From 48f943a855fa850977db9071250db2b9e12287ce Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Wed, 5 Apr 2017 17:40:29 +0100
Subject: [PATCH 41/62] efi: Lock down the kernel if booted in secure boot mode
Patch-mainline: No, submitted https://patchwork.kernel.org/patch/9665015/
References: fate#314486
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: Lee, Chun-Yi <jlee@suse.com>
---
arch/x86/Kconfig | 12 ++++++++++++
arch/x86/kernel/setup.c | 8 +++++++-
2 files changed, 19 insertions(+), 1 deletion(-)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1858,6 +1858,18 @@ config EFI_MIXED
If unsure, say N.
+config EFI_SECURE_BOOT_LOCK_DOWN
+ def_bool n
+ depends on EFI
+ prompt "Lock down the kernel 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 and that
+ userspace is prevented from directly changing the running kernel
+ image. Say Y here to automatically lock down the kernel when a
+ system boots with UEFI Secure Boot enabled.
+
config SECCOMP
def_bool y
prompt "Enable seccomp to safely compute untrusted bytecode"
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -70,6 +70,7 @@
#include <linux/tboot.h>
#include <linux/jiffies.h>
#include <linux/mem_encrypt.h>
+#include <linux/security.h>
#include <linux/usb/xhci-dbgp.h>
#include <video/edid.h>
@@ -1200,7 +1201,12 @@ void __init setup_arch(char **cmdline_p)
break;
case efi_secureboot_mode_enabled:
set_bit(EFI_SECURE_BOOT, &efi.flags);
- pr_info("Secure boot enabled\n");
+ if (IS_ENABLED(CONFIG_EFI_SECURE_BOOT_LOCK_DOWN)) {
+ lock_kernel_down();
+ pr_info("Secure boot enabled and kernel locked down\n");
+ } else {
+ pr_info("Secure boot enabled\n");
+ }
break;
default:
pr_info("Secure boot could not be determined\n");