From e17b29e90f188888a56d090e1a672d7a38042254 Mon Sep 17 00:00:00 2001

From: Matthew Garrett <matthew.garrett@nebula.com>

Date: Fri, 9 Aug 2013 18:36:30 -0400

Subject: [PATCH] Add option to automatically enforce module signatures when 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 enforces this automatically when enabled.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>

---

 Documentation/x86/zero-page.txt       |  2 ++

 arch/x86/Kconfig                      | 10 ++++++++++

 arch/x86/boot/compressed/eboot.c      | 36 +++++++++++++++++++++++++++++++++++

 arch/x86/include/uapi/asm/bootparam.h |  3 ++-

 arch/x86/kernel/setup.c               |  6 ++++++

 include/linux/module.h                |  6 ++++++

 kernel/module.c                       |  7 +++++++

 7 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/Documentation/x86/zero-page.txt b/Documentation/x86/zero-page.txt

index 199f453cb4de..ec38acf00b40 100644

--- a/Documentation/x86/zero-page.txt

+++ b/Documentation/x86/zero-page.txt

@@ -30,6 +30,8 @@ Offset	Proto	Name		Meaning

 1E9/001	ALL	eddbuf_entries	Number of entries in eddbuf (below)

 1EA/001	ALL	edd_mbr_sig_buf_entries	Number of entries in edd_mbr_sig_buffer

 				(below)

+1EB/001	ALL     kbd_status      Numlock is enabled

+1EC/001	ALL     secure_boot	Secure boot is enabled in the firmware

 1EF/001	ALL	sentinel	Used to detect broken bootloaders

 290/040	ALL	edd_mbr_sig_buffer EDD MBR signatures

 2D0/A00	ALL	e820_map	E820 memory map table

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig

index 778178f4c7d1..8899dc333793 100644

--- a/arch/x86/Kconfig

+++ b/arch/x86/Kconfig

@@ -1565,6 +1565,16 @@ config EFI_MIXED

 	   If unsure, say N.

+config EFI_SECURE_BOOT_SIG_ENFORCE

+        def_bool n

+	prompt "Force module signing when UEFI Secure Boot is enabled"

+	---help---

+	  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.

+	  Say Y here to automatically enable module signature enforcement

+	  when a system boots with UEFI Secure Boot enabled.

+

 config SECCOMP

 	def_bool y

 	prompt "Enable seccomp to safely compute untrusted bytecode"

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c

index f277184e2ac1..88edd48f03e9 100644

--- a/arch/x86/boot/compressed/eboot.c

+++ b/arch/x86/boot/compressed/eboot.c

@@ -12,6 +12,7 @@

 #include <asm/efi.h>

 #include <asm/setup.h>

 #include <asm/desc.h>

+#include <asm/bootparam_utils.h>

 #undef memcpy			/* Use memcpy from misc.c */

@@ -803,6 +804,37 @@ out:

 	return status;

 }

+static int get_secure_boot(void)

+{

+	u8 sb, setup;

+	unsigned long datasize = sizeof(sb);

+	efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;

+	efi_status_t status;

+

+	status = efi_early->call((unsigned long)sys_table->runtime->get_variable,

+				L"SecureBoot", &var_guid, NULL, &datasize, &sb);

+

+	if (status != EFI_SUCCESS)

+		return 0;

+

+	if (sb == 0)

+		return 0;

+

+

+	status = efi_early->call((unsigned long)sys_table->runtime->get_variable,

+				L"SetupMode", &var_guid, NULL, &datasize,

+				&setup);

+

+	if (status != EFI_SUCCESS)

+		return 0;

+

+	if (setup == 1)

+		return 0;

+

+	return 1;

+}

+

+

 /*

  * See if we have Graphics Output Protocol

  */

@@ -1374,6 +1406,10 @@ struct boot_params *efi_main(struct efi_config *c,

 	else

 		setup_boot_services32(efi_early);

+	sanitize_boot_params(boot_params);

+

+	boot_params->secure_boot = get_secure_boot();

+

 	setup_graphics(boot_params);

 	status = setup_efi_pci(boot_params);

diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h

index 225b0988043a..90dbfb73e11f 100644

--- a/arch/x86/include/uapi/asm/bootparam.h

+++ b/arch/x86/include/uapi/asm/bootparam.h

@@ -133,7 +133,8 @@ struct boot_params {

 	__u8  eddbuf_entries;				/* 0x1e9 */

 	__u8  edd_mbr_sig_buf_entries;			/* 0x1ea */

 	__u8  kbd_status;				/* 0x1eb */

-	__u8  _pad5[3];					/* 0x1ec */

+	__u8  secure_boot;				/* 0x1ec */

+	__u8  _pad5[2];					/* 0x1ed */

 	/*

 	 * The sentinel is set to a nonzero value (0xff) in header.S.

 	 *

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

index 41ead8d3bc0b..5a5cf7395724 100644

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

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

@@ -1142,6 +1142,12 @@ void __init setup_arch(char **cmdline_p)

 	io_delay_init();

+#ifdef CONFIG_EFI_SECURE_BOOT_SIG_ENFORCE

+	if (boot_params.secure_boot) {

+		enforce_signed_modules();

+	}

+#endif

+

 	/*

 	 * Parse the ACPI tables for possible boot-time SMP configuration.

 	 */

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

index 341a73ecea2e..cca08ac450e2 100644

--- a/include/linux/module.h

+++ b/include/linux/module.h

@@ -188,6 +188,12 @@ const struct exception_table_entry *search_exception_tables(unsigned long add);

 struct notifier_block;

+#ifdef CONFIG_MODULE_SIG

+extern void enforce_signed_modules(void);

+#else

+static inline void enforce_signed_modules(void) {};

+#endif

+

 #ifdef CONFIG_MODULES

 extern int modules_disabled; /* for sysctl */

diff --git a/kernel/module.c b/kernel/module.c

index 1f7b4664300e..866417ecc76a 100644

--- a/kernel/module.c

+++ b/kernel/module.c

@@ -3843,6 +3843,13 @@ void module_layout(struct module *mod,

 EXPORT_SYMBOL(module_layout);

 #endif

+#ifdef CONFIG_MODULE_SIG

+void enforce_signed_modules(void)

+{

+	sig_enforce = true;

+}

+#endif

+

 bool secure_modules(void)

 {

 #ifdef CONFIG_MODULE_SIG

-- 

1.9.3