On Tue, Jan 25, 2022 at 09:58:26PM -0500, Eric Snowberg wrote: > Back in 2013 Linus requested a feature to allow end-users to have the > ability "to add their own keys and sign modules they trust". This was > his *second* order outlined here [1]. There have been many attempts > over the years to solve this problem, all have been rejected. Many > of the failed attempts loaded all preboot firmware keys into the kernel, > including the Secure Boot keys. Many distributions carry one of these > rejected attempts [2], [3], [4]. This series tries to solve this problem > with a solution that takes into account all the problems brought up in > the previous attempts. > > On UEFI based systems, this series introduces a new Linux kernel keyring > containing the Machine Owner Keys (MOK) called machine. It also defines > a new MOK variable in shim. This variable allows the end-user to decide > if they want to load MOK keys into the machine keyring. > > By default, nothing changes; MOK keys are not loaded into the machine > keyring. They are only loaded after the end-user makes the decision > themselves. The end-user would set this through mokutil using a new > --trust-mok option [5]. This would work similar to how the kernel uses > MOK variables to enable/disable signature validation as well as use/ignore > the db. Any kernel operation that uses either the builtin or secondary > trusted keys as a trust source shall also reference the new machine > keyring as a trust source. > > Secure Boot keys will never be loaded into the machine keyring. They > will always be loaded into the platform keyring. If an end-user wanted > to load one, they would need to enroll it into the MOK. > > Unlike previous versions of this patch set, IMA support has been removed > to simplify the series. After acceptance, a follow-on series will add IMA > support. > > Steps required by the end user: > > Sign kernel module with user created key: > $ /usr/src/kernels/$(uname -r)/scripts/sign-file sha512 \ > machine_signing_key.priv machine_signing_key.x509 my_module.ko > > Import the key into the MOK > $ mokutil --import machine_signing_key.x509 > > Setup the kernel to load MOK keys into the .machine keyring > $ mokutil --trust-mok > > Then reboot, the MokManager will load and ask if you want to trust the > MOK key and enroll the MOK into the MOKList. Afterwards the signed kernel > module will load. > > I have included a link to the mokutil [5] changes I have made to support > this new functionality. The shim changes have now been accepted > upstream [6]. > > Upstream shim is located here [7], the build instructions are here [8]. > TLDR: > > $ git clone --recurse-submodules https://github.com/rhboot/shim > $ cd shim > $ make > > After building shim, move shimx64.efi and mmx64.efi to the vendor or > distribution specific directory on your EFI System Partition (assuming > you are building on x86). The instructions above are the minimal > steps needed to build shim to test this feature. It is assumed > Secure Boot shall not be enabled for this testing. To do testing > with Secure Boot enabled, all steps in the build instructions [8] > must be followed. > > Instructions for building mokutil (including the new changes): > > $ git clone -b mokvars-v3 https://github.com/esnowberg/mokutil.git > $ cd mokutil/ > $ ./autogen.sh > $ make > > [1] https://marc.info/?l=linux-kernel&m=136185386310140&w=2 > [2] https://lore.kernel.org/lkml/1479737095.2487.34.camel@xxxxxxxxxxxxxxxxxx/ > [3] https://lore.kernel.org/lkml/1556221605.24945.3.camel@xxxxxxxxxxxxxxxxxxxxx/ > [4] https://lore.kernel.org/linux-integrity/1e41f22b1f11784f1e943f32bf62034d4e054cdb.camel@xxxxxxxxxxxxxxxxxxxxx/ > [5] https://github.com/esnowberg/mokutil/tree/mokvars-v3 > [6] https://github.com/rhboot/shim/commit/4e513405b4f1641710115780d19dcec130c5208f > [7] https://github.com/rhboot/shim > [8] https://github.com/rhboot/shim/blob/main/BUILDING > > Eric Snowberg (8): > integrity: Fix warning about missing prototypes > integrity: Introduce a Linux keyring called machine > integrity: add new keyring handler for mok keys > KEYS: store reference to machine keyring > KEYS: Introduce link restriction for machine keys > efi/mokvar: move up init order > integrity: Trust MOK keys if MokListTrustedRT found > integrity: Only use machine keyring when uefi_check_trust_mok_keys is > true > > certs/system_keyring.c | 44 ++++++++++- > drivers/firmware/efi/mokvar-table.c | 2 +- > include/keys/system_keyring.h | 14 ++++ > security/integrity/Kconfig | 13 ++++ > security/integrity/Makefile | 1 + > security/integrity/digsig.c | 15 +++- > security/integrity/integrity.h | 17 +++- > .../platform_certs/keyring_handler.c | 18 ++++- > .../platform_certs/keyring_handler.h | 5 ++ > security/integrity/platform_certs/load_uefi.c | 4 +- > .../platform_certs/machine_keyring.c | 77 +++++++++++++++++++ > 11 files changed, 202 insertions(+), 8 deletions(-) > create mode 100644 security/integrity/platform_certs/machine_keyring.c > > > base-commit: e783362eb54cd99b2cac8b3a9aeac942e6f6ac07 > -- > 2.18.4 > Thank you. I'll pick these soon. Is there any objections? /Jarkko
