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Message-ID: <YhLNYxBTbKW62vtC@iki.fi>
Date: Mon, 21 Feb 2022 00:23:15 +0100
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Eric Snowberg <eric.snowberg@...cle.com>
Cc: keyrings@...r.kernel.org, linux-integrity@...r.kernel.org,
zohar@...ux.ibm.com, dhowells@...hat.com, dwmw2@...radead.org,
herbert@...dor.apana.org.au, davem@...emloft.net,
jmorris@...ei.org, serge@...lyn.com, keescook@...omium.org,
torvalds@...ux-foundation.org, weiyongjun1@...wei.com,
nayna@...ux.ibm.com, ebiggers@...gle.com, ardb@...nel.org,
nramas@...ux.microsoft.com, lszubowi@...hat.com, jason@...c4.com,
linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
linux-efi@...r.kernel.org, linux-security-module@...r.kernel.org,
James.Bottomley@...senpartnership.com, pjones@...hat.com,
konrad.wilk@...cle.com
Subject: Re: [PATCH v8 00/17] Enroll kernel keys thru MOK
On Tue, Nov 23, 2021 at 11:41:07PM -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. Mimi has suggested
> that only CA keys contained within the MOK be loaded into the machine
> keyring. All other certs will load into the platform keyring instead.
>
> 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.
>
> 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@linux.vnet.ibm.com/
> [3] https://lore.kernel.org/lkml/1556221605.24945.3.camel@HansenPartnership.com/
> [4] https://lore.kernel.org/linux-integrity/1e41f22b1f11784f1e943f32bf62034d4e054cdb.camel@HansenPartnership.com/
> [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 (17):
> KEYS: Create static version of public_key_verify_signature
> integrity: Fix warning about missing prototypes
> integrity: Introduce a Linux keyring called machine
> integrity: Do not allow machine keyring updates following init
> X.509: Parse Basic Constraints for CA
> KEYS: CA link restriction
> integrity: restrict INTEGRITY_KEYRING_MACHINE to restrict_link_by_ca
> integrity: add new keyring handler for mok keys
> KEYS: Rename get_builtin_and_secondary_restriction
> KEYS: add a reference to machine keyring
> KEYS: Introduce link restriction for machine keys
> KEYS: integrity: change link restriction to trust the machine keyring
> integrity: store reference to machine keyring
> KEYS: link machine trusted keys to secondary_trusted_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 | 48 +++++++++++-
> crypto/asymmetric_keys/restrict.c | 43 +++++++++++
> crypto/asymmetric_keys/x509_cert_parser.c | 9 +++
> drivers/firmware/efi/mokvar-table.c | 2 +-
> include/crypto/public_key.h | 25 ++++++
> include/keys/system_keyring.h | 14 ++++
> security/integrity/Kconfig | 12 +++
> security/integrity/Makefile | 1 +
> security/integrity/digsig.c | 23 +++++-
> 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 +++++++++++++++++++
> 14 files changed, 287 insertions(+), 11 deletions(-)
> create mode 100644 security/integrity/platform_certs/machine_keyring.c
>
>
> base-commit: 136057256686de39cc3a07c2e39ef6bc43003ff6
> --
> 2.18.4
>
When I try to apply this:
$ b4 am 20211124044124.998170-8-eric.snowberg@...cle.com
Looking up https://lore.kernel.org/r/20211124044124.998170-8-eric.snowberg%40oracle.com
Analyzing 40 messages in the thread
Checking attestation on all messages, may take a moment...
# ...
$ git am -3 v8_20211123_eric_snowberg_enroll_kernel_keys_thru_mok.mbx
Applying: KEYS: Create static version of public_key_verify_signature
Applying: integrity: Fix warning about missing prototypes
Applying: integrity: Introduce a Linux keyring called machine
Applying: integrity: Do not allow machine keyring updates following init
Applying: X.509: Parse Basic Constraints for CA
Applying: KEYS: CA link restriction
error: sha1 information is lacking or useless (include/crypto/public_key.h).
error: could not build fake ancestor
Patch failed at 0006 KEYS: CA link restriction
hint: Use 'git am --show-current-patch=diff' to see the failed patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".
BR, Jarkko
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