Commit 9dc92c45 authored by Nayna Jain's avatar Nayna Jain Committed by Mimi Zohar
Browse files

integrity: Define a trusted platform keyring 



On secure boot enabled systems, a verified kernel may need to kexec
additional kernels. For example, it may be used as a bootloader needing
to kexec a target kernel or it may need to kexec a crashdump kernel. In
such cases, it may want to verify the signature of the next kernel
image.

It is further possible that the kernel image is signed with third party
keys which are stored as platform or firmware keys in the 'db' variable.
The kernel, however, can not directly verify these platform keys, and an
administrator may therefore not want to trust them for arbitrary usage.
In order to differentiate platform keys from other keys and provide the
necessary separation of trust, the kernel needs an additional keyring to
store platform keys.

This patch creates the new keyring called ".platform" to isolate keys
provided by platform from keys by kernel. These keys are used to
facilitate signature verification during kexec. Since the scope of this
keyring is only the platform/firmware keys, it cannot be updated from
userspace.

This keyring can be enabled by setting CONFIG_INTEGRITY_PLATFORM_KEYRING.

Signed-off-by: default avatarNayna Jain <nayna@linux.ibm.com>
Reviewed-by: default avatarMimi Zohar <zohar@linux.ibm.com>
Acked-by: default avatarSerge Hallyn <serge@hallyn.com>
Reviewed-by: default avatarJames Morris <james.morris@microsoft.com>
Reviewed-by: default avatarThiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: default avatarMimi Zohar <zohar@linux.ibm.com>
parent a802ed0d

security/integrity/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -51,6 +51,17 @@ config INTEGRITY_TRUSTED_KEYRING 
	   .evm keyrings be signed by a key on the system trusted

	   keyring.



config INTEGRITY_PLATFORM_KEYRING

        bool "Provide keyring for platform/firmware trusted keys"

        depends on INTEGRITY_ASYMMETRIC_KEYS

        depends on SYSTEM_BLACKLIST_KEYRING

        depends on EFI

        help

         Provide a separate, distinct keyring for platform trusted keys, which

         the kernel automatically populates during initialization from values

         provided by the platform for verifying the kexec'ed kerned image

         and, possibly, the initramfs signature.



config INTEGRITY_AUDIT

	bool "Enables integrity auditing support "

	depends on AUDIT

security/integrity/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ integrity-y := iint.o 
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



subdir-$(CONFIG_IMA)			+= ima

obj-$(CONFIG_IMA)			+= ima/

security/integrity/digsig.c

+32 −15
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = { 
	".ima",

#endif

	"_module",

	".platform",

};



#ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
@@ -73,26 +74,14 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen, 
	return -EOPNOTSUPP;

}



int __init integrity_init_keyring(const unsigned int id)

static int __integrity_init_keyring(const unsigned int id, key_perm_t perm,

				    struct key_restriction *restriction)

{

	const struct cred *cred = current_cred();

	struct key_restriction *restriction;

	int err = 0;



	if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))

		return 0;



	restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);

	if (!restriction)

		return -ENOMEM;



	restriction->check = restrict_link_to_ima;



	keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),

				    KGIDT_INIT(0), cred,

				    ((KEY_POS_ALL & ~KEY_POS_SETATTR) |

				     KEY_USR_VIEW | KEY_USR_READ |

				     KEY_USR_WRITE | KEY_USR_SEARCH),

				    KGIDT_INIT(0), cred, perm,

				    KEY_ALLOC_NOT_IN_QUOTA,

				    restriction, NULL);

	if (IS_ERR(keyring[id])) {
@@ -101,9 +90,37 @@ int __init integrity_init_keyring(const unsigned int id) 
			keyring_name[id], err);

		keyring[id] = NULL;

	}



	return err;

}



int __init integrity_init_keyring(const unsigned int id)

{

	struct key_restriction *restriction;

	key_perm_t perm;



	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW

		| KEY_USR_READ | KEY_USR_SEARCH;



	if (id == INTEGRITY_KEYRING_PLATFORM) {

		restriction = NULL;

		goto out;

	}



	if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))

		return 0;



	restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);

	if (!restriction)

		return -ENOMEM;



	restriction->check = restrict_link_to_ima;

	perm |= KEY_USR_WRITE;



out:

	return __integrity_init_keyring(id, perm, restriction);

}



int __init integrity_load_x509(const unsigned int id, const char *path)

{

	key_ref_t key;

security/integrity/integrity.h

+2 −1
Original line number Diff line number Diff line
@@ -142,7 +142,8 @@ int integrity_kernel_read(struct file *file, loff_t offset, 
#define INTEGRITY_KEYRING_EVM		0

#define INTEGRITY_KEYRING_IMA		1

#define INTEGRITY_KEYRING_MODULE	2

#define INTEGRITY_KEYRING_MAX		3

#define INTEGRITY_KEYRING_PLATFORM	3

#define INTEGRITY_KEYRING_MAX		4



extern struct dentry *integrity_dir;

security/integrity/platform_certs/platform_keyring.c

0 → 100644
+35 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0+

/*

 * Platform keyring for firmware/platform keys

 *

 * Copyright IBM Corporation, 2018

 * Author(s): Nayna Jain <nayna@linux.ibm.com>

 */



#include <linux/export.h>

#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/cred.h>

#include <linux/err.h>

#include <linux/slab.h>

#include "../integrity.h"



/*

 * Create the trusted keyrings.

 */

static __init int platform_keyring_init(void)

{

	int rc;



	rc = integrity_init_keyring(INTEGRITY_KEYRING_PLATFORM);

	if (rc)

		return rc;



	pr_notice("Platform Keyring initialized\n");

	return 0;

}



/*

 * Must be initialised before we try and load the keys into the keyring.

 */

device_initcall(platform_keyring_init);

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