Re: [OE-core] [PATCH] linux-yocto: enable strict kernel module signing by default

[Bruce Ashfield <bruce.ashfield@gmail.com>]

On Fri, Nov 25, 2022 at 11:11 AM Jack Mitchell <ml@embed.me.uk> wrote:
>
> On 25/11/2022 15:54, Mikko Rapeli wrote:
> > It's a good default and used in many Linux distributions.
> > Did not test out of tree modules if they do correct things but
> > any such failures should be fixed.
> >
> > One way to verify that kernel module signing also works:
> >
> > root@qemux86-64:~# dmesg|grep X.509
> > [    1.298936] Loading compiled-in X.509 certificates
> > [    1.328280] Loaded X.509 cert 'Build time autogenerated kernel key: ee1bed6d845358744c764683bf73b4404cc79287'
> >
> > These logs in dmesg show that signing in kernel is enabled and
> > key is found. Then if any kernel modules load, they were
> > signed correctly. Additionally modinfo tool from kmod shows kernel module
> > signing details:
>
> Hi Mikko,
>
> Do the kernel modules get properly stripped, last time I was looking at
> this it was skipped when signed and as such root filesystem sizes
> ballooned with signed modules.

oe package.py still does skip stripping for signed modules.

I'm sure it is fixable, but we need someone to step up and have a closer look.

Richard can probably comment better than I can, but there's a variety
of use cases (from SDKs, to debug, to SBOM, etc) that all need to deal
with whether binaries are stripped and be able to find the
non-stripped executables in order to work properly.

So to answer the follow up suggestion of using the kernel's module
strip directly .. it also might be feasible, but we need to make sure
that all the other uses cases still work. My preference is to do the
work in package.py, so that we don't have to worry about the kernel
provider and any additional features have code in the same place as a
baseline.

