT);
safe_free(integers);
PRINT_POINTER("int* integers (after freeing)", integers);
fflush(stdout);
safe_free(integers);
PRINT_POINTER("int* integers (after two free() calls)", integers);
return EXIT_SUCCESS;
}