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 29/31] 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
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 b74e7bfed6ab..7da1712c89c9 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1158,19 +1158,7 @@ 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 5f9f5039de50..7a0a6378203e 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
 
 arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.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 100ce4a4aff6..62361b647a75 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1155,6 +1155,14 @@ 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
 /*
@@ -1198,6 +1206,8 @@ static inline bool efi_enabled(int feature)
 extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused);

 extern bool efi_is_table_address(unsigned long phys_addr);
+
+extern void __init efi_set_secure_boot(enum efi_secureboot_mode mode);
 #else
 static inline bool efi_enabled(int feature)
 {
@@ -1216,6 +1226,8 @@ static inline bool efi_is_table_address(unsigned long phys_addr)
 {
 	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);
@@ -1577,12 +1589,6 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg,
 #endif
 
 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
-- 
2.19.1

From d78bf678059f83e22bec8ada1a448e22b9b90203 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Tue, 27 Feb 2018 10:04:55 +0000
Subject: [PATCH 30/31] 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>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
cc: linux-efi@vger.kernel.org
---
 arch/x86/kernel/setup.c |  6 ++++--
 fs/debugfs/inode.c      |  2 +-
 security/Kconfig        | 14 ++++++++++++++
 security/lock_down.c    |  5 +++++
 4 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index adeee6329f55..27a54ec878bd 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -65,6 +65,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/ctype.h>
 #include <linux/uaccess.h>
+#include <linux/security.h>
 
 #include <linux/percpu.h>
 #include <linux/crash_dump.h>
@@ -1005,6 +1006,10 @@ void __init setup_arch(char **cmdline_p)
 	if (efi_enabled(EFI_BOOT))
 		efi_init();
 
+	efi_set_secure_boot(boot_params.secure_boot);
+
+	init_lockdown();
+
 	dmi_setup();
 
 	/*
@@ -1159,8 +1164,6 @@ void __init setup_arch(char **cmdline_p)
 	/* Allocate bigger log buffer */
 	setup_log_buf(1);
 
-	efi_set_secure_boot(boot_params.secure_boot);
-
 	reserve_initrd();
 
 	acpi_table_upgrade();
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index ce261e1765ff..7aff55b309a6 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -40,7 +40,7 @@ static bool debugfs_registered;
 static int debugfs_setattr(struct dentry *dentry, struct iattr *ia)
 {
 	if ((ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) &&
-	    kernel_is_locked_down("debugfs"))
+	    kernel_is_locked_down("changing perms in debugfs"))
 		return -EPERM;
 	return simple_setattr(dentry, ia);
 }
diff --git a/security/Kconfig b/security/Kconfig
index 9c343f262bdd..30788bc47863 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -244,6 +244,20 @@ config LOCK_DOWN_KERNEL_FORCE
         help
           Enable the kernel lock down functionality automatically at boot.
 
+config LOCK_DOWN_IN_EFI_SECURE_BOOT
+	bool "Lock down the kernel in EFI Secure Boot mode"
+	default n
+	select LOCK_DOWN_KERNEL
+	depends on EFI
+	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 turns on results in kernel lockdown being
+	  triggered if EFI Secure Boot is set.
+
 source "security/selinux/Kconfig"
 source "security/smack/Kconfig"
 source "security/tomoyo/Kconfig"
diff --git a/security/lock_down.c b/security/lock_down.c
index ee00ca2677e7..bb4dc7838f3e 100644
--- a/security/lock_down.c
+++ b/security/lock_down.c
@@ -12,6 +12,7 @@
 
 #include <linux/security.h>
 #include <linux/export.h>
+#include <linux/efi.h>
 
 static __ro_after_init bool kernel_locked_down;
 
@@ -44,6 +45,10 @@ void __init init_lockdown(void)
 #ifdef CONFIG_LOCK_DOWN_FORCE
 	lock_kernel_down("Kernel configuration");
 #endif
+#ifdef CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT
+	if (efi_enabled(EFI_SECURE_BOOT))
+		lock_kernel_down("EFI secure boot");
+#endif
 }
 
 /**
-- 
2.14.3