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To: Mimi Zohar <email@example.com>,
Taras Kondratiuk <firstname.lastname@example.org>,
Al Viro <email@example.com>, Arnd Bergmann <firstname.lastname@example.org>,
Rob Landley <email@example.com>, Jonathan Corbet <firstname.lastname@example.org>,
James McMechan <email@example.com>
Cc: firstname.lastname@example.org, Victor Kamensky <email@example.com>,
Subject: Re: [PATCH v3 01/15] Documentation: add newcx initramfs format description
Date: Sat, 17 Feb 2018 16:24:40 -0800 [thread overview]
Message-ID: <80AFCC79-14B2-4CF2-A601-89B18764C9BC@zytor.com> (raw)
On February 17, 2018 4:15:12 PM PST, Mimi Zohar <firstname.lastname@example.org> wrote:
>On Fri, 2018-02-16 at 12:59 -0800, H. Peter Anvin wrote:
>> On 02/16/18 12:33, Taras Kondratiuk wrote:
>> > Many of the Linux security/integrity features are dependent on file
>> > metadata, stored as extended attributes (xattrs), for making
>> > These features need to be initialized during initcall and enabled
>> > early as possible for complete security coverage.
>> > Initramfs (tmpfs) supports xattrs, but newc CPIO archive format
>> > support including them into the archive.
>> > This patch describes "extended" newc format (newcx) that is based
>> > newc and has following changes:
>> > - extended attributes support
>> > - increased size of filesize to support files >4GB
>> > - increased mtime field size to have 64 bits of seconds and added a
>> > field for nanoseconds
>> > - removed unused checksum field
>> If you are going to implement a new, non-backwards-compatible format,
>> you shouldn't replicate the mistakes of the current format.
>> 1. The use of ASCII-encoded fixed-length numbers is an idiotic legacy
>> from an era before there were any portable way of dealing with
>> with prespecified endianness. If you are going to use ASCII, make
>> delimited so that they don't have fixed limits, or just use binary.
>> The cpio header isn't fixed size, so that argument goes away, in fact
>> the only way to determine the end of the header is to scan forward.
>> 2. Alignment sensitivity! Because there is no header length
>> information, the above scan tells you where the header ends, but
>> is padding before the data, and the size of that padding is only
>> by alignment.
>> 3. Inband encoding of EOF: if you actually have a filename
>> you have problems.
>> But first, before you define a whole new format for which no tools
>> (you will have to work with the maintainers of the GNU tools to add
>> support) you should see how complex it would be to support the POSIX
>> tar/pax format, which already has all the features you are seeking,
>> by now is well-supported.
>The discussion about including xattrs in the initramfs didn't start
>yesterday. It's been on the list of measurement/appraisal gaps that
>need to be closed for years. Initially I planned on using tar, but at
>the 2014 Kernel Summit I spoke with Al at length. At the time, he was
>very clear that tar is unnecessarily overly complicated and
>recommended extending CPIO.
>I took his advice. Unfortunately, as soon as I posted an initial
>patch set to include xattrs in CPIO, all of the problems with CPIO had
>to be addressed before defining a new CPIO number. Unfortunately,
>this wasn't the only measurement/appraisal gap that needed to be
>addressed. I've been working on closing other gaps.
>I'm really happy that someone has taken the time to work on this.
> Instead of derailing their attempt of extending CPIO to include
>xattrs, I'd appreciate your making constructive suggestions.
I'm not trying to derail anything, but I do want to see it done well if it is going to be done. I have several ideas already, but I may not have a chance to write them down properly until after the weekend due to family obligations.
The assessment of pax/tar is useful; it should be added to the patch documentation in a future set.
Sent from my Android device with K-9 Mail. Please excuse my brevity.
next prev parent reply other threads:[~2018-02-18 0:25 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-16 20:33 [PATCH v3 00/15] extend initramfs archive format to support xattrs Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 01/15] Documentation: add newcx initramfs format description Taras Kondratiuk
2018-02-16 20:59 ` H. Peter Anvin
2018-02-16 21:25 ` Rob Landley
2018-02-16 21:47 ` Victor Kamensky
2018-02-17 0:00 ` hpa
2018-02-17 10:04 ` Taras Kondratiuk
2018-02-17 17:32 ` Rob Landley
2018-02-18 0:15 ` Mimi Zohar
2018-02-18 0:24 ` hpa [this message]
2018-02-18 0:26 ` hpa
2018-02-18 0:47 ` Mimi Zohar
2018-02-16 20:33 ` [PATCH v3 02/15] initramfs: replace states with function pointers Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 03/15] initramfs: store file name in name_buf Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 04/15] initramfs: remove unnecessary symlinks processing shortcut Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 05/15] initramfs: move files creation into separate state Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 06/15] initramfs: separate reading cpio method from header Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 07/15] initramfs: split header layout information from parsing function Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 08/15] initramfs: add newcx format Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 09/15] initramfs: set extended attributes Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 10/15] gen_init_cpio: move header formatting into function Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 11/15] gen_init_cpio: add newcx format Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 12/15] gen_init_cpio: set extended attributes for " Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 12/14] gen_initramfs_list.sh: add -x option to enable " Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 13/15] " Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 13/14] selinux: allow setxattr on rootfs so initramfs code can set them Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 14/15] " Taras Kondratiuk
2018-02-20 19:01 ` Stephen Smalley
2018-03-11 3:07 ` Victor Kamensky
2018-03-20 16:33 ` [Non-DoD Source] " Stephen Smalley
2018-02-16 20:33 ` [PATCH v3 14/14] selinux: delay sid population for rootfs till init is complete Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 15/15] " Taras Kondratiuk
2018-02-20 18:56 ` Stephen Smalley
2018-03-07 16:51 ` Rob Landley
2018-03-07 17:26 ` Victor Kamensky
2018-03-11 3:08 ` Victor Kamensky
2018-03-20 16:30 ` [Non-DoD Source] " Stephen Smalley
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