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

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Date:	Fri, 1 Mar 2013 00:02:43 +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:

> > Let me formulate my point more clearly -- Microsoft very likely going to 
> > sign hello world EFI PE binary, no matter the contents of .keylist 
> > section, as they don't give a damn about this section, as it has zero 
> > semantic value to them, right?
> > 
> > They sign the binary. By signing the binary, they are *NOT* establishing 
> > cryptographic chain of trust to the key stored in .keylist, but your 
> > patchset seems to imply so.
> 
> Mr Evil Blackhat's binary is then a mechanism for circumventing the 
> Windows trust mechanism, 

Yes, the "hello world" one. 

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.

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?

If so, that's a clear difference from normal X.509 chain of trust (i.e. 
the difference between having the key signed, and having the binary 
signed).

-- 
Jiri Kosina
SUSE Labs
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