[Bug 2009078] Re: rebuild debian-installer against current boot stack (SecureBoot security updates / revocations)

[Steve Langasek]

Configured a new VM under virt-manager, using the option 'Customize
configuration before install' and selecting 'OVMF_CODE_4M.ms.fd' as the
firmware.  Booted Ubuntu 22.04.2 install media.  Verified firmware
settings were as expected with 'mokutil --db' and 'mokutil --sb-state'.
Verified that SBAT had been applied by confirming
/sys/firmware/efi/efivars/SbatLevelRT-605dab50-e046-4300-abb6-3dd810dd8b23
was present.

Enabled focal-proposed in sources and ran 'apt install secureboot-
db=1.6~20.04.1'.  Confirmed with 'mokutil --dbx' that the Canonical 2012
signing key was present.

Shut down the VM, reconfigured to boot 20.04.5.  20.04.5 booted to grub
without a security error.  So the test case is incomplete, working on
revising.

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https://bugs.launchpad.net/bugs/2009078

Title:
  rebuild debian-installer against current boot stack (SecureBoot
  security updates / revocations)

Status in debian-installer package in Ubuntu:
  Invalid
Status in debian-installer source package in Focal:
  Fix Released

Bug description:
  [Justification]
  There is another round of security updates for secureboot that result in SBAT revocations of all the previous shims/grubs.  Since the 20.04.5 point release inadvertently went out without a current UEFI bootloader and was thus already revoked before release, we have agreed to do an exceptional 20.04.6 point release.  That should include the current version of shim and grub2.

  [Test case]
  * Build a daily PROPOSED=1 focal image that pulls in the new d-i boot bits.
  * On a system with SecureBoot enabled, boot the 22.04.2 install media.  This will cause SBAT to be updated and the system to refuse to boot older shims.
  * Install secureboot-db 1.6~20.04.1 from focal-proposed, to force an update of dbx as well.
  * Try to boot Ubuntu 20.04.5 media.  Confirm that the boot is blocked with a security error.
  * Boot the 20.04 daily media.  Confirm that the image boots.

  [Where problems could occur]
  We are pulling grub2-signed and shim2-signed from focal-proposed.  If something happens that prevents these from being released, then we would need to respin.  Otherwise, this change should only increase the set of machines on which it's possible for us to boot the point release media.

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