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

On Sep 9, 2021, at 9:19 AM, Mimi Zohar [off-list ref] wrote:

On Tue, 2021-09-07 at 12:00 -0400, Eric Snowberg wrote:

quoted

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.

quoted

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

quoted

+++ 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.