linux-kernel - Re: RFC: sign the modules at install time

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Date:	Wed, 17 Oct 2012 16:21:29 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Josh Boyer <jwboyer@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Rusty Russell <rusty@...tcorp.com.au>,
	David Howells <dhowells@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: RFC: sign the modules at install time

On Wed, Oct 17, 2012 at 4:07 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Hmm. It *should* work for them too, because the debuginfo modules stay
> around in the object tree, and never get stripped there. None of this
> is different from what we used to do before: we stripped the modules
> as we copied them to /lib/modules (where the RPM build obviously would
> have that $RPM_BUILD_ROOT prefix on the module install path).

Ok, I read your description of the odd way fedora builds debuginfo kernels.

I actually think that works fine too. I do agree with adding a "make
sign_modules" target, but it would *re-sign* them after "make
modules_install" has already signed them once.

Why?

What you'd do for your debuginfo requirements is:

 - do the normal kernel build, and install modules (with *my* patch,
which does signing at install time)

   This does the normal (conditionally stripped - you just wouldn't
strip them, but you cannot have done that before either) modules,
installs them, and signs then.

   Ta-daa, you have your debuginfo modules installed, and they are
signed. Create the debuginfo rpm.

 - now, strip the modules. This obviously destroys the signatures

 - do the extra "make sign_modules" that you added, that re-signs the
already installed modules, and now you can create the non-debuginfo
rpm.

Voila. "make modules_install" does the right thing for everybody -
including normal users. And it does so without the incredible baroque
code. And no normal user is expected to ever use the new "make
sign_modules", but it allows for the Fedora "we'll want to sign them
again".

That said, you could even just do "make sign-modules" on your own
without any makefile targets. After all, it would just be something
like

   find $MODULEDIR --name '*.ko | while read i; do script/sign-file
keyfile x509file $i; done

so it could even be done in that rpm script directly.

       Linus
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