[PATCH 00/30] security, efi: Add kernel lockdown

[PATCH 00/30] security, efi: Add kernel lockdown

[David Howells]

Here's a set of patches to institute a "locked-down mode" in the kernel and
to trigger that mode if the kernel is booted in secure-boot mode or through
the command line.

Enabling CONFIG_LOCK_DOWN_KERNEL makes lockdown mode available.

Enabling CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ will allow a SysRq combination
to lift the lockdown.  On x86 this is SysRq+x.  The keys must be pressed on
an attached keyboard.

Enabling CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT will cause EFI secure boot to
trigger kernel lockdown.

Inside the kernel, kernel_is_locked_down() is used to check if the kernel
is in lockdown mode.

Note that the secure boot mode entry doesn't work if the kernel is booted
from older versions of i386/x86_64 Grub as there's a bug in Grub whereby it
doesn't initialise the boot_params correctly.  The incorrect initialisation
causes sanitize_boot_params() to be triggered, thereby zapping the secure
boot flag determined by the EFI boot wrapper.

A manual page, kernel_lockdown.7, is proposed, to which people will be
directed by messages in dmesg.  This lists the features that are restricted
amongst other things.  [Note: I need to update this to mention IMA, so I'll
reply with that later].

Changes:

 (*) Made /dev/mem and /dev/kmem explicitly unopenable in lockdown mode,
     rather than being unopenable as a side effect of /dev/port being made
     unopenable.

 (*) Added lockdowns for ftrace and kprobes.

 (*) Made the bpf lockdown prohibit the use of sys_bpf entirely.

 (*) Made IMA require secure_boot rules in lockdown mode.

 (*) Made module signing and kexec allow unsigned images if IMA has been
     used to validate the image.


The patches can be found here also:

	http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=efi-lock-down

David
---
Chun-Yi Lee (1):
      kexec_file: Restrict at runtime if the kernel is locked down

Dave Young (1):
      Copy secure_boot flag in boot params across kexec reboot

David Howells (14):
      Add the ability to lock down access to the running kernel image
      Enforce module signatures if the kernel is locked down
      scsi: Lock down the eata driver
      Prohibit PCMCIA CIS storage when the kernel is locked down
      Lock down TIOCSSERIAL
      Lock down module params that specify hardware parameters (eg. ioport)
      x86/mmiotrace: Lock down the testmmiotrace module
      debugfs: Disallow use of debugfs files when the kernel is locked down
      Lock down /proc/kcore
      Lock down ftrace
      Lock down kprobes
      bpf: Restrict kernel image access functions when the kernel is locked down
      efi: Add an EFI_SECURE_BOOT flag to indicate secure boot mode
      efi: Lock down the kernel if booted in secure boot mode

Josh Boyer (2):
      hibernate: Disable when the kernel is locked down
      acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down

Kyle McMartin (1):
      Add a SysRq option to lift kernel lockdown

Linn Crosetto (2):
      acpi: Disable ACPI table override if the kernel is locked down
      acpi: Disable APEI error injection if the kernel is locked down

Matthew Garrett (8):
      Restrict /dev/{mem,kmem,port} when the kernel is locked down
      kexec: Disable at runtime if the kernel is locked down
      uswsusp: Disable when the kernel is locked down
      PCI: Lock down BAR access when the kernel is locked down
      x86: Lock down IO port access when the kernel is locked down
      x86/msr: Restrict MSR access when the kernel is locked down
      asus-wmi: Restrict debugfs interface when the kernel is locked down
      ACPI: Limit access to custom_method when the kernel is locked down

Mimi Zohar (1):
      ima: require secure_boot rules in lockdown mode


 arch/x86/include/asm/setup.h        |    2 +
 arch/x86/kernel/ioport.c            |    6 +-
 arch/x86/kernel/kexec-bzimage64.c   |    1 
 arch/x86/kernel/msr.c               |   10 +++
 arch/x86/kernel/setup.c             |   18 +-----
 arch/x86/mm/testmmiotrace.c         |    3 +
 drivers/acpi/apei/einj.c            |    3 +
 drivers/acpi/custom_method.c        |    3 +
 drivers/acpi/osl.c                  |    2 -
 drivers/acpi/tables.c               |    5 ++
 drivers/char/mem.c                  |    2 +
 drivers/firmware/efi/Makefile       |    1 
 drivers/firmware/efi/secureboot.c   |   38 ++++++++++++
 drivers/input/misc/uinput.c         |    1 
 drivers/pci/pci-sysfs.c             |    9 +++
 drivers/pci/proc.c                  |    9 +++
 drivers/pci/syscall.c               |    3 +
 drivers/pcmcia/cistpl.c             |    3 +
 drivers/platform/x86/asus-wmi.c     |    9 +++
 drivers/scsi/eata.c                 |    5 +-
 drivers/tty/serial/serial_core.c    |    6 ++
 drivers/tty/sysrq.c                 |   19 ++++--
 fs/debugfs/file.c                   |    6 ++
 fs/proc/kcore.c                     |    2 +
 include/linux/efi.h                 |   16 +++--
 include/linux/input.h               |    5 ++
 include/linux/kernel.h              |   17 ++++++
 include/linux/security.h            |    8 +++
 include/linux/sysrq.h               |    8 ++-
 kernel/bpf/syscall.c                |    3 +
 kernel/debug/kdb/kdb_main.c         |    2 -
 kernel/kexec.c                      |    7 ++
 kernel/kexec_file.c                 |    8 +++
 kernel/kprobes.c                    |    3 +
 kernel/module.c                     |   19 ++++--
 kernel/params.c                     |   26 +++++++-
 kernel/power/hibernate.c            |    2 -
 kernel/power/user.c                 |    3 +
 kernel/trace/ftrace.c               |   22 +++++++
 security/Kconfig                    |   32 ++++++++++
 security/Makefile                   |    3 +
 security/integrity/ima/ima_policy.c |   39 +++++++++----
 security/lock_down.c                |  108 +++++++++++++++++++++++++++++++++++
 43 files changed, 440 insertions(+), 57 deletions(-)
 create mode 100644 drivers/firmware/efi/secureboot.c
 create mode 100644 security/lock_down.c

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[PATCH 01/30] Add the ability to lock down access to the running kernel image

[David Howells]

Provide a single call to allow kernel code to determine whether the system
should be locked down, thereby disallowing various accesses that might
allow the running kernel image to be changed including the loading of
modules that aren't validly signed with a key we recognise, fiddling with
MSR registers and disallowing hibernation,

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <james.l.morris@oracle.com>
---

 include/linux/kernel.h   |   17 +++++++++++++
 include/linux/security.h |    8 ++++++
 security/Kconfig         |    8 ++++++
 security/Makefile        |    3 ++
 security/lock_down.c     |   60 ++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 96 insertions(+)
 create mode 100644 security/lock_down.c

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 0ad4c3044cf9..362da2e4bf53 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -287,6 +287,23 @@ static inline void refcount_error_report(struct pt_regs *regs, const char *err)
 { }
 #endif
 
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+extern bool __kernel_is_locked_down(const char *what, bool first);
+#else
+static inline bool __kernel_is_locked_down(const char *what, bool first)
+{
+	return false;
+}
+#endif
+
+#define kernel_is_locked_down(what)					\
+	({								\
+		static bool message_given;				\
+		bool locked_down = __kernel_is_locked_down(what, !message_given); \
+		message_given = true;					\
+		locked_down;						\
+	})
+
 /* Internal, do not use. */
 int __must_check _kstrtoul(const char *s, unsigned int base, unsigned long *res);
 int __must_check _kstrtol(const char *s, unsigned int base, long *res);
diff --git a/include/linux/security.h b/include/linux/security.h
index ce6265960d6c..310775476b68 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1753,5 +1753,13 @@ static inline void free_secdata(void *secdata)
 { }
 #endif /* CONFIG_SECURITY */
 
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+extern void __init init_lockdown(void);
+#else
+static inline void __init init_lockdown(void)
+{
+}
+#endif
+
 #endif /* ! __LINUX_SECURITY_H */
 
diff --git a/security/Kconfig b/security/Kconfig
index e8e449444e65..8e01fd59ae7e 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -205,6 +205,14 @@ config STATIC_USERMODEHELPER_PATH
 	  If you wish for all usermode helper programs to be disabled,
 	  specify an empty string here (i.e. "").
 
+config LOCK_DOWN_KERNEL
+	bool "Allow the kernel to be 'locked down'"
+	help
+	  Allow the kernel to be locked down under certain circumstances, for
+	  instance if UEFI secure boot is enabled.  Locking down the kernel
+	  turns off various features that might otherwise allow access to the
+	  kernel image (eg. setting MSR registers).
+
 source security/selinux/Kconfig
 source security/smack/Kconfig
 source security/tomoyo/Kconfig
diff --git a/security/Makefile b/security/Makefile
index f2d71cdb8e19..8c4a43e3d4e0 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -29,3 +29,6 @@ obj-$(CONFIG_CGROUP_DEVICE)		+= device_cgroup.o
 # Object integrity file lists
 subdir-$(CONFIG_INTEGRITY)		+= integrity
 obj-$(CONFIG_INTEGRITY)			+= integrity/
+
+# Allow the kernel to be locked down
+obj-$(CONFIG_LOCK_DOWN_KERNEL)		+= lock_down.o
diff --git a/security/lock_down.c b/security/lock_down.c
new file mode 100644
index 000000000000..d8595c0e6673
--- /dev/null
+++ b/security/lock_down.c
@@ -0,0 +1,60 @@
+/* Lock down the kernel
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells at 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.
+ */
+
+#include <linux/security.h>
+#include <linux/export.h>
+
+static __ro_after_init bool kernel_locked_down;
+
+/*
+ * Put the kernel into lock-down mode.
+ */
+static void __init lock_kernel_down(const char *where)
+{
+	if (!kernel_locked_down) {
+		kernel_locked_down = true;
+		pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n",
+			  where);
+	}
+}
+
+static int __init lockdown_param(char *ignored)
+{
+	lock_kernel_down("command line");
+	return 0;
+}
+
+early_param("lockdown", lockdown_param);
+
+/*
+ * Lock the kernel down from very early in the arch setup.  This must happen
+ * prior to things like ACPI being initialised.
+ */
+void __init init_lockdown(void)
+{
+#ifdef CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT
+	if (efi_enabled(EFI_SECURE_BOOT))
+		lock_kernel_down("EFI secure boot");
+#endif
+}
+
+/**
+ * kernel_is_locked_down - Find out if the kernel is locked down
+ * @what: Tag to use in notice generated if lockdown is in effect
+ */
+bool __kernel_is_locked_down(const char *what, bool first)
+{
+	if (what && first && kernel_locked_down)
+		pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n",
+			  what);
+	return kernel_locked_down;
+}
+EXPORT_SYMBOL(__kernel_is_locked_down);

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[PATCH 02/30] Add a SysRq option to lift kernel lockdown

[David Howells]

From: Kyle McMartin <kyle@redhat.com>

Make an option to provide a sysrq key that will lift the kernel lockdown,
thereby allowing the running kernel image to be accessed and modified.

On x86 this is triggered with SysRq+x, but this key may not be available on
all arches, so it is set by setting LOCKDOWN_LIFT_KEY in asm/setup.h.
Since this macro must be defined in an arch to be able to use this facility
for that arch, the Kconfig option is restricted to arches that support it.

