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

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Date:   Tue, 14 May 2019 18:39:16 -0500
From:   Rob Landley <rob@...dley.net>
To:     James Bottomley <James.Bottomley@...senPartnership.com>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Arvind Sankar <niveditas98@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        linux-integrity <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 5/14/19 2:18 PM, James Bottomley wrote:
>> I think Rob is right here.  If /init was statically built into the
>> kernel image, it has no more ability to compromise the kernel than
>> anything else in the kernel.  What's the problem here?
> 
> The specific problem is that unless you own the kernel signing key,
> which is really untrue for most distribution consumers because the
> distro owns the key, you cannot build the initrd statically into the
> kernel.  You can take the distro signed kernel, link it with the initrd
> then resign the combination with your key, provided you insert your key
> into the MoK variables as a trusted secure boot key, but the distros
> have been unhappy recommending this as standard practice.
> 
> If our model for security is going to be to link the kernel and the
> initrd statically to give signature protection over the aggregate then
> we need to figure out how to execute this via the distros.  If we
> accept that the split model, where the distro owns and signs the kernel
> but the machine owner builds and is responsible for the initrd, then we
> need to explore split security models like this proposal.

You can have a built-in and an external initrd? The second extracts over the
first? (I know because once upon a time conflicting files would append. It
sounds like the desired behavior here is O_EXCL fail and move on.)

Rob