[PATCH v2 0/3] initramfs: add support for xattrs in the initial ram disk

[Andy Lutomirski]

On Thu, May 9, 2019 at 4:27 AM Roberto Sassu <roberto.sassu at huawei.com> wrote:
>
> This patch set aims at solving the following use case: appraise files from
> the initial ram disk. To do that, IMA checks the signature/hash from the
> security.ima xattr. Unfortunately, this use case cannot be implemented
> currently, as the CPIO format does not support xattrs.
>
> This proposal consists in marshaling pathnames and xattrs in a file called
> .xattr-list. They are unmarshaled by the CPIO parser after all files have
> been extracted.
>
> The difference from v1 (https://lkml.org/lkml/2018/11/22/1182) is that all
> xattrs are stored in a single file and not per file (solves the file name
> limitation issue, as it is not necessary to add a suffix to files
> containing xattrs).
>
> The difference with another proposal
> (https://lore.kernel.org/patchwork/cover/888071/) is that xattrs can be
> included in an image without changing the image format, as opposed to
> defining a new one. As seen from the discussion, if a new format has to be
> defined, it should fix the issues of the existing format, which requires
> more time.

I read some of those emails.  ISTM that adding TAR support should be
seriously considered.  Sure, it's baroque, but it's very, very well
supported, and it does exactly what we need.

--Andy