[PATCH 1/5] efi: Move the x86 secure boot switch to generic code

* [PATCH 1/5] efi: Move the x86 secure boot switch to generic code
@ 2017-04-06 12:49 ` David Howells
  0 siblings, 0 replies; 47+ messages in thread
From: David Howells @ 2017-04-06 12:49 UTC (permalink / raw)
  To: ard.biesheuvel
  Cc: dhowells, matthew.garrett, linux-security-module, linux-efi,
	linux-kernel

Move the switch-statement in x86's setup_arch() that inteprets the
secure_boot boot parameter to generic code.

Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 arch/x86/kernel/setup.c            |   14 +-------------
 drivers/firmware/efi/Kconfig       |   23 +++++++++++++++++++++++
 drivers/firmware/efi/Makefile      |    3 ++-
 drivers/firmware/efi/secure_boot.c |   34 ++++++++++++++++++++++++++++++++++
 include/linux/efi.h                |    6 ++++++
 5 files changed, 66 insertions(+), 14 deletions(-)
 create mode 100644 drivers/firmware/efi/secure_boot.c

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 4bf0c8926a1c..b89979ffa6e5 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1178,19 +1178,7 @@ 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/Kconfig b/drivers/firmware/efi/Kconfig
index 2e78b0b96d74..4b902ffbfcf4 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -84,6 +84,29 @@ config EFI_PARAMS_FROM_FDT
 config EFI_RUNTIME_WRAPPERS
 	bool
 
+config EFI_SECURE_BOOT
+	bool "Support UEFI Secure Boot and lock down the kernel in secure boot mode"
+	default n
+	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 BIOS if not
+	  indicated by the boot parameters.
+
+	  Enabling this option turns on support for UEFI secure boot in the
+	  kernel.  This will result in various kernel facilities being locked
+	  away from userspace if the kernel detects that it has been booted in
+	  secure boot mode.  If it hasn't been booted in secure boot mode, or
+	  this cannot be determined, the lock down doesn't occur.
+
+	  The kernel facilities that get locked down include:
+	  - Viewing or changing the kernel's memory
+	  - Directly accessing ioports
+	  - Directly specifying ioports and other hardware parameters to drivers
+	  - Storing the kernel image unencrypted for hibernation
+	  - Loading unsigned modules
+	  - Kexec'ing unsigned images
+
 config EFI_ARMSTUB
 	bool
 
diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index ad67342313ed..65969f840685 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -22,7 +22,8 @@ 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-$(CONFIG_APPLE_PROPERTIES)		+= apple-properties.o
+obj-$(CONFIG_EFI_SECURE_BOOT)		+= secure_boot.o
+obj-$(CONFIG_APPLE_PROPERTIES)		+= apple-properties.oo
 
 arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.o
 obj-$(CONFIG_ARM)			+= $(arm-obj-y)
diff --git a/drivers/firmware/efi/secure_boot.c b/drivers/firmware/efi/secure_boot.c
new file mode 100644
index 000000000000..cf5bccae15e8
--- /dev/null
+++ b/drivers/firmware/efi/secure_boot.c
@@ -0,0 +1,34 @@
+/* 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.
+ */
+
+#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:
+			pr_info("Secure boot enabled\n");
+			break;
+		default:
+			pr_info("Secure boot could not be determined\n");
+			break;
+		}
+	}
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 94d34e0be24f..d8938a780290 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1488,6 +1488,12 @@ enum efi_secureboot_mode {
 };
 enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table);
 
+#ifdef CONFIG_EFI_SECURE_BOOT
+void __init efi_set_secure_boot(enum efi_secureboot_mode mode);
+#else
+static inline void efi_set_secure_boot(enum efi_secureboot_mode mode) {}
+#endif
+
 /*
  * Arch code can implement the following three template macros, avoiding
  * reptition for the void/non-void return cases of {__,}efi_call_virt():

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