From: David Howells <dhowells@redhat.com>
Date: Wed, 8 Nov 2017 15:11:37 +0000 (+0000)
Subject: efi: Lock down the kernel if booted in secure boot mode
X-Git-Tag: archive/raspbian/4.18.10-2+rpi1^2~28
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=22d39a0cc69407ab8377681da1c4aa2a6a3b815c;p=linux.git

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

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0029-efi-Lock-down-the-kernel-if-booted-in-secure-boot-mo.patch
---

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 64c020dff2b..48a2c5d850b 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>
@@ -1008,6 +1009,9 @@ 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_scan_machine();
 	dmi_memdev_walk();
 	dmi_set_dump_stack_arch_desc();
@@ -1161,8 +1165,6 @@ 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/security/Kconfig b/security/Kconfig
index 9463195e27c..05eef5e0ce5 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -257,6 +257,20 @@ config ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
 	  Allow the lockdown on a kernel to be lifted, by pressing a SysRq key
 	  combination on a wired keyboard.
 
+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
diff --git a/security/lock_down.c b/security/lock_down.c
index 2c6b00f0c22..527f7e51dc8 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/sysrq.h>
+#include <linux/efi.h>
 #include <asm/setup.h>
 
 #ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