On Mon, May 13, 2019 at 02:36:24PM -0400, Mimi Zohar wrote: > > > > How does this work today then? Is it actually the case that initramfs > > > just cannot be used on an IMA-enabled system, or it can but it leaves > > > the initramfs unverified and we're trying to fix that? I had assumed the > > > latter. > > Oooh, it's done not by starting IMA appraisal later, but by loading a > > default policy to ignore initramfs? > > Right, when rootfs is a tmpfs filesystem, it supports xattrs, allowing > for finer grained policies to be defined. This patch set would allow > a builtin IMA appraise policy to be defined which includes tmpfs. > > Mimi > Ok, but wouldn't my idea still work? Leave the default compiled-in policy set to not appraise initramfs. The embedded /init sets all the xattrs, changes the policy to appraise tmpfs, and then exec's the real init? Then everything except the embedded /init and the file with the xattrs will be appraised, and the embedded /init was verified as part of the kernel image signature. The only additional kernel change needed then is to add a config option to the kernel to disallow overwriting the embedded initramfs (or at least the embedded /init).
