linux-kernel - Re: [PATCH 00/23] Crypto keys and module signing

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Date:	Sun, 10 Jun 2012 15:17:29 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	David Howells <dhowells@...hat.com>
Cc:	dhowells@...hat.com, kyle@...artin.ca, dmitry.kasatkin@...el.com,
	zohar@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, keyrings@...ux-nfs.org
Subject: Re: [PATCH 00/23] Crypto keys and module signing

On Tue, 05 Jun 2012 14:35:56 +0100, David Howells <dhowells@...hat.com> wrote:
> Rusty Russell <rusty@...tcorp.com.au> wrote:
> 
> > > If you prefer to have userspace extract the module signature and pass it in
> > > uargs, here's a tree that will do that:
> > > 
> > > 	http://git.kernel.org/?p=linux/kernel/git/dhowells/linux-modsign.git;a=shortlog;h=refs/heads/modsign-uarg
> > 
> > OK, there's merit in this approach: it certainly moves the argument
> > about how to encode the signature out of my backyard :)
> 
> Not really.  The signature still has to be created by the kernel build.  It's
> just that you no longer have to care about the trade off when it comes to
> parsing it.

Yes, exactly.

> > Should we just bite the bullet and create a new syscall:
> > 
> > SYSCALL_DEFINE5(init_module2, void __user *, umod,
> > 		unsigned long, len, const char __user *, uargs,
> >                 unsigned int, siglen, const char __user *, sig)
> > 
> > But I'm easily swayed if you prefer the current approach.
> 
> "The current approach" being to attach signature to the blob?  Or to pass the
> signature separately but in the uargs?

The former.

> I would very much prefer to keep the signature in the blob and have the kernel
> extract it as there's no particular need for it to be detached - even if you
> are using IMA.
> 
> However, I don't think an extra syscall would hurt particularly - except that
> it uses up more space in the syscall table...  It would, however, be smaller
> in the signature verification department as the signature neither needs
> decoding from uargs nor extracting from the blob.

Good.  Let's have init_module2(), and let userspace decide where to get
the signature from.

Thanks,
Rusty.
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