diff mbox series

[v7,01/17] integrity: Introduce a Linux keyring called machine

Message ID 20211116001545.2639333-2-eric.snowberg@oracle.com (mailing list archive)
State New, archived
Headers show
Series Enroll kernel keys thru MOK | expand

Commit Message

Eric Snowberg Nov. 16, 2021, 12:15 a.m. UTC
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.

Define a new Linux keyring called machine.  This keyring shall contain just
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
v6: Depend on EFI in kconfig  (suggested by Mimi)
    Test to see if ".platform" keyring is configured in
      add_to_machine_keyring (suggested by Mimi)
v7: Depend on LOAD_UEFI_KEYS instead EFI for mokvar code
---
 security/integrity/Kconfig                    | 12 ++++++
 security/integrity/Makefile                   |  1 +
 security/integrity/digsig.c                   |  1 +
 security/integrity/integrity.h                | 12 +++++-
 .../platform_certs/machine_keyring.c          | 42 +++++++++++++++++++
 5 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 security/integrity/platform_certs/machine_keyring.c

Comments

Mimi Zohar Nov. 17, 2021, 1:01 p.m. UTC | #1
Hi Eric,

On Mon, 2021-11-15 at 19:15 -0500, 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.

, which can be used to verify kexec'ed kernel images.

> Define a new Linux keyring called machine.  This keyring shall contain just
> 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.

 allowing, for example, keys to be loaded onto the trusted IMA keyring.

> 
> Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>

Thank you for all the work!  Just letting you know I'm slowly making my
through the patch set.  With the previous patch re-organization, we
should be able to test everything up to the introduction of the MOK
variable support.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
diff mbox series

Patch

diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
index 71f0177e8716..12879dec251d 100644
--- a/security/integrity/Kconfig
+++ b/security/integrity/Kconfig
@@ -62,6 +62,18 @@  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
+	depends on LOAD_UEFI_KEYS
+	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.
+
 config LOAD_UEFI_KEYS
        depends on INTEGRITY_PLATFORM_KEYRING
        depends on EFI
diff --git a/security/integrity/Makefile b/security/integrity/Makefile
index 7ee39d66cf16..d0ffe37dc1d6 100644
--- a/security/integrity/Makefile
+++ b/security/integrity/Makefile
@@ -10,6 +10,7 @@  integrity-$(CONFIG_INTEGRITY_AUDIT) += integrity_audit.o
 integrity-$(CONFIG_INTEGRITY_SIGNATURE) += digsig.o
 integrity-$(CONFIG_INTEGRITY_ASYMMETRIC_KEYS) += digsig_asymmetric.o
 integrity-$(CONFIG_INTEGRITY_PLATFORM_KEYRING) += platform_certs/platform_keyring.o
+integrity-$(CONFIG_INTEGRITY_MACHINE_KEYRING) += platform_certs/machine_keyring.o
 integrity-$(CONFIG_LOAD_UEFI_KEYS) += platform_certs/efi_parser.o \
 				      platform_certs/load_uefi.o \
 				      platform_certs/keyring_handler.o
diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index 3b06a01bd0fd..8c315be8ad99 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -30,6 +30,7 @@  static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
 	".ima",
 #endif
 	".platform",
+	".machine",
 };
 
 #ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 547425c20e11..730771eececd 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -151,7 +151,8 @@  int integrity_kernel_read(struct file *file, loff_t offset,
 #define INTEGRITY_KEYRING_EVM		0
 #define INTEGRITY_KEYRING_IMA		1
 #define INTEGRITY_KEYRING_PLATFORM	2
-#define INTEGRITY_KEYRING_MAX		3
+#define INTEGRITY_KEYRING_MACHINE	3
+#define INTEGRITY_KEYRING_MAX		4
 
 extern struct dentry *integrity_dir;
 
@@ -283,3 +284,12 @@  static inline void __init add_to_platform_keyring(const char *source,
 {
 }
 #endif
+
+#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
+void __init add_to_machine_keyring(const char *source, const void *data, size_t len);
+#else
+static inline void __init add_to_machine_keyring(const char *source,
+						  const void *data, size_t len)
+{
+}
+#endif
diff --git a/security/integrity/platform_certs/machine_keyring.c b/security/integrity/platform_certs/machine_keyring.c
new file mode 100644
index 000000000000..ea2ac2f9f2b5
--- /dev/null
+++ 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 && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING))
+		rc = integrity_load_cert(INTEGRITY_KEYRING_PLATFORM, source,
+					 data, len, perm);
+
+	if (rc)
+		pr_info("Error adding keys to machine keyring %s\n", source);
+}