From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752472AbcFWTeP (ORCPT ); Thu, 23 Jun 2016 15:34:15 -0400 Received: from outbound1a.ore.mailhop.org ([54.213.22.21]:55701 "EHLO outbound1a.ore.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751547AbcFWTeK (ORCPT ); Thu, 23 Jun 2016 15:34:10 -0400 X-MHO-User: 814a3b8d-3979-11e6-a0ff-e511cd071b9b X-Report-Abuse-To: https://support.duocircle.com/support/solutions/articles/5000540958-duocircle-standard-smtp-abuse-information X-Originating-IP: 74.99.78.160 X-Mail-Handler: DuoCircle Outbound SMTP X-DKIM: OpenDKIM Filter v2.6.8 io DEADF8002F Date: Thu, 23 Jun 2016 19:33:58 +0000 From: Jason Cooper To: Kees Cook Cc: Thomas Garnier , "kernel-hardening@lists.openwall.com" , Ingo Molnar , Andy Lutomirski , "x86@kernel.org" , Borislav Petkov , Baoquan He , Yinghai Lu , Juergen Gross , Matt Fleming , Toshi Kani , Andrew Morton , Dan Williams , "Kirill A. Shutemov" , Dave Hansen , Xiao Guangrong , Martin Schwidefsky , "Aneesh Kumar K.V" , Alexander Kuleshov , Alexander Popov , Dave Young , Joerg Roedel , Lv Zheng , Mark Salter , Dmitry Vyukov , Stephen Smalley , Boris Ostrovsky , Christian Borntraeger , Jan Beulich , LKML , Jonathan Corbet , "linux-doc@vger.kernel.org" Subject: Re: [kernel-hardening] [PATCH v7 0/9] x86/mm: memory area address KASLR Message-ID: <20160623193358.GL9922@io.lakedaemon.net> References: <1466556426-32664-1-git-send-email-keescook@chromium.org> <20160622124707.GC9922@io.lakedaemon.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hey Kees, Thomas, On Wed, Jun 22, 2016 at 10:05:51AM -0700, Kees Cook wrote: > On Wed, Jun 22, 2016 at 8:59 AM, Thomas Garnier wrote: > > On Wed, Jun 22, 2016 at 5:47 AM, Jason Cooper wrote: > >> Hey Kees, > >> > >> On Tue, Jun 21, 2016 at 05:46:57PM -0700, Kees Cook wrote: > >>> Notable problems that needed solving: > >> ... > >>> - Reasonable entropy is needed early at boot before get_random_bytes() > >>> is available. > >> > >> This series is targetting x86, which typically has RDRAND/RDSEED > >> instructions. Are you referring to other arches? Older x86? Also, > >> isn't this the same requirement for base address KASLR? > >> > >> Don't get me wrong, I want more diverse entropy sources available > >> earlier in the boot process as well. :-) I'm just wondering what's > >> different about this series vs base address KASLR wrt early entropy > >> sources. > >> > > > > I think Kees was referring to the refactor I did to get the similar > > entropy generation than KASLR module randomization. Our approach was > > to provide best entropy possible even if you have an older processor > > or under virtualization without support for these instructions. > > Unfortunately common on companies with a large number of older > > machines. > > Right, the memory offset KASLR uses the same routines as the kernel > base KASLR. The issue is with older x86 systems, which continue to be > very common. We have the same issue in embedded. :-( Compounded by the fact that there is no rand instruction (at least not on ARM). So, even if there's a HW-RNG, you can't access it until the driver is loaded. This is compounded by the fact that most systems deployed today have bootloaders a) without hw-rng drivers, b) without dtb editing, and c) without dtb support at all. My current thinking is to add a devicetree property "userspace,random-seed" . This way, existing, deployed boards can append a dtb to a modern kernel with the property set. The factory bootloader then only needs to amend its boot scripts to read random-seed from the fs to the given address. Modern systems that receive a seed from the bootloader via the random-seed property (typically from the hw-rng) can mix both sources for increased resilience. Unfortunately, I'm not very familiar with the internals of x86 bootstrapping. Could GRUB be scripted to do a similar task? How would the address and size of the seed be passed to the kernel? command line? thx, Jason. From mboxrd@z Thu Jan 1 00:00:00 1970 Reply-To: kernel-hardening@lists.openwall.com Date: Thu, 23 Jun 2016 19:33:58 +0000 From: Jason Cooper Message-ID: <20160623193358.GL9922@io.lakedaemon.net> References: <1466556426-32664-1-git-send-email-keescook@chromium.org> <20160622124707.GC9922@io.lakedaemon.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [kernel-hardening] [PATCH v7 0/9] x86/mm: memory area address KASLR To: Kees Cook Cc: Thomas Garnier , "kernel-hardening@lists.openwall.com" , Ingo Molnar , Andy Lutomirski , "x86@kernel.org" , Borislav Petkov , Baoquan He , Yinghai Lu , Juergen Gross , Matt Fleming , Toshi Kani , Andrew Morton , Dan Williams , "Kirill A. Shutemov" , Dave Hansen , Xiao Guangrong , Martin Schwidefsky , "Aneesh Kumar K.V" , Alexander Kuleshov , Alexander Popov , Dave Young , Joerg Roedel , Lv Zheng , Mark Salter , Dmitry Vyukov , Stephen Smalley , Boris Ostrovsky , Christian Borntraeger , Jan Beulich , LKML , Jonathan Corbet , "linux-doc@vger.kernel.org" List-ID: Hey Kees, Thomas, On Wed, Jun 22, 2016 at 10:05:51AM -0700, Kees Cook wrote: > On Wed, Jun 22, 2016 at 8:59 AM, Thomas Garnier wrote: > > On Wed, Jun 22, 2016 at 5:47 AM, Jason Cooper wrote: > >> Hey Kees, > >> > >> On Tue, Jun 21, 2016 at 05:46:57PM -0700, Kees Cook wrote: > >>> Notable problems that needed solving: > >> ... > >>> - Reasonable entropy is needed early at boot before get_random_bytes() > >>> is available. > >> > >> This series is targetting x86, which typically has RDRAND/RDSEED > >> instructions. Are you referring to other arches? Older x86? Also, > >> isn't this the same requirement for base address KASLR? > >> > >> Don't get me wrong, I want more diverse entropy sources available > >> earlier in the boot process as well. :-) I'm just wondering what's > >> different about this series vs base address KASLR wrt early entropy > >> sources. > >> > > > > I think Kees was referring to the refactor I did to get the similar > > entropy generation than KASLR module randomization. Our approach was > > to provide best entropy possible even if you have an older processor > > or under virtualization without support for these instructions. > > Unfortunately common on companies with a large number of older > > machines. > > Right, the memory offset KASLR uses the same routines as the kernel > base KASLR. The issue is with older x86 systems, which continue to be > very common. We have the same issue in embedded. :-( Compounded by the fact that there is no rand instruction (at least not on ARM). So, even if there's a HW-RNG, you can't access it until the driver is loaded. This is compounded by the fact that most systems deployed today have bootloaders a) without hw-rng drivers, b) without dtb editing, and c) without dtb support at all. My current thinking is to add a devicetree property "userspace,random-seed" . This way, existing, deployed boards can append a dtb to a modern kernel with the property set. The factory bootloader then only needs to amend its boot scripts to read random-seed from the fs to the given address. Modern systems that receive a seed from the bootloader via the random-seed property (typically from the hw-rng) can mix both sources for increased resilience. Unfortunately, I'm not very familiar with the internals of x86 bootstrapping. Could GRUB be scripted to do a similar task? How would the address and size of the seed be passed to the kernel? command line? thx, Jason.