linux-kernel - Re: [RFC 2/2] initramfs with digital signature protection

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Message-ID: <CALLzPKavbsZgHoJrk5iQ0F1fO21SaeEHmCVCh1G1UKCKB3WZZQ@mail.gmail.com>
Date:	Tue, 5 Feb 2013 23:55:09 +0200
From:	"Kasatkin, Dmitry" <dmitry.kasatkin@...el.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/2] initramfs with digital signature protection

On Tue, Feb 5, 2013 at 8:34 PM, Vivek Goyal <vgoyal@...hat.com> wrote:
> On Tue, Feb 05, 2013 at 06:19:26PM +0000, Matthew Garrett wrote:
>> On Tue, Feb 05, 2013 at 02:34:50PM +0200, Dmitry Kasatkin wrote:
>>
>> > Digitally signed initramfs can be used to provide protected user-space
>> > environment for initialization purpose. For example, LSM, IMA/EVM can be
>> > securely initialized using such approach.
>>
>> What stops an attacker from simply removing the signed image from the
>> initramfs and running modified versions of the same tools from the
>> unsigned image?
>
> Looks like having signed initramfs image is mandatory otherwise system
> panics.
>
> +       if (sys_access(initramfs_img, 0))
> +               panic("signed initramfs image not found (INITRAMFS_SIG is
> +anabled)\n");
>
> Also I am assuming that from signed initramfs, keys will be loaded in
> appropriate keyrings and then keyring will be locked so that any
> tools from unsigned initramfs can not load additional keys.
>

Exactly like that.


> Thanks
> Vivek
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