Bruce

>
> Regards,
> Jack.
>
> >
> > root@qemux86-64:~# lsmod
> > Module                  Size  Used by
> > sch_fq_codel           20480  1
> > root@qemux86-64:~# modinfo sch_fq_codel
> > filename:
> > /lib/modules/5.19.9-yocto-standard/kernel/net/sched/sch_fq_codel.ko
> > description:    Fair Queue CoDel discipline
> > license:        GPL
> > author:         Eric Dumazet
> > depends:
> > retpoline:      Y
> > intree:         Y
> > name:           sch_fq_codel
> > vermagic:       5.19.9-yocto-standard SMP preempt mod_unload
> > sig_id:         PKCS#7
> > signer:         Build time autogenerated kernel key
> > sig_key:        2B:2A:BE:7D:B5:92:DC:98:A9:F8:D7:00:A6:73:35:20:10:D8:19:EE
> > sig_hashalgo:   sha512
> > signature:      72:6C:E1:78:7C:A7:7B:CC:C4:33:23:6B:95:EC:1B:2A:BD:D9:EC:7A:
> >                 85:07:05:B2:70:3C:C9:64:F6:78:8A:01:A0:E3:64:C7:47:BB:5D:0E:
> >                 86:BA:C1:DD:40:05:AE:1F:19:D4:F0:98:49:86:CC:61:14:3C:AB:1E:
> >                 4A:1C:83:47:1D:FA:6D:E4:83:79:3A:2B:3F:7D:B6:E0:09:AE:B4:01:
> >                 07:EE:C9:5B:99:70:4F:49:8A:64:E4:7D:84:AA:37:F5:DB:5F:16:5C:
> >                 D4:DC:0C:33:73:5D:D9:8D:7E:71:5B:A1:ED:61:81:5E:1C:ED:A2:D8:
> >                 76:46:99:B3:78:08:F7:7F:0D:4B:94:26:21:63:47:B0:75:9F:A4:EA:
> >                 3D:14:D4:09:CC:59:F3:FC:80:AC:BF:56:1E:8C:73:FD:CB:07:27:C6:
> >                 3D:98:4C:E4:C3:9C:C0:AD:90:53:46:8F:AE:66:FE:10:C8:92:7F:BA:
> >                 74:C2:B0:E3:6E:47:66:AB:39:25:41:12:66:91:20:27:1A:58:77:75:
> >                 4F:C0:3F:F1:8E:5F:AB:0A:BD:8B:62:4F:2B:01:5A:5C:4E:5C:31:39:
> >                 FB:F4:14:2E:BF:D8:51:4B:C8:D0:E2:0A:20:80:95:05:80:E3:46:75:
> >                 43:80:30:63:6F:A4:25:82:59:35:34:E8:6A:DC:FF:93:F8:32:BB:FA:
> >                 66:2D:B9:08:75:1A:3A:3A:5D:57:F4:63:85:01:B4:EB:96:1B:CE:6F:
> >                 4D:61:FC:AA:6C:39:7F:D6:37:C9:84:0A:84:17:FB:BE:FC:20:CB:EE:
> >                 8C:2F:93:92:F6:48:F4:07:50:84:D8:2C:B5:2E:A7:7D:3A:3F:DC:E9:
> >                 B9:17:EF:47:49:EC:BA:62:1C:C4:C6:58:9C:0C:8D:26:41:6E:1F:C1:
> >                 95:A7:8B:57:5D:1D:4B:B4:04:00:F6:68:24:9E:E2:BF:11:EC:05:6C:
> >                 83:E8:C6:DB:BB:3D:22:8B:31:BB:99:1A:44:E1:15:71:C3:AA:FA:01:
> >                 98:BA:6B:20:26:D6:9C:61:5C:6F:81:29:09:B1:EA:C5:28:15:F3:98:
> >                 C0:18:FE:08:8B:40:A5:F3:3C:71:4B:C6:41:CD:38:51:79:EA:5D:C9:
> >                 13:39:B5:FD:A3:D1:BB:11:94:66:F7:7B:6A:DC:2C:01:5F:AB:73:08:
> >                 68:24:32:BE:BC:7A:90:E5:FD:97:17:6C:DD:46:D0:0E:2C:03:31:66:
> >                 B3:7C:B2:48:E1:E0:1A:63:20:48:4C:D4:55:56:71:04:3B:5F:3B:28:
> >                 BF:64:6C:52:A9:07:6D:FF:21:E9:06:35:E8:A1:D7:F4:C2:F9:D7:7B:
> >                 9D:D2:90:16:2F:68:1E:3F:BE:43:ED:64
> >
> > Failures in signed kernel module loading should show as errors at
> > runtime, for example systemd services, or as oeqa parselogs test
> > failures which detects signature verification error messages from the
> > kernel.
> >
> > Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
> > ---
> >  meta/recipes-kernel/linux/linux-yocto.inc | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/meta/recipes-kernel/linux/linux-yocto.inc b/meta/recipes-kernel/linux/linux-yocto.inc
> > index 091003ed82..bab1f21479 100644
> > --- a/meta/recipes-kernel/linux/linux-yocto.inc
> > +++ b/meta/recipes-kernel/linux/linux-yocto.inc
> > @@ -37,6 +37,9 @@ KERNEL_FEATURES:append = " ${@bb.utils.contains('MACHINE_FEATURES', 'efi', 'cfg/
> >  KERNEL_FEATURES:append = " ${@bb.utils.contains('MACHINE_FEATURES', 'numa', 'features/numa/numa.scc', '', d)}"
> >  KERNEL_FEATURES:append = " ${@bb.utils.contains('MACHINE_FEATURES', 'vfat', 'cfg/fs/vfat.scc', '', d)}"
> >
> > +# enable module signing by default
> > +KERNEL_FEATURES:append = " features/module-signing/force-signing.scc"
> > +
> >  # A KMACHINE is the mapping of a yocto $MACHINE to what is built
> >  # by the kernel. This is typically the branch that should be built,
> >  # and it can be specific to the machine or shared
> >
> >
> >
> >
> >
>
> --
> Jack Mitchell, Consultant
> https://www.tuxable.co.uk
>
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