From owner-freebsd-questions@FreeBSD.ORG  Mon Jan  8 21:18:28 2007
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
X-Original-To: freebsd-questions@freebsd.org
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
	by hub.freebsd.org (Postfix) with ESMTP id DF66816A407
	for <freebsd-questions@freebsd.org>;
	Mon,  8 Jan 2007 21:18:28 +0000 (UTC)
	(envelope-from fbsd06@mlists.homeunix.com)
Received: from mxout-03.mxes.net (mxout-03.mxes.net [216.86.168.178])
	by mx1.freebsd.org (Postfix) with ESMTP id B866313C442
	for <freebsd-questions@freebsd.org>;
	Mon,  8 Jan 2007 21:18:26 +0000 (UTC)
	(envelope-from fbsd06@mlists.homeunix.com)
Received: from gumby.homeunix.com (unknown [87.81.140.128])
	(using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by smtp.mxes.net (Postfix) with ESMTP id 6AD7F51980
	for <freebsd-questions@freebsd.org>;
	Mon,  8 Jan 2007 16:18:25 -0500 (EST)
Date: Mon, 8 Jan 2007 21:18:23 +0000
From: RW <fbsd06@mlists.homeunix.com>
To: freebsd-questions@freebsd.org
Message-ID: <20070108211823.4c4b51c9@gumby.homeunix.com>
In-Reply-To: <EAE5160D-6B80-4C6A-BB8F-70518EE0711F@u.washington.edu>
References: <20070108175314.27ce391f@gumby.homeunix.com>
	<20070108183645.GF41724@dan.emsphone.com>
	<EAE5160D-6B80-4C6A-BB8F-70518EE0711F@u.washington.edu>
X-Mailer: Sylpheed-Claws 2.6.0 (GTK+ 2.10.6; i386-portbld-freebsd6.1)
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Subject: Re: pwgen's seeding looks insecure
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 08 Jan 2007 21:18:29 -0000

On Mon, 8 Jan 2007 10:56:50 -0800
Garrett Cooper <youshi10@u.washington.edu> wrote:

> On Jan 8, 2007, at 10:36 AM, Dan Nelson wrote:
> 
> > In the last episode (Jan 08), RW said:
> >> Someone recently recommended sysutils/pwgen for generating user
> >> passwords.  Out of curiosity I had a look at how it works, and I
> >> don't like the look of its PRNG initialization:
> >>
> >>
> >> #ifdef RAND48
> >>   srand48((time(0)<<9) ^ (getpgrp()<<15) ^ (getpid()) ^ (time(0) 
> >> >>11));
> >> #else
> >>   srand(time(0) ^ (getpgrp() << 8) + getpid());
> >> #endif
> >>
> >> If pwgen is called from an account creation script, time(0) can be
> >> inferred from timestamps, e.g. on a home-directory, so that just  
> >> leaves
> >> getpid() and  getpgrp(). PIDs are allocated sequentially and  
> >> globally,
> >> so getpid() is highly predictable. I don't know much about
> >> getpgrp(), but from the manpage it doesn't appear to be any better.
> >
> > Even better: make RANDOM() call random() instead of rand()

I wasn't suggesting the use of getpgrp(), it's one of the existing three
sources of entropy . The other two sources are can be inferred by any
user (assuming that pwgen is run close to the point at which the
account is created). What I was wondering is how much secure entropy
there is in getpgrp() alone.

I just wrote a little test program, and getpgrp() seems to return the
same number as getpid. If I haven't screwed-up and that is generally
correct, then any user can log PIDs verses time and find the password
of a newly created account from the datestamp of its home directory,
within a few attempts.