This has been broken for almost two years; the signature format switched to PKCS#7 and modinfo doesn't support it.   It's not as simple as just patching kmod because evidently the kernel change regressed or disrespected the relevent structure in the modules in a way that makes it impossible for kmod to even make sense of.   Details here:  https://github.com/coreos/bugs/issues/1054

-David

On Wed, Apr 11, 2018 at 4:39 PM, Ben Mezger <su@seds.nl> wrote:
Greetings,

I have enabled module signature verification on my kernel, and it does
seem to be enabled upon boot:

$  dmesg | grep -i 'x.*509'
[    1.259988] Asymmetric key parser 'x509' registered
[    1.811026] Loading compiled-in X.509 certificates
[    1.813833] Loaded X.509 cert 'Build time autogenerated kernel key:
77e716fc52a6293567d953cd24a5977e55b41a5e'

and doing a cat /proc/keys seems to show the key enabled:

$ cat /proc/keys
...
37c67374 I------     1 perm 1f030000     0     0 asymmetri Build time
autogenerated kernel key: 77e716fc52a6293567d953cd24a5977e55b41a5e:
X509.rsa 55b41a5e []
...

However, if I do a modinfo to see the key on a module, it seems empty:

$modinfo ntfs
filename:       /lib/modules/4.9.76-gentoo-r1/kernel/fs/ntfs/ntfs.ko
license:        GPL
version:        2.1.32
description:    NTFS 1.2/3.x driver - Copyright (c) 2001-2014 Anton
Altaparmakov and Tuxera Inc.
author:         Anton Altaparmakov <anton@tuxera.com>
alias:          fs-ntfs
srcversion:     0D7ACE93F603E9350827FB8
depends:
intree:         Y
vermagic:       4.9.76-gentoo-r1 SMP mod_unload
signat:         PKCS#7
signer:
sig_key:
sig_hashalgo:   md4

And hex dump does show me the digital signature appended at the end:

$ hexdump -C /lib64/modules/4.9.76-gentoo-r1/kernel/fs/ntfs/ntfs.ko| tail
0004e8c0  e3 dd 54 9d 5e f1 1a 12  56 47 4e 54 91 b9 fa ce  |..T.^...VGNT....|
0004e8d0  e6 01 db 37 eb 83 f3 77  10 f0 b5 f8 11 fd 4e 86  |...7...w......N.|
0004e8e0  6c 81 8a 61 c2 15 6d 5a  35 93 8b 33 c0 32 2f e4  |l..a..mZ5..3.2/.|
0004e8f0  8c 15 71 de c8 c5 39 58  cc e8 65 e1 be 36 e6 02  |..q...9X..e..6..|
0004e900  b0 75 b5 a2 73 d8 4d 22  e7 2f 53 1f 42 fb ee 58  |.u..s.M"./S.B..X|
0004e910  f2 65 44 13 26 30 7b 31  1c 58 12 5a f2 5d b1 45  |.eD.&0{1.X.Z.].E|
0004e920  3a f0 a5 79 74 f4 00 00  02 00 00 00 00 00 00 00  |:..yt...........|
0004e930  02 9e 7e 4d 6f 64 75 6c  65 20 73 69 67 6e 61 74  |..~Module signat|
0004e940  75 72 65 20 61 70 70 65  6e 64 65 64 7e 0a        |ure appended~.|
0004e94e

My question is: why doesn't modinfo show me the key fingerprint?

--
Kind regards,
Met een vriendelijke groet,

Ben Mezger
https://seds.nl
PGP: C473 DDC9 D1B1 40AF 2051  1CF6 18C4 6052 1688 92F7