This probably should not have been closed as Fix Released quite yet. A
gsbx64.efi binary was being built, which allowed enforcement.
Now, the proper fix to never allow unsigned / invalidly signed kernels
has landed in Cosmic; so proceeding with the SRUs.
** No longer affects: grub2 (Ubuntu Zesty)
** No longer affects: grub2 (Ubuntu Yakkety)
** No longer affects: grub2-signed (Ubuntu Yakkety)
** No longer affects: grub2-signed (Ubuntu Zesty)
** Also affects: grub2 (Ubuntu Bionic)
Importance: Undecided
Status: New
** Also affects: grub2-signed (Ubuntu Bionic)
Importance: Undecided
Status: New
** Changed in: grub2 (Ubuntu Bionic)
Status: New => In Progress
** Changed in: grub2-signed (Ubuntu Bionic)
Status: New => In Progress
** Changed in: grub2-signed (Ubuntu Bionic)
Assignee: (unassigned) => Mathieu Trudel-Lapierre (cyphermox)
** Changed in: grub2 (Ubuntu Bionic)
Assignee: (unassigned) => Mathieu Trudel-Lapierre (cyphermox)
** Changed in: grub2 (Ubuntu Xenial)
Status: Confirmed => Triaged
** Changed in: grub2 (Ubuntu Trusty)
Status: Confirmed => Triaged
** Changed in: grub2-signed (Ubuntu Trusty)
Status: Confirmed => Triaged
** Changed in: grub2-signed (Ubuntu)
Status: Triaged => Fix Released
** Changed in: grub2-signed (Ubuntu Xenial)
Status: Confirmed => Triaged
** Changed in: grub2-signed (Ubuntu Bionic)
Importance: Undecided => High
** Changed in: grub2-signed (Ubuntu Xenial)
Importance: Undecided => High
** Changed in: grub2-signed (Ubuntu Trusty)
Importance: Undecided => High
** Changed in: grub2 (Ubuntu Bionic)
Importance: Undecided => High
** Changed in: grub2 (Ubuntu Xenial)
Importance: Undecided => High
** Changed in: grub2 (Ubuntu Trusty)
Importance: Undecided => High
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Matching subscriptions: Ubuntu 16.04 Bugs
https://bugs.launchpad.net/bugs/1401532
Title:
GRUB's Secure Boot implementation loads unsigned kernel without
warning
Status in grub2 package in Ubuntu:
Fix Released
Status in grub2-signed package in Ubuntu:
Fix Released
Status in grub2 source package in Trusty:
Triaged
Status in grub2-signed source package in Trusty:
Triaged
Status in grub2 source package in Xenial:
Triaged
Status in grub2-signed source package in Xenial:
Triaged
Status in grub2 source package in Bionic:
In Progress
Status in grub2-signed source package in Bionic:
In Progress
Bug description:
[Rationale]
GRUB should help us enforce that in UEFI mode, only signed kernels are
loaded. It should not silently fall back to loading unsigned kernels.
[Impact]
All our users booting in UEFI; on all supported releases.
[Test cases]
= grub2 =
Booting unsigned kernels:
1) Try to boot a custom kernel
2) Verify that the kernel will not be loaded by grub (you should see an error
message about the signature)
Booting signed kernels:
1) Try to boot an official signed kernel (from -release or -updates)
2) Verify that the system boots normally and no warnings are shown about
signature.
[Regression Potential]
Any failure to boot presenting as a failure to load the kernel from within
grub, with an "invalid signature" type error message or not, should be
investigated as a potential regression of this stable update.
---
Me and some other students have conducted some various experiments on
Secure Boot enabled machines. The main focus of the tests was to
circumvent Secure Boot and load unsigned kernels or kernels that have
been signed with other keys.
On your SecureBoot (https://wiki.ubuntu.com/SecurityTeam/SecureBoot)
it is outlined that GRUB will boot unsigned kernels when the kernel is
unsigned. During one of our experiments it seemed that this statement
was true and that GRUB loads unsigned kernels as described on your
page. We understand that for various reasons GRUB should still support
the use-case when an unsigned kernel must be loaded, but with the
current approach the user isn't aware if there is a whole chain of
trust. For example, it could still be possible to load some malware
before it boots the Operating System itself (bootkits). One of the
many reasons that Secure Boot has been developed is to protect the
user from these kind of attacks.
With the current approach the purpose of Secure Boot is somewhat
defeated, and the user doesn't know if the whole chain has been
verified or not. It could easily be the case that an unsigned kernel
has been loaded by Ubuntu without the user noticing. From our point of
view, a better approach would be to inform the user that an unsigned
kernel will be loaded and that the user can make a choice if he/she
wants to proceed. The default action could be to accept the option,
remember the user's option and sometimes remind the user of the fact
that it is loading an unsigned kernel.
This problem is of course related to GRUB itself and not to Ubuntu
itself. The reason for filing this bug and informing the SecurityTeam
of Ubuntu is to ask for their opinions and what your point of view is
on the current approach and to see if other users classify this as a
"bug".
GRUB2 versions: grub-2.02~beta2, 1.34.1+2.02~beta2-9ubuntu1
Ubuntu version: Trusty (will also affect newer and older versions, GRUB
specific problem)
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1401532/+subscriptions
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