Signed-off-by: Kyle McMartin <kyle@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: x86 at kernel.org
---

 arch/x86/include/asm/setup.h |    2 ++
 drivers/input/misc/uinput.c  |    1 +
 drivers/tty/sysrq.c          |   19 ++++++++++++-----
 include/linux/input.h        |    5 ++++
 include/linux/sysrq.h        |    8 ++++++-
 kernel/debug/kdb/kdb_main.c  |    2 +-
 security/Kconfig             |   10 +++++++++
 security/lock_down.c         |   47 ++++++++++++++++++++++++++++++++++++++++++
 8 files changed, 86 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index a65cf544686a..863f77582c09 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -8,6 +8,8 @@
 #include <linux/linkage.h>
 #include <asm/page_types.h>
 
+#define LOCKDOWN_LIFT_KEY 'x'
+
 #ifdef __i386__
 
 #include <linux/pfn.h>
diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index 443151de90c6..45a1f5460805 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -408,6 +408,7 @@ static int uinput_allocate_device(struct uinput_device *udev)
 	if (!udev->dev)
 		return -ENOMEM;
 
+	udev->dev->flags |= INPUTDEV_FLAGS_SYNTHETIC;
 	udev->dev->event = uinput_dev_event;
 	input_set_drvdata(udev->dev, udev);
 
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 3ffc1ce29023..8b766dbad6dd 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -481,6 +481,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
 	/* x: May be registered on mips for TLB dump */
 	/* x: May be registered on ppc/powerpc for xmon */
 	/* x: May be registered on sparc64 for global PMU dump */
+	/* x: May be registered on x86_64 for disabling secure boot */
 	NULL,				/* x */
 	/* y: May be registered on sparc64 for global register dump */
 	NULL,				/* y */
@@ -524,7 +525,7 @@ static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
                 sysrq_key_table[i] = op_p;
 }
 
-void __handle_sysrq(int key, bool check_mask)
+void __handle_sysrq(int key, unsigned int from)
 {
 	struct sysrq_key_op *op_p;
 	int orig_log_level;
@@ -544,11 +545,15 @@ void __handle_sysrq(int key, bool check_mask)
 
         op_p = __sysrq_get_key_op(key);
         if (op_p) {
+		/* Ban synthetic events from some sysrq functionality */
+		if ((from == SYSRQ_FROM_PROC || from == SYSRQ_FROM_SYNTHETIC) &&
+		    op_p->enable_mask & SYSRQ_DISABLE_USERSPACE)
+			printk("This sysrq operation is disabled from userspace.\n");
 		/*
 		 * Should we check for enabled operations (/proc/sysrq-trigger
 		 * should not) and is the invoked operation enabled?
 		 */
-		if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
+		if (from == SYSRQ_FROM_KERNEL || sysrq_on_mask(op_p->enable_mask)) {
 			pr_cont("%s\n", op_p->action_msg);
 			console_loglevel = orig_log_level;
 			op_p->handler(key);
@@ -580,7 +585,7 @@ void __handle_sysrq(int key, bool check_mask)
 void handle_sysrq(int key)
 {
 	if (sysrq_on())
-		__handle_sysrq(key, true);
+		__handle_sysrq(key, SYSRQ_FROM_KERNEL);
 }
 EXPORT_SYMBOL(handle_sysrq);
 
@@ -661,7 +666,7 @@ static void sysrq_do_reset(unsigned long _state)
 static void sysrq_handle_reset_request(struct sysrq_state *state)
 {
 	if (state->reset_requested)
-		__handle_sysrq(sysrq_xlate[KEY_B], false);
+		__handle_sysrq(sysrq_xlate[KEY_B], SYSRQ_FROM_KERNEL);
 
 	if (sysrq_reset_downtime_ms)
 		mod_timer(&state->keyreset_timer,
@@ -812,8 +817,10 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 
 	default:
 		if (sysrq->active && value && value != 2) {
+			int from = sysrq->handle.dev->flags & INPUTDEV_FLAGS_SYNTHETIC ?
+					SYSRQ_FROM_SYNTHETIC : 0;
 			sysrq->need_reinject = false;
-			__handle_sysrq(sysrq_xlate[code], true);
+			__handle_sysrq(sysrq_xlate[code], from);
 		}
 		break;
 	}
@@ -1097,7 +1104,7 @@ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
 
 		if (get_user(c, buf))
 			return -EFAULT;
-		__handle_sysrq(c, false);
+		__handle_sysrq(c, SYSRQ_FROM_PROC);
 	}
 
 	return count;
diff --git a/include/linux/input.h b/include/linux/input.h
index fb5e23c7ed98..9d2b45a21ade 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -42,6 +42,7 @@ struct input_value {
  * @phys: physical path to the device in the system hierarchy
  * @uniq: unique identification code for the device (if device has it)
  * @id: id of the device (struct input_id)
+ * @flags: input device flags (SYNTHETIC, etc.)
  * @propbit: bitmap of device properties and quirks
  * @evbit: bitmap of types of events supported by the device (EV_KEY,
  *	EV_REL, etc.)
@@ -124,6 +125,8 @@ struct input_dev {
 	const char *uniq;
 	struct input_id id;
 
+	unsigned int flags;
+
 	unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];
 
 	unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
@@ -190,6 +193,8 @@ struct input_dev {
 };
 #define to_input_dev(d) container_of(d, struct input_dev, dev)
 
+#define	INPUTDEV_FLAGS_SYNTHETIC	0x000000001
+
 /*
  * Verify that we are in sync with input_device_id mod_devicetable.h #defines
  */
diff --git a/include/linux/sysrq.h b/include/linux/sysrq.h
index 387fa7d05c98..f7c52a9ea394 100644
--- a/include/linux/sysrq.h
+++ b/include/linux/sysrq.h
@@ -28,6 +28,8 @@
 #define SYSRQ_ENABLE_BOOT	0x0080
 #define SYSRQ_ENABLE_RTNICE	0x0100
 
+#define SYSRQ_DISABLE_USERSPACE	0x00010000
+
 struct sysrq_key_op {
 	void (*handler)(int);
 	char *help_msg;
@@ -42,8 +44,12 @@ struct sysrq_key_op {
  * are available -- else NULL's).
  */
 
+#define SYSRQ_FROM_KERNEL	0x0001
+#define SYSRQ_FROM_PROC		0x0002
+#define SYSRQ_FROM_SYNTHETIC	0x0004
+
 void handle_sysrq(int key);
-void __handle_sysrq(int key, bool check_mask);
+void __handle_sysrq(int key, unsigned int from);
 int register_sysrq_key(int key, struct sysrq_key_op *op);
 int unregister_sysrq_key(int key, struct sysrq_key_op *op);
 struct sysrq_key_op *__sysrq_get_key_op(int key);
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index c8146d53ca67..b480cadf9272 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1970,7 +1970,7 @@ static int kdb_sr(int argc, const char **argv)
 		return KDB_ARGCOUNT;
 
 	kdb_trap_printk++;
-	__handle_sysrq(*argv[1], check_mask);
+	__handle_sysrq(*argv[1], check_mask ? SYSRQ_FROM_KERNEL : 0);
 	kdb_trap_printk--;
 
 	return 0;
diff --git a/security/Kconfig b/security/Kconfig
index 8e01fd59ae7e..1e997be94ba2 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -213,6 +213,16 @@ config LOCK_DOWN_KERNEL
 	  turns off various features that might otherwise allow access to the
 	  kernel image (eg. setting MSR registers).
 
+config ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
+	bool "Allow the kernel lockdown to be lifted by SysRq"
+	depends on LOCK_DOWN_KERNEL
+	depends on MAGIC_SYSRQ
+	depends on X86
+	help
+	  Allow the lockdown on a kernel to be lifted, by pressing a SysRq key
+	  combination on a wired keyboard.
+
+
 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 d8595c0e6673..2c6b00f0c229 100644
--- a/security/lock_down.c
+++ b/security/lock_down.c
@@ -11,8 +11,14 @@
 
 #include <linux/security.h>
 #include <linux/export.h>
+#include <linux/sysrq.h>
+#include <asm/setup.h>
 
+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
+static __read_mostly bool kernel_locked_down;
+#else
 static __ro_after_init bool kernel_locked_down;
+#endif
 
 /*
  * Put the kernel into lock-down mode.
@@ -58,3 +64,44 @@ bool __kernel_is_locked_down(const char *what, bool first)
 	return kernel_locked_down;
 }
 EXPORT_SYMBOL(__kernel_is_locked_down);
+
+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
+
+/*
+ * Take the kernel out of lockdown mode.
+ */
+static void lift_kernel_lockdown(void)
+{
+	pr_notice("Lifting lockdown\n");
+	kernel_locked_down = false;
+}
+
+/*
+ * Allow lockdown to be lifted by pressing something like SysRq+x (and not by
+ * echoing the appropriate letter into the sysrq-trigger file).
+ */
+static void sysrq_handle_lockdown_lift(int key)
+{
+	if (kernel_locked_down)
+		lift_kernel_lockdown();
+}
+
+static struct sysrq_key_op lockdown_lift_sysrq_op = {
+	.handler	= sysrq_handle_lockdown_lift,
+	.help_msg	= "unSB(x)",
+	.action_msg	= "Disabling Secure Boot restrictions",
+	.enable_mask	= SYSRQ_DISABLE_USERSPACE,
+};
+
+static int __init lockdown_lift_sysrq(void)
+{
+	if (kernel_locked_down) {
+		lockdown_lift_sysrq_op.help_msg[5] = LOCKDOWN_LIFT_KEY;
+		register_sysrq_key(LOCKDOWN_LIFT_KEY, &lockdown_lift_sysrq_op);
+	}
+	return 0;
+}
+
+late_initcall(lockdown_lift_sysrq);
+
+#endif /* CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ */

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[PATCH 03/30] ima: require secure_boot rules in lockdown mode

[David Howells]

From: Mimi Zohar <zohar@linux.vnet.ibm.com>

Require the "secure_boot" rules, whether or not it is specified
on the boot command line, for both the builtin and custom policies
in secure boot lockdown mode.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 security/integrity/ima/ima_policy.c |   39 ++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 95209a5f8595..49c75e2a1ec5 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -427,14 +427,21 @@ void ima_update_policy_flag(void)
  */
 void __init ima_init_policy(void)
 {
-	int i, measure_entries, appraise_entries, secure_boot_entries;
+	int i;
+	int measure_entries = 0;
+	int appraise_entries = 0;
+	int secure_boot_entries = 0;
+	bool kernel_locked_down = __kernel_is_locked_down(NULL, false);
 
 	/* if !ima_policy set entries = 0 so we load NO default rules */
-	measure_entries = ima_policy ? ARRAY_SIZE(dont_measure_rules) : 0;
-	appraise_entries = ima_use_appraise_tcb ?
-			 ARRAY_SIZE(default_appraise_rules) : 0;
-	secure_boot_entries = ima_use_secure_boot ?
-			ARRAY_SIZE(secure_boot_rules) : 0;
+	if (ima_policy)
+		measure_entries = ARRAY_SIZE(dont_measure_rules);
+
+	if (ima_use_appraise_tcb)
+		appraise_entries = ARRAY_SIZE(default_appraise_rules);
+
+	if (ima_use_secure_boot || kernel_locked_down)
+		secure_boot_entries = ARRAY_SIZE(secure_boot_rules);
 
 	for (i = 0; i < measure_entries; i++)
 		list_add_tail(&dont_measure_rules[i].list, &ima_default_rules);
@@ -455,11 +462,23 @@ void __init ima_init_policy(void)
 
 	/*
 	 * Insert the appraise rules requiring file signatures, prior to
-	 * any other appraise rules.
+	 * any other appraise rules.  In secure boot lock-down mode, also
+	 * require these appraise rules for custom policies.
 	 */
-	for (i = 0; i < secure_boot_entries; i++)
-		list_add_tail(&secure_boot_rules[i].list,
-			      &ima_default_rules);
+	for (i = 0; i < secure_boot_entries; i++) {
+		struct ima_rule_entry *entry;
+
+		/* Include for builtin policies */
+		list_add_tail(&secure_boot_rules[i].list, &ima_default_rules);
+
+		/* Include for custom policies */
+		if (kernel_locked_down) {
+			entry = kmemdup(&secure_boot_rules[i], sizeof(*entry),
+					GFP_KERNEL);
+			if (entry)
+				list_add_tail(&entry->list, &ima_policy_rules);
+		}
+	}
 
 	for (i = 0; i < appraise_entries; i++) {
 		list_add_tail(&default_appraise_rules[i].list,

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[PATCH 04/30] Enforce module signatures if the kernel is locked down

[David Howells]

If the kernel is locked down, require that all modules have valid
signatures that we can verify or that IMA can validate the file.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
---

 kernel/module.c |   19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index de66ec825992..0ce29c8aa75a 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -64,6 +64,7 @@
 #include <linux/bsearch.h>
 #include <linux/dynamic_debug.h>
 #include <linux/audit.h>
+#include <linux/ima.h>
 #include <uapi/linux/module.h>
 #include "module-internal.h"
 
@@ -2757,7 +2758,8 @@ static inline void kmemleak_load_module(const struct module *mod,
 #endif
 
