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update arc4random from bug #885
Add config option to provide arc4random without device access. Signed-off-by: Peter S. Mazinger <ps.m@gmx.net> Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
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Peter S. Mazinger
committed by
Bernhard Reutner-Fischer
Bernhard Reutner-Fischer
parent
1c17b766a9
commit
d6f8248cc3
110
docs/man/arc4random.3
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110
docs/man/arc4random.3
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.\" $OpenBSD: arc4random.3,v 1.19 2005/07/17 08:50:55 jaredy Exp $
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.\"
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.\" Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Niels Provos.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" Manual page, using -mandoc macros
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.\"
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.Dd April 15, 1997
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.Dt ARC4RANDOM 3
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.Os
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.Sh NAME
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.Nm arc4random ,
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.Nm arc4random_stir ,
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.Nm arc4random_addrandom
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.Nd arc4 random number generator
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.Sh SYNOPSIS
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.Fd #include <stdlib.h>
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.Ft uint32_t
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.Fn arc4random "void"
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.Ft void
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.Fn arc4random_stir "void"
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.Ft void
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.Fn arc4random_addrandom "u_char *dat" "int datlen"
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.Sh DESCRIPTION
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The
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.Fn arc4random
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function provides a high quality 32-bit pseudo-random
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number very quickly.
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.Fn arc4random
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seeds itself on a regular basis from the kernel strong random number
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subsystem described in
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.Xr random 4 .
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On each call, an ARC4 generator is used to generate a new result.
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The
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.Fn arc4random
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function uses the ARC4 cipher key stream generator,
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which uses 8*8 8-bit S-Boxes.
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The S-Boxes can be in about (2**1700) states.
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.Pp
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.Fn arc4random
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fits into a middle ground not covered by other subsystems such as
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the strong, slow, and resource expensive random
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devices described in
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.Xr random 4
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versus the fast but poor quality interfaces described in
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.Xr rand 3 ,
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.Xr random 3 ,
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and
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.Xr drand48 3 .
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.Pp
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The
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.Fn arc4random_stir
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function reads data from a pseudo-random device, usually
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.Pa /dev/urandom,
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and uses it to permute the S-Boxes via
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.Fn arc4random_addrandom .
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.Pp
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There is no need to call
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.Fn arc4random_stir
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before using
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.Fn arc4random ,
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since
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.Fn arc4random
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automatically initializes itself.
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.Sh SEE ALSO
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.Xr rand 3 ,
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.Xr rand48 3 ,
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.Xr random 3
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.Sh HISTORY
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An algorithm called
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.Pa RC4
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was designed by RSA Data Security, Inc.
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It was considered a trade secret.
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Because it was a trade secret, it obviously could not be patented.
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A clone of this was posted anonymously to USENET and confirmed to
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be equivalent by several sources who had access to the original cipher.
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Because of the trade secret situation, RSA Data Security, Inc. can do
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nothing about the release of the ARC4 algorithm.
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Since
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.Pa RC4
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used to be a trade secret, the cipher is now referred to as
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.Pa ARC4 .
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.Pp
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These functions first appeared in
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.Ox 2.1 .
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@@ -2087,6 +2087,17 @@ config UCLIBC_HAS_ARC4RANDOM
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Most people will answer N.
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config ARC4RANDOM_USES_NODEV
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bool "Do not use /dev/urandom with arc4random()"
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depends on UCLIBC_HAS_ARC4RANDOM
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default n
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help
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Answer Y to use gettimeofday(2) and getpid(2) exclusively for
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arc4random(). This is not a bad idea for a diskless system, but
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it uses a lot of syscalls to stir each array element.
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Most people will answer N.
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config HAVE_NO_SSP
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bool
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@@ -1,24 +1,29 @@
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/* $$$: arc4random.c 2005/02/08 robert */
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/* $NetBSD: arc4random.c,v 1.5.2.1 2004/03/26 22:52:50 jmc Exp $ */
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/* $OpenBSD: arc4random.c,v 1.6 2001/06/05 05:05:38 pvalchev Exp $ */
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/*
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* Arc4 random number generator for OpenBSD.
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* Copyright 1996 David Mazieres <dm@lcs.mit.edu>.
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* Copyright (c) 1996, David Mazieres <dm@uun.org>
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*
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* Modification and redistribution in source and binary forms is
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* permitted provided that due credit is given to the author and the
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* OpenBSD project by leaving this copyright notice intact.
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* Arc4 random number generator for OpenBSD.
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*
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* This code is derived from section 17.1 of Applied Cryptography,
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* second edition, which describes a stream cipher allegedly
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* compatible with RSA Labs "RC4" cipher (the actual description of
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* which is a trade secret). The same algorithm is used as a stream
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* cipher called "arcfour" in Tatu Ylonen's ssh package.
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*
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* Here the stream cipher has been modified always to include the time
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* Here the stream cipher has been modified always to include entropy
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* when initializing the state. That makes it impossible to
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* regenerate the same random sequence twice, so this can't be used
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* for encryption, but will generate good random numbers.
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@@ -26,17 +31,15 @@
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* RC4 is a registered trademark of RSA Laboratories.
