int	 getentropy(void *, size_t);

	getentropy.2 \

	getentropy;

	__sys_getentropy;

	_getentropy;

.\"	$OpenBSD: getentropy.2,v 1.6 2014/07/18 18:20:17 deraadt Exp $

.\"

.\" Copyright (c) 2014 Theo de Raadt

.\"

.\" Permission to use, copy, modify, and 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.

.\"

.Dd $Mdocdate: July 18 2014 $

.Dt GETENTROPY 2

.Os

.Sh NAME

.Nm getentropy

.Nd get entropy

.Sh SYNOPSIS

.Fd #include <unistd.h>

.Ft int

.Fn getentropy "void *buf" "size_t buflen"

.Sh DESCRIPTION

.Nm

fills a buffer with high-quality entropy, which can be used

as input for process-context pseudorandom generators like

.Xr arc4random 3 .

.Pp

The maximum buffer size permitted is 256 bytes.

Even if

.Va buflen

exceeds this.

.Pp

.Nm

is not intended for regular code; please use the

.Xr arc4random 3

family of functions instead.

.Sh RETURN VALUES

Upon successful completion, a value of 0 is returned.

Otherwise, a value of \-1 is returned and

.Va errno

is set to indicate the error.

.Sh ERRORS

.Fn getentropy

will succeed unless:

.Bl -tag -width Er

.It Bq Er EFAULT

The

.Fa buf

parameter points to an

invalid address.

.El

.Sh SEE ALSO

.Xr arc4random 3

.Sh HISTORY

The

.Nm

function appeared in

.Ox 5.6 .

545	AUE_NULL	NOPROTO	{ int getentropy(void *ptr, \

				    size_t len); }

kern/sys_random.c		standard

/*-

 * Copyright (c) 2014, by Theo de Raadt

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. The name of the author may not be used to endorse or promote products

 *    derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 *

 * $FreeBSD$

 */

#include <sys/cdefs.h>

__FBSDID("$FreeBSD$");

#include <sys/sysent.h>

#include <sys/sysproto.h>

#include <sys/libkern.h>

#include <sys/proc.h>

#ifndef	_SYS_SYSPROTO_H_

struct getentropy_args {

	void	*ptr;

	size_t	len;

};

#endif

int

sys_getentropy(struct thread *td, struct getentropy_args *uap)

{

	char buf[256];

	size_t len;

	int error;

	len = MIN(sizeof(buf), uap->len);

	arc4rand(buf, len, 1);

	if ((error = copyout(buf, uap->ptr, len)) != 0)	

		return (error);

	memset(buf, 0, sizeof(buf));

	return (0);

}

545	AUE_NULL	STD	{ int getentropy(void *ptr, size_t len); }