[Bug 2045552] Re: nullboot 0.5.0: shim 15.7-0ubuntu1 update

[Chris Halse Rogers]

Ok. You've convinced me this is the minimal reasonable change :)

I've still got a couple of questions about the process of testing:

It's not entirely clear to me what the scope of possible failures is here:
* failure to boot is a pleasantly obvious failure mode, but is this influenced by user configuration, or does it booting *anywhere* mean it will boot *everywhere*?
* My understanding of the TPM stack is limited, but my understanding is that if it boots *at all* then it must have booted an expected image - is this correct, or should we also be testing that the update correctly *fails* to boot unexpected images?

And to clarify:
> Double check bios_measurements_log to ensure that the newly update shim was used for boot (https://github.com/canonical/tcglog-parser/tree/master/tcglog-dump can be used to extract checksum of the shim binary used at boot and compared to the one shipped in nullboot

>From package contents I assume you'd be checking against the checksum of
/usr/lib/nullboot/shim/shimx64.efi.signed, but what checksum algorithm?

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https://bugs.launchpad.net/bugs/2045552

Title:
  nullboot 0.5.0: shim 15.7-0ubuntu1 update

Status in nullboot package in Ubuntu:
  Fix Released
Status in nullboot source package in Focal:
  New
Status in nullboot source package in Jammy:
  New

Bug description:
  [Impact]
  Security update for shim

  [Test plan]

  * Deploy Azure CVM and TPM FDE
  * Upgrade to this new package and reboot
  * Boot should be successful
  * Double check bios_measurements_log to ensure that the newly update shim was used for boot (https://github.com/canonical/tcglog-parser/tree/master/tcglog-dump can be used to extract checksum of the shim binary used at boot and compared to the one shipped in nullboot)

  * CPC - build new image with nullboot preinstalled, and attempt to
  register and boot such an images as first time.

  [Where problems could occur]

  Resealing could fail

  Shim could fail to boot

  Limited to Azure confidential VMs in scope

  Upgrade to and usage of interim lunar & mantic ubuntu releases is not
  supported on the Azure CVMs and does not work, hence this bug targets
  SRUs for LTS releases only.

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