From 478a0cff698409224330ea9e25eb332220b55dbb Mon Sep 17 00:00:00 2001

From: Jeremy Cline <jcline@redhat.com>

Date: Mon, 30 Sep 2019 21:22:47 +0000

Subject: [PATCH 1/3] security: lockdown: expose a hook to lock the kernel down

In order to automatically lock down kernels running on UEFI machines

booted in Secure Boot mode, expose the lock_kernel_down() hook.

Signed-off-by: Jeremy Cline <jcline@redhat.com>

---

 include/linux/lsm_hooks.h    | 8 ++++++++

 include/linux/security.h     | 5 +++++

 security/lockdown/lockdown.c | 1 +

 security/security.c          | 6 ++++++

 4 files changed, 20 insertions(+)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h

index a3763247547c..8d76d1f153ed 100644

--- a/include/linux/lsm_hooks.h

+++ b/include/linux/lsm_hooks.h

@@ -1454,6 +1454,12 @@

  *     code execution in kernel space should be permitted.

  *

  *     @what: kernel feature being accessed

+ *

+ * @lock_kernel_down

+ *     Put the kernel into lock-down mode.

+ *

+ *     @where: Where the lock-down is originating from (e.g. command line option)

+ *     @level: The lock-down level (can only increase)

  */

 union security_list_options {

 	int (*binder_set_context_mgr)(const struct cred *mgr);

@@ -1818,6 +1824,7 @@ union security_list_options {

 	void (*bpf_prog_free_security)(struct bpf_prog_aux *aux);

 #endif /* CONFIG_BPF_SYSCALL */

 	int (*locked_down)(enum lockdown_reason what);

+	int (*lock_kernel_down)(const char *where, enum lockdown_reason level);

 };

 struct security_hook_heads {

@@ -2060,6 +2067,7 @@ struct security_hook_heads {

 	struct hlist_head bpf_prog_free_security;

 #endif /* CONFIG_BPF_SYSCALL */

 	struct hlist_head locked_down;

+	struct hlist_head lock_kernel_down;

 } __randomize_layout;

 /*

diff --git a/include/linux/security.h b/include/linux/security.h

index a8d59d612d27..467b9ccdf993 100644

--- a/include/linux/security.h

+++ b/include/linux/security.h

@@ -445,6 +445,7 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);

 int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);

 int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);

 int security_locked_down(enum lockdown_reason what);

+int security_lock_kernel_down(const char *where, enum lockdown_reason level);

 #else /* CONFIG_SECURITY */

 static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)

@@ -1277,6 +1278,10 @@ static inline int security_locked_down(enum lockdown_reason what)

 {

 	return 0;

 }

+static inline int security_lock_kernel_down(const char *where, enum lockdown_reason level)

+{

+	return 0;

+}

 #endif	/* CONFIG_SECURITY */

 #ifdef CONFIG_SECURITY_NETWORK

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c

index 8a10b43daf74..72a623075749 100644

--- a/security/lockdown/lockdown.c

+++ b/security/lockdown/lockdown.c

@@ -100,6 +100,7 @@ static int lockdown_is_locked_down(enum lockdown_reason what)

 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = {

 	LSM_HOOK_INIT(locked_down, lockdown_is_locked_down),

+	LSM_HOOK_INIT(lock_kernel_down, lock_kernel_down),

 };

 static int __init lockdown_lsm_init(void)

diff --git a/security/security.c b/security/security.c

index 1bc000f834e2..1506b95427cf 100644

--- a/security/security.c

+++ b/security/security.c

@@ -2404,3 +2404,9 @@ int security_locked_down(enum lockdown_reason what)

 	return call_int_hook(locked_down, 0, what);

 }

 EXPORT_SYMBOL(security_locked_down);

+

+int security_lock_kernel_down(const char *where, enum lockdown_reason level)

+{

+	return call_int_hook(lock_kernel_down, 0, where, level);

+}

+EXPORT_SYMBOL(security_lock_kernel_down);

-- 

2.21.0

From b5123d0553f4ed5e734f6457696cdd30228d1eee Mon Sep 17 00:00:00 2001

From: David Howells <dhowells@redhat.com>

Date: Tue, 27 Feb 2018 10:04:55 +0000

Subject: [PATCH 2/3] efi: Add an EFI_SECURE_BOOT flag to indicate secure

 boot mode

UEFI machines can be booted in Secure Boot mode.  Add an EFI_SECURE_BOOT

flag that can be passed to efi_enabled() to find out whether secure boot is

enabled.

