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

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Message-ID: <20190515005959.GC88615@rani.riverdale.lan>
Date:   Tue, 14 May 2019 21:00:00 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Roberto Sassu <roberto.sassu@...wei.com>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Rob Landley <rob@...dley.net>,
        Arvind Sankar <niveditas98@...il.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-integrity@...r.kernel.org,
        initramfs@...r.kernel.org
Subject: Re: [PATCH v2 0/3] initramfs: add support for xattrs in the initial
 ram disk

On Tue, May 14, 2019 at 07:44:42PM +0200, Roberto Sassu wrote:
> On 5/14/2019 5:57 PM, Arvind Sankar wrote:
> > On Tue, May 14, 2019 at 11:27:04AM -0400, Arvind Sankar wrote:
> >> It's also much easier to change/customize it for the end
> >> system's requirements rather than setting the process in stone by
> >> putting it inside the kernel.
> > 
> > As an example, if you allow unverified external initramfs, it seems to
> > me that it can try to play games that wouldn't be prevented by the
> > in-kernel code: setup /dev in a weird way to try to trick /init, or more
> > easily, replace /init by /bin/sh so you get a shell prompt while only
> > the initramfs is loaded. It's easy to imagine that a system would want
> > to lock itself down to prevent abuses like this.
> 
> Yes, these issues should be addressed. But the purpose of this patch set
> is simply to set xattrs. And existing protection mechanisms can be
> improved later when the basic functionality is there.
> 
Yeah but it's much easier to enhance it when it lives in userspace and
can be tailored to a particular system's requirements. Eg a lot of the
issues will disappear if you don't have to allow for external initramfs
at all, so those systems can have a very simple embedded /init that
doesn't have to do much.
> 
> > So you might already want an embedded initramfs that can be trusted and
> > that can't be overwritten by an external one even outside the
> > security.ima stuff.
> 
> The same problems exist also the root filesystem. These should be solved
> regardless of the filesystem used, for remote attestation and for local
> enforcement.
> 
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