From: Petko Manolov <petkan@mip-labs.com>
To: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: "Woodhouse, David" <david.woodhouse@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"seth.forshee@canonical.com" <seth.forshee@canonical.com>,
"zohar@linux.vnet.ibm.com" <zohar@linux.vnet.ibm.com>,
"mricon@kernel.org" <mricon@kernel.org>,
"dhowells@redhat.com" <dhowells@redhat.com>,
"rusty@rustcorp.com.au" <rusty@rustcorp.com.au>,
"linux-security-module@vger.kernel.org"
<linux-security-module@vger.kernel.org>,
"jlee@suse.de" <jlee@suse.de>,
"kyle@kernel.org" <kyle@kernel.org>,
"gnomes@lxorguk.ukuu.org.uk" <gnomes@lxorguk.ukuu.org.uk>,
"james.l.morris@oracle.com" <james.l.morris@oracle.com>,
"mcgrof@suse.com" <mcgrof@suse.com>,
"serge@hallyn.com" <serge@hallyn.com>,
"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: Re: [RFD] linux-firmware key arrangement for firmware signing
Date: Thu, 21 May 2015 20:14:38 +0300 [thread overview]
Message-ID: <20150521171438.GK18164@localhost> (raw)
In-Reply-To: <20150521170236.GC12932@kroah.com>
On 15-05-21 10:02:36, gregkh@linuxfoundation.org wrote:
> On Thu, May 21, 2015 at 04:03:02PM +0000, Woodhouse, David wrote:
> >
> > In a lot of cases we have loadable firmware precisely to allow us to
> > reduce the cost of the hardware. Adding cryptographic capability in the
> > 'load firmware' state of the device isn't really compatible with that
> > :)
>
> We do? What devices want this? That's really a bad hardware design to trust
> the kernel to get all of this correct.
Which means nearly all hardware we use today is badly designed... :)
> And I say this as someone who is currently working on a hardware design that
> does just this for a very tiny device. It's only a few hundred bytes of
> firmware size to be able to do proper key verification that the firmware image
> is correct and can be "trusted".
And a "few" more bytes for the hash algorithm along the one for asymmetric key
computation and management. :)
> > In the case where kernel and modules are signed, it *is* useful for a kernel
> > device driver also to be able to validate that what it's about to load into
> > a device is authentic. Where 'authentic' will originally just mean that it's
> > come from the linux-firmware.git repository or the same entity that built
> > (and signed) the kernel, but actually I *do* expect vendors who are actively
> > maintaining the firmware images in linux-firmware.git to start providing
> > detached signatures of their own.
>
> Again, why have a detached signature and not just part of the firmware blob?
> The device needs to be caring about this, not the kernel.
In ideal world this is what should be done. However, adding the simplest (read
slowest) MD5 implementation requires a few K's of ram on 32bit cpu. MD5 is
dead. So we need SHA-something, which isn't smaller in terms of code size. Add
the asymmetric cryptography to the picture and we've already put away all
vendors.
> As the kernel doesn't know/care about what the firmware blob really is, I
> don't see why it should be caring about firmware signing as that's a binary
> running on a separate "computer". Do we want to take this the next logical
> step further and start requiring networked devices to attest their kernels are
> signed correctly before we can talk to them?
I think it is enough for you to know that your iwlwifi's firmware comes from
Intel and not from a random Internet punk. If you trust Intel with your wifi
adapter you probably trust them to write good firmware for it.
Petko
next prev parent reply other threads:[~2015-05-21 17:15 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-19 20:02 [RFD] linux-firmware key arrangement for firmware signing Luis R. Rodriguez
2015-05-19 20:40 ` Luis R. Rodriguez
2015-05-19 20:59 ` Andy Lutomirski
2015-05-19 22:11 ` Luis R. Rodriguez
2015-05-19 22:40 ` Andy Lutomirski
2015-05-19 23:30 ` Julian Calaby
2015-05-19 23:42 ` Andy Lutomirski
2015-05-20 0:39 ` Luis R. Rodriguez
2015-05-20 0:41 ` Andy Lutomirski
2015-05-21 22:26 ` Luis R. Rodriguez
2015-05-21 23:15 ` Casey Schaufler
2015-05-21 15:51 ` David Howells
2015-05-21 16:30 ` Mimi Zohar
2015-05-21 16:39 ` Andy Lutomirski
2015-05-21 16:51 ` Petko Manolov
2015-05-21 16:55 ` Andy Lutomirski
2015-05-21 17:44 ` Petko Manolov
2015-05-21 16:43 ` Petko Manolov
2015-05-21 16:48 ` Andy Lutomirski
2015-05-21 16:58 ` Petko Manolov
2015-05-21 16:59 ` Mimi Zohar
2015-05-19 21:48 ` Mimi Zohar
2015-05-19 22:19 ` Luis R. Rodriguez
2015-05-19 23:37 ` Mimi Zohar
2015-05-20 0:22 ` Luis R. Rodriguez
2015-05-20 1:06 ` Mimi Zohar
2015-05-20 1:29 ` Andy Lutomirski
2015-05-20 2:05 ` Mimi Zohar
2015-05-20 2:10 ` Andy Lutomirski
2015-05-20 15:49 ` Petko Manolov
2015-05-20 16:08 ` Petko Manolov
2015-05-20 14:04 ` Seth Forshee
2015-05-20 16:24 ` One Thousand Gnomes
2015-05-20 16:46 ` Petko Manolov
2015-05-21 4:41 ` Greg Kroah-Hartman
2015-05-21 5:41 ` Petko Manolov
2015-05-21 6:14 ` Greg Kroah-Hartman
2015-05-21 13:05 ` Mimi Zohar
2015-05-21 15:45 ` Greg Kroah-Hartman
2015-05-21 15:53 ` Petko Manolov
2015-05-21 16:57 ` Greg Kroah-Hartman
2015-05-26 17:08 ` One Thousand Gnomes
2015-05-26 19:15 ` Petko Manolov
2015-05-26 19:52 ` Mimi Zohar
2015-05-26 23:06 ` David Howells
2015-05-21 16:03 ` Woodhouse, David
2015-05-21 16:22 ` Mimi Zohar
2015-05-21 16:31 ` Woodhouse, David
2015-05-21 17:02 ` gregkh
2015-05-21 17:14 ` Petko Manolov [this message]
2015-05-21 18:23 ` Luis R. Rodriguez
2015-05-21 18:30 ` Luis R. Rodriguez
2015-05-21 19:32 ` Woodhouse, David
2015-05-21 17:49 ` Luis R. Rodriguez
2015-05-21 14:45 ` Petko Manolov
2015-05-21 22:50 ` Luis R. Rodriguez
2015-05-20 20:35 ` Kyle McMartin
2015-05-20 15:08 ` David Howells
2015-05-20 15:47 ` Seth Forshee
2015-05-21 16:23 ` David Howells
2015-05-20 15:14 ` David Howells
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