linux-kernel - Re: Linux Firmware Signing

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Message-ID: <31228.1440671938@warthog.procyon.org.uk>
Date:	Thu, 27 Aug 2015 11:38:58 +0100
From:	David Howells <dhowells@...hat.com>
To:	"Luis R. Rodriguez" <mcgrof@...e.com>
Cc:	dhowells@...hat.com, Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Andy Lutomirski <luto@...capital.net>,
	Kees Cook <keescook@...omium.org>,
	"Roberts, William C" <william.c.roberts@...el.com>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
	"james.l.morris@...cle.com" <james.l.morris@...cle.com>,
	"serge@...lyn.com" <serge@...lyn.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Paul Moore <paul@...l-moore.com>,
	Eric Paris <eparis@...isplace.org>, selinux@...ho.nsa.gov,
	Stephen Smalley <sds@...ho.nsa.gov>,
	"Schaufler, Casey" <casey.schaufler@...el.com>,
	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Peter Jones <pjones@...hat.com>, Takashi Iwai <tiwai@...e.de>,
	dwmw2@...radead.org, Ming Lei <ming.lei@...onical.com>,
	Joey Lee <jlee@...e.de>,
	Vojtěch Pavlík <vojtech@...e.com>,
	Kyle McMartin <kyle@...nel.org>,
	Seth Forshee <seth.forshee@...onical.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Johannes Berg <johannes@...solutions.net>
Subject: Re: Linux Firmware Signing

Luis R. Rodriguez <mcgrof@...e.com> wrote:

> "PKCS#7: Add an optional authenticated attribute to hold firmware name"
> https://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/commit/?h=fwsign-pkcs7&id=1448377a369993f864915743cfb34772e730213good
> 
>         1.3.6.1.4.1.2312.16     Linux kernel
>         1.3.6.1.4.1.2312.16.2   - PKCS#7/CMS SignerInfo attribute types
>         1.3.6.1.4.1.2312.16.2.1   - firmwareName
> 
> I take it you are referring to this?

Yes.

> If we follow this model we'd then need something like:
> 
>         1.3.6.1.4.1.2312.16.2.2   - seLinuxPolicyName
> 
> That should mean each OID that has different file names would need to be
> explicit about and have a similar entry on the registry. I find that pretty
> redundant and would like to avoid that if possible.

firmwareName is easy for people to understand - it's the name the kernel asks
for and the filename of the blob.  seLinuxPolicyName is, I think, a lot more
tricky since a lot of people don't use SELinux, and most that do don't
understand it (most people that use it aren't even really aware of it).

If you can use the firmwareName as the SELinux/LSM key, I would suggest doing
so - even if you dress it up as a path (/lib/firmware/<firmwareName>).

David
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