Re: [PATCH v5 01/12] integrity: Introduce a Linux keyring called machine

Eric Snowberg
2021-09-09T17:32:58Z

> On Sep 9, 2021, at 9:19 AM, Mimi Zohar <zohar@linux.ibm.com> wrote:
>
> On Tue, 2021-09-07 at 12:00 -0400, Eric Snowberg wrote:
>> Many UEFI Linux distributions boot using shim. The UEFI shim provides
>> what is called Machine Owner Keys (MOK). Shim uses both the UEFI Secure
>> Boot DB and MOK keys to validate the next step in the boot chain. The
>> MOK facility can be used to import user generated keys. These keys can
>> be used to sign an end-users development kernel build. When Linux
>> boots, both UEFI Secure Boot DB and MOK keys get loaded in the Linux
>> .platform keyring.
>>
>> Add a new Linux keyring called machine. This keyring shall contain just
>
> ^Define

I’ll change this in the next round.

>
>> MOK CA keys and not the remaining keys in the platform keyring. This new
>> machine keyring will be used in follow on patches. Unlike keys in the
>> platform keyring, keys contained in the machine keyring will be trusted
>> within the kernel if the end-user has chosen to do so.
>>
>> Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
>> ---
>> v1: Initial version
>> v2: Removed destory keyring code
>> v3: Unmodified from v2
>> v4: Add Kconfig, merged in "integrity: add add_to_mok_keyring"
>> v5: Rename to machine keyring
>> ---
>> security/integrity/Kconfig | 11 +++++
>> security/integrity/Makefile | 1 +
>> security/integrity/digsig.c | 1 +
>> security/integrity/integrity.h | 12 +++++-
>> .../platform_certs/machine_keyring.c | 42 +++++++++++++++++++
>> 5 files changed, 66 insertions(+), 1 deletion(-)
>> create mode 100644 security/integrity/platform_certs/machine_keyring.c
>>
>> diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
>> index 71f0177e8716..52193b86768a 100644
>> --- a/security/integrity/Kconfig
>> +++ b/security/integrity/Kconfig
>> @@ -62,6 +62,17 @@ config INTEGRITY_PLATFORM_KEYRING
>> provided by the platform for verifying the kexec'ed kerned image
>> and, possibly, the initramfs signature.
>>
>> +config INTEGRITY_MACHINE_KEYRING
>> + bool "Provide a keyring to which CA Machine Owner Keys may be added"
>> + depends on SECONDARY_TRUSTED_KEYRING
>> + depends on INTEGRITY_ASYMMETRIC_KEYS
>> + depends on SYSTEM_BLACKLIST_KEYRING
>> + help
>> + If set, provide a keyring to which CA Machine Owner Keys (MOK) may
>> + be added. This keyring shall contain just CA MOK keys. Unlike keys
>> + in the platform keyring, keys contained in the .machine keyring will
>> + be trusted within the kernel.
>
> No sense in creating the ".machine" keyring, unless it is possible to
> safely load CA certificates on it. At least for the time being, this
> should also be dependent on EFI.
>

Will also add a depends for EFI

>> +++ b/security/integrity/platform_certs/machine_keyring.c
>> @@ -0,0 +1,42 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Machine keyring routines.
>> + *
>> + * Copyright (c) 2021, Oracle and/or its affiliates.
>> + */
>> +
>> +#include "../integrity.h"
>> +
>> +static __init int machine_keyring_init(void)
>> +{
>> + int rc;
>> +
>> + rc = integrity_init_keyring(INTEGRITY_KEYRING_MACHINE);
>> + if (rc)
>> + return rc;
>> +
>> + pr_notice("Machine keyring initialized\n");
>> + return 0;
>> +}
>> +device_initcall(machine_keyring_init);
>> +
>> +void __init add_to_machine_keyring(const char *source, const void *data, size_t len)
>> +{
>> + key_perm_t perm;
>> + int rc;
>> +
>> + perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW;
>> + rc = integrity_load_cert(INTEGRITY_KEYRING_MACHINE, source, data, len, perm);
>> +
>> + /*
>> + * Some MOKList keys may not pass the machine keyring restrictions.
>> + * If the restriction check does not pass and the platform keyring
>> + * is configured, try to add it into that keyring instead.
>> + */
>> + if (rc)
>
> In addition to the comment, also test to see if the ".platform" keyring
> is configured.

and will add this too. Thanks.