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/*
* Platform-specific and custom entropy polling functions
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
#if defined(__linux__) || defined(__midipix__) && !defined(_GNU_SOURCE)
/* Ensure that syscall() is available even when compiling with -std=c99 */
#define _GNU_SOURCE
#endif
#include "common.h"
#include <string.h>
#if defined(MBEDTLS_ENTROPY_C)
#include "mbedtls/entropy.h"
#include "entropy_poll.h"
#include "mbedtls/error.h"
#if defined(MBEDTLS_TIMING_C)
#include "mbedtls/timing.h"
#endif
#include "mbedtls/platform.h"
#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
#if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
!defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \
!defined(__HAIKU__) && !defined(__midipix__) && !defined(__MVS__)
#error \
"Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in mbedtls_config.h"
#endif
#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
#include <windows.h>
#include <bcrypt.h>
#include <intsafe.h>
int mbedtls_platform_entropy_poll(void *data, unsigned char *output, size_t len,
size_t *olen)
{
((void) data);
*olen = 0;
/*
* BCryptGenRandom takes ULONG for size, which is smaller than size_t on
* 64-bit Windows platforms. Extract entropy in chunks of len (dependent
* on ULONG_MAX) size.
*/
while (len != 0) {
unsigned long ulong_bytes =
(len > ULONG_MAX) ? ULONG_MAX : (unsigned long) len;
if (!BCRYPT_SUCCESS(BCryptGenRandom(NULL, output, ulong_bytes,
BCRYPT_USE_SYSTEM_PREFERRED_RNG))) {
return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
}
*olen += ulong_bytes;
len -= ulong_bytes;
}
return 0;
}
#else /* _WIN32 && !EFIX64 && !EFI32 */
/*
* Test for Linux getrandom() support.
* Since there is no wrapper in the libc yet, use the generic syscall wrapper
* available in GNU libc and compatible libc's (eg uClibc).
*/
#if ((defined(__linux__) && defined(__GLIBC__)) || defined(__midipix__))
#include <unistd.h>
#include <sys/syscall.h>
#if defined(SYS_getrandom)
#define HAVE_GETRANDOM
#include <errno.h>
static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags)
{
/* MemSan cannot understand that the syscall writes to the buffer */
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
memset(buf, 0, buflen);
#endif
#endif
return (int) syscall(SYS_getrandom, buf, buflen, flags);
}
#endif /* SYS_getrandom */
#endif /* __linux__ || __midipix__ */
#if defined(__FreeBSD__) || defined(__DragonFly__)
#include <sys/param.h>
#if (defined(__FreeBSD__) && __FreeBSD_version >= 1200000) || \
(defined(__DragonFly__) && __DragonFly_version >= 500700)
#include <errno.h>
#include <sys/random.h>
#define HAVE_GETRANDOM
static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags)
{
return (int) getrandom(buf, buflen, flags);
}
#endif /* (__FreeBSD__ && __FreeBSD_version >= 1200000) ||
(__DragonFly__ && __DragonFly_version >= 500700) */
#endif /* __FreeBSD__ || __DragonFly__ */
/*
* Some BSD systems provide KERN_ARND.
* This is equivalent to reading from /dev/urandom, only it doesn't require an
* open file descriptor, and provides up to 256 bytes per call (basically the
* same as getentropy(), but with a longer history).
*
* Documentation: https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7
*/
#if (defined(__FreeBSD__) || defined(__NetBSD__)) && !defined(HAVE_GETRANDOM)
#include <sys/param.h>
#include <sys/sysctl.h>
#if defined(KERN_ARND)
#define HAVE_SYSCTL_ARND
static int sysctl_arnd_wrapper(unsigned char *buf, size_t buflen)
{
int name[2];
size_t len;
name[0] = CTL_KERN;
name[1] = KERN_ARND;
while (buflen > 0) {
len = buflen > 256 ? 256 : buflen;
if (sysctl(name, 2, buf, &len, NULL, 0) == -1) {
return -1;
}
buflen -= len;
buf += len;
}
return 0;
}
#endif /* KERN_ARND */
#endif /* __FreeBSD__ || __NetBSD__ */
#include <stdio.h>
int mbedtls_platform_entropy_poll(void *data,
unsigned char *output, size_t len, size_t *olen)
{
FILE *file;
size_t read_len;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
((void) data);
#if defined(HAVE_GETRANDOM)
ret = getrandom_wrapper(output, len, 0);
if (ret >= 0) {
*olen = (size_t) ret;
return 0;
} else if (errno != ENOSYS) {
return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
}
/* Fall through if the system call isn't known. */
#else
((void) ret);
#endif /* HAVE_GETRANDOM */
#if defined(HAVE_SYSCTL_ARND)
((void) file);
((void) read_len);
if (sysctl_arnd_wrapper(output, len) == -1) {
return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
}
*olen = len;
return 0;
#else
*olen = 0;
file = fopen("/dev/urandom", "rb");
if (file == NULL) {
return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
}
/* Ensure no stdio buffering of secrets, as such buffers cannot be wiped. */
mbedtls_setbuf(file, NULL);
read_len = fread(output, 1, len, file);
if (read_len != len) {
fclose(file);
return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
}
fclose(file);
*olen = len;
return 0;
#endif /* HAVE_SYSCTL_ARND */
}
#endif /* _WIN32 && !EFIX64 && !EFI32 */
#endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */
#if defined(MBEDTLS_ENTROPY_NV_SEED)
int mbedtls_nv_seed_poll(void *data,
unsigned char *output, size_t len, size_t *olen)
{
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
((void) data);
memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);
if (mbedtls_nv_seed_read(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) < 0) {
return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
}
if (len < use_len) {
use_len = len;
}
memcpy(output, buf, use_len);
*olen = use_len;
return 0;
}
#endif /* MBEDTLS_ENTROPY_NV_SEED */
#endif /* MBEDTLS_ENTROPY_C */
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