Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752797AbcDUPQ4 (ORCPT ); Thu, 21 Apr 2016 11:16:56 -0400 Received: from mail.eperm.de ([89.247.134.16]:53002 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751902AbcDUPQy convert rfc822-to-8bit (ORCPT ); Thu, 21 Apr 2016 11:16:54 -0400 From: Stephan Mueller To: Nikos Mavrogiannopoulos Cc: Ted Tso , Herbert Xu , Linux Crypto Mailing List , Linux Kernel Mailing List , Sandy Harris Subject: Re: [RFC][PATCH 0/6] /dev/random - a new approach Date: Thu, 21 Apr 2016 17:16:51 +0200 Message-ID: <1499137.D4Mft7n8bh@tauon.atsec.com> User-Agent: KMail/4.14.10 (Linux/4.4.6-301.fc23.x86_64; KDE/4.14.18; x86_64; ; ) In-Reply-To: References: <9192755.iDgo3Omyqe@positron.chronox.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1342 Lines: 31 Am Donnerstag, 21. April 2016, 15:03:37 schrieb Nikos Mavrogiannopoulos: Hi Nikos, > > [quote from pdf] > > > ... DRBG is “minimally” seeded with 112^6 bits of entropy. > > This is commonly achieved even before user space is initiated. > > Unfortunately one of the issues of the /dev/urandom interface is the > fact that it may start providing random numbers even before the > seeding is complete. From the above quote, I understand that this > issue is not addressed by the new interface. That's a serious > limitation (of the current and inherited by the new implementation), > since most/all newly deployed systems from "cloud" images generate > keys using /dev/urandom (for sshd for example) on boot, and it is > unknown to these applications whether they operate with uninitialized > seed. One more item to consider: If you do not want to change to use getrandom(2), the LRNG provides you with another means. You may use the /proc/sys/kernel/random/drbg_minimally_seeded or drbg_fully_seeded booleans. If you poll on those, you will obtain the indication whether the secondary DRBG feeding /dev/random is seeded with 112 bits (drbg_minimally_seeded or 256 bits (drbg_fully_seeded). Those two booleans are exported for exactly that purpose: allow user space to know about initial seeding status of the LRNG. Ciao Stephan