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

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Date:	Tue, 05 Jun 2012 10:35:56 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	David Howells <dhowells@...hat.com>, kyle@...artin.ca,
	dmitry.kasatkin@...el.com, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, keyrings@...ux-nfs.org,
	"Tim Abbott" <tabbott@...lice.com>
Subject: Re: [PATCH 00/23] Crypto keys and module signing

On Mon, 04 Jun 2012 08:47:51 -0400, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
> On Mon, 2012-06-04 at 11:01 +0930, Rusty Russell wrote:
> > On Fri, 25 May 2012 16:42:19 +0100, David Howells <dhowells@...hat.com> wrote:
> > > 
> > > Hi Rusty,
> > > 
> > > 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 :)
> > 
> > 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.
> > 
> > Thanks,
> > Rusty.
> 
> If you're really considering creating a new syscall, then perhaps this
> discussion should include passing the file descriptor instead of a
> buffer and signature.  As I said https://lkml.org/lkml/2012/5/25/261, I
> don't know the historical reasons for passing a buffer instead of the
> file descriptor itself.  If the file descriptor was passed, it would
> allow IMA-appraisal, which is in the process of being upstreamed, to
> verify and enforce file data and metadata integrity like on the other
> hooks open, execve, and mmap.

It's flexible.  Compressed modules, for example.  And who knew if we
would be runtime generating modules?  But I don't think even the ksplice
guys generate modules on the fly for insertion.

modprobe has --force-vermagic and --force-modversion, but frankly that
could be replaced by a single "force" flag handed to the kernel.

If there's real benefit, it could be done.  Do we still want a separate
signature blob?

SYSCALL_DEFINE5(init_module_fd,
                int, fd,
                unsigned int, flags,
                const char *__user *, uargs,
                unsigned int, siglen,
                const char __user *, sig);

Cheers,
Rusty.
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