[Bug 1865515] Re: Chainbooting from grub over the network to local shim breaks chain of trust

[Lee Trager]

@Jeff MAAS uses the same bits as what the ISO uses. What is different is
how local booting happens with MAAS vs with the ISO. When installed with
the ISO the local boot process is UEFI Firmware -> Shim(from disk) ->
GRUB(from disk) -> Boot local kernel. When installed with MAAS the local
boot process is UEFI Firmware -> Shim(from network) -> GRUB(from
network) -> Shim(from disk) -> Grub(from disk) -> Boot local kernel. The
chain of trust when switching going from GRUB(from network) to Shim(from
disk). I suspect but haven't verified that this may be due to the shim
not being signed with a key GRUB has.

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https://bugs.launchpad.net/bugs/1865515

Title:
  Chainbooting from grub over the network to local shim breaks chain of
  trust

Status in MAAS:
  Confirmed
Status in grub package in Ubuntu:
  Confirmed
Status in shim-signed package in Ubuntu:
  Confirmed

Bug description:
  MAAS (2.4.2 and 2.6.2) cannot deploy to a server with Secure Boot
  active. This appears to be a regression of bug #1711203; the symptoms
  are identical. Namely:

  1) The system can begin deployment fine.
  2) After deployment is complete except for the final reboot, the
     system will reboot.
  3) GRUB appears briefly on the screen.
  4) The system console briefly displays the message:
     Bootloader has not verified loaded image
     System is compromised.  halting.
  5) The node powers off.
  6) Eventually MAAS times out on the deployment and declares
     that it's failed.

  I've verified this on three MAAS servers and one node each (jehan, a
  Quanta QuantaGrid D52B-1U in 18T; capella, a Supermicro SYS-6028U-TR4+
  in 1SS, and brennan, an Intel NUC DC53427HYE on my home network).

  Two of the MAAS servers are running MAAS
  2.6.2-7841-ga10625be3-0ubuntu1~18.04.1; the third is on
  2.4.2-7034-g2f5deb8b8-0ubuntu1.

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