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 <dhowe...@redhat.com> --- arch/x86/Kconfig | 12 ++++++++++++ arch/x86/kernel/setup.c | 8 +++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index cc98d5a294ee..21f39855661d 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1817,6 +1817,18 @@ 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" diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 396285bddb93..85dfa745c442 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -69,6 +69,7 @@ #include <linux/crash_dump.h> #include <linux/tboot.h> #include <linux/jiffies.h> +#include <linux/security.h> #include <video/edid.h> @@ -1185,7 +1186,12 @@ 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");