 #ifdef CONFIG_MODULE_SIG
-static int module_sig_check(struct load_info *info, int flags)
+static int module_sig_check(struct load_info *info, int flags,
+			    bool can_do_ima_check)
 {
 	int err = -ENOKEY;
 	const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
@@ -2781,13 +2783,16 @@ static int module_sig_check(struct load_info *info, int flags)
 	}
 
 	/* Not having a signature is only an error if we're strict. */
-	if (err == -ENOKEY && !sig_enforce)
+	if (err == -ENOKEY && !sig_enforce &&
+	    (!can_do_ima_check || !is_ima_appraise_enabled()) &&
+	    !kernel_is_locked_down("Loading of unsigned modules"))
 		err = 0;
 
 	return err;
 }
 #else /* !CONFIG_MODULE_SIG */
-static int module_sig_check(struct load_info *info, int flags)
+static int module_sig_check(struct load_info *info, int flags,
+			    bool can_do_ima_check)
 {
 	return 0;
 }
@@ -3630,13 +3635,13 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname,
 /* Allocate and load the module: note that size of section 0 is always
    zero, and we rely on this for optional sections. */
 static int load_module(struct load_info *info, const char __user *uargs,
-		       int flags)
+		       int flags, bool can_do_ima_check)
 {
 	struct module *mod;
 	long err;
 	char *after_dashes;
 
-	err = module_sig_check(info, flags);
+	err = module_sig_check(info, flags, can_do_ima_check);
 	if (err)
 		goto free_copy;
 
@@ -3830,7 +3835,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 	if (err)
 		return err;
 
-	return load_module(&info, uargs, 0);
+	return load_module(&info, uargs, 0, false);
 }
 
 SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
@@ -3857,7 +3862,7 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
 	info.hdr = hdr;
 	info.len = size;
 
-	return load_module(&info, uargs, flags);
+	return load_module(&info, uargs, flags, true);
 }
 
 static inline int within(unsigned long addr, void *start, unsigned long size)

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[PATCH 05/30] Restrict /dev/{mem, kmem, port} when the kernel is locked down

[David Howells]

From: Matthew Garrett <matthew.garrett@nebula.com>

Allowing users to read and write to core kernel memory makes it possible
for the kernel to be subverted, avoiding module loading restrictions, and
also to steal cryptographic information.

Disallow /dev/mem and /dev/kmem from being opened this when the kernel has
been locked down to prevent this.

Also disallow /dev/port from being opened to prevent raw ioport access and
thus DMA from being used to accomplish the same thing.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
---

 drivers/char/mem.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 593a8818aca9..0ce5ac0a5c6b 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -762,6 +762,8 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 
 static int open_port(struct inode *inode, struct file *filp)
 {
+	if (kernel_is_locked_down("/dev/mem,kmem,port"))
+		return -EPERM;
 	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 }
 

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[PATCH 06/30] kexec: Disable at runtime if the kernel is locked down

[David Howells]

From: Matthew Garrett <matthew.garrett@nebula.com>

kexec permits the loading and execution of arbitrary code in ring 0, which
is something that lock-down is meant to prevent. It makes sense to disable
kexec in this situation.

This does not affect kexec_file_load() which can check for a signature on the
image to be booted.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
cc: kexec at lists.infradead.org
---

 kernel/kexec.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index e62ec4dc6620..7dadfed9b676 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -202,6 +202,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 		return -EPERM;
 
 	/*
+	 * kexec can be used to circumvent module loading restrictions, so
+	 * prevent loading in that case
+	 */
+	if (kernel_is_locked_down("kexec of unsigned images"))
+		return -EPERM;
+
+	/*
 	 * Verify we have a legal set of flags
 	 * This leaves us room for future extensions.
 	 */

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[PATCH 07/30] Copy secure_boot flag in boot params across kexec reboot

[David Howells]

From: Dave Young <dyoung@redhat.com>

Kexec reboot in case secure boot being enabled does not keep the secure
boot mode in new kernel, so later one can load unsigned kernel via legacy
kexec_load.  In this state, the system is missing the protections provided
by secure boot.

Adding a patch to fix this by retain the secure_boot flag in original
kernel.

secure_boot flag in boot_params is set in EFI stub, but kexec bypasses the
stub.  Fixing this issue by copying secure_boot flag across kexec reboot.

Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: kexec at lists.infradead.org
---

 arch/x86/kernel/kexec-bzimage64.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index fb095ba0c02f..7d0fac5bcbbe 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -179,6 +179,7 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
 	if (efi_enabled(EFI_OLD_MEMMAP))
 		return 0;
 
+	params->secure_boot = boot_params.secure_boot;
 	ei->efi_loader_signature = current_ei->efi_loader_signature;
 	ei->efi_systab = current_ei->efi_systab;
 	ei->efi_systab_hi = current_ei->efi_systab_hi;

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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[David Howells]

From: Chun-Yi Lee <joeyli.kernel@gmail.com>

When KEXEC_VERIFY_SIG is not enabled, kernel should not load images through
kexec_file systemcall if the kernel is locked down unless IMA can be used
to validate the image.

This code was showed in Matthew's patch but not in git:
https://lkml.org/lkml/2015/3/13/778

Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Chun-Yi Lee <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
cc: kexec at lists.infradead.org
---

 kernel/kexec_file.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 9f48f4412297..3ba28fc3fab0 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -255,6 +255,14 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
 	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 		return -EPERM;
 
+	/* Don't permit images to be loaded into trusted kernels if we're not
+	 * going to verify the signature on them
+	 */
+	if (!IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG) &&
+	    !is_ima_appraise_enabled() &&
+	    kernel_is_locked_down("kexec of unsigned images"))
+		return -EPERM;
+
 	/* Make sure we have a legal set of flags */
 	if (flags != (flags & KEXEC_FILE_FLAGS))
 		return -EINVAL;

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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[Jiri Bohac]

Hi,

sorry for replying to such an old thread.

On Thu, Nov 09, 2017 at 05:31:38PM +0000, David Howells wrote:
> When KEXEC_VERIFY_SIG is not enabled, kernel should not load images through
> kexec_file systemcall if the kernel is locked down unless IMA can be used
> to validate the image.

I don't like the idea that the lockdown (which is a runtime
thing) requires a compile time option (KEXEC_VERIFY_SIG) that
forces the verification even when the kernel is then not locked
down at runtime.

Distribution kernels will then have KEXEC_VERIFY_SIG on and
everyone will need signed kexec images even when totally
uninterested in secureboot.

So instead of this patch, I propose the two followup patches that
split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE just as
we have with modules:

[PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE
[PATCH 08b/30] kexec_file: Restrict at runtime if the kernel is locked down

Lockdown would not require KEXEC_SIG_FORCE but when enabled it
would check the signature.

Thanks,

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE

[Jiri Bohac]

This is a preparatory patch for kexec lockdown. A locked down kernel needs to
prevent unsigned kernel images to be loaded with kexec_file_load. Currently,
the only way to force the signature verification is compiling with
KEXEC_VERIFY_SIG. This prevents loading usigned images even when the kernel is
not locked down at runtime.

This patch spilts KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE.
Analogous to the MODULE_SIG and MODULE_SIG_FORCE for modules, KEXEC_SIG turns
on the signature verification but allows unsigned images to be loaded.
KEXEC_SIG_FORCE disallows images without a valid signature.

Signed-off-by: Jiri Bohac <jbohac@suse.cz>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8eed3f94bfc7..f25facb0df96 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1951,20 +1951,28 @@ config KEXEC_FILE
 	  for kernel and initramfs as opposed to list of segments as
 	  accepted by previous system call.
 
-config KEXEC_VERIFY_SIG
+config KEXEC_SIG
 	bool "Verify kernel signature during kexec_file_load() syscall"
 	depends on KEXEC_FILE
 	---help---
-	  This option makes kernel signature verification mandatory for
-	  the kexec_file_load() syscall.
+	  This option makes the kexec_file_load() syscall check for a valid
+	  signature of the kernel image. The image can still be loaded without
+	  a valid signature unless you also enable KEXEC_SIG_FORCE.
 
-	  In addition to that option, you need to enable signature
+	  In addition to this option, you need to enable signature
 	  verification for the corresponding kernel image type being
 	  loaded in order for this to work.
 
+config KEXEC_SIG_FORCE
+	bool "Require a valid signature in kexec_file_load() syscall"
+	depends on KEXEC_SIG
+	---help---
+	  This option makes kernel signature verification mandatory for
+	  the kexec_file_load() syscall.
+
 config KEXEC_BZIMAGE_VERIFY_SIG
 	bool "Enable bzImage signature verification support"
-	depends on KEXEC_VERIFY_SIG
+	depends on KEXEC_SIG
 	depends on SIGNED_PE_FILE_VERIFICATION
 	select SYSTEM_TRUSTED_KEYRING
 	---help---
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 1f790cf9d38f..3fbe35b923ef 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -406,7 +406,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 	return image->fops->cleanup(image->image_loader_data);
 }
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 int arch_kexec_kernel_verify_sig(struct kimage *image, void *kernel,
 				 unsigned long kernel_len)
 {
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index f16f6ceb3875..19652372f3ee 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -121,7 +121,7 @@ typedef void *(kexec_load_t)(struct kimage *image, char *kernel_buf,
 			     unsigned long cmdline_len);
 typedef int (kexec_cleanup_t)(void *loader_data);
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 typedef int (kexec_verify_sig_t)(const char *kernel_buf,
 				 unsigned long kernel_len);
 #endif
@@ -130,7 +130,7 @@ struct kexec_file_ops {
 	kexec_probe_t *probe;
 	kexec_load_t *load;
 	kexec_cleanup_t *cleanup;
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 	kexec_verify_sig_t *verify_sig;
 #endif
 };
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -45,7 +45,7 @@ int __weak arch_kimage_file_post_load_cleanup(struct kimage *image)
 	return -EINVAL;
 }
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
 					unsigned long buf_len)
 {
@@ -116,7 +116,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 			     const char __user *cmdline_ptr,
 			     unsigned long cmdline_len, unsigned flags)
 {
-	int ret = 0;
+	int ret = 0, sig_err = -EPERM;
 	void *ldata;
 	loff_t size;
 
@@ -135,15 +135,20 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 	if (ret)
 		goto out;
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
-	ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
+#ifdef CONFIG_KEXEC_SIG
+	sig_err = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
 					   image->kernel_buf_len);
-	if (ret) {
+	if (sig_err)
 		pr_debug("kernel signature verification failed.\n");
+	else
+		pr_debug("kernel signature verification successful.\n");
+#endif
+
+	if (sig_err && IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
+		ret = sig_err;
 		goto out;
 	}
-	pr_debug("kernel signature verification successful.\n");
-#endif
+
 	/* It is possible that there no initramfs is being loaded */
 	if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
 		ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 08b/30] kexec_file: Restrict at runtime if the kernel is locked down

[Jiri Bohac]

When KEXEC_VERIFY_SIG is not enabled, kernel should not load images through
kexec_file systemcall if the kernel is locked down unless IMA can be used
to validate the image.

Signed-off-by: Jiri Bohac <jbohac@suse.cz>

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -144,7 +144,13 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 		pr_debug("kernel signature verification successful.\n");
 #endif
 
-	if (sig_err && IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
+	/* Don't permit images to be loaded into trusted kernels without
+	 * a valid signature on them
+	 */
+	if (sig_err &&
+	    (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE) ||
+	     (!is_ima_appraise_enabled() &&
+	      kernel_is_locked_down("kexec of unsigned images")))) {
 		ret = sig_err;
 		goto out;
 	}

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE

[David Howells]

I think that your code isn't quite right.  Looking at the patched code:

    #ifdef CONFIG_KEXEC_SIG
	sig_err = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
					   image->kernel_buf_len);
	if (sig_err)
		pr_debug("kernel signature verification failed.\n");
	else
		pr_debug("kernel signature verification successful.\n");
    #endif

	if (sig_err && IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
		ret = sig_err;
		goto out;
	}

If the signature check fails because the signature is bad, but
CONFIG_KEXEC_SIG_FORCE=n then it now won't fail when it should.

If sig_err is -EKEYREJECTED, -EKEYEXPIRED or -EKEYREVOKED then it must fail,
even if the signature check isn't forced.

