From: Stephan Mueller 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> References: <9192755.iDgo3Omyqe@positron.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Ted Tso , Herbert Xu , Linux Crypto Mailing List , Linux Kernel Mailing List , Sandy Harris To: Nikos Mavrogiannopoulos Return-path: 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 In-Reply-To: Sender: linux-crypto-owner@vger.kernel.org List-ID: Am Donnerstag, 21. April 2016, 15:03:37 schrieb Nikos Mavrogiannopoulos= : Hi Nikos, >=20 > [quote from pdf] >=20 > > ... DRBG is =E2=80=9Cminimally=E2=80=9D seeded with 112^6 bits of e= ntropy. > > This is commonly achieved even before user space is initiated. >=20 > 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 getrando= m(2),=20 the LRNG provides you with another means. You may use the=20 /proc/sys/kernel/random/drbg_minimally_seeded or drbg_fully_seeded bool= eans.=20 If you poll on those, you will obtain the indication whether the second= ary=20 DRBG feeding /dev/random is seeded with 112 bits (drbg_minimally_seeded= or 256=20 bits (drbg_fully_seeded). Those two booleans are exported for exactly that purpose: allow user sp= ace to=20 know about initial seeding status of the LRNG. Ciao Stephan