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SubjectRe: [PATCH 00/23] Crypto keys and module signing
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On Mon, 04 Jun 2012 08:47:51 -0400, Mimi Zohar <zohar@linux.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@redhat.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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