Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423480Ab2KNVOL (ORCPT ); Wed, 14 Nov 2012 16:14:11 -0500 Received: from mail-oa0-f46.google.com ([209.85.219.46]:36070 "EHLO mail-oa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932331Ab2KNVOI (ORCPT ); Wed, 14 Nov 2012 16:14:08 -0500 MIME-Version: 1.0 In-Reply-To: <20121114130909.2dcc5b75.akpm@linux-foundation.org> References: <5099F133.5030305@oracle.com> <5099FBAA.6000200@oracle.com> <509A078D.8060705@oracle.com> <20121114130909.2dcc5b75.akpm@linux-foundation.org> Date: Wed, 14 Nov 2012 13:14:07 -0800 X-Google-Sender-Auth: cDU2fyzellYu-bbe1xLlQfr4Mhs Message-ID: Subject: Re: [RESEND PATCH V3] binfmt_elf.c: use get_random_int() to fix entropy depleting From: Kees Cook To: Andrew Morton Cc: Jeff Liu , LKML , Andreas Dilger , John Sobecki , "viro@zeniv.linux.org.uk" , Alan Cox , "arnd@arndb.de" , James Morris , "Ted Ts'o" , "gregkh@linuxfoundation.org" , jakub@redhat.com, drepper@redhat.com, "linux-fsdevel@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1671 Lines: 41 On Wed, Nov 14, 2012 at 1:09 PM, Andrew Morton wrote: > On Tue, 6 Nov 2012 23:13:54 -0800 > Kees Cook wrote: > >> On Tue, Nov 6, 2012 at 11:02 PM, Jeff Liu wrote: >> > On 11/07/2012 02:21 PM, Kees Cook wrote: >> >> I still want to hear at least from Ted about this changes -- we would >> >> be potentially increasing the predictability of these bytes... >> > >> > We would not increasing that if this routine would be used for AT_RANDOM >> > only(and if the array keeping aligned to 4 bytes). >> > Otherwise, it would be, so let's waiting for further feedbacks. >> >> get_random_int() comes from a different pool than get_random_bytes(), >> IIUC. I'd like to hear some convincing reasoning as to why this change >> doesn't compromise predictability. :) > > But the original "ELF: implement AT_RANDOM for glibc PRNG seeding" > compromised predictability. That's the whole point of this patch. It doesn't compromise predictability. It just used entropy. The idea was that userspace had an actual need for it. > What was so important about that patch that justified gobbling down so > much of the system's entropy accumulation? That does seem to be the core question here. If Ted doesn't think this patch is a problem, then I don't object. Mostly I just had questions about the strength of these various RNGs. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/