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kernel/efi-secureboot.patch
Jeremy Cline e21e52b608 Linux v5.3-13236-g97f9a3c4eee5 
This is a first pass at getting the secureboot patches working with the
upstream lockdown patches that got merged. The final patch from our
lockdown set is the sysrq patch which also needs work. For the present
it is not applied.
2019-10-01 14:20:23 +00:00

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From 478a0cff698409224330ea9e25eb332220b55dbb Mon Sep 17 00:00:00 2001
From: Jeremy Cline <jcline@redhat.com>
Date: Mon, 30 Sep 2019 21:22:47 +0000
Subject: [PATCH 1/3] security: lockdown: expose a hook to lock the kernel down
In order to automatically lock down kernels running on UEFI machines
booted in Secure Boot mode, expose the lock_kernel_down() hook.
Signed-off-by: Jeremy Cline <jcline@redhat.com>
---
include/linux/lsm_hooks.h | 8 ++++++++
include/linux/security.h | 5 +++++
security/lockdown/lockdown.c | 1 +
security/security.c | 6 ++++++
4 files changed, 20 insertions(+)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index a3763247547c..8d76d1f153ed 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1454,6 +1454,12 @@
* code execution in kernel space should be permitted.
*
* @what: kernel feature being accessed
+ *
+ * @lock_kernel_down
+ * Put the kernel into lock-down mode.
+ *
+ * @where: Where the lock-down is originating from (e.g. command line option)
+ * @level: The lock-down level (can only increase)
*/
union security_list_options {
int (*binder_set_context_mgr)(struct task_struct *mgr);
@@ -1818,6 +1824,7 @@ union security_list_options {
void (*bpf_prog_free_security)(struct bpf_prog_aux *aux);
#endif /* CONFIG_BPF_SYSCALL */
int (*locked_down)(enum lockdown_reason what);
+ int (*lock_kernel_down)(const char *where, enum lockdown_reason level);
};
struct security_hook_heads {
@@ -2060,6 +2067,7 @@ struct security_hook_heads {
struct hlist_head bpf_prog_free_security;
#endif /* CONFIG_BPF_SYSCALL */
struct hlist_head locked_down;
+ struct hlist_head lock_kernel_down;
} __randomize_layout;
/*
diff --git a/include/linux/security.h b/include/linux/security.h
index a8d59d612d27..467b9ccdf993 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -442,6 +442,7 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
int security_locked_down(enum lockdown_reason what);
+int security_lock_kernel_down(const char *where, enum lockdown_reason level);
#else /* CONFIG_SECURITY */
static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -1269,6 +1270,10 @@ static inline int security_locked_down(enum lockdown_reason what)
{
return 0;
}
+static inline int security_lock_kernel_down(const char *where, enum lockdown_reason level);
+{
+ return 0;
+}
#endif /* CONFIG_SECURITY */
#ifdef CONFIG_SECURITY_NETWORK
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 8a10b43daf74..72a623075749 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -97,6 +97,7 @@ static int lockdown_is_locked_down(enum lockdown_reason what)
static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(locked_down, lockdown_is_locked_down),
+ LSM_HOOK_INIT(lock_kernel_down, lock_kernel_down),
};
static int __init lockdown_lsm_init(void)
diff --git a/security/security.c b/security/security.c
index 1bc000f834e2..1506b95427cf 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2404,3 +2404,9 @@ int security_locked_down(enum lockdown_reason what)
return call_int_hook(locked_down, 0, what);
}
EXPORT_SYMBOL(security_locked_down);
+
+int security_lock_kernel_down(const char *where, enum lockdown_reason level)
+{
+ return call_int_hook(lock_kernel_down, 0, where, level);
+}
+EXPORT_SYMBOL(security_lock_kernel_down);
--
2.21.0
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 2/3] 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
[Rebased for context; efi_is_table_address was moved to arch/x86]
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 bbe35bf879f5..7e528b6af86b 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1179,19 +1179,7 @@ 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 4ac2de4dfa72..195b078a423c 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
obj-$(CONFIG_EFI_RCI2_TABLE) += rci2-table.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 21d81021c1f4..758ec061d03b 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1204,6 +1204,14 @@ 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
/*
@@ -1214,6 +1222,8 @@ static inline bool efi_enabled(int feature)
return test_bit(feature, &efi.flags) != 0;
}
extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused);
+
+extern void __init efi_set_secure_boot(enum efi_secureboot_mode mode);
#else
static inline bool efi_enabled(int feature)
{
@@ -1227,6 +1237,8 @@ efi_capsule_pending(int *reset_type)
{
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);
@@ -1619,12 +1631,6 @@ static inline bool efi_runtime_disabled(void) { return true; }
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
--
2.21.0
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
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>
---
arch/x86/kernel/setup.c | 8 ++++++++
security/lockdown/Kconfig | 13 +++++++++++++
2 files changed, 21 insertions(+)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 77ea96b794bd..a119e1bc9623 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -73,6 +73,7 @@
#include <linux/jiffies.h>
#include <linux/mem_encrypt.h>
#include <linux/sizes.h>
+#include <linux/security.h>
#include <linux/usb/xhci-dbgp.h>
#include <video/edid.h>
@@ -1027,6 +1028,13 @@ 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();
/*
diff --git a/security/lockdown/Kconfig b/security/lockdown/Kconfig
index e84ddf484010..d0501353a4b9 100644
--- 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
--
2.21.0
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