linux-kernel - Re: [PATCH v12 01/11] MODSIGN: Export module signature definitions

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Date:   Thu, 4 Jul 2019 12:54:27 +0200
From:   Philipp Rudo <prudo@...ux.ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Cc:     Jessica Yu <jeyu@...nel.org>, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Corbet <corbet@....net>,
        "AKASHI\, Takahiro" <takahiro.akashi@...aro.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH v12 01/11] MODSIGN: Export module signature definitions

Hi Thiago,


On Thu, 04 Jul 2019 03:42:57 -0300
Thiago Jung Bauermann <bauerman@...ux.ibm.com> wrote:

> Jessica Yu <jeyu@...nel.org> writes:
> 
> > +++ Thiago Jung Bauermann [27/06/19 23:19 -0300]:  
> >>IMA will use the module_signature format for append signatures, so export
> >>the relevant definitions and factor out the code which verifies that the
> >>appended signature trailer is valid.
> >>
> >>Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
> >>and be able to use mod_check_sig() without having to depend on either
> >>CONFIG_MODULE_SIG or CONFIG_MODULES.
> >>
> >>Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
> >>Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
> >>Cc: Jessica Yu <jeyu@...nel.org>
> >>---
> >> include/linux/module.h           |  3 --
> >> include/linux/module_signature.h | 44 +++++++++++++++++++++++++
> >> init/Kconfig                     |  6 +++-
> >> kernel/Makefile                  |  1 +
> >> kernel/module.c                  |  1 +
> >> kernel/module_signature.c        | 46 ++++++++++++++++++++++++++
> >> kernel/module_signing.c          | 56 +++++---------------------------
> >> scripts/Makefile                 |  2 +-
> >> 8 files changed, 106 insertions(+), 53 deletions(-)
> >>
> >>diff --git a/include/linux/module.h b/include/linux/module.h
> >>index 188998d3dca9..aa56f531cf1e 100644
> >>--- a/include/linux/module.h
> >>+++ b/include/linux/module.h
> >>@@ -25,9 +25,6 @@
> >> #include <linux/percpu.h>
> >> #include <asm/module.h>
> >>
> >>-/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
> >>-#define MODULE_SIG_STRING "~Module signature appended~\n"
> >>-  
> >
> > Hi Thiago, apologies for the delay.  
> 
> Hello Jessica, thanks for reviewing the patch!
> 
> > It looks like arch/s390/kernel/machine_kexec_file.c also relies on
> > MODULE_SIG_STRING being defined, so module_signature.h will need to be
> > included there too, otherwise we'll run into a compilation error.  
> 
> Indeed. Thanks for spotting that. The patch below fixes it. It's
> identical to the previous version except for the changes in 
> arch/s390/kernel/machine_kexec_file.c and their description in the
> commit message. I'm also copying some s390 people in this email.

to me the s390 part looks good but for one minor nit.

In arch/s390/Kconfig KEXEC_VERIFY_SIG currently depends on
SYSTEM_DATA_VERIFICATION. I'd prefer when you update this to the new
MODULE_SIG_FORMAT. It shouldn't make any difference right now, as we don't
use mod_check_sig in our code path. But it could cause problems in the future,
when more code might be shared.

Thanks
Philipp

> > Other than that, the module-related changes look good to me:
> >
> > Acked-by: Jessica Yu <jeyu@...nel.org>  
> 
> Thank you very much!
>