David
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[PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE

[Jiri Bohac]

On Tue, Jan 16, 2018 at 04:31:51PM +0000, David Howells wrote:
> I think that your code isn't quite right.  Looking at the patched code:
> 
>     #ifdef CONFIG_KEXEC_SIG
> 	sig_err = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
> 					   image->kernel_buf_len);
> 	if (sig_err)
> 		pr_debug("kernel signature verification failed.\n");
> 	else
> 		pr_debug("kernel signature verification successful.\n");
>     #endif
> 
> 	if (sig_err && IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
> 		ret = sig_err;
> 		goto out;
> 	}
> 
> If the signature check fails because the signature is bad, but
> CONFIG_KEXEC_SIG_FORCE=n then it now won't fail when it should.
> 
> If sig_err is -EKEYREJECTED, -EKEYEXPIRED or -EKEYREVOKED then it must fail,
> even if the signature check isn't forced.

It wasn't my intention to fail in these cases. What additional
security does this bring? If simply stripping an invalid
signature from the image before loading will make it pass, why
should the image with an invalid signature be rejected?

Indeed, the module signing code, the semantics of which I wanted
to mimic, also won't load modules with invalid signatures. It
will load modules without any signatuire, it will load  modules
with the MODULE_SIG_STRING modified and it will load modules with
either of MODULE_INIT_IGNORE_MODVERSIONS or
MODULE_INIT_IGNORE_VERMAGIC passed as flags to the finit_module
syscall. In all these cases, it will taint the kernel, which
might be something we want for kexec_file_load as well (?).

But I don't see why it distinguishes between ENOKEY and other
errors when it's so easy for the caller to strip the invalid
signature. And why kexec_file_load should do the same.

What am I missing?

Thanks,

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE

[David Howells]

Jiri Bohac <jbohac@suse.cz> wrote:

> > If sig_err is -EKEYREJECTED, -EKEYEXPIRED or -EKEYREVOKED then it must fail,
> > even if the signature check isn't forced.
> 
> It wasn't my intention to fail in these cases. What additional
> security does this bring? If simply stripping an invalid
> signature from the image before loading will make it pass, why
> should the image with an invalid signature be rejected?

If there is a signature, then if we're checking signatures, in my opinion we
should check it - and fail if the signature can't be parsed, is revoked, we
have a key and the signature doesn't match - or even if we run out of memory.

The cases for which enforcement is required are when (a) there is no
signature, (b) we don't support the algorithms used, or (c) we don't have a
key.

If we're going to completely discard the result, why do your patches even
bother to check the signature at all?

David
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[PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE

[Jiri Bohac]

On Wed, Jan 17, 2018 at 04:34:24PM +0000, David Howells wrote:
> Jiri Bohac <jbohac@suse.cz> wrote:
> 
> > > If sig_err is -EKEYREJECTED, -EKEYEXPIRED or -EKEYREVOKED then it must fail,
> > > even if the signature check isn't forced.
> > 
> > It wasn't my intention to fail in these cases. What additional
> > security does this bring? If simply stripping an invalid
> > signature from the image before loading will make it pass, why
> > should the image with an invalid signature be rejected?
> 
> If there is a signature, then if we're checking signatures, in my opinion we
> should check it - and fail if the signature can't be parsed, is revoked, we
> have a key and the signature doesn't match - or even if we run out of memory.

Key verification may and will fail for lots of reasons which is
just going to make a user's life harder. E.g. you want to kexec
an old kernel with an expired key. Or your date is just wrong and
you get -EKEYEXPIRED. And you don't care about the signing at
all; it's just compiled in because your distro also needs to work
with secureboot. As a user, you will have to debug what's wrong
for no good reason. And an actual attacker will just strip the
signature off the image and load it.

This makes no sense.
 
> The cases for which enforcement is required are when (a) there is no
> signature, (b) we don't support the algorithms used, or (c) we don't have a
> key.
> 
> If we're going to completely discard the result, why do your patches even
> bother to check the signature at all?

I thought that the debug message might be useful. E.g. when
you're testing a kernel and you see "kernel signature
verification failed" in dmesg then you know this would fail on a
system with secure boot. 

But if ignoring the return code seems like too bad a thing, I would
rather skip the signature checking if it's not going to be
enforced with lockdown or CONFIG_KEXEC_SIG_FORCE.

Also, only now I found that some of the error codes the crypto
code returns yield really confusing messages (e.g.
kexec_file_load of an unsigned kernel returns -ELIBBAD which
makes kexec exit with "kexec_file_load failed: Accessing a
corrupted shared library").
Maybe the error code could be unified to -EKEYREJECTED for all
sorts of key verification failures?

Thanks,

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE

[David Howells]

Jiri Bohac <jbohac@suse.cz> wrote:

> Key verification may and will fail for lots of reasons which is
> just going to make a user's life harder. E.g. you want to kexec
> an old kernel with an expired key. Or your date is just wrong and
> you get -EKEYEXPIRED.

Note that we can't check for expired keys as we can't trust the system clock
to be correct at this point.

> Also, only now I found that some of the error codes the crypto
> code returns yield really confusing messages (e.g.
> kexec_file_load of an unsigned kernel returns -ELIBBAD which
> makes kexec exit with "kexec_file_load failed: Accessing a
> corrupted shared library").

Yeah, that should be fixed.

> Maybe the error code could be unified to -EKEYREJECTED for all
> sorts of key verification failures?

Things like ENOMEM and EINTR definitely need to stay separate (not that I
allow interruption at the moment).

ENOKEY (couldn't find matching key), EINVAL (didn't recognise identifier),
ENOPKG (couldn't find a crypto algo) and EBADMSG (couldn't parse signature)
are arguable.  I think there's a valid case for treating ENOKEY, EINVAL and
ENOPKG differently to EKEYREJECTED - more so for ENOKEY.  In my opinion,
ENOKEY, EINVAL and ENOPKG are not fatal errors if we're not enforcing
signature checking, but EKEYREJECTED and EBADMSG are.

David
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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[David Howells]

Jiri Bohac <jbohac@suse.cz> wrote:

> I don't like the idea that the lockdown (which is a runtime
> thing) requires a compile time option (KEXEC_VERIFY_SIG) that
> forces the verification even when the kernel is then not locked
> down at runtime.

It doesn't.  The EPERM only triggers if:

 (1) File signatures aren't mandatory (ie. CONFIG_KEXEC_VERIFY_SIG) is not
     set, and

 (2) you're not using IMA appraisal to validate the file contents, and

 (3) lockdown mode is enabled.

If file signatures are mandatory or IMA appraisal is in use, then the lockdown
state doesn't need to be checked.

David
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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[David Howells]

David Howells <dhowells@redhat.com> wrote:

> > I don't like the idea that the lockdown (which is a runtime
> > thing) requires a compile time option (KEXEC_VERIFY_SIG) that
> > forces the verification even when the kernel is then not locked
> > down at runtime.
> 
> It doesn't.  The EPERM only triggers if:
> 
>  (1) File signatures aren't mandatory (ie. CONFIG_KEXEC_VERIFY_SIG) is not
>      set, and
> 
>  (2) you're not using IMA appraisal to validate the file contents, and
> 
>  (3) lockdown mode is enabled.
> 
> If file signatures are mandatory or IMA appraisal is in use, then the lockdown
> state doesn't need to be checked.

Having said that, I do see your point, I think.  We should still let through
validly signed images, even if signatures aren't mandatory in lockdown mode.

David
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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[Jiri Bohac]

On Thu, Jan 11, 2018 at 12:47:57PM +0000, David Howells wrote:
> > > I don't like the idea that the lockdown (which is a runtime
> > > thing) requires a compile time option (KEXEC_VERIFY_SIG) that
> > > forces the verification even when the kernel is then not locked
> > > down at runtime.
> > 
> > It doesn't.  The EPERM only triggers if:
> > 
> >  (1) File signatures aren't mandatory (ie. CONFIG_KEXEC_VERIFY_SIG) is not
> >      set, and
> > 
> >  (2) you're not using IMA appraisal to validate the file contents, and
> > 
> >  (3) lockdown mode is enabled.
> > 
> > If file signatures are mandatory or IMA appraisal is in use, then the lockdown
> > state doesn't need to be checked.
> 
> Having said that, I do see your point, I think.  We should still let through
> validly signed images, even if signatures aren't mandatory in lockdown mode.

yes, to be clear, the problem I'm trying to fix is:
- without CONFIG_KEXEC_VERIFY_SIG kexec in a locked down kernel
  will not work at all -> every distro that wants to support
  secureboot will need to enable CONFIG_KEXEC_VERIFY_SIG;

- once CONFIG_KEXEC_VERIFY_SIG is enabled, kexec images need to
  be signed even if secureboot is not used

The problem is that CONFIG_KEXEC_VERIFY_SIG enables both the
implementation and the enforcement of the signature checking.

What I'm proposing are new config options that allow a kernel to
be compiled in such a way that:
- kexec works even without signatures if secureboot is off
- kexec works with secureboot but requires signed images

The semantics should be the same as with signed modules, because
requiring kexec signatures when you can load unsigned modules is
futile. But with your original patchset, that's exactly what
distro kernels will be doing when booted with secureboot off,
MODULE_SIG_FORCE=n and KEXEC_VERIFY_SIG=y.

Thanks,

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[David Howells]

Jiri Bohac <jbohac@suse.cz> wrote:

> > Having said that, I do see your point, I think.  We should still let through
> > validly signed images, even if signatures aren't mandatory in lockdown mode.
> 
> yes, to be clear, the problem I'm trying to fix is:
> - without CONFIG_KEXEC_VERIFY_SIG kexec in a locked down kernel
>   will not work at all -> every distro that wants to support
>   secureboot will need to enable CONFIG_KEXEC_VERIFY_SIG;
> 
> - once CONFIG_KEXEC_VERIFY_SIG is enabled, kexec images need to
>   be signed even if secureboot is not used
>
> The problem is that CONFIG_KEXEC_VERIFY_SIG enables both the
> implementation and the enforcement of the signature checking.

Yep.  I understand that.

> What I'm proposing are new config options that allow a kernel to
> be compiled in such a way that:
> - kexec works even without signatures if secureboot is off
> - kexec works with secureboot but requires signed images

Agreed to both of those.  I also agree with making it possible to
configurationally require signatures, which your first patch does.

> The semantics should be the same as with signed modules, because
> requiring kexec signatures when you can load unsigned modules is
> futile. But with your original patchset, that's exactly what
> distro kernels will be doing when booted with secureboot off,
> MODULE_SIG_FORCE=n and KEXEC_VERIFY_SIG=y.

I should fix that.

David
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[PATCH 09/30] hibernate: Disable when the kernel is locked down

[David Howells]

From: Josh Boyer <jwboyer@fedoraproject.org>

There is currently no way to verify the resume image when returning
from hibernate.  This might compromise the signed modules trust model,
so until we can work with signed hibernate images we disable it when the
kernel is locked down.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: linux-pm at vger.kernel.org
---

 kernel/power/hibernate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index a5c36e9c56a6..f2eafefeec50 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -70,7 +70,7 @@ static const struct platform_hibernation_ops *hibernation_ops;
 
 bool hibernation_available(void)
 {
-	return (nohibernate == 0);
+	return nohibernate == 0 && !kernel_is_locked_down("Hibernation");
 }
 
 /**

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[PATCH 10/30] uswsusp: Disable when the kernel is locked down

[David Howells]

From: Matthew Garrett <mjg59@srcf.ucam.org>

uswsusp allows a user process to dump and then restore kernel state, which
makes it possible to modify the running kernel.  Disable this if the kernel
is locked down.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
cc: linux-pm at vger.kernel.org
---

 kernel/power/user.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 22df9f7ff672..678ade9decfe 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -52,6 +52,9 @@ static int snapshot_open(struct inode *inode, struct file *filp)
 	if (!hibernation_available())
 		return -EPERM;
 
+	if (kernel_is_locked_down("/dev/snapshot"))
+		return -EPERM;
+
 	lock_system_sleep();
 
 	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {

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[PATCH 11/30] PCI: Lock down BAR access when the kernel is locked down

[David Howells]

From: Matthew Garrett <matthew.garrett@nebula.com>

Any hardware that can potentially generate DMA has to be locked down in
order to avoid it being possible for an attacker to modify kernel code,
allowing them to circumvent disabled module loading or module signing.
Default to paranoid - in future we can potentially relax this for
sufficiently IOMMU-isolated devices.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: linux-pci at vger.kernel.org
---

 drivers/pci/pci-sysfs.c |    9 +++++++++
 drivers/pci/proc.c      |    9 ++++++++-
 drivers/pci/syscall.c   |    3 ++-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 1eecfa301f7f..e1a3b0e765c2 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -881,6 +881,9 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
 	loff_t init_off = off;
 	u8 *data = (u8 *) buf;
 
