From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arvind Sankar Subject: Re: [PATCH v2 0/3] initramfs: add support for xattrs in the initial ram disk Date: Mon, 13 May 2019 14:47:45 -0400 Message-ID: <20190513184744.GA12386@rani.riverdale.lan> References: <20190512194322.GA71658@rani.riverdale.lan> <3fe0e74b-19ca-6081-3afe-e05921b1bfe6@huawei.com> <4f522e28-29c8-5930-5d90-e0086b503613@landley.net> <20190513172007.GA69717@rani.riverdale.lan> <20190513175250.GC69717@rani.riverdale.lan> <1557772584.4969.62.camel@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <1557772584.4969.62.camel@linux.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: Mimi Zohar Cc: Arvind Sankar , Roberto Sassu , Rob Landley , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, initramfs@vger.kernel.org List-Id: linux-api@vger.kernel.org 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).