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

[Thiago Jung Bauermann]

Hello Philipp,

Philipp Rudo <prudo@xxxxxxxxxxxxx> writes:

> Hi Thiago,
>
>
> On Thu, 04 Jul 2019 03:42:57 -0300
> Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx> wrote:
>
>> Jessica Yu <jeyu@xxxxxxxxxx> 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@xxxxxxxxxxxxx>
>> >>Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
>> >>Cc: Jessica Yu <jeyu@xxxxxxxxxx>
>> >>---
>> >> 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.

Thanks for the prompt review!

> 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.

Makes sense. Here is the updated patch with the Kconfig change.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center