From 15368f76d4997912318d35c52bfeb9041d85098e Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Mon, 30 Sep 2019 21:28:16 +0000
Subject: [PATCH 3/3] efi: Lock down the kernel if booted in secure boot mode
Patch-mainline: Never, Fedora Core 32
References: jsc#SLE-9870
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>
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
arch/x86/kernel/setup.c | 8 ++++++++
security/lockdown/Kconfig | 13 +++++++++++++
2 files changed, 21 insertions(+)
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -25,6 +25,7 @@
#include <linux/static_call.h>
#include <linux/swiotlb.h>
#include <linux/random.h>
+#include <linux/security.h>
#include <uapi/linux/mount.h>
@@ -1036,6 +1037,13 @@ void __init setup_arch(char **cmdline_p)
if (efi_enabled(EFI_BOOT))
efi_init();
+ efi_set_secure_boot(boot_params.secure_boot);
+
+#ifdef CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT
+ if (efi_enabled(EFI_SECURE_BOOT))
+ security_lock_kernel_down("EFI Secure Boot mode", LOCKDOWN_CONFIDENTIALITY_MAX);
+#endif
+
dmi_setup();
/*
--- a/security/lockdown/Kconfig
+++ b/security/lockdown/Kconfig
@@ -16,6 +16,19 @@ config SECURITY_LOCKDOWN_LSM_EARLY
subsystem is fully initialised. If enabled, lockdown will
unconditionally be called before any other LSMs.
+config LOCK_DOWN_IN_EFI_SECURE_BOOT
+ bool "Lock down the kernel in EFI Secure Boot mode"
+ default n
+ depends on EFI && SECURITY_LOCKDOWN_LSM_EARLY
+ 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 results in kernel lockdown being triggered if
+ EFI Secure Boot is set.
+
choice
prompt "Kernel default lockdown mode"
default LOCK_DOWN_KERNEL_FORCE_NONE