Re: [gentoo-dev] [PATCH] linux-mod.eclass: support module signing

[Georgy Yakovlev]

On Mon, 2022-06-27 at 17:50 -0400, Mike Gilbert wrote:
> On Mon, Jun 27, 2022 at 5:11 PM Georgy Yakovlev
> <gyakovlev@g.o> wrote:
> >
> > On Mon, 2022-06-27 at 15:49 -0400, Mike Gilbert wrote:
> > > On Mon, Jun 27, 2022 at 3:42 PM Georgy Yakovlev
> > > <gyakovlev@g.o> wrote:
> > > >
> > > > On Mon, 2022-06-27 at 14:56 -0400, Mike Gilbert wrote:
> > > > > On Mon, Jun 27, 2022 at 2:35 PM Kenton Groombridge
> > > > > <concord@g.o> wrote:
> > > > > > > so looks like we need to combine both methods and do the
> > > > > > > following:
> > > > > > >  - if signing requested without compression - sign in
> > > > > > > pkg_preinst.
> > > > > > >  - if signing requested with compression - sign in
> > > > > > > src_install
> > > > > > >
> > > > > >
> > > > > > Why can't we do both in pkg_preinst? I am thinking it would
> > > > > > be
> > > > > > best
> > > > > > if
> > > > > > we drop the current compression implementation and rework
> > > > > > your
> > > > > > old
> > > > > > code
> > > > > > to handle both compression and signing since the signing
> > > > > > code
> > > > > > is
> > > > > > more or
> > > > > > less already complete.
> > > > >
> > > > > Signing modules in pkg_preinst seems like a bad idea to me.
> > > > > That
> > > > > means
> > > > > you need to copy your private keys around to every host where
> > > > > the
> > > > > package might be installed.
> > > > >
> > > > > If you sign in src_compile or src_install, you only need
> > > > > private
> > > > > keys
> > > > > on the system building your binpkg.
> > > > >
> > > >
> > > > unfortunately portage will unconditionally strip .ko objects,
> > > > rendering
> > > > modules unloadable by stripping signature,  unless we do
> > > > dostrip -x
> > > > (requires EAPI7+, which should not be a problem nowadays, but
> > > > was a
> > > > problem back in 2018), which can be quite unfortunate on debug
> > > > enabled
> > > > kernels.
> > >
> > > Sounds like something to fix/change in Portage. It could probably
> > > be
> > > updated to not strip the signature. However, I would guess the
> > > signature needs to be updated after the binary is modified in any
> > > case.
> > >
> > > Or as a workaround you could disable automatic striping via
> > > dostrip -
> > > x
> > > and run the proper commands to strip the modules in src_install
> > > as
> > > well.
> > >
> > I think even strip itself does not have proper options not to break
> > module. Several years back it was the case, basically one has to
> > strip
> > first, sign second, otherwise module will be unloadable.
> >
> > "Signed modules are BRITTLE as the signature is outside of the
> > defined
> > ELF container. Thus they MAY NOT be stripped once the signature is
> > computed and attached. Note the entire module is the signed
> > payload,
> > including any and all debug information present at the time of
> > signing."
> >
> > https://www.kernel.org/doc/html/v4.15/admin-guide/module-signing.html#signed-modules-and-stripping
> >
>
> In that case, I think the only viable way to make this work is to
> disable automatic stripping and handle stripping via custom code in
> the ebuild/eclass.
>
might work indeed if we do something like (pseudo-bash)

if [[ module_sign == yes ]]; then
    dostrip -x /lib/modules # to stop portage stripping .ko objects
    manual-strip-respecting-features-nostrip -r /lib/modules
    sign-all-modules -r /lib/modules
fi
[[ compress_modules == yes ]] && compress-modules -r /lib/modules


this will equire eapi-bumping couple of packages
https://qa-reports.gentoo.org/output/eapi-per-eclass/linux-mod.eclass/6.txt
and restricting linux-mod.eclass to eapi7 or later.