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	if (off > dev->cfg_size)
 		return 0;
 	if (off + count > dev->cfg_size) {
@@ -1175,6 +1178,9 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
 	enum pci_mmap_state mmap_type;
 	struct resource *res = &pdev->resource[bar];
 
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
 		return -EINVAL;
 
@@ -1255,6 +1261,9 @@ static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
 				     struct bin_attribute *attr, char *buf,
 				     loff_t off, size_t count)
 {
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	return pci_resource_io(filp, kobj, attr, buf, off, count, true);
 }
 
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 098360d7ff81..a6c53d855daa 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -116,6 +116,9 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
 	int size = dev->cfg_size;
 	int cnt;
 
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	if (pos >= size)
 		return 0;
 	if (nbytes >= size)
@@ -195,6 +198,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 #endif /* HAVE_PCI_MMAP */
 	int ret = 0;
 
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	switch (cmd) {
 	case PCIIOC_CONTROLLER:
 		ret = pci_domain_nr(dev->bus);
@@ -236,7 +242,8 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
 	struct pci_filp_private *fpriv = file->private_data;
 	int i, ret, write_combine = 0, res_bit = IORESOURCE_MEM;
 
-	if (!capable(CAP_SYS_RAWIO))
+	if (!capable(CAP_SYS_RAWIO) ||
+	    kernel_is_locked_down("Direct PCI access"))
 		return -EPERM;
 
 	if (fpriv->mmap_state == pci_mmap_io) {
diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index 9bf993e1f71e..afa01cc3ceec 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -92,7 +92,8 @@ SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
 	u32 dword;
 	int err = 0;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) ||
+	    kernel_is_locked_down("Direct PCI access"))
 		return -EPERM;
 
 	dev = pci_get_bus_and_slot(bus, dfn);

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[PATCH 12/30] x86: Lock down IO port access when the kernel is locked down

[David Howells]

From: Matthew Garrett <matthew.garrett@nebula.com>

IO port access would permit users to gain access to PCI configuration
registers, which in turn (on a lot of hardware) give access to MMIO
register space. This would potentially permit root to trigger arbitrary
DMA, so lock it down by default.

This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and
KDDISABIO console ioctls.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: x86 at kernel.org
---

 arch/x86/kernel/ioport.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 9c3cf0944bce..2c0f058651c5 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -30,7 +30,8 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
 
 	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
 		return -EINVAL;
-	if (turn_on && !capable(CAP_SYS_RAWIO))
+	if (turn_on && (!capable(CAP_SYS_RAWIO) ||
+			kernel_is_locked_down("ioperm")))
 		return -EPERM;
 
 	/*
@@ -120,7 +121,8 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 		return -EINVAL;
 	/* Trying to gain more privileges? */
 	if (level > old) {
-		if (!capable(CAP_SYS_RAWIO))
+		if (!capable(CAP_SYS_RAWIO) ||
+		    kernel_is_locked_down("iopl"))
 			return -EPERM;
 	}
 	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |

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[PATCH 13/30] x86/msr: Restrict MSR access when the kernel is locked down

[David Howells]

From: Matthew Garrett <matthew.garrett@nebula.com>

Writing to MSRs should not be allowed if the kernel is locked down, since
it could lead to execution of arbitrary code in kernel mode.  Based on a
patch by Kees Cook.

MSR accesses are logged for the purposes of building up a whitelist as per
Alan Cox's suggestion.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: x86 at kernel.org
---

 arch/x86/kernel/msr.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index ef688804f80d..dfb61d358196 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -84,6 +84,11 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
 	int err = 0;
 	ssize_t bytes = 0;
 
+	if (kernel_is_locked_down("Direct MSR access")) {
+		pr_info("Direct access to MSR %x\n", reg);
+		return -EPERM;
+	}
+
 	if (count % 8)
 		return -EINVAL;	/* Invalid chunk size */
 
@@ -135,6 +140,11 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 			err = -EFAULT;
 			break;
 		}
+		if (kernel_is_locked_down("Direct MSR access")) {
+			pr_info("Direct access to MSR %x\n", regs[1]); /* Display %ecx */
+			err = -EPERM;
+			break;
+		}
 		err = wrmsr_safe_regs_on_cpu(cpu, regs);
 		if (err)
 			break;

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[PATCH 14/30] asus-wmi: Restrict debugfs interface when the kernel is locked down

[David Howells]

From: Matthew Garrett <matthew.garrett@nebula.com>

We have no way of validating what all of the Asus WMI methods do on a given
machine - and there's a risk that some will allow hardware state to be
manipulated in such a way that arbitrary code can be executed in the
kernel, circumventing module loading restrictions.  Prevent that if the
kernel is locked down.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: acpi4asus-user at lists.sourceforge.net
cc: platform-driver-x86 at vger.kernel.org
---

 drivers/platform/x86/asus-wmi.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 48e1541dc8d4..ef5587469337 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1905,6 +1905,9 @@ static int show_dsts(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (kernel_is_locked_down("Asus WMI"))
+		return -EPERM;
+
 	err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval);
 
 	if (err < 0)
@@ -1921,6 +1924,9 @@ static int show_devs(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (kernel_is_locked_down("Asus WMI"))
+		return -EPERM;
+
 	err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param,
 				    &retval);
 
@@ -1945,6 +1951,9 @@ static int show_call(struct seq_file *m, void *data)
 	union acpi_object *obj;
 	acpi_status status;
 
+	if (kernel_is_locked_down("Asus WMI"))
+		return -EPERM;
+
 	status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID,
 				     0, asus->debug.method_id,
 				     &input, &output);

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[PATCH 15/30] ACPI: Limit access to custom_method when the kernel is locked down

[David Howells]

From: Matthew Garrett <matthew.garrett@nebula.com>

custom_method effectively allows arbitrary access to system memory, making
it possible for an attacker to circumvent restrictions on module loading.
Disable it if the kernel is locked down.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: linux-acpi at vger.kernel.org
---

 drivers/acpi/custom_method.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
index c68e72414a67..b33fba70ec51 100644
--- a/drivers/acpi/custom_method.c
+++ b/drivers/acpi/custom_method.c
@@ -29,6 +29,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 	struct acpi_table_header table;
 	acpi_status status;
 
+	if (kernel_is_locked_down("ACPI custom methods"))
+		return -EPERM;
+
 	if (!(*ppos)) {
 		/* parse the table header to get the table length */
 		if (count <= sizeof(struct acpi_table_header))

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[PATCH 16/30] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down

[David Howells]

From: Josh Boyer <jwboyer@redhat.com>

This option allows userspace to pass the RSDP address to the kernel, which
makes it possible for a user to modify the workings of hardware .  Reject
the option when the kernel is locked down.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: Dave Young <dyoung@redhat.com>
cc: linux-acpi at vger.kernel.org
---

 drivers/acpi/osl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index db78d353bab1..36c6527c1b0a 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -192,7 +192,7 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
 	acpi_physical_address pa = 0;
 
 #ifdef CONFIG_KEXEC
-	if (acpi_rsdp)
+	if (acpi_rsdp && !kernel_is_locked_down("ACPI RSDP specification"))
 		return acpi_rsdp;
 #endif
 

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[PATCH 17/30] acpi: Disable ACPI table override if the kernel is locked down

[David Howells]

From: Linn Crosetto <linn@hpe.com>

>From the kernel documentation (initrd_table_override.txt):

  If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible
  to override nearly any ACPI table provided by the BIOS with an
  instrumented, modified one.

When securelevel is set, the kernel should disallow any unauthenticated
changes to kernel space.  ACPI tables contain code invoked by the kernel,
so do not allow ACPI tables to be overridden if the kernel is locked down.

Signed-off-by: Linn Crosetto <linn@hpe.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: linux-acpi at vger.kernel.org
---

 drivers/acpi/tables.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
index 80ce2a7d224b..5cc13c42daf9 100644
--- a/drivers/acpi/tables.c
+++ b/drivers/acpi/tables.c
@@ -526,6 +526,11 @@ void __init acpi_table_upgrade(void)
 	if (table_nr == 0)
 		return;
 
+	if (kernel_is_locked_down("ACPI table override")) {
+		pr_notice("kernel is locked down, ignoring table override\n");
+		return;
+	}
+
 	acpi_tables_addr =
 		memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS,
 				       all_tables_size, PAGE_SIZE);

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[PATCH 18/30] acpi: Disable APEI error injection if the kernel is locked down

[David Howells]

From: Linn Crosetto <linn@hpe.com>

ACPI provides an error injection mechanism, EINJ, for debugging and testing
the ACPI Platform Error Interface (APEI) and other RAS features.  If
supported by the firmware, ACPI specification 5.0 and later provide for a
way to specify a physical memory address to which to inject the error.

Injecting errors through EINJ can produce errors which to the platform are
indistinguishable from real hardware errors.  This can have undesirable
side-effects, such as causing the platform to mark hardware as needing
replacement.

While it does not provide a method to load unauthenticated privileged code,
the effect of these errors may persist across reboots and affect trust in
the underlying hardware, so disable error injection through EINJ if
the kernel is locked down.

Signed-off-by: Linn Crosetto <linn@hpe.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: linux-acpi at vger.kernel.org
---

 drivers/acpi/apei/einj.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
index b38737c83a24..6d71e1e97b20 100644
--- a/drivers/acpi/apei/einj.c
+++ b/drivers/acpi/apei/einj.c
@@ -518,6 +518,9 @@ static int einj_error_inject(u32 type, u32 flags, u64 param1, u64 param2,
 	int rc;
 	u64 base_addr, size;
 
+	if (kernel_is_locked_down("ACPI error injection"))
+		return -EPERM;
+
 	/* If user manually set "flags", make sure it is legal */
 	if (flags && (flags &
 		~(SETWA_FLAGS_APICID|SETWA_FLAGS_MEM|SETWA_FLAGS_PCIE_SBDF)))

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Re: [PATCH 18/30] acpi: Disable APEI error injection if the kernel is locked down

[Joey Lee]

Hi experts,

On Thu, Nov 09, 2017 at 05:32:53PM +0000, David Howells wrote:
> From: Linn Crosetto <linn@hpe.com>
> 
> ACPI provides an error injection mechanism, EINJ, for debugging and testing
> the ACPI Platform Error Interface (APEI) and other RAS features.  If
> supported by the firmware, ACPI specification 5.0 and later provide for a
> way to specify a physical memory address to which to inject the error.
> 
> Injecting errors through EINJ can produce errors which to the platform are
> indistinguishable from real hardware errors.  This can have undesirable
> side-effects, such as causing the platform to mark hardware as needing
> replacement.
> 
> While it does not provide a method to load unauthenticated privileged code,
> the effect of these errors may persist across reboots and affect trust in
> the underlying hardware, so disable error injection through EINJ if
> the kernel is locked down.
> 
> Signed-off-by: Linn Crosetto <linn@hpe.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
> cc: linux-acpi@vger.kernel.org

I was looking at the lockdown pathes in v5.4-rc kernel and found that the
"acpi: Disable APEI error injection if the kernel is locked down" did not
merged with lockdown patch set. This patch be sent with Matthew's pull
request lockdown patches for 5.2:
    http://kernsec.org/pipermail/linux-security-module-archive/2019-March/012033.html

But it didn't show in Morris's git:
    https://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git/log/?h=next-lockdown

Maybe I missed some detail of this patch. Could anyone point out the
concern of this patch please?

