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/* SPDX-License-Identifier: MIT
* Copyright (c) 2026 Leah Rowe <leah@libreboot.org>
*
* Random number generation
*/
#ifndef RAND_H
#define RAND_H
#ifdef __OpenBSD__
#include <sys/param.h>
#endif
#include <sys/types.h>
#ifndef USE_URANDOM
#define USE_URANDOM 0
#endif
#include <errno.h>
#if defined(USE_URANDOM) && \
((USE_URANDOM) > 0)
#include <fcntl.h> /* if not arc4random: /dev/urandom */
#endif
#include <limits.h>
#include <stddef.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include "../include/common.h"
void
rset(void *buf, size_t n)
{
int saved_errno = errno;
#if (defined(__OpenBSD__) || defined(__FreeBSD__) || \
defined(__NetBSD__) || defined(__APPLE__) || \
defined(__DragonFly__)) && !(defined(USE_URANDOM) && \
((USE_URANDOM) > 0))
arc4random_buf(buf, n);
goto out;
#else
size_t off = errno = 0;
ssize_t rc = 0;
#if defined(USE_URANDOM) && \
((USE_URANDOM) > 0)
int fd = -1;
if ((fd = open("/dev/urandom", O_RDONLY)) < 0)
goto err;
retry_rand:
if ((rc = read(fd, buf, n)) < 0) {
#elif defined(__linux__)
retry_rand:
if ((rc = (ssize_t)syscall(SYS_getrandom,
buf + off, n - off, 0)) < 0) {
#else
#error Unsupported operating system (possibly unsecure randomisation)
#endif
if (errno == EINTR ||
errno == EAGAIN) {
usleep(100);
goto retry_rand;
}
goto err; /* possibly unsupported by kernel */
}
if ((off += (size_t)rc) < n)
goto retry_rand;
goto out;
err:
err_no_cleanup(1, ECANCELED,
"Randomisation failure, possibly unsupported in your kernel.");
exit(EXIT_FAILURE);
#endif
out:
errno = saved_errno;
}
#endif
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