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/*
* Load entropy.
*
* Copyright (c) 2014 Marko Kreen
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#define _CRT_RAND_S
#include <usual/crypto/entropy.h>
#include <usual/err.h>
#include <usual/string.h>
#ifndef HAVE_GETENTROPY
/*
* Load system entropy.
*/
#if defined(_WIN32) || defined(_WIN64)
/*
* Windows
*
* It's possible to get entropy via:
* - CryptGenRandom. Uses RtlGenRandom, requires CryptoAPI.
* - rand_s(). Uses RtlGenRandom, Requires VS2005 CRT, WindowsXP+.
* - RtlGenRandom(). Internal func, no public definition.
*/
int getentropy(void *dst, size_t len)
{
uint8_t *d = dst;
unsigned int val, n;
errno_t err;
while (len > 0) {
err = rand_s(&val);
if (err != 0)
return -1;
n = (len > sizeof(val)) ? sizeof(val) : len;
memcpy(d, &val, n);
d += n;
}
explicit_bzero(&val, sizeof(val));
return 0;
}
#elif defined(HAVE_GETRANDOM)
int getentropy(void *dst, size_t len)
{
int res;
if (len > 256)
goto eio;
res = getrandom(dst, len, 0);
if (res < 0)
return -1;
if (res == len)
return res;
eio:
errno = EIO;
return -1;
}
#else /* UNIX-like system */
#include <sys/stat.h>
#include <fcntl.h>
/* open and check device node */
static int open_devrandom(const char *dev)
{
int fd;
int oflags = O_RDONLY;
#ifdef O_CLOEXEC
oflags |= O_CLOEXEC;
#endif
open_loop:
fd = open(dev, oflags);
if (fd == -1) {
if (errno == EINTR)
goto open_loop;
return -1;
}
#ifndef O_CLOEXEC
fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
#endif
/*
* Lightly verify that the device node looks sane
*/
{
struct stat st;
if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode))
goto fail;
}
#ifdef RNDGETENTCNT
{
int cnt;
if (ioctl(fd, RNDGETENTCNT, &cnt) == -1)
goto fail;
}
#endif
/* seems fine */
return fd;
fail:
close(fd);
return -1;
}
/*
* Read normal random devices under /dev.
*/
static const char *devlist[] = {
"/dev/urandom",
"/dev/random",
NULL,
};
int getentropy(void *dst, size_t bytes)
{
uint8_t *d = dst;
size_t need = bytes;
int fd, res;
unsigned int i;
for (i = 0; devlist[i]; i++) {
reopen:
fd = open_devrandom(devlist[i]);
if (fd == -1)
continue;
while (need > 0) {
res = read(fd, d, need);
if (res > 0) {
/* successful read */
need -= res;
d += res;
} else if (res == 0) {
/* eof - open again */
close(fd);
goto reopen;
} else if (errno == EINTR) {
/* signal - retry read */
} else {
close(fd);
/* random error, fail */
return -1;
}
}
close(fd);
return 0;
}
errno = EIO;
return -1;
}
#endif /* unix */
#endif /* !HAVE_GETENTROPY */
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