> ---
> 
>  drivers/acpi/apei/einj.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
> index b38737c83a24..6d71e1e97b20 100644
> --- a/drivers/acpi/apei/einj.c
> +++ b/drivers/acpi/apei/einj.c
> @@ -518,6 +518,9 @@ static int einj_error_inject(u32 type, u32 flags, u64 param1, u64 param2,
>  	int rc;
>  	u64 base_addr, size;
>  
> +	if (kernel_is_locked_down("ACPI error injection"))
> +		return -EPERM;
> +
>  	/* If user manually set "flags", make sure it is legal */
>  	if (flags && (flags &
>  		~(SETWA_FLAGS_APICID|SETWA_FLAGS_MEM|SETWA_FLAGS_PCIE_SBDF)))
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-efi" in
> the body of a message to majordomo@vger.kernel.org
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Thanks
Joey Lee

Re: [PATCH 18/30] acpi: Disable APEI error injection if the kernel is locked down

[joeyli]

Hi all,

On Thu, Nov 07, 2019 at 04:21:31PM +0800, joeyli wrote:
> Hi experts,
> 
> On Thu, Nov 09, 2017 at 05:32:53PM +0000, David Howells wrote:
> > From: Linn Crosetto <linn@hpe.com>
> > 
> > ACPI provides an error injection mechanism, EINJ, for debugging and testing
> > the ACPI Platform Error Interface (APEI) and other RAS features.  If
> > supported by the firmware, ACPI specification 5.0 and later provide for a
> > way to specify a physical memory address to which to inject the error.
> > 
> > Injecting errors through EINJ can produce errors which to the platform are
> > indistinguishable from real hardware errors.  This can have undesirable
> > side-effects, such as causing the platform to mark hardware as needing
> > replacement.
> > 
> > While it does not provide a method to load unauthenticated privileged code,
> > the effect of these errors may persist across reboots and affect trust in
> > the underlying hardware, so disable error injection through EINJ if
> > the kernel is locked down.
> > 
> > Signed-off-by: Linn Crosetto <linn@hpe.com>
> > Signed-off-by: David Howells <dhowells@redhat.com>
> > Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
> > cc: linux-acpi@vger.kernel.org
> 
> I was looking at the lockdown pathes in v5.4-rc kernel and found that the
> "acpi: Disable APEI error injection if the kernel is locked down" did not
> merged with lockdown patch set. This patch be sent with Matthew's pull
> request lockdown patches for 5.2:
>     http://kernsec.org/pipermail/linux-security-module-archive/2019-March/012033.html
> 
> But it didn't show in Morris's git:
>     https://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git/log/?h=next-lockdown
> 
> Maybe I missed some detail of this patch. Could anyone point out the
> concern of this patch please?
>

After a couple of years, we still didn't have this patch in mainline. 
Does that mean the "APEI error injection" doesn't need to be locked down?

Actually this patch is against a CVE-2016-3695:
https://nvd.nist.gov/vuln/detail/CVE-2016-3695

It's before lockdown patchset be merged to kernel mainline. So this CVE
happened in downstream destro. Just search CVE-2016-3695 then we can see
many distros has this.

If mainline kernel doesn't have this patch, then I believe that the
CVE-2016-3695 is also in current mainline kernel.

Then why this patch not be acceptted?

Thanks!
Joey Lee
 
> > ---
> > 
> >  drivers/acpi/apei/einj.c |    3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
> > index b38737c83a24..6d71e1e97b20 100644
> > --- a/drivers/acpi/apei/einj.c
> > +++ b/drivers/acpi/apei/einj.c
> > @@ -518,6 +518,9 @@ static int einj_error_inject(u32 type, u32 flags, u64 param1, u64 param2,
> >  	int rc;
> >  	u64 base_addr, size;
> >  
> > +	if (kernel_is_locked_down("ACPI error injection"))
> > +		return -EPERM;
> > +
> >  	/* If user manually set "flags", make sure it is legal */
> >  	if (flags && (flags &
> >  		~(SETWA_FLAGS_APICID|SETWA_FLAGS_MEM|SETWA_FLAGS_PCIE_SBDF)))
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-efi" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> Thanks
> Joey Lee

[PATCH 19/30] scsi: Lock down the eata driver

[David Howells]

When the kernel is running in secure boot mode, we lock down the kernel to
prevent userspace from modifying the running kernel image.  Whilst this
includes prohibiting access to things like /dev/mem, it must also prevent
access by means of configuring driver modules in such a way as to cause a
device to access or modify the kernel image.

The eata driver takes a single string parameter that contains a slew of
settings, including hardware resource configuration.  Prohibit use of the
parameter if the kernel is locked down.

Suggested-by: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Dario Ballabio <ballabio_dario@emc.com>
cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
cc: "Martin K. Petersen" <martin.petersen@oracle.com>
cc: linux-scsi at vger.kernel.org
---

 drivers/scsi/eata.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/eata.c b/drivers/scsi/eata.c
index 6501c330d8c8..72fceaa8f3da 100644
--- a/drivers/scsi/eata.c
+++ b/drivers/scsi/eata.c
@@ -1552,8 +1552,11 @@ static int eata2x_detect(struct scsi_host_template *tpnt)
 
 	tpnt->proc_name = "eata2x";
 
-	if (strlen(boot_options))
+	if (strlen(boot_options)) {
+		if (kernel_is_locked_down("Command line-specified device addresses, irqs and dma channels"))
+			return -EPERM;
 		option_setup(boot_options);
+	}
 
 #if defined(MODULE)
 	/* io_port could have been modified when loading as a module */

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[PATCH 20/30] Prohibit PCMCIA CIS storage when the kernel is locked down

[David Howells]

Prohibit replacement of the PCMCIA Card Information Structure when the
kernel is locked down.

Suggested-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-pcmcia at lists.infradead.org
---

 drivers/pcmcia/cistpl.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pcmcia/cistpl.c b/drivers/pcmcia/cistpl.c
index 55ef7d1fd8da..b7a0e42eeb25 100644
--- a/drivers/pcmcia/cistpl.c
+++ b/drivers/pcmcia/cistpl.c
@@ -1578,6 +1578,9 @@ static ssize_t pccard_store_cis(struct file *filp, struct kobject *kobj,
 	struct pcmcia_socket *s;
 	int error;
 
+	if (kernel_is_locked_down("Direct PCMCIA CIS storage"))
+		return -EPERM;
+
 	s = to_socket(container_of(kobj, struct device, kobj));
 
 	if (off)

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[PATCH 21/30] Lock down TIOCSSERIAL

[David Howells]

Lock down TIOCSSERIAL as that can be used to change the ioport and irq
settings on a serial port.  This only appears to be an issue for the serial
drivers that use the core serial code.  All other drivers seem to either
ignore attempts to change port/irq or give an error.

Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jiri Slaby <jslaby@suse.com>
---

 drivers/tty/serial/serial_core.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 3a14cccbd7ff..41f0922ad842 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -842,6 +842,12 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
 	new_flags = (__force upf_t)new_info->flags;
 	old_custom_divisor = uport->custom_divisor;
 
+	if ((change_port || change_irq) &&
+	    kernel_is_locked_down("Using TIOCSSERIAL to change device addresses, irqs and dma channels")) {
+		retval = -EPERM;
+		goto exit;
+	}
+
 	if (!capable(CAP_SYS_ADMIN)) {
 		retval = -EPERM;
 		if (change_irq || change_port ||

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[PATCH 22/30] Lock down module params that specify hardware parameters (eg. ioport)

[David Howells]

Provided an annotation for module parameters that specify hardware
parameters (such as io ports, iomem addresses, irqs, dma channels, fixed
dma buffers and other types).

Suggested-by: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 kernel/params.c |   26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/kernel/params.c b/kernel/params.c
index 60b2d8101355..422979adb60a 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -108,13 +108,19 @@ bool parameq(const char *a, const char *b)
 	return parameqn(a, b, strlen(a)+1);
 }
 
-static void param_check_unsafe(const struct kernel_param *kp)
+static bool param_check_unsafe(const struct kernel_param *kp,
+			       const char *doing)
 {
 	if (kp->flags & KERNEL_PARAM_FL_UNSAFE) {
 		pr_warn("Setting dangerous option %s - tainting kernel\n",
 			kp->name);
 		add_taint(TAINT_USER, LOCKDEP_STILL_OK);
 	}
+
+	if (kp->flags & KERNEL_PARAM_FL_HWPARAM &&
+	    kernel_is_locked_down("Command line-specified device addresses, irqs and dma channels"))
+		return false;
+	return true;
 }
 
 static int parse_one(char *param,
@@ -144,8 +150,10 @@ static int parse_one(char *param,
 			pr_debug("handling %s with %p\n", param,
 				params[i].ops->set);
 			kernel_param_lock(params[i].mod);
-			param_check_unsafe(&params[i]);
-			err = params[i].ops->set(val, &params[i]);
+			if (param_check_unsafe(&params[i], doing))
+				err = params[i].ops->set(val, &params[i]);
+			else
+				err = -EPERM;
 			kernel_param_unlock(params[i].mod);
 			return err;
 		}
@@ -556,6 +564,12 @@ static ssize_t param_attr_show(struct module_attribute *mattr,
 	return count;
 }
 
+#ifdef CONFIG_MODULES
+#define mod_name(mod) (mod)->name
+#else
+#define mod_name(mod) "unknown"
+#endif
+
 /* sysfs always hands a nul-terminated string in buf.  We rely on that. */
 static ssize_t param_attr_store(struct module_attribute *mattr,
 				struct module_kobject *mk,
@@ -568,8 +582,10 @@ static ssize_t param_attr_store(struct module_attribute *mattr,
 		return -EPERM;
 
 	kernel_param_lock(mk->mod);
-	param_check_unsafe(attribute->param);
-	err = attribute->param->ops->set(buf, attribute->param);
+	if (param_check_unsafe(attribute->param, mod_name(mk->mod)))
+		err = attribute->param->ops->set(buf, attribute->param);
+	else
+		err = -EPERM;
 	kernel_param_unlock(mk->mod);
 	if (!err)
 		return len;

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[PATCH 23/30] x86/mmiotrace: Lock down the testmmiotrace module

[David Howells]

The testmmiotrace module shouldn't be permitted when the kernel is locked
down as it can be used to arbitrarily read and write MMIO space.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Howells <dhowells at redhat.com
cc: Thomas Gleixner <tglx@linutronix.de>
cc: Steven Rostedt <rostedt@goodmis.org>
cc: Ingo Molnar <mingo@kernel.org>
cc: "H. Peter Anvin" <hpa@zytor.com>
cc: x86 at kernel.org
---

 arch/x86/mm/testmmiotrace.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c
index f6ae6830b341..bbaad357f5d7 100644
--- a/arch/x86/mm/testmmiotrace.c
+++ b/arch/x86/mm/testmmiotrace.c
@@ -115,6 +115,9 @@ static int __init init(void)
 {
 	unsigned long size = (read_far) ? (8 << 20) : (16 << 10);
 
+	if (kernel_is_locked_down("MMIO trace testing"))
+		return -EPERM;
+
 	if (mmio_address == 0) {
 		pr_err("you have to use the module argument mmio_address.\n");
 		pr_err("DO NOT LOAD THIS MODULE UNLESS YOU REALLY KNOW WHAT YOU ARE DOING!\n");

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[PATCH 24/30] debugfs: Disallow use of debugfs files when the kernel is locked down

[David Howells]

Disallow opening of debugfs files when the kernel is locked down as various
drivers give raw access to hardware through debugfs.

Accesses to tracefs should use /sys/kernel/tracing/ rather than
/sys/kernel/debug/tracing/.  Possibly a symlink should be emplaced.

Normal device interaction should be done through configfs or a miscdev, not
debugfs.

Note that this makes it unnecessary to specifically lock down show_dsts(),
show_devs() and show_call() in the asus-wmi driver.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Andy Shevchenko <andy.shevchenko@gmail.com>
cc: acpi4asus-user at lists.sourceforge.net
cc: platform-driver-x86 at vger.kernel.org
cc: Matthew Garrett <matthew.garrett@nebula.com>
cc: Thomas Gleixner <tglx@linutronix.de>
---

 fs/debugfs/file.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 6dabc4a10396..32b5168a7e91 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -103,6 +103,9 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
 	const struct file_operations *real_fops = NULL;
 	int srcu_idx, r;
 
+	if (kernel_is_locked_down("debugfs"))
+		return -EPERM;
+
 	r = debugfs_use_file_start(dentry, &srcu_idx);
 	if (r) {
 		r = -ENOENT;
@@ -232,6 +235,9 @@ static int full_proxy_open(struct inode *inode, struct file *filp)
 	struct file_operations *proxy_fops = NULL;
 	int srcu_idx, r;
 
+	if (kernel_is_locked_down("debugfs"))
+		return -EPERM;
+
 	r = debugfs_use_file_start(dentry, &srcu_idx);
 	if (r) {
 		r = -ENOENT;

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[PATCH 25/30] Lock down /proc/kcore

[David Howells]

Disallow access to /proc/kcore when the kernel is locked down to prevent
access to cryptographic data.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
---

 fs/proc/kcore.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 45629f4b5402..176cf749e650 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -549,6 +549,8 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 
 static int open_kcore(struct inode *inode, struct file *filp)
 {
+	if (kernel_is_locked_down("/proc/kcore"))
+		return -EPERM;
 	if (!capable(CAP_SYS_RAWIO))
 		return -EPERM;
 

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[PATCH 26/30] Lock down ftrace

[David Howells]

Disallow the use of ftrace when the kernel is locked down.  This patch
turns off ftrace_enabled late in the kernel boot so that the selftest can
still be potentially be run.

