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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 6C1A0C282DC for ; Wed, 22 May 2019 20:28:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 33E6B20868 for ; Wed, 22 May 2019 20:28:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=cisco.com header.i=@cisco.com header.b="DTcF023b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729887AbfEVU2L (ORCPT ); Wed, 22 May 2019 16:28:11 -0400 Received: from alln-iport-7.cisco.com ([173.37.142.94]:60032 "EHLO alln-iport-7.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728761AbfEVU2K (ORCPT ); Wed, 22 May 2019 16:28:10 -0400 X-Greylist: delayed 426 seconds by postgrey-1.27 at vger.kernel.org; Wed, 22 May 2019 16:28:09 EDT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=5573; q=dns/txt; s=iport; t=1558556889; x=1559766489; h=mime-version:content-transfer-encoding:to:from: in-reply-to:cc:references:message-id:subject:date; bh=5ZVlBUw1vSKJZaYc/jBoJa7SC61n5XMCpHwyOOfomTQ=; b=DTcF023b2YqWzj+cGnhQVeqLAT5ehX0PvJ+ox6pEqTTNMzULRYZiJxsQ vNHKvjRr5/9yQvBO6EXKvbw+2MF9BOXMm9+8dYkfyV+Ozka2yROrrYn1C Sv98hrdeHvQkKrZyAPXnlx3540njlcrUMImzhw+RBYK9zqedQBDqcRS7k 4=; X-IronPort-AV: E=Sophos;i="5.60,500,1549929600"; d="scan'208";a="274622354" Received: from rcdn-core-4.cisco.com ([173.37.93.155]) by alln-iport-7.cisco.com with ESMTP/TLS/DHE-RSA-SEED-SHA; 22 May 2019 20:21:02 +0000 Received: from localhost ([10.156.154.45]) by rcdn-core-4.cisco.com (8.15.2/8.15.2) with ESMTP id x4MKL2YY023597; Wed, 22 May 2019 20:21:02 GMT Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable To: Arvind Sankar , Rob Landley , Roberto Sassu , hpa@zytor.com From: Taras Kondratiuk In-Reply-To: <3839583c-5466-6573-3048-0da7e6778c88@landley.net> Cc: viro@zeniv.linux.org.uk, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, initramfs@vger.kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, zohar@linux.vnet.ibm.com, silviu.vlasceanu@huawei.com, dmitry.kasatkin@huawei.com, kamensky@cisco.com, arnd@arndb.de, james.w.mcmechan@gmail.com, niveditas98@gmail.com References: <20190517165519.11507-1-roberto.sassu@huawei.com> <20190517165519.11507-3-roberto.sassu@huawei.com> <20190517210219.GA5998@rani.riverdale.lan> <20190517221731.GA11358@rani.riverdale.lan> <7bdca169-7a01-8c55-40e4-a832e876a0e5@huawei.com> <9C5B9F98-2067-43D3-B149-57613F38DCD4@zytor.com> <3839583c-5466-6573-3048-0da7e6778c88@landley.net> Message-ID: <155855646075.4574.2642646033980450856@takondra-t460s> User-Agent: alot/0.6 Subject: Re: [PATCH v3 2/2] initramfs: introduce do_readxattrs() Date: Wed, 22 May 2019 13:21:00 -0700 X-Outbound-SMTP-Client: 10.156.154.45, [10.156.154.45] X-Outbound-Node: rcdn-core-4.cisco.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Rob Landley (2019-05-22 12:26:43) > = > = > On 5/22/19 11:17 AM, hpa@zytor.com wrote: > > On May 20, 2019 2:39:46 AM PDT, Roberto Sassu wrote: > >> On 5/18/2019 12:17 AM, Arvind Sankar wrote: > >>> On Fri, May 17, 2019 at 02:47:31PM -0700, H. Peter Anvin wrote: > >>>> On 5/17/19 2:02 PM, Arvind Sankar wrote: > >>>>> On Fri, May 17, 2019 at 01:18:11PM -0700, hpa@zytor.com wrote: > >>>>>> > >>>>>> Ok... I just realized this does not work for a modular initramfs, > >> composed at load time from multiple files, which is a very real > >> problem. Should be easy enough to deal with: instead of one large file, > >> use one companion file per source file, perhaps something like > >> filename..xattrs (suggesting double dots to make it less likely to > >> conflict with a "real" file.) No leading dot, as it makes it more > >> likely that archivers will sort them before the file proper. > >>>>> This version of the patch was changed from the previous one exactly > >> to deal with this case -- > >>>>> it allows for the bootloader to load multiple initramfs archives, > >> each > >>>>> with its own .xattr-list file, and to have that work properly. > >>>>> Could you elaborate on the issue that you see? > >>>>> > >>>> > >>>> Well, for one thing, how do you define "cpio archive", each with its > >> own > >>>> .xattr-list