MokSBStateRT strictly inferior to /proc/sys/kernel/moksbstate_disabled

[Steve Langasek]

[SRU Justification]
In some cases, incorrect locally-set EFI variables can prevent the shim-signed package from detecting that SecureBoot is active on the system. As a result, the user will not be prompted to disable SecureBoot, and will be left with non-functional dkms modules after reboot to the new kernel.

[Test case]
1. Install Ubuntu on a system (or VM) with SecureBoot enabled.
2. As root, run "printf '\x07\x00\x00\x00\x01' > /sys/firmware/efi/efivars/MokSBStateRT-605dab50-e046-4300-abb6-3dd810dd8b23".
3. Install shim-signed from -updates.
4. Install the dahdi-dkms package.
5. Confirm that you are not prompted to disable secureboot.
6. Install shim-signed from -proposed.
7. Confirm that you *are* prompted to disable secureboot.
8. Run 'sudo rm /sys/firmware/efi/efivars/MokSBStateRT-605dab50-e046-4300-abb6-3dd810dd8b23'.

[Regression potential]
Since /proc/sys/kernel/moksbstate_disabled will not be present on older kernels, and /sys/firmware/efi/efivars/MokSBStateRT-605dab50-e046-4300-abb6-3dd810dd8b23 is always less authoritative than /proc/sys/kernel/moksbstate_disabled if present, I don't see any way that this could regress.

update-secureboot-policy tries to check whether MOK's override has disabled SecureBoot state. However, since the real variable in nvram is not accessible after boot, it needs to use a proxy for this information. There are two that it tries to use:
 - We've specified how shim can mirror the MokSBState variable to MokSBStateRT at boot time, to expose this information to the OS (but this is not implemented in current shim).
 - The recent kernels which honor MokSBState also include support for exposing this value as /proc/sys/kernel/moksbstate_disabled.

Neither of these is guaranteed to be present on any given system. However, if present, the kernel variable should be *unconditionally* preferred over the efi "shadow" variable - because the kernel variable is immutable, whereas MokSBStateRT is just another nvram variable that things can overwrite (though they shouldn't).

We have heard at least one report internally of a system where something other than our shim is setting the value of MokSBStateRT and confusing update-secureboot-policy, so this will be a priority to also fix in SRU.

[Launchpad Janitor (janitor)]

This bug was fixed in the package shim-signed - 1.18

---------------
shim-signed (1.18) yakkety; urgency=medium

  * update-secureboot-policy: If /proc/sys/kernel/moksbstate_disabled is
    present, prefer this unconditionally over MokSBStateRT. LP: #1604873.

 -- Steve Langasek <email address hidden> Wed, 20 Jul 2016 08:31:17 -0700

[Adam Conrad (adconrad)]

Hello Steve, or anyone else affected,

Accepted shim-signed into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/shim-signed/1.18~16.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Adam Conrad (adconrad)]

Hello Steve, or anyone else affected,

Accepted shim-signed into wily-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/shim-signed/1.18~15.10.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Adam Conrad (adconrad)]

Hello Steve, or anyone else affected,

Accepted shim-signed into trusty-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/shim-signed/1.18~14.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Adam Conrad (adconrad)]

Hello Steve, or anyone else affected,

Accepted shim-signed into precise-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/shim-signed/1.18~12.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Taihsiang Ho (tai271828)]

tested on 201508-18805 - Dell XPS 13 9350 - Dino 2 SKL with Xenial.
I could reproduce the test case, except that the step2 and the step8 would get "permission denied" and "operation not permitted" respectively.

[Taihsiang Ho (tai271828)]

tested on 201508-18805 - Dell XPS 13 9350 - Dino 2 SKL with 14.04.4.
I could reproduce the test case, except that the step2 and the step8 would get "permission denied" and "operation not permitted" respectively.
There is no prompt at step5 and there is prompt at step7.

[Taihsiang Ho (tai271828)]

I could not reproduce the test case on 201508-18805 - Dell XPS 13 9350 - Dino 2 SKL with Ubuntu 12.04.5.

Both of the step5 and step7 did not prompt.

I collected the log as the attachment 201508-18805-12.04.5.tar.gz, which was collected right after the step7.

[Launchpad Janitor (janitor)]

This bug was fixed in the package shim-signed - 1.18~14.04.1

---------------
shim-signed (1.18~14.04.1) trusty; urgency=medium

  * update-secureboot-policy: If /proc/sys/kernel/moksbstate_disabled is
    present, prefer this unconditionally over MokSBStateRT. LP: #1604873.

 -- Steve Langasek <email address hidden> Wed, 20 Jul 2016 16:21:36 -0700

[Brian Murray (brian-murray)]

The verification of the Stable Release Update for shim-signed has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

[Launchpad Janitor (janitor)]

This bug was fixed in the package shim-signed - 1.18~16.04.1

---------------
shim-signed (1.18~16.04.1) xenial; urgency=medium

  * update-secureboot-policy: If /proc/sys/kernel/moksbstate_disabled is
    present, prefer this unconditionally over MokSBStateRT. LP: #1604873.

 -- Steve Langasek <email address hidden> Wed, 20 Jul 2016 12:09:58 -0700

[Launchpad Janitor (janitor)]

This bug was fixed in the package shim-signed - 1.18~15.10.1

---------------
shim-signed (1.18~15.10.1) wily; urgency=medium

  * update-secureboot-policy: If /proc/sys/kernel/moksbstate_disabled is
    present, prefer this unconditionally over MokSBStateRT. LP: #1604873.

 -- Steve Langasek <email address hidden> Wed, 20 Jul 2016 16:20:26 -0700

[Launchpad Janitor (janitor)]

This bug was fixed in the package shim-signed - 1.18~12.04.1

---------------
shim-signed (1.18~12.04.1) precise; urgency=medium

  * update-secureboot-policy: If /proc/sys/kernel/moksbstate_disabled is
    present, prefer this unconditionally over MokSBStateRT. LP: #1604873.

 -- Steve Langasek <email address hidden> Wed, 20 Jul 2016 16:22:42 -0700