The sysctl that controls ftrace_enables is also disallowed when the kernel
is locked down.  If the lockdown is lifted, then the sysctl can be used to
reenable ftrace - if ftrace was compiled with CONFIG_DYNAMIC_FTRACE, that
is; if it wasn't then it won't be possible to reenable it.

This prevents crypto data theft by analysis of execution patterns, and, if
in future ftrace also logs the register contents at the time, will prevent
data theft by that mechanism also.

Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 kernel/trace/ftrace.c |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 6abfafd7f173..9c7135963d80 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6508,6 +6508,9 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 {
 	int ret = -ENODEV;
 
+	if (kernel_is_locked_down("Use of ftrace"))
+		return -EPERM;
+
 	mutex_lock(&ftrace_lock);
 
 	if (unlikely(ftrace_disabled))
@@ -6896,3 +6899,22 @@ void ftrace_graph_exit_task(struct task_struct *t)
 	kfree(ret_stack);
 }
 #endif
+
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+static int __init ftrace_lock_down(void)
+{
+	mutex_lock(&ftrace_lock);
+
+	if (!ftrace_disabled && ftrace_enabled &&
+	    kernel_is_locked_down("Use of ftrace")) {
+		ftrace_enabled = false;
+		last_ftrace_enabled = false;
+		ftrace_trace_function = ftrace_stub;
+		ftrace_shutdown_sysctl();
+	}
+
+	mutex_unlock(&ftrace_lock);
+	return 0;
+}
+late_initcall(ftrace_lock_down);
+#endif

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[PATCH 26/30] Lock down ftrace

[Jiri Kosina]

On Thu, 9 Nov 2017, David Howells wrote:

> Disallow the use of ftrace when the kernel is locked down.  This patch
> turns off ftrace_enabled late in the kernel boot so that the selftest can
> still be potentially be run.
> 
> The sysctl that controls ftrace_enables is also disallowed when the kernel
> is locked down.  If the lockdown is lifted, then the sysctl can be used to
> reenable ftrace - if ftrace was compiled with CONFIG_DYNAMIC_FTRACE, that
> is; if it wasn't then it won't be possible to reenable it.
> 
> This prevents crypto data theft by analysis of execution patterns, and, if
> in future ftrace also logs the register contents at the time, will prevent
> data theft by that mechanism also.

I fail to see how this fits into the secure boot security model, could you 
please explain?

Secure boot is about having a constant proof / verification that the code 
you're running in ring0 can be trusted (IOW is the one that has been 
signed and verified by the whole boot chain).

Checking execution patterns doesn't seem to fit at all.

Thanks,

-- 
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SUSE Labs
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[PATCH 26/30] Lock down ftrace

[David Howells]

Jiri Kosina <jikos@kernel.org> wrote:

> > This prevents crypto data theft by analysis of execution patterns, and, if
> > in future ftrace also logs the register contents at the time, will prevent
> > data theft by that mechanism also.
> 
> I fail to see how this fits into the secure boot security model, could you 
> please explain?

The idea is to prevent cryptographic data for filesystems and other things
from being read out of the kernel memory as well as to prevent unauthorised
modification of kernel memory.

> Secure boot is about having a constant proof / verification that the code 
> you're running in ring0 can be trusted (IOW is the one that has been 
> signed and verified by the whole boot chain).
> 
> Checking execution patterns doesn't seem to fit at all.

I'll defer this question to Alexei since he suggested I needed to deal with
this too.

David
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[PATCH 26/30] Lock down ftrace

[Jiri Kosina]

On Fri, 10 Nov 2017, David Howells wrote:

> > I fail to see how this fits into the secure boot security model, could you 
> > please explain?
> 
> The idea is to prevent cryptographic data for filesystems and other things
> from being read out of the kernel memory as well as to prevent unauthorised
> modification of kernel memory.

Then it would make sense to actually lock down dumping of registers / 
function arguments (kprobes can currently do that, ftrace eventually could 
as well I guess), but disabling the whole ftrace altogether seems like a 
totally unnecessary overkill.

> > Secure boot is about having a constant proof / verification that the code 
> > you're running in ring0 can be trusted (IOW is the one that has been 
> > signed and verified by the whole boot chain).
> > 
> > Checking execution patterns doesn't seem to fit at all.
> 
> I'll defer this question to Alexei since he suggested I needed to deal 
> with this too.

Thanks.

-- 
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SUSE Labs

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[PATCH 26/30] Lock down ftrace

[David Howells]

Jiri Kosina <jikos@kernel.org> wrote:

> > The idea is to prevent cryptographic data for filesystems and other things
> > from being read out of the kernel memory as well as to prevent unauthorised
> > modification of kernel memory.
> 
> Then it would make sense to actually lock down dumping of registers / 
> function arguments (kprobes can currently do that, ftrace eventually could 
> as well I guess), but disabling the whole ftrace altogether seems like a 
> totally unnecessary overkill.

That would be fine by me.  I have a patch that locks down kprobes in this
series.  Steven says that ftrace might acquire the ability to dump registers
in the future.

David
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[PATCH 26/30] Lock down ftrace

[Jiri Kosina]

On Fri, 10 Nov 2017, David Howells wrote:

> That would be fine by me.  I have a patch that locks down kprobes in this
> series.  

Which AFAICS renders locking down ftrace as-is unnecessary ...

> Steven says that ftrace might acquire the ability to dump registers in 
> the future.

... and even if that happens, locking down only that particular feature of 
ftrace would be needed.

Thanks,

-- 
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SUSE Labs

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[PATCH 26/30] Lock down ftrace

[David Howells]

Okay, I've dropped the ftrace lockdown patch for the moment from my git
branch.

David
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[PATCH 27/30] Lock down kprobes

[David Howells]

Disallow the creation of kprobes when the kernel is locked down by
preventing their registration.  This prevents kprobes from being used to
access kernel memory, either to make modifications or to steal crypto data.

Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 kernel/kprobes.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index a1606a4224e1..f06023b0936c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1530,6 +1530,9 @@ int register_kprobe(struct kprobe *p)
 	struct module *probed_mod;
 	kprobe_opcode_t *addr;
 
+	if (kernel_is_locked_down("Use of kprobes"))
+		return -EPERM;
+
 	/* Adjust probe address from symbol */
 	addr = kprobe_addr(p);
 	if (IS_ERR(addr))

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[PATCH 28/30] bpf: Restrict kernel image access functions when the kernel is locked down

[David Howells]

There are some bpf functions can be used to read kernel memory:
bpf_probe_read, bpf_probe_write_user and bpf_trace_printk.  These allow
private keys in kernel memory (e.g. the hibernation image signing key) to
be read by an eBPF program and kernel memory to be altered without
restriction.

Completely prohibit the use of BPF when the kernel is locked down.

Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: netdev at vger.kernel.org
cc: Chun-Yi Lee <jlee@suse.com>
cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
---

 kernel/bpf/syscall.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 25d074920a00..fa58ad74cde6 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1458,6 +1458,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
 	if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled)
 		return -EPERM;
 
+	if (kernel_is_locked_down("BPF"))
+		return -EPERM;
+
 	err = check_uarg_tail_zero(uattr, sizeof(attr), size);
 	if (err)
 		return err;

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[PATCH 29/30] efi: Add an EFI_SECURE_BOOT flag to indicate secure boot mode

[David Howells]

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 at vger.kernel.org
---

 arch/x86/kernel/setup.c           |   14 +-------------
 drivers/firmware/efi/Makefile     |    1 +
 drivers/firmware/efi/secureboot.c |   38 +++++++++++++++++++++++++++++++++++++
 include/linux/efi.h               |   16 ++++++++++------
 4 files changed, 50 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 0957dd73d127..7c2162f9e769 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1197,19 +1197,7 @@ 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 0329d319d89a..883f9f7eefc6 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -23,6 +23,7 @@ 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 at 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 66f4a4e79f4b..7c7a7e33e4d1 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1103,6 +1103,14 @@ 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
 /*
@@ -1115,6 +1123,7 @@ 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)
 {
@@ -1133,6 +1142,7 @@ 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);
@@ -1518,12 +1528,6 @@ 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);
 
-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

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[PATCH 30/30] efi: Lock down the kernel if booted in secure boot mode

[David Howells]

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 at vger.kernel.org
---

 arch/x86/kernel/setup.c |    6 ++++--
 security/Kconfig        |   14 ++++++++++++++
 security/lock_down.c    |    1 +
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 7c2162f9e769..4e38327efb2e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -64,6 +64,7 @@
 #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>
@@ -1039,6 +1040,9 @@ 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();
@@ -1197,8 +1201,6 @@ 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/security/Kconfig b/security/Kconfig
index 1e997be94ba2..a4fa8b826039 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -222,6 +222,20 @@ config ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
 	  Allow the lockdown on a kernel to be lifted, by pressing a SysRq key
 	  combination on a wired keyboard.
 
+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
diff --git a/security/lock_down.c b/security/lock_down.c
index 2c6b00f0c229..527f7e51dc8d 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/sysrq.h>
+#include <linux/efi.h>
 #include <asm/setup.h>
 
 #ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ

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[PATCH 04/30] Enforce module signatures if the kernel is locked down

[David Howells]

I'm considering folding the attached changes into this patch.

It adjusts the errors generated:

 (1) If there's no signature (ENODATA) or we can't check it (ENOPKG, ENOKEY),
     then:

     (a) If signatures are enforced then EKEYREJECTED is returned.

     (b) If IMA will have validated the image, return 0 (okay).

     (c) If there's no signature or we can't check it, but the kernel is
	 locked down then EPERM is returned (this is then consistent with
	 other lockdown cases).

 (2) If the signature is unparseable (EBADMSG, EINVAL), the signature fails
     the check (EKEYREJECTED) or a system error occurs (eg. ENOMEM), we return
     the error we got.

Note that the X.509 code doesn't check for key expiry as the RTC might not be
valid or might not have been transferred to the kernel's clock yet.

David
---
diff --git a/kernel/module.c b/kernel/module.c
index 1eb06a0ccbfb..62419cf48ef6 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2769,8 +2769,9 @@ static inline void kmemleak_load_module(const struct module *mod,
 static int module_sig_check(struct load_info *info, int flags,
 			    bool can_do_ima_check)
 {
-	int err = -ENOKEY;
+	int err = -ENODATA;
 	const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
+	const char *reason;
 	const void *mod = info->hdr;
 
 	/*
@@ -2785,18 +2786,42 @@ static int module_sig_check(struct load_info *info, int flags,
 		err = mod_verify_sig(mod, &info->len);
 	}
 
-	if (!err) {
+	switch (err) {
+	case 0:
 		info->sig_ok = true;
 		return 0;
-	}
 
-	/* Not having a signature is only an error if we're strict. */
-	if (err == -ENOKEY && !sig_enforce &&
-	    (!can_do_ima_check || !is_ima_appraise_enabled()) &&
-	    !kernel_is_locked_down("Loading of unsigned modules"))
-		err = 0;
+		/* We don't permit modules to be loaded into trusted kernels
+		 * without a valid signature on them, but if we're not
+		 * enforcing, certain errors are non-fatal.
+		 */
+	case -ENODATA:
+		reason = "Loading of unsigned module";
+		goto decide;
+	case -ENOPKG:
+		reason = "Loading of module with unsupported crypto";
+		goto decide;
+	case -ENOKEY:
+		reason = "Loading of module with unavailable key";
+	decide:
+		if (sig_enforce) {
+			pr_notice("%s is rejected\n", reason);
+			return -EKEYREJECTED;
+		}
 
-	return err;
+		if (can_do_ima_check && is_ima_appraise_enabled())
+			return 0;
+		if (kernel_is_locked_down(reason))
+			return -EPERM;
+		return 0;
+
+		/* All other errors are fatal, including nomem, unparseable
+		 * signatures and signature check failures - even if signatures
+		 * aren't required.
+		 */
+	default:
+		return err;
+	}
 }
 #else /* !CONFIG_MODULE_SIG */
 static int module_sig_check(struct load_info *info, int flags,
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[PATCH 04/30] Enforce module signatures if the kernel is locked down

[Jiri Bohac]

On Thu, Feb 22, 2018 at 01:07:57PM +0000, David Howells wrote:
> I'm considering folding the attached changes into this patch.
> 
> It adjusts the errors generated:
> 
>  (1) If there's no signature (ENODATA) or we can't check it (ENOPKG, ENOKEY),
>      then:
> 
>      (a) If signatures are enforced then EKEYREJECTED is returned.
> 
>      (b) If IMA will have validated the image, return 0 (okay).
> 
>      (c) If there's no signature or we can't check it, but the kernel is
> 	 locked down then EPERM is returned (this is then consistent with
> 	 other lockdown cases).
> 
>  (2) If the signature is unparseable (EBADMSG, EINVAL), the signature fails
>      the check (EKEYREJECTED) or a system error occurs (eg. ENOMEM), we return
>      the error we got.
> 
> Note that the X.509 code doesn't check for key expiry as the RTC might not be
> valid or might not have been transferred to the kernel's clock yet.

