linux-kernel - Re: [Linux-ima-user] Initramfs and IMA Appraisal

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Date:	Mon, 29 Dec 2014 18:25:55 -0800 (PST)
From:	David Lang <david@...g.hm>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
cc:	Rob Landley <rob@...dley.net>, Christophe Fillot <cf@....fr>,
	linux-ima-user@...ts.sourceforge.net,
	linux-security-module <linux-security-module@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [Linux-ima-user] Initramfs and IMA Appraisal

On Mon, 29 Dec 2014, Mimi Zohar wrote:

> Thanks Rob for the explanation.  The problem is that ramfs does not
> support extended attributes, while tmpfs does.  The boot loader could
> "measure" (trusted boot) the initramfs, but as the initramfs is
> generated on the target system, the initramfs is not signed, preventing
> it from being appraised (secure Boot). To close the initramfs integrity
> appraisal gap requires verifying the individual initramfs file
> signatures, which are stored as extended attributes.

what's the point of checking the files on the filesystem against signatures 
stored on the same filesystem? If someone could alter the file contents they can 
alter the signatures as well.

David Lang
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