linux-kernel - Re: [PATCH 0/8] MODSIGN: Use PKCS#7 for module signatures [ver #4]

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Message-ID: <20150520162059.GC10473@localhost>
Date:	Wed, 20 May 2015 19:21:00 +0300
From:	Petko Manolov <petkan@...-labs.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	David Howells <dhowells@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Michal Marek <mmarek@...e.cz>,
	Matthew Garrett <mjg59@...f.ucam.org>, keyrings@...ux-nfs.org,
	Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
	Luis Rodriguez <mcgrof@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Seth Forshee <seth.forshee@...onical.com>,
	LSM List <linux-security-module@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH 0/8] MODSIGN: Use PKCS#7 for module signatures [ver #4]

On 15-05-20 08:56:21, Andy Lutomirski wrote:
> 
> Would it make more sense to permit X.509 chains to be loaded into the keyring 
> instead if we actually need that feature?  IOW, let userspace (or early 
> initramfs stuff) extend our keyring trust to intermediate certs that validly 
> chain to already-trusted things?  I think that a reasonable design goal would 
> be that everything overcomplicated that's involved should be optional, and 
> moving toward embedding PKCS#7 signatures in the modules themselves does the 
> other direction?

This is similar to what i am doing right now - create CA hierarchy so we can 
have something like:

                               +-> KeyB
                               |
RootCA --->  CertA ---> CertB ---> CertC ---> KeyC
                    |
                    +-> CertA' ---> KeyA"

The RootCA may be the one whose private key was used to sign the modules and all 
downstream certificates are either directly signed by it or one of the others.  
Not all of the infrastructure is in the mainline kernel, but this can easily be 
rectified.

Now, as Mimi pointed out this scheme is flawed and should be used with care if 
at all.  Revoking certificates is always a PITA.  Being valid for one year only 
adds to the fun.


		Petko
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