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

From: Petko Manolov <petkan@mip-labs.com>
To: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>,
	"Luis R. Rodriguez" <mcgrof@suse.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Andy Lutomirski <luto@kernel.org>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Michal Marek <mmarek@suse.cz>,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	keyrings@linux-nfs.org,
	Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Seth Forshee <seth.forshee@canonical.com>,
	LSM List <linux-security-module@vger.kernel.org>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH 0/8] MODSIGN: Use PKCS#7 for module signatures [ver #4]
Date: Sun, 24 May 2015 13:52:55 +0300	[thread overview]
Message-ID: <20150524105255.GC7238@localhost> (raw)
In-Reply-To: <1432297697.2450.53.camel@linux.vnet.ibm.com>

On 15-05-22 08:28:17, Mimi Zohar wrote:
> On Fri, 2015-05-22 at 08:48 +0100, David Howells wrote:
> > Luis R. Rodriguez <mcgrof@suse.com> wrote:
> > 
> > > > 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"
> > > 
> > > How exactly do you go about uploading CertB to the kernel BTW?
> > 
> > Assuming RootCA or CertA is present in the kernel, the idea would be to use 
> > the add_key() system call or the request_key() mechanism to add the key to 
> > the system keyring.  The key in the cert would only be added to the keyring 
> > if it is trusted by a key already there.
> 
> From Petko's description, the RootCA is on the system keyring, but CertA is on 
> a new IMA trusted CA keyring.  So everything you said is true, but on this 
> new, yet to be upstreamed, IMA trusted CA keyring.

I only named this intermediate keyring .ima_root_ca because this is how i use 
it.  However, it is system-wide trusted keyring, which accepts keys that are 
either trusted by CAs in the .system_keyring or higher level CA is already in 
.ima_root_ca.  For example CertC will be accepted in .ima_root_ca if CertB is 
already there.

The name (.ima_root_ca) is misleading and should be replaced with something that 
better describes it's functionality.  As far as i see there is no reason this 
keyring not to hold the CA that verifies module's signature.

		Petko