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

[Mimi Zohar]

On Sun, 2019-05-12 at 17:31 +0200, Dominik Brodowski wrote:
> On Sun, May 12, 2019 at 08:52:47AM -0400, Mimi Zohar wrote:


> > It's too late.  The /init itself should be signed and verified.
> 
> Could you elaborate a bit more about the threat model, and why deferring
> this to the initramfs is too late?

The IMA policy defines a number of different methods of identifying
which files to measure, appraise, audit.[1] ÂWithout xattrs, the
granularity of the policy rules is severely limited. ÂWithout xattrs,
a filesystem is either in policy, or not.

With an IMA policy rule requiring rootfs (tmpfs) files to be verified,
then /init needs to be properly labeled, otherwise /init will fail to
execute.

Mimi

[1] Documentation/ABI/testing/ima_policy