Move the switch-statement in x86's setup_arch() that inteprets the

secure_boot boot parameter to generic code and set the bit there.

Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Signed-off-by: David Howells <dhowells@redhat.com>

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

cc: linux-efi@vger.kernel.org

[Rebased for context; efi_is_table_address was moved to arch/x86]

Signed-off-by: Jeremy Cline <jcline@redhat.com>

---

 arch/x86/kernel/setup.c           | 14 +-----------

 drivers/firmware/efi/Makefile     |  1 +

 drivers/firmware/efi/secureboot.c | 38 +++++++++++++++++++++++++++++++

 include/linux/efi.h               | 18 ++++++++++-----

 4 files changed, 52 insertions(+), 19 deletions(-)

 create mode 100644 drivers/firmware/efi/secureboot.c

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c

index bbe35bf879f5..7e528b6af86b 100644

--- a/arch/x86/kernel/setup.c

+++ b/arch/x86/kernel/setup.c

@@ -1179,19 +1179,7 @@ void __init setup_arch(char **cmdline_p)

 	/* Allocate bigger log buffer */

 	setup_log_buf(1);

-	if (efi_enabled(EFI_BOOT)) {

-		switch (boot_params.secure_boot) {

-		case efi_secureboot_mode_disabled:

-			pr_info("Secure boot disabled\n");

-			break;

-		case efi_secureboot_mode_enabled:

-			pr_info("Secure boot enabled\n");

-			break;

-		default:

-			pr_info("Secure boot could not be determined\n");

-			break;

-		}

-	}

+	efi_set_secure_boot(boot_params.secure_boot);

 	reserve_initrd();

diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile

index 4ac2de4dfa72..195b078a423c 100644

--- a/drivers/firmware/efi/Makefile

+++ b/drivers/firmware/efi/Makefile

@@ -24,6 +24,7 @@ obj-$(CONFIG_EFI_FAKE_MEMMAP)		+= fake_mem.o

 obj-$(CONFIG_EFI_BOOTLOADER_CONTROL)	+= efibc.o

 obj-$(CONFIG_EFI_TEST)			+= test/

 obj-$(CONFIG_EFI_DEV_PATH_PARSER)	+= dev-path-parser.o

+obj-$(CONFIG_EFI)			+= secureboot.o

 obj-$(CONFIG_APPLE_PROPERTIES)		+= apple-properties.o

 obj-$(CONFIG_EFI_RCI2_TABLE)		+= rci2-table.o

diff --git a/drivers/firmware/efi/secureboot.c b/drivers/firmware/efi/secureboot.c

new file mode 100644

index 000000000000..9070055de0a1

--- /dev/null

+++ b/drivers/firmware/efi/secureboot.c

@@ -0,0 +1,38 @@

+/* Core kernel secure boot support.

+ *

+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.

+ * Written by David Howells (dhowells@redhat.com)

+ *

+ * This program is free software; you can redistribute it and/or

+ * modify it under the terms of the GNU General Public Licence

+ * as published by the Free Software Foundation; either version

+ * 2 of the Licence, or (at your option) any later version.

+ */

+

+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+

+#include <linux/efi.h>

+#include <linux/kernel.h>

+#include <linux/printk.h>

+

+/*

+ * Decide what to do when UEFI secure boot mode is enabled.

+ */

+void __init efi_set_secure_boot(enum efi_secureboot_mode mode)

+{

+	if (efi_enabled(EFI_BOOT)) {

+		switch (mode) {

+		case efi_secureboot_mode_disabled:

+			pr_info("Secure boot disabled\n");

+			break;

+		case efi_secureboot_mode_enabled:

+			set_bit(EFI_SECURE_BOOT, &efi.flags);

+			pr_info("Secure boot enabled\n");

+			break;

+		default:

+			pr_warning("Secure boot could not be determined (mode %u)\n",

+				   mode);

+			break;

+		}

+	}

+}

diff --git a/include/linux/efi.h b/include/linux/efi.h

index 21d81021c1f4..758ec061d03b 100644

--- a/include/linux/efi.h

+++ b/include/linux/efi.h

@@ -1204,6 +1204,14 @@ extern int __init efi_setup_pcdp_console(char *);

 #define EFI_DBG			8	/* Print additional debug info at runtime */

 #define EFI_NX_PE_DATA		9	/* Can runtime data regions be mapped non-executable? */

 #define EFI_MEM_ATTR		10	/* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */

