Comment 0 for bug 1798863

On a system with Ubuntu 18.10, with secure boot enabled, and a key enrolled in the MOK database, I am observing the following peculiar behaviors:

* Signature verification appears to be disabled, and cannot be enabled again. It appeared to be enabled previously, as loading of unsigned modules was failing, and `mokutil --enable-validation` runs without incident; however, upon the next boot when attempting to confirm the change, MokManager prints an error message "Unable to delete Secure Boot state" after completing the password challenge.
* As a result of signature verification being disabled, modules signed with untrusted keys taint the kernel instead of failing to load outright.
* Regardless of signature verification being enabled or not, it seems that the key enrolled in the MOK is not being used for validating kernel module signatures. Modules signed with the key still fail the signature verification test and taint the kernel, even though the key is visible in the output of `mokutil --list-enrolled`, and testing the key with `mokutil --test-key` shows that it's enrolled. Also, a message acknowledging the key appears in dmesg: Loaded UEFI:MokListRT cert 'nvidia-installer generated signing key: 90c957eb56dfb04d8734d54fb614ef5af6c69318' linked to secondary sys keyring
* Also, somewhat strangely, in this state with module signature verification not being enforced, attempting to load a completely unsigned kernel module suceeds, and doesn't even log a kernel message about a missing/invalid signature, or taint the kernel.

Apport report attached, which includes dmesg log showing the kernel acknowledging the key enrolled in the MOK database, and a signature verification failure and subsequent successful loading of a module signed with that key:

 [ 4.234093] Loaded UEFI:MokListRT cert 'nvidia-installer generated signing key: 90c957eb56dfb04d8734d54fb614ef5af6c69318' linked to secondary sys keyring
...
 [ 6.628452] nvidia: module verification failed: signature and/or required key missing - tainting kernel
...
 [ 6.637252] nvidia-nvlink: Nvlink Core is being initialized, major device number 238
 [ 6.637507] nvidia 0000:01:00.0: enabling device (0006 -> 0007)
 [ 6.637620] nvidia 0000:01:00.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=none:owns=none
 [ 6.737216] NVRM: loading NVIDIA UNIX x86_64 Kernel Module 410.66 Wed Oct 10 12:01:53 CDT 2018 (using threaded interrupts)