Looks good. 

Reviewed-by: Jiri Bohac <jbohac@suse.cz>

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[David Howells]

I'm intending on inserting the attached patch before this one.

David
---
commit 87a39b258eca2e15884ee90c3fcd5758d6057b17
Author: David Howells <dhowells@redhat.com>
Date:   Thu Feb 22 13:42:04 2018 +0000

    kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE
    
    This is a preparatory patch for kexec_file_load() lockdown.  A locked down
    kernel needs to prevent unsigned kernel images to be loaded with
    kexec_file_load().  Currently, the only way to force the signature
    verification is compiling with KEXEC_VERIFY_SIG.  This prevents loading
    usigned images even when the kernel is not locked down at runtime.
    
    This patch splits KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE.
    Analogous to the MODULE_SIG and MODULE_SIG_FORCE for modules, KEXEC_SIG
    turns on the signature verification but allows unsigned images to be
    loaded.  KEXEC_SIG_FORCE disallows images without a valid signature.
    
    [Modified by David Howells such that:
    
     (1) verify_pefile_signature() differentiates between no-signature and
         sig-didn't-match in its returned errors.
    
     (2) kexec fails with EKEYREJECTED and logs an appropriate message if
         signature checking is enforced and an signature is not found, uses
         unsupported crypto or has no matching key.
    
     (3) kexec fails with EKEYREJECTED if there is a signature for which we
         have a key, but signature doesn't match - even if in non-forcing mode.
    
     (4) kexec fails with EBADMSG or some other error if there is a signature
         which cannot be parsed - even if in non-forcing mode.
    
     (5) kexec fails with ELIBBAD if the PE file cannot be parsed to extract
         the signature - even if in non-forcing mode.
    
    ]
    
    Signed-off-by: Jiri Bohac <jbohac@suse.cz>
    Signed-off-by: David Howells <dhowells@redhat.com>
    cc: Matthew Garrett <mjg59@srcf.ucam.org>
    cc: Chun-Yi Lee <jlee@suse.com>
    cc: kexec at lists.infradead.org

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c1236b187824..cb6e67b7442d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2019,20 +2019,30 @@ config KEXEC_FILE
 	  for kernel and initramfs as opposed to list of segments as
 	  accepted by previous system call.
 
-config KEXEC_VERIFY_SIG
+config KEXEC_SIG
 	bool "Verify kernel signature during kexec_file_load() syscall"
 	depends on KEXEC_FILE
 	---help---
-	  This option makes kernel signature verification mandatory for
-	  the kexec_file_load() syscall.
 
-	  In addition to that option, you need to enable signature
+	  This option makes the kexec_file_load() syscall check for a valid
+	  signature of the kernel image.  The image can still be loaded without
+	  a valid signature unless you also enable KEXEC_SIG_FORCE, though if
+	  there's a signature that we can check, then it must be valid.
+
+	  In addition to this option, you need to enable signature
 	  verification for the corresponding kernel image type being
 	  loaded in order for this to work.
 
+config KEXEC_SIG_FORCE
+	bool "Require a valid signature in kexec_file_load() syscall"
+	depends on KEXEC_SIG
+	---help---
+	  This option makes kernel signature verification mandatory for
+	  the kexec_file_load() syscall.
+
 config KEXEC_BZIMAGE_VERIFY_SIG
 	bool "Enable bzImage signature verification support"
-	depends on KEXEC_VERIFY_SIG
+	depends on KEXEC_SIG
 	depends on SIGNED_PE_FILE_VERIFICATION
 	select SYSTEM_TRUSTED_KEYRING
 	---help---
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 1f790cf9d38f..3fbe35b923ef 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -406,7 +406,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 	return image->fops->cleanup(image->image_loader_data);
 }
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 int arch_kexec_kernel_verify_sig(struct kimage *image, void *kernel,
 				 unsigned long kernel_len)
 {
diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c
index d178650fd524..4473cea1e877 100644
--- a/crypto/asymmetric_keys/verify_pefile.c
+++ b/crypto/asymmetric_keys/verify_pefile.c
@@ -100,7 +100,7 @@ static int pefile_parse_binary(const void *pebuf, unsigned int pelen,
 
 	if (!ddir->certs.virtual_address || !ddir->certs.size) {
 		pr_debug("Unsigned PE binary\n");
-		return -EKEYREJECTED;
+		return -ENODATA;
 	}
 
 	chkaddr(ctx->header_size, ddir->certs.virtual_address,
@@ -408,6 +408,8 @@ static int pefile_digest_pe(const void *pebuf, unsigned int pelen,
  *  (*) 0 if at least one signature chain intersects with the keys in the trust
  *	keyring, or:
  *
+ *  (*) -ENODATA if there is no signature present.
+ *
  *  (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
  *	chain.
  *
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index f16f6ceb3875..19652372f3ee 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -121,7 +121,7 @@ typedef void *(kexec_load_t)(struct kimage *image, char *kernel_buf,
 			     unsigned long cmdline_len);
 typedef int (kexec_cleanup_t)(void *loader_data);
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 typedef int (kexec_verify_sig_t)(const char *kernel_buf,
 				 unsigned long kernel_len);
 #endif
@@ -130,7 +130,7 @@ struct kexec_file_ops {
 	kexec_probe_t *probe;
 	kexec_load_t *load;
 	kexec_cleanup_t *cleanup;
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 	kexec_verify_sig_t *verify_sig;
 #endif
 };
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index e5bcd94c1efb..d5931e392050 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -45,7 +45,7 @@ int __weak arch_kimage_file_post_load_cleanup(struct kimage *image)
 	return -EINVAL;
 }
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
 					unsigned long buf_len)
 {
@@ -116,7 +116,8 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 			     const char __user *cmdline_ptr,
 			     unsigned long cmdline_len, unsigned flags)
 {
-	int ret = 0;
+	const char *reason;
+	int ret;
 	void *ldata;
 	loff_t size;
 
@@ -135,15 +136,48 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 	if (ret)
 		goto out;
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 	ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
 					   image->kernel_buf_len);
-	if (ret) {
-		pr_debug("kernel signature verification failed.\n");
+#else
+	ret = -ENODATA;
+#endif
+
+	switch (ret) {
+	case 0:
+		break;
+
+		/* Certain verification errors are non-fatal if we're not
+		 * checking errors, provided we aren't mandating that there
+		 * must be a valid signature.
+		 */
+	case -ENODATA:
+		reason = "kexec of unsigned image";
+		goto decide;
+	case -ENOPKG:
+		reason = "kexec of image with unsupported crypto";
+		goto decide;
+	case -ENOKEY:
+		reason = "kexec of image with unavailable key";
+	decide:
+		if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
+			pr_notice("%s rejected\n", reason);
+			ret = -EKEYREJECTED;
+			goto out;
+		}
+
+		ret = 0;
+		break;
+
+		/* All other errors are fatal, including nomem, unparseable
+		 * signatures and signature check failures - even if signatures
+		 * aren't required.
+		 */
+	default:
+		pr_notice("kernel signature verification failed (%d).\n", ret);
 		goto out;
 	}
-	pr_debug("kernel signature verification successful.\n");
-#endif
+
 	/* It is possible that there no initramfs is being loaded */
 	if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
 		ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[Jiri Bohac]

On Thu, Feb 22, 2018 at 02:20:43PM +0000, David Howells wrote:
> commit 87a39b258eca2e15884ee90c3fcd5758d6057b17
> Author: David Howells <dhowells@redhat.com>
> Date:   Thu Feb 22 13:42:04 2018 +0000
> 
>     kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE
>     
>     This is a preparatory patch for kexec_file_load() lockdown.  A locked down
>     kernel needs to prevent unsigned kernel images to be loaded with

s/to be loaded/from being loaded/
(my own mistake :-))

Otherwise looks good. Thanks for improving my idea.

Reviewed-by: Jiri Bohac <jbohac@suse.cz>

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[David Howells]

David Howells <dhowells@redhat.com> wrote:

> I'm intending on inserting the attached patch before this one.

And replacing this patch with the attached.

David
---
commit ed0424c531d7dd25adebdec0ee6a78a5784f207a
Author: David Howells <dhowells@redhat.com>
Date:   Thu Feb 22 14:01:49 2018 +0000

    kexec_file: Restrict at runtime if the kernel is locked down
    
    When KEXEC_VERIFY_SIG is not enabled, kernel should not load images through
    kexec_file systemcall if the kernel is locked down unless IMA can be used
    to validate the image.
    
    [Modified by David Howells to fit with modifications to the previous patch
     and to return -EPERM if the kernel is locked down for consistency with
     other lockdowns]
    
    Signed-off-by: Jiri Bohac <jbohac@suse.cz>
    Signed-off-by: David Howells <dhowells@redhat.com>
    Cc: Matthew Garrett <mjg59@srcf.ucam.org>
    cc: Chun-Yi Lee <jlee@suse.com>
    cc: kexec at lists.infradead.org

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index d5931e392050..c47c4de604cd 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -167,6 +167,14 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 		}
 
 		ret = 0;
+		if (is_ima_appraise_enabled())
+			break;
+
+		if (kernel_is_locked_down(reason)) {
+			ret = -EPERM;
+			goto out;
+		}
+
 		break;
 
 		/* All other errors are fatal, including nomem, unparseable
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[PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[Jiri Bohac]

On Thu, Feb 22, 2018 at 02:21:53PM +0000, David Howells wrote:
> commit ed0424c531d7dd25adebdec0ee6a78a5784f207a
> Author: David Howells <dhowells@redhat.com>
> Date:   Thu Feb 22 14:01:49 2018 +0000
> 
>     kexec_file: Restrict at runtime if the kernel is locked down
>     
>     When KEXEC_VERIFY_SIG is not enabled, kernel should not load images through

s/KEXEC_VERIFY_SIG/KEXEC_SIG/
Again, my mistake :/

Other than that, looks OK. Much cleaner than my version. Thanks!

Reviewed-by: Jiri Bohac <jbohac@suse.cz>

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

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[PATCH 00/30] security, efi: Add kernel lockdown

[Andrew Morton]

On Thu,  9 Nov 2017 17:30:36 +0000 David Howells <dhowells@redhat.com> wrote:

> Here's a set of patches to institute a "locked-down mode" in the kernel and
> to trigger that mode if the kernel is booted in secure-boot mode or through
> the command line.
> 
> Enabling CONFIG_LOCK_DOWN_KERNEL makes lockdown mode available.
> 
> Enabling CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ will allow a SysRq combination
> to lift the lockdown.  On x86 this is SysRq+x.  The keys must be pressed on
> an attached keyboard.
> 
> Enabling CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT will cause EFI secure boot to
> trigger kernel lockdown.
> 
> Inside the kernel, kernel_is_locked_down() is used to check if the kernel
> is in lockdown mode.
> 
> Note that the secure boot mode entry doesn't work if the kernel is booted
> from older versions of