+#define EFI_SECURE_BOOT		11	/* Are we in Secure Boot mode? */

+

+enum efi_secureboot_mode {

+	efi_secureboot_mode_unset,

+	efi_secureboot_mode_unknown,

+	efi_secureboot_mode_disabled,

+	efi_secureboot_mode_enabled,

+};

 #ifdef CONFIG_EFI

 /*

@@ -1214,6 +1222,8 @@ static inline bool efi_enabled(int feature)

 	return test_bit(feature, &efi.flags) != 0;

 }

 extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused);

+

+extern void __init efi_set_secure_boot(enum efi_secureboot_mode mode);

 #else

 static inline bool efi_enabled(int feature)

 {

@@ -1227,6 +1237,8 @@ efi_capsule_pending(int *reset_type)

 {

 	return false;

 }

+

+static inline void efi_set_secure_boot(enum efi_secureboot_mode mode) {}

 #endif

 extern int efi_status_to_err(efi_status_t status);

@@ -1619,12 +1631,6 @@ static inline bool efi_runtime_disabled(void) { return true; }

 extern void efi_call_virt_check_flags(unsigned long flags, const char *call);

 extern unsigned long efi_call_virt_save_flags(void);

-enum efi_secureboot_mode {

-	efi_secureboot_mode_unset,

-	efi_secureboot_mode_unknown,

-	efi_secureboot_mode_disabled,

-	efi_secureboot_mode_enabled,

-};

 enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table);

 #ifdef CONFIG_RESET_ATTACK_MITIGATION

-- 

2.21.0

From 15368f76d4997912318d35c52bfeb9041d85098e Mon Sep 17 00:00:00 2001

From: David Howells <dhowells@redhat.com>

Date: Mon, 30 Sep 2019 21:28:16 +0000

Subject: [PATCH 3/3] efi: Lock down the kernel if booted in secure boot mode

UEFI Secure Boot provides a mechanism for ensuring that the firmware

will only load signed bootloaders and kernels.  Certain use cases may

also require that all kernel modules also be signed.  Add a

configuration option that to lock down the kernel - which includes

requiring validly signed modules - if the kernel is secure-booted.

Signed-off-by: David Howells <dhowells@redhat.com>

Signed-off-by: Jeremy Cline <jcline@redhat.com>

---

 arch/x86/kernel/setup.c   |  8 ++++++++

 security/lockdown/Kconfig | 13 +++++++++++++

 2 files changed, 21 insertions(+)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c

index 77ea96b794bd..a119e1bc9623 100644

--- a/arch/x86/kernel/setup.c

+++ b/arch/x86/kernel/setup.c

@@ -73,6 +73,7 @@

 #include <linux/jiffies.h>

 #include <linux/mem_encrypt.h>

 #include <linux/sizes.h>

+#include <linux/security.h>

 #include <linux/usb/xhci-dbgp.h>

 #include <video/edid.h>

@@ -1027,6 +1028,13 @@ void __init setup_arch(char **cmdline_p)

 	if (efi_enabled(EFI_BOOT))

 		efi_init();

+	efi_set_secure_boot(boot_params.secure_boot);

+

+#ifdef CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT

+	if (efi_enabled(EFI_SECURE_BOOT))

+		security_lock_kernel_down("EFI Secure Boot mode", LOCKDOWN_CONFIDENTIALITY_MAX);

+#endif

+

 	dmi_setup();

 	/*

diff --git a/security/lockdown/Kconfig b/security/lockdown/Kconfig

index e84ddf484010..d0501353a4b9 100644

--- a/security/lockdown/Kconfig

+++ b/security/lockdown/Kconfig

@@ -16,6 +16,19 @@ config SECURITY_LOCKDOWN_LSM_EARLY

 	  subsystem is fully initialised. If enabled, lockdown will

 	  unconditionally be called before any other LSMs.

+config LOCK_DOWN_IN_EFI_SECURE_BOOT

+	bool "Lock down the kernel in EFI Secure Boot mode"

+	default n

+	depends on EFI && SECURITY_LOCKDOWN_LSM_EARLY

+	help

+	  UEFI Secure Boot provides a mechanism for ensuring that the firmware

+	  will only load signed bootloaders and kernels.  Secure boot mode may

+	  be determined from EFI variables provided by the system firmware if

+	  not indicated by the boot parameters.

+

+	  Enabling this option results in kernel lockdown being triggered if

+	  EFI Secure Boot is set.

+

 choice

 	prompt "Kernel default lockdown mode"

 	default LOCK_DOWN_KERNEL_FORCE_NONE

-- 

2.21.0