linux-kernel - Re: [PATCH] MODSIGN: Only sign modules if built in-tree

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Message-ID: <20121101112655.GM6627@hansolo.jdub.homelinux.org>
Date:	Thu, 1 Nov 2012 07:26:56 -0400
From:	Josh Boyer <jwboyer@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Bruno Wolff III <bruno@...ff.to>, dhowells@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MODSIGN: Only sign modules if built in-tree

On Thu, Nov 01, 2012 at 05:38:15PM +1030, Rusty Russell wrote:
> Josh Boyer <jwboyer@...hat.com> writes:
> > When building out-of-tree modules, the current modules_install target
> > will attempt to sign them if module signing is enabled.  This will only
> > work if the signing keys are present in the build tree.  That will
> > often not be the case for modules that are built out-of-tree against
> > distribution kernel development packages.  This distros will not include
> > the signing keys, and build errors such as:
> >
> >     INSTALL /home/bruno/rpmbuild/BUILD/dahdi-linux-2.6.1/drivers/dahdi/dahdi_dyamic_eth.ko
> >     Can't read private key
> >     make[2]: *** [/home/bruno/rpmbuild/BUILD/dahdi-linux-2.6.1/drivers/dahdi/dahdi_dynamic.ko] Error 2
> >
> > will prevent such modules from successfully being installed.  This changes
> > the mod_sign_cmd to only sign the modules if they are built in-tree.  Those
> > built externally can sign them manually.
> 
> I prefer something like this (untested):
> 
> diff --git a/Makefile b/Makefile
> index 42d0e56..cb66c8d 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -722,8 +722,14 @@ export mod_strip_cmd
>  ifeq ($(CONFIG_MODULE_SIG),y)
>  MODSECKEY = ./signing_key.priv
>  MODPUBKEY = ./signing_key.x509
> +ifeq ($(KBUILD_EXTMOD),)
> +SIGNFAIL = false
> +else
> +# External builds might not have a signing key, don't break module_install.
> +SIGNFAIL = true
> +endif # KBUILD_EXTMOD
>  export MODPUBKEY
> -mod_sign_cmd = perl $(srctree)/scripts/sign-file $(MODSECKEY) $(MODPUBKEY)
> +mod_sign_cmd = perl $(srctree)/scripts/sign-file $(MODSECKEY) $(MODPUBKEY) || $(SIGNFAIL)
>  else
>  mod_sign_cmd = true
>  endif

OK.  I'll give this a spin locally today, but at first glance it seems
like it would do the same.

josh
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