From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9B136C433ED for ; Thu, 8 Apr 2021 23:55:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7090B610F7 for ; Thu, 8 Apr 2021 23:55:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233044AbhDHXzn (ORCPT ); Thu, 8 Apr 2021 19:55:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:37036 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233009AbhDHXzm (ORCPT ); Thu, 8 Apr 2021 19:55:42 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1018861151; Thu, 8 Apr 2021 23:55:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1617926130; bh=SUv1EmiHLV/4OjfzTusbiqGWcCkMUz2DyvyUUnJ+SZ4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AiXVaVzfdo5Rr24r5RglJ24YvxSbVdSR9sUJMKrZNgIS5DA9xS7v9lUeDGp6SeG1P y4SWJnCy2xrKfe8M0sEyjIAgPZePczJVNorjOkijUz9h9FahY7iwPtcq5y8EWiJFlX DxHh/zmIhOd/GEfvrvvrfBu826zfgbBVRQAnlYDNZQD4M8zsGmJg00LKQiUyTWpahR q8oqYve83TKwtCYjHXIqxOJ2/VZFW2vswrEF3aSYC/nQLCCkLuw943eo28Bpp0BbuN zAy/6ORAIDY1L8DctfUMkLWcIa8AX7RtusWbAMPl0pXlIAb10NS/UnIbFbwY6E7fsQ 2aX2RrxjLEToA== Date: Thu, 8 Apr 2021 16:55:28 -0700 From: Eric Biggers To: Chris von Recklinghausen Cc: ardb@kernel.org, simo@redhat.com, rafael@kernel.org, decui@microsoft.com, linux-pm@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 1/1] use crc32 instead of md5 for hibernation e820 integrity check Message-ID: References: <20210408131506.17941-1-crecklin@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 08, 2021 at 11:53:59AM -0400, Chris von Recklinghausen wrote: > On 4/8/21 11:30 AM, Eric Biggers wrote: > > On Thu, Apr 08, 2021 at 09:15:06AM -0400, Chris von Recklinghausen wrote: > > > Suspend fails on a system in fips mode because md5 is used for the e820 > > > integrity check and is not available. Use crc32 instead. > > > > > > This patch changes the integrity check algorithm from md5 to > > > crc32. This integrity check is used only to verify accidental > > > corruption of the hybernation data and is not intended as a > > > cryptographic integrity check. > > > Md5 is overkill in this case and also disabled in FIPS mode because it > > > is known to be broken for cryptographic purposes. > > > > > > Fixes: 62a03defeabd ("PM / hibernate: Verify the consistent of e820 memory map > > > by md5 digest") > > > > > > Tested-by: Dexuan Cui > > > Reviewed-by: Dexuan Cui > > > Signed-off-by: Chris von Recklinghausen > > > --- > > > v1 -> v2 > > > bump up RESTORE_MAGIC > > > v2 -> v3 > > > move embelishment from cover letter to commit comments (no code change) > > > v3 -> v4 > > > add note to comments that md5 isn't used for encryption here. > > > v4 -> v5 > > > reword comment per Simo's suggestion > > > > > > arch/x86/power/hibernate.c | 35 +++++++++++++++++++---------------- > > > 1 file changed, 19 insertions(+), 16 deletions(-) > > > > > > diff --git a/arch/x86/power/hibernate.c b/arch/x86/power/hibernate.c > > > index cd3914fc9f3d..b56172553275 100644 > > > --- a/arch/x86/power/hibernate.c > > > +++ b/arch/x86/power/hibernate.c > > > @@ -55,31 +55,31 @@ int pfn_is_nosave(unsigned long pfn) > > > } > > > -#define MD5_DIGEST_SIZE 16 > > > +#define CRC32_DIGEST_SIZE 16 > > > struct restore_data_record { > > > unsigned long jump_address; > > > unsigned long jump_address_phys; > > > unsigned long cr3; > > > unsigned long magic; > > > - u8 e820_digest[MD5_DIGEST_SIZE]; > > > + u8 e820_digest[CRC32_DIGEST_SIZE]; > > > }; > > > -#if IS_BUILTIN(CONFIG_CRYPTO_MD5) > > > +#if IS_BUILTIN(CONFIG_CRYPTO_CRC32) > > Should CONFIG_CRYPTO_CRC32 be getting selected from somewhere? > > > Yes, presumably from the same source that sets CONFIG_CRYPTO_MD5. Also > presumably there's value to not forcing the check if the config value is not > set. I wouldn't be so sure about that. It might just be a bug that CONFIG_CRYPTO_MD5 wasn't being selected. Where is it documented that the user needed to set CONFIG_CRYPTO_MD5=y if they wanted the hibernation image checksumming to work? > > > > If that is too hard because it would pull in too much of the crypto API, maybe > > using the library interface to CRC-32 (lib/crc32.c) would be a better fit? > > > Based on my statement above, the intent is to provide a simple drop in > replacement for md5 so that users of FIPS mode can suspend/resume without > any errors. > It's possible that most people have CONFIG_CRYPTO_MD5 enabled for some unrelated reason so the hibernation image checksumming works by chance. CONFIG_CRYPTO_CRC32 is a different option so the same is not necessarily true. However, note that CONFIG_HIBERNATION already selects CONFIG_CRC32 (the library interface to CRC-32) but not CONFIG_CRYPTO_CRC32 (shash interface to CRC-32). So, if this code just used the library interface crc32_le(), it will always be available and the IS_BUILTIN() checks can be removed... - Eric