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

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Date:	Thu, 11 Apr 2013 11:08:05 +0300
From:	Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>, Josh Boyer <jwboyer@...il.com>,
	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

Hello,

(in plain text)

I respond to the original question of this thread.
signed initramfs allows not only to add keys to the keyrings but
perform other initialization,
which requires user-space.
Keys can be embedded into the kernel. This is fine.

Regards

- Dmitry


On Thu, Apr 11, 2013 at 12:05 AM, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
> On Wed, 2013-04-10 at 15:42 -0400, Vivek Goyal wrote:
>> On Tue, Apr 09, 2013 at 11:07:10PM -0400, Mimi Zohar wrote:
>>
>> [..]
>> > The module keyring is a special case.  Loading these keys from the
>> > kernel and, presumably, locking the keyring is probably fine.  In the
>> > case of IMA, however, files will be signed by any number of package
>> > owners.  If the _ima keyring is locked by the kernel, how would you add
>> > these other keys?
>>
>> Who are package owners here. IOW, in typical IMA setup, where are the keys
>> and when are these keys loaded in ima keyring?
>
> Suppose I install third party packages not signed by the distro, but by
> the package owner (eg. google, rpmfusion, ...).  Not only does the
> package signature need to be verified on installation, but the files
> need to be installed with signatures.  For IMA to enforce file
> integrity, the package owner's public key needs to be added to the _ima
> keyring.
>
>> If we trust root and keys can be loaded any time later, then signed
>> initramfs will not solve the problem either.
>
> Locking the keyring in the kernel will limit the set of permitted keys
> to only those specified in UEFI db or builtin.  Locking the keyring in
> the "early" initramfs, will allow the system owner, whose key is in the
> UEFI db, to specify additional keys, such as those for third party
> packages.  Not all public keys belong in the UEFI db.
>
> Mimi
>
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