linux-kernel - Re: [RFC PATCH v2] fw_lockdown: new micro LSM module to prevent loading unsigned firmware

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Date:   Mon, 13 Nov 2017 15:11:12 -0500
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     David Howells <dhowells@...hat.com>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Kyle McMartin <kyle@...nel.org>,
        Ben Hutchings <ben@...adent.org.uk>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>
Subject: Re: [RFC PATCH v2] fw_lockdown: new micro LSM module to prevent
 loading unsigned firmware

On Mon, 2017-11-13 at 20:51 +0100, Luis R. Rodriguez wrote:
> On Mon, Nov 13, 2017 at 02:36:47PM -0500, Mimi Zohar wrote:

> > Huh, I kind of lost you here.  What does "it" refer to in the above
> > sentence?  IMA is in the kernel.  So, who does what checks in
> > userspace?
> 
> Sorry I thought some checks were done in userspace, given that is clarified,
> what I meant is that say a device driver has a signing specification written
> out in the driver, should/can IMA use that on the LSM to verify the detached
> signature file for the firmware?

IMA-appraisal currently supports file signatures as extended
attributes.  Thiago Bauermann posted patches for including appended
signature support to IMA-appraisal.  If someone is interested in
adding detached signature support, they're welcome to do so.

> If it can be all done in kernel, it has me wondering if perhaps one option for
> IMA might be to do only vetting for these types of checks, where the info and
> description to appraise files is all in-kernel. IMA would not be required
> for other files.

We probably can defer this discussion until it is applicable.

Mimi