file? Second, that would seem to depend on the ordering, > >> no, > >>>> in which case you depend critically on .xattr-list file following > >> the > >>>> files, which most archivers won't do. > >>>> > >>>> Either way it seems cleaner to have this per file; especially if/as > >> it > >>>> can be done without actually mucking up the format. > >>>> > >>>> I need to run, but I'll post a more detailed explanation of what I > >> did > >>>> in a little bit. > >>>> > >>>> -hpa > >>>> > >>> Not sure what you mean by how do I define it? Each cpio archive will > >>> contain its own .xattr-list file with signatures for the files within > >>> it, that was the idea. > >>> > >>> You need to review the code more closely I think -- it does not > >> depend > >>> on the .xattr-list file following the files to which it applies. > >>> > >>> The code first extracts .xattr-list as though it was a regular file. > >> If > >>> a later dupe shows up (presumably from a second archive, although the > >>> patch will actually allow a second one in the same archive), it will > >>> then process the existing .xattr-list file and apply the attributes > >>> listed within it. It then will proceed to read the second one and > >>> overwrite the first one with it (this is the normal behaviour in the > >>> kernel cpio parser). At the end once all the archives have been > >>> extracted, if there is an .xattr-list file in the rootfs it will be > >>> parsed (it would've been the last one encountered, which hasn't been > >>> parsed yet, just extracted). > >>> > >>> Regarding the idea to use the high 16 bits of the mode field in > >>> the header that's another possibility. It would just require > >> additional > >>> support in the program that actually creates the archive though, > >> which > >>> the current patch doesn't. > >> > >> Yes, for adding signatures for a subset of files, no changes to the ram > >> disk generator are necessary. Everything is done by a custom module. To > >> support a generic use case, it would be necessary to modify the > >> generator to execute getfattr and the awk script after files have been > >> placed in the temporary directory. > >> > >> If I understood the new proposal correctly, it would be task for cpio > >> to > >> read file metadata after the content and create a new record for each > >> file with mode 0x18000, type of metadata encoded in the file name and > >> metadata as file content. I don't know how easy it would be to modify > >> cpio. Probably the amount of changes would be reasonable. > = > I could make toybox cpio do it in a weekend, and could probably throw a p= atch at > usr/gen_init_cpio.c while I'm at it. I prototyped something like that a c= ouple > years ago, it's not hard. > = > The real question is scripts/gen_initramfs_list.sh and the text format it > produces. We can currently generate cpio files with different ownership a= nd > permissions than the host system can represent (when not building as root= , on a > filesystem that may not support xattrs or would get unhappy about conflic= ting > selinux annotations). We work around it by having the metadata represented > textually in the initramfs_list file gen_initramfs_list.sh produces and > gen_init_cpio.c consumes. > = > xattrs are a terrible idea the Macintosh invented so Finder could remembe= r where > you moved a file's icon in its folder without having to modify the file, = and > then things like OS/2 copied it and Windows picked it up from there and w= ent "Of > course, this is a security mechanism!" and... sigh. > = > This is "data that is not data", it's metadata of unbounded size. It seem= s like > it should go in gen_initramfs_list.sh but as what, keyword=3Dvalue pairs = that > might have embedded newlines in them? A base64 encoding? Something else? I the previous try to add xattrs to cpio I've used hex encoding in gen_initramfs_list.sh: https://lkml.org/lkml/2018/1/24/851 - gen_init_cpio: set extended attribute= s for newcx format https://lkml.org/lkml/2018/1/24/852 - gen_initramfs_list.sh: add -x option = to enable newcx format