random.c

// SPDX-License-Identifier: CDDL-1.0
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or https://opensource.org/licenses/CDDL-1.0.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
 * Copyright (c) 2016 Actifio, Inc. All rights reserved.
 * Copyright (c) 2025, Klara, Inc.
 */

#include <stdint.h>
#include <fcntl.h>
#include <assert.h>
#include <sys/random.h>
#include "libspl_impl.h"

#define	RANDOM_PATH	"/dev/random"
#define	URANDOM_PATH	"/dev/urandom"

static int random_fd = -1, urandom_fd = -1;

static boolean_t force_pseudo = B_FALSE;

void
random_init(void)
{
	/* Handle multiple calls. */
	if (random_fd != -1) {
		ASSERT3U(urandom_fd, !=, -1);
		return;
	}

	VERIFY((random_fd = open(RANDOM_PATH, O_RDONLY | O_CLOEXEC)) != -1);
	VERIFY((urandom_fd = open(URANDOM_PATH, O_RDONLY | O_CLOEXEC)) != -1);
}

void
random_fini(void)
{
	close(random_fd);
	close(urandom_fd);

	random_fd = -1;
	urandom_fd = -1;
}

void
random_force_pseudo(boolean_t onoff)
{
	force_pseudo = onoff;
}

static int
random_get_bytes_common(uint8_t *ptr, size_t len, int fd)
{
	size_t resid = len;
	ssize_t bytes;

	ASSERT(fd != -1);

	while (resid != 0) {
		bytes = read(fd, ptr, resid);
		ASSERT3S(bytes, >=, 0);
		ptr += bytes;
		resid -= bytes;
	}

	return (0);
}

int
random_get_bytes(uint8_t *ptr, size_t len)
{
	if (force_pseudo)
		return (random_get_pseudo_bytes(ptr, len));
	return (random_get_bytes_common(ptr, len, random_fd));
}

int
random_get_pseudo_bytes(uint8_t *ptr, size_t len)
{
	return (random_get_bytes_common(ptr, len, urandom_fd));
}