112 lines
3.0 KiB
C
112 lines
3.0 KiB
C
// Copyright 2013-2022 Nicholas J. Kain <njkain at gmail dot com>
|
|
// SPDX-License-Identifier: MIT
|
|
#include <stdint.h>
|
|
#include <string.h>
|
|
#include <stdbool.h>
|
|
#include <unistd.h>
|
|
#include <errno.h>
|
|
#include <time.h>
|
|
#include <sys/types.h>
|
|
#include <sys/stat.h>
|
|
#include <fcntl.h>
|
|
#include "nk/hwrng.h"
|
|
#include "nk/log.h"
|
|
#include "nk/io.h"
|
|
|
|
#ifdef NK_NO_GETRANDOM_SYSCALL
|
|
static bool nk_getrandom(char *seed, size_t len)
|
|
{
|
|
(void)seed;
|
|
(void)len;
|
|
return false;
|
|
}
|
|
#else
|
|
#ifdef NK_NO_GETRANDOM_LIBC
|
|
#include <sys/syscall.h>
|
|
#include <linux/random.h>
|
|
#define NK_GETRANDOM_CALL(A,B,C) syscall(SYS_getrandom, (A), (B), (C))
|
|
#else
|
|
#include <sys/random.h>
|
|
#define NK_GETRANDOM_CALL(A,B,C) getrandom((A), (B), (C))
|
|
#endif
|
|
|
|
static bool nk_getrandom(char *seed, size_t len)
|
|
{
|
|
size_t fetched = 0;
|
|
while (fetched < len) {
|
|
int r = NK_GETRANDOM_CALL(seed + fetched, len - fetched, 0);
|
|
if (r <= 0) {
|
|
if (r == 0) {
|
|
// Failsafe to guard against infinite loops.
|
|
log_line("%s: getrandom() returned no entropy", __func__);
|
|
return false;
|
|
}
|
|
if (errno == EINTR) continue;
|
|
if (errno == ENOSYS) return false; // Kernel doesn't support syscall
|
|
log_line("%s: getrandom() failed: %s", __func__, strerror(errno));
|
|
return false;
|
|
}
|
|
fetched += (size_t)r;
|
|
}
|
|
return true;
|
|
}
|
|
#endif
|
|
#undef NK_GETRANDOM_CALL
|
|
|
|
static bool nk_get_rnd_clk(char *seed, size_t len)
|
|
{
|
|
struct timespec ts;
|
|
for (size_t i = 0; i < len; ++i) {
|
|
int r = clock_gettime(CLOCK_REALTIME, &ts);
|
|
if (r < 0) {
|
|
log_line("%s: Could not call clock_gettime(CLOCK_REALTIME): %s",
|
|
__func__, strerror(errno));
|
|
return false;
|
|
}
|
|
char *p = (char *)&ts.tv_sec;
|
|
char *q = (char *)&ts.tv_nsec;
|
|
for (size_t j = 0; j < sizeof ts.tv_sec; ++j)
|
|
seed[i] ^= p[j];
|
|
for (size_t j = 0; j < sizeof ts.tv_nsec; ++j)
|
|
seed[i] ^= q[j];
|
|
// Force some scheduler jitter.
|
|
static const struct timespec st = { .tv_sec=0, .tv_nsec=1 };
|
|
nanosleep(&st, (struct timespec *)0);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static bool nk_get_urandom(char *seed, size_t len)
|
|
{
|
|
int fd = open("/dev/urandom", O_RDONLY);
|
|
if (fd < 0) {
|
|
log_line("%s: Could not open /dev/urandom: %s", __func__,
|
|
strerror(errno));
|
|
return false;
|
|
}
|
|
bool ret = true;
|
|
int r = safe_read(fd, seed, len);
|
|
if (r < 0) {
|
|
ret = false;
|
|
log_line("%s: Could not read /dev/urandom: %s",
|
|
__func__, strerror(errno));
|
|
}
|
|
close(fd);
|
|
return ret;
|
|
}
|
|
|
|
void nk_get_hwrng(void *seed, size_t len)
|
|
{
|
|
char *s = (char *)seed;
|
|
if (nk_getrandom(s, len))
|
|
return;
|
|
if (nk_get_urandom(s, len))
|
|
return;
|
|
log_line("%s: Seeding PRNG via system clock. May be predictable.",
|
|
__func__);
|
|
if (nk_get_rnd_clk(s, len))
|
|
return;
|
|
suicide("%s: All methods to seed PRNG failed. Exiting.", __func__);
|
|
}
|
|
|