linux-kernel - Re: [PATCH 2/3] binfmt_elf: Verify signature of signed elf binary

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Date:	Wed, 16 Jan 2013 13:08:35 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, pjones@...hat.com, hpa@...or.com,
	dhowells@...hat.com, jwboyer@...hat.com,
	Dmitry Kasatkin <dmitry.kasatkin@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 2/3] binfmt_elf: Verify signature of signed elf binary

On Wed, 2013-01-16 at 11:34 -0500, Vivek Goyal wrote:

> I read the comment in ima_bprm_check() being called from security_bprm_check(). 
> It says that files already open for write can't executed and files already
> open for exec can't be open for writes. That's fine. 
> 
> I was worried about anonymous pages being modified on swap and then
> faulted back in. It is not necessarily signature verification but making
> sure signed processes memory is not modified later by any unsigned process
> in anyway. And that includes disabling ptrace too.
> 
> So IMA stuff does not do anything to protect against process memory being
> modified using ptrace or by playing tricks with swap.

> I am not sure what will happen if I can bypass the file system and directly
> write on a disk block and modify executable. (Assuming one can get block
> information somehow). Does anything protect such modification? Will IMA
> detect it?

Sorry, this is out of scope for IMA.  Dmitry has looked into this, but
I'm not sure where it stands at the moment.

thanks,

Mimi

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