linux-kernel - Re: [GIT PULL] Load keys from signed PE binaries

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Date:	Fri, 1 Mar 2013 00:45:23 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	David Howells <dhowells@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	jwboyer@...hat.com, pjones@...hat.com, vgoyal@...hat.com,
	keescook@...omium.org, keyrings@...ux-nfs.org,
	linux-kernel@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
	Florian Weimer <fw@...eb.enyo.de>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [GIT PULL] Load keys from signed PE binaries

On Thu, 28 Feb 2013, Matthew Garrett wrote:

> > But the real harm is being done by the i_own_your_ring0.ko module, which 
> > can be modprobed on all the systems where the signed "hello world" binary 
> > has been keyctl-ed before it was blacklisted.
> 
> Sure, if you've been infected before the revocation, you'll still be 
> infected. There's not really any good way around that.

Which is a very substantial difference to normal X509 chain of trust, 
isn't it?

This security model seems to be quite seriously flawed to me (in a sense 
that it has nothing to do with chain of trust as mandated by X509 even 
though it tries to pretend the opposite)

And frankly, Linus' proposal at [1] doesn't really make it any better in 
principle, it just keeps the whole thing out of kernel.

[1] https://lkml.org/lkml/2013/2/21/228

> > In other words -- you blacklist the population of the key on systems by 
> > blakclisting the key-carrying binary, but the key remains trusted on 
> > whatever system the binary has been processed by keyctl before. Right?
> 
> You have to re-load it on every boot, it's not a permanent thing.

That unfortunately seems to be very weak security measure as well.

Thanks,

-- 
Jiri Kosina
SUSE Labs
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