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 0F90CC43461 for ; Mon, 12 Apr 2021 17:45:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D821F61355 for ; Mon, 12 Apr 2021 17:45:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244412AbhDLRpy (ORCPT ); Mon, 12 Apr 2021 13:45:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:45860 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239032AbhDLRpw (ORCPT ); Mon, 12 Apr 2021 13:45:52 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3EA2F61354; Mon, 12 Apr 2021 17:45:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618249534; bh=hjXOIbROE3wx3QWF7DGqV3HSLhGxUvo3LHE4nDAEZa0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nJr0jyHk7pflX0oLpJJgsdtYEo0c/0ApOWTY3jpy6MrOQUXgRWbDsV7xmAbJk22NF +aBV65BwNrdz53qBGGPUvAFnVespNYQ1hOKY4VRJqrL0Q0wrM7WIUsGtK0ILDmyuR3 y1ZlMJ9U5qKwJAXzvZL3oVhzonUyYL11zzkQm2E4lHv2ir2UNkdDeY2BgdQeEkxvTx IW0EqOURG+F3Oe2bwk9O5gcURJi77kNEq03P2TvaBO6pVRZzM/J/9RSKsct5Fn73n4 3p13J0i2KgfOrdIqiEm1zsdYcXUJmR/uAyna3XznChoLgCk305sMS/y74B9/JBaHyG QN/UQdZshqwHg== Date: Mon, 12 Apr 2021 10:45:32 -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 v6 1/1] use crc32 instead of md5 for hibernation e820 integrity check Message-ID: References: <20210412140932.31162-1-crecklin@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210412140932.31162-1-crecklin@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 12, 2021 at 10:09:32AM -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. > > The purpose of the integrity check is to detect possible differences > between the memory map used at the time when the hibernation image is > about to be loaded into memory and the memory map used at the image > creation time, because it is generally unsafe to load the image if the > current memory map doesn't match the one used when it was created. so > it is not intended as a cryptographic integrity check. This still doesn't actually explain why a non-cryptographic checksum is sufficient. "Detection of possible differences" could very well require cryptographic authentication; it depends on whether malicious changes need to be detected or not. > > Fixes: 62a03defeabd ("PM / hibernate: Verify the consistent of e820 memory map > by md5 digest") > > 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 > v5 -> v6 > use wording from Eric Biggers, use crc32_le instead of crc32 from crypto > framework (crc32_le is in the core API and removes need for #defines) > > arch/x86/power/hibernate.c | 76 +++++++++++--------------------------- > 1 file changed, 22 insertions(+), 54 deletions(-) > > diff --git a/arch/x86/power/hibernate.c b/arch/x86/power/hibernate.c > index cd3914fc9f3d..f39e507e34ca 100644 > --- a/arch/x86/power/hibernate.c > +++ b/arch/x86/power/hibernate.c > @@ -13,6 +13,8 @@ > #include > #include > #include > +#include > +#include > > #include crypto/hash.h is no longer needed. > > @@ -55,94 +57,60 @@ int pfn_is_nosave(unsigned long pfn) > } > > > -#define MD5_DIGEST_SIZE 16 > +#define CRC32_DIGEST_SIZE (sizeof (u32)) > > 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]; > }; It would be simpler to just make this field 'unsigned long'. Then there would be no need to deal with memcpy(). > -#if IS_BUILTIN(CONFIG_CRYPTO_MD5) > /** > - * get_e820_md5 - calculate md5 according to given e820 table > + * get_e820_crc32 - calculate crc32 according to given e820 table Calling this "compute_e820_crc32()" would avoid confusion with retrieving the previously-stored crc32 value. > + ret = crc32_le(0, (unsigned char const *)table, size); It would be better to do ~crc32_le(~0, ...) (i.e., invert at beginning and end) to match the recommended usage of CRC-32. Unfortunately the library function doesn't do the inversions by default. > static int hibernation_e820_save(void *buf) > { > - return get_e820_md5(e820_table_firmware, buf); > + return get_e820_crc32(e820_table_firmware, buf); > } This should be inlined into arch_hibernation_header_save(). Also note that it can no longer fail. > > static bool hibernation_e820_mismatch(void *buf) > { This should be inlined into arch_hibernation_header_restore(). > int ret; > - u8 result[MD5_DIGEST_SIZE]; > + u8 result[CRC32_DIGEST_SIZE]; > > - memset(result, 0, MD5_DIGEST_SIZE); > + memset(result, 0, CRC32_DIGEST_SIZE); > /* If there is no digest in suspend kernel, let it go. */ > - if (!memcmp(result, buf, MD5_DIGEST_SIZE)) > + if (!memcmp(result, buf, CRC32_DIGEST_SIZE)) > return false; There's no need to handle the "no digest" case anymore, right? Since crc32_le() is always available. - Eric