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*/
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/* $OpenBSD: arc4random.c,v 1.16 2007/02/12 19:58:47 otto Exp $ */
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#include <features.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/time.h>
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#ifdef __ARC4RANDOM_USE_ERANDOM__
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#include <sys/sysctl.h>
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#endif
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struct arc4_stream {
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u_int8_t i;
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@@ -46,6 +49,8 @@ struct arc4_stream {
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static smallint rs_initialized;
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static struct arc4_stream rs;
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static pid_t arc4_stir_pid;
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static int arc4_count;
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static __inline__ void
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arc4_init(struct arc4_stream *as)
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@@ -92,53 +97,84 @@ arc4_addrandom(struct arc4_stream *as, u_char *dat, int datlen)
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static void
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arc4_stir(struct arc4_stream *as)
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{
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int fd;
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struct {
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struct timeval tv;
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uint rnd[(128 - sizeof(struct timeval)) / sizeof(uint)];
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} rdat;
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int n;
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u_char rnd[128];
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struct timeval tv;
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#ifndef __ARC4RANDOM_USES_NODEV__
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int fd;
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gettimeofday(&rdat.tv, NULL);
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fd = open("/dev/urandom", O_RDONLY);
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if (fd != -1) {
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read(fd, rdat.rnd, sizeof(rdat.rnd));
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read(fd, rnd, sizeof(rnd));
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close(fd);
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}
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#ifdef __ARC4RANDOM_USE_ERANDOM__
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else {
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int mib[3];
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uint i;
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size_t len;
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/* Did the pseudo-random device fail? Use gettimeofday(). */
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else
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#endif
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if (gettimeofday(&tv, NULL) != (-1)) {
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/* Device could not be opened, we might be chrooted, take
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* randomness from sysctl. */
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/* Initialize the first element so it's hopefully not '0',
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* to help out the next loop. Tossing in some prime numbers
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* probably can't hurt. */
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rnd[0] = (tv.tv_sec % 10000) * 3 + tv.tv_usec * 7 + \
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(getpid() % 1000) * 13;
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mib[0] = CTL_KERN;
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mib[1] = KERN_RANDOM;
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mib[2] = RANDOM_ERANDOM;
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for (n = 1; n < 127 ; n++) {
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for (i = 0; i < sizeof(rdat.rnd) / sizeof(uint); i++) {
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len = sizeof(uint);
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if (sysctl(mib, 3, &rdat.rnd[i], &len, NULL, 0) == -1)
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break;
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/* Take advantage of the stack space. Only initialize
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* elements equal to '0'. This will make the rnd[]
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* array much less vulnerable to timing attacks. Here
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* we'll stir getpid() into the value of the previous
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* element. Approximately 1 in 128 elements will still
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* become '0'. */
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if (rnd[n] == 0) {
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rnd[n] = ((rnd[n - 1] + n) ^ \
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((getpid() % 1000) * 17));
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}
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}
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}
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#endif
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else {
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/* gettimeofday() failed? Do the same thing as above, but only
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* with getpid(). */
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arc4_addrandom(as, (void *) &rdat, sizeof(rdat));
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rnd[0] = (getpid() % 1000) * 19;
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for (n = 1; n < 127 ; n++) {
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if (rnd[n] == 0) {
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rnd[n] = ((rnd[n - 1] + n) ^ \
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((getpid() % 1000) * 23));
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}
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}
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}
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arc4_stir_pid = getpid();
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arc4_addrandom(as, rnd, sizeof(rnd));
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/*
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* Throw away the first N words of output, as suggested in the
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* paper "Weaknesses in the Key Scheduling Algorithm of RC4"
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* by Fluher, Mantin, and Shamir. N = 1024 is based on
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* suggestions in the paper "(Not So) Random Shuffles of RC4"
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* by Ilya Mironov.
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* Discard early keystream, as per recommendations in:
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* http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
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*/
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for (n = 0; n < 1024; n++)
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arc4_getbyte(as);
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for (n = 0; n < 256; n++)
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(void)arc4_getbyte(as);
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arc4_count = 1600000;
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}
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#if 0
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static void __arc4random_stir(void);
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/*
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* __arc4_getbyte() is a libc private function intended for use
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* with malloc.
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*/
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u_int8_t
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__arc4_getbyte(void)
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{
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if (--arc4_count == 0 || !rs_initialized)
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__arc4random_stir();
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return arc4_getbyte(&rs);
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}
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#endif
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static __inline__ u_int32_t
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arc4_getword(struct arc4_stream *as)
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{
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@@ -172,20 +208,8 @@ arc4random_addrandom(u_char *dat, int datlen)
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u_int32_t
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arc4random(void)
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{
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if (!rs_initialized)
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arc4_count -= 4;
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if (arc4_count <= 0 || !rs_initialized || arc4_stir_pid != getpid())
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__arc4random_stir();
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return arc4_getword(&rs);
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}
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#if 0
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/*-------- Test code --------*/
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#include <stdlib.h>
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#include <stdio.h>
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int main(void) {
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int random_number;
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random_number = arc4random() % 65536;
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printf("%d\n", random_number);
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return 0;
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}
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#endif
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12
test/stdlib/testarc4random.c
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12
test/stdlib/testarc4random.c
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#include <stdlib.h>
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#include <stdio.h>
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int main(void)
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{
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#ifdef __UCLIBC_HAS_ARC4RANDOM__
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int random_number;
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random_number = arc4random() % 65536;
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printf("%d\n", random_number);
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#endif
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return 0;
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}
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