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kernel/efi-secureboot.patch

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From b5123d0553f4ed5e734f6457696cdd30228d1eee Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
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 <ard.biesheuvel@linaro.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
cc: linux-efi@vger.kernel.org
Signed-off-by: Jeremy Cline <jcline@redhat.com>
---
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 <linux/efi.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+
+/*
+ * 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,
#endif
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 <dhowells@redhat.com>
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 <dhowells@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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 <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>
@@ -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_setup();
/*
@@ -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
Allow the lockdown on a kernel to be lifted, by pressing a SysRq key
combination on a wired keyboard. On x86, this is SysRq+x.
+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 <linux/security.h>
#include <linux/export.h>
+#include <linux/efi.h>
#include <linux/sysrq.h>
#include <asm/setup.h>
@@ -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
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