From b5123d0553f4ed5e734f6457696cdd30228d1eee Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 27 Feb 2018 10:04:55 +0000 Subject: [PATCH 29/31] efi: Add an EFI_SECURE_BOOT flag to indicate secure boot mode UEFI machines can be booted in Secure Boot mode. Add an EFI_SECURE_BOOT flag that can be passed to efi_enabled() to find out whether secure boot is enabled. Move the switch-statement in x86's setup_arch() that inteprets the secure_boot boot parameter to generic code and set the bit there. Suggested-by: Ard Biesheuvel Signed-off-by: David Howells Reviewed-by: Ard Biesheuvel cc: linux-efi@vger.kernel.org Signed-off-by: Jeremy Cline --- arch/x86/kernel/setup.c | 14 +----------- drivers/firmware/efi/Makefile | 1 + drivers/firmware/efi/secureboot.c | 38 +++++++++++++++++++++++++++++++ include/linux/efi.h | 18 ++++++++++----- 4 files changed, 52 insertions(+), 19 deletions(-) create mode 100644 drivers/firmware/efi/secureboot.c diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index b74e7bfed6ab..7da1712c89c9 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1158,19 +1158,7 @@ void __init setup_arch(char **cmdline_p) /* Allocate bigger log buffer */ setup_log_buf(1); - if (efi_enabled(EFI_BOOT)) { - switch (boot_params.secure_boot) { - case efi_secureboot_mode_disabled: - pr_info("Secure boot disabled\n"); - break; - case efi_secureboot_mode_enabled: - pr_info("Secure boot enabled\n"); - break; - default: - pr_info("Secure boot could not be determined\n"); - break; - } - } + efi_set_secure_boot(boot_params.secure_boot); reserve_initrd(); diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile index 5f9f5039de50..7a0a6378203e 100644 --- a/drivers/firmware/efi/Makefile +++ b/drivers/firmware/efi/Makefile @@ -24,6 +24,7 @@ obj-$(CONFIG_EFI_FAKE_MEMMAP) += fake_mem.o obj-$(CONFIG_EFI_BOOTLOADER_CONTROL) += efibc.o obj-$(CONFIG_EFI_TEST) += test/ obj-$(CONFIG_EFI_DEV_PATH_PARSER) += dev-path-parser.o +obj-$(CONFIG_EFI) += secureboot.o obj-$(CONFIG_APPLE_PROPERTIES) += apple-properties.o arm-obj-$(CONFIG_EFI) := arm-init.o arm-runtime.o diff --git a/drivers/firmware/efi/secureboot.c b/drivers/firmware/efi/secureboot.c new file mode 100644 index 000000000000..9070055de0a1 --- /dev/null +++ b/drivers/firmware/efi/secureboot.c @@ -0,0 +1,38 @@ +/* Core kernel secure boot support. + * + * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include + +/* + * Decide what to do when UEFI secure boot mode is enabled. + */ +void __init efi_set_secure_boot(enum efi_secureboot_mode mode) +{ + if (efi_enabled(EFI_BOOT)) { + switch (mode) { + case efi_secureboot_mode_disabled: + pr_info("Secure boot disabled\n"); + break; + case efi_secureboot_mode_enabled: + set_bit(EFI_SECURE_BOOT, &efi.flags); + pr_info("Secure boot enabled\n"); + break; + default: + pr_warning("Secure boot could not be determined (mode %u)\n", + mode); + break; + } + } +} diff --git a/include/linux/efi.h b/include/linux/efi.h index 100ce4a4aff6..62361b647a75 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1155,6 +1155,14 @@ extern int __init efi_setup_pcdp_console(char *); #define EFI_DBG 8 /* Print additional debug info at runtime */ #define EFI_NX_PE_DATA 9 /* Can runtime data regions be mapped non-executable? */ #define EFI_MEM_ATTR 10 /* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */ +#define EFI_SECURE_BOOT 11 /* Are we in Secure Boot mode? */ + +enum efi_secureboot_mode { + efi_secureboot_mode_unset, + efi_secureboot_mode_unknown, + efi_secureboot_mode_disabled, + efi_secureboot_mode_enabled, +}; #ifdef CONFIG_EFI /* @@ -1198,6 +1206,8 @@ static inline bool efi_enabled(int feature) extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused); extern bool efi_is_table_address(unsigned long phys_addr); + +extern void __init efi_set_secure_boot(enum efi_secureboot_mode mode); #else static inline bool efi_enabled(int feature) { @@ -1216,6 +1226,8 @@ static inline bool efi_is_table_address(unsigned long phys_addr) { return false; } + +static inline void efi_set_secure_boot(enum efi_secureboot_mode mode) {} #endif extern int efi_status_to_err(efi_status_t status); @@ -1577,12 +1589,6 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg, bool efi_runtime_disabled(void); extern void efi_call_virt_check_flags(unsigned long flags, const char *call); extern unsigned long efi_call_virt_save_flags(void); -enum efi_secureboot_mode { - efi_secureboot_mode_unset, - efi_secureboot_mode_unknown, - efi_secureboot_mode_disabled, - efi_secureboot_mode_enabled, -}; enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table); #ifdef CONFIG_RESET_ATTACK_MITIGATION -- 2.19.1 From d78bf678059f83e22bec8ada1a448e22b9b90203 Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 27 Feb 2018 10:04:55 +0000 Subject: [PATCH 30/31] 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 Acked-by: Ard Biesheuvel cc: linux-efi@vger.kernel.org --- arch/x86/kernel/setup.c | 6 ++++-- fs/debugfs/inode.c | 2 +- security/Kconfig | 14 ++++++++++++++ security/lock_down.c | 5 +++++ 4 files changed, 20 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index adeee6329f55..27a54ec878bd 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -65,6 +65,7 @@ #include #include #include +#include #include #include @@ -1005,6 +1006,10 @@ 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(); @@ -1159,8 +1164,6 @@ 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/fs/debugfs/inode.c b/fs/debugfs/inode.c index ce261e1765ff..7aff55b309a6 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -40,7 +40,7 @@ static bool debugfs_registered; static int debugfs_setattr(struct dentry *dentry, struct iattr *ia) { if ((ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) && - kernel_is_locked_down("debugfs")) + kernel_is_locked_down("changing perms in debugfs")) return -EPERM; return simple_setattr(dentry, ia); } diff --git a/security/Kconfig b/security/Kconfig index 9c343f262bdd..30788bc47863 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -244,6 +244,20 @@ config LOCK_DOWN_KERNEL_FORCE help Enable the kernel lock down functionality automatically at boot. +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" source "security/tomoyo/Kconfig" diff --git a/security/lock_down.c b/security/lock_down.c index ee00ca2677e7..bb4dc7838f3e 100644 --- a/security/lock_down.c +++ b/security/lock_down.c @@ -12,6 +12,7 @@ #include #include +#include static __ro_after_init bool kernel_locked_down; @@ -44,6 +45,10 @@ void __init init_lockdown(void) #ifdef CONFIG_LOCK_DOWN_FORCE lock_kernel_down("Kernel configuration"); #endif +#ifdef CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT + if (efi_enabled(EFI_SECURE_BOOT)) + lock_kernel_down("EFI secure boot"); +#endif } /** -- 2.14.3