From owner-freebsd-security@FreeBSD.ORG  Fri Jul 18 20:53:07 2014
Return-Path: <owner-freebsd-security@FreeBSD.ORG>
Delivered-To: freebsd-security@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id 491EC181
 for <freebsd-security@freebsd.org>; Fri, 18 Jul 2014 20:53:07 +0000 (UTC)
Received: from manchester-1.man.uk.cluster.ok24.net
 (manchester-1.man.uk.cluster.ok24.net [213.138.100.64])
 (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 052DB2E15
 for <freebsd-security@freebsd.org>; Fri, 18 Jul 2014 20:53:06 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=simple/simple; d=pyro.eu.org;
 s=07.2014; 
 h=Content-Transfer-Encoding:Content-Type:In-Reply-To:References:Subject:To:MIME-Version:From:Date:Message-ID;
 bh=hwpLYTN3cHciVVARnx0SwYOc6fR8utSmOOBFPwLg0J0=; 
 b=N0M0BdhY2fvxrvJx1yUliLDtzVxYX2AgTbwX6taUsgMqJk4YVLL7CGKUZWLggUhub7ypClly74LetWiVB0trAkzS8nnXFJRuVHXs26WU11u9dWU87gG/47kXaBxMWSSXlXm9nX4bZhnnglOLitvXcM7Q1NXlaZ82+eanT15QXxc=;
X-Spam-Status: No, score=-1.1 required=2.0 tests=ALL_TRUSTED, BAYES_00,
 DKIM_ADSP_DISCARD
Received: from guisborough-1.rcc.uk.cluster.ok24.net ([217.155.40.118])
 by manchester-1.man.uk.cluster.ok24.net with esmtps (TLSv1:AES256-SHA:256)
 (Exim 4.80) (envelope-from <steven@pyro.eu.org>) id 1X8F9L-0001Aa-56
 for freebsd-security@freebsd.org; Fri, 18 Jul 2014 21:53:04 +0100
Received: from [10.0.1.191]
 by guisborough-1.rcc.uk.cluster.ok24.net with esmtpsa
 (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.69)
 (envelope-from <steven@pyro.eu.org>) id 1X8F9K-0002jQ-Ea
 for freebsd-security@freebsd.org; Fri, 18 Jul 2014 21:53:02 +0100
Message-ID: <53C9892D.1050002@pyro.eu.org>
Date: Fri, 18 Jul 2014 21:53:01 +0100
From: Steven Chamberlain <steven@pyro.eu.org>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
 rv:24.0) Gecko/20100101 Icedove/24.6.0
MIME-Version: 1.0
To: freebsd-security@freebsd.org
Subject: Re: Speed and security of /dev/urandom
References: <53C85F42.1000704@pyro.eu.org> <53C9857D.6000806@freebsd.org>
In-Reply-To: <53C9857D.6000806@freebsd.org>
X-Enigmail-Version: 1.6
Content-Type: text/plain; charset=KOI8-R
Content-Transfer-Encoding: 7bit
X-BeenThere: freebsd-security@freebsd.org
X-Mailman-Version: 2.1.18
Precedence: list
List-Id: "Security issues \[members-only posting\]"
 <freebsd-security.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-security>, 
 <mailto:freebsd-security-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-security/>
List-Post: <mailto:freebsd-security@freebsd.org>
List-Help: <mailto:freebsd-security-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-security>, 
 <mailto:freebsd-security-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 18 Jul 2014 20:53:07 -0000

On 18/07/14 21:37, Andrey Chernov wrote:
> One of the reason I hear is that true random entropy bits can be quickly
> exhausted if every userland program will drain them so much.

True of Linux at least, I assume that's why they must make /dev/random
block when the estimated entropy in the pool is low.  Applications have
been encouraged to not excessively read even from /dev/urandom, for the
same reason, so it makes sense on Linux to stretch with RC4 or something.

Regards,
-- 
Steven Chamberlain
steven@pyro.eu.org