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

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Date:   Thu, 9 Sep 2021 11:32:01 -0600
From:   Eric Snowberg <eric.snowberg@...cle.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     keyrings@...r.kernel.org,
        linux-integrity <linux-integrity@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>, jarkko@...nel.org,
        jmorris@...ei.org, serge@...lyn.com, keescook@...omium.org,
        gregkh@...uxfoundation.org, torvalds@...ux-foundation.org,
        scott.branden@...adcom.com, weiyongjun1@...wei.com,
        nayna@...ux.ibm.com, ebiggers@...gle.com, ardb@...nel.org,
        nramas@...ux.microsoft.com, lszubowi@...hat.com,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James.Bottomley@...senPartnership.com, pjones@...hat.com,
        "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Subject: Re: [PATCH v5 01/12] integrity: Introduce a Linux keyring called
 machine


> On Sep 9, 2021, at 9:19 AM, Mimi Zohar <zohar@...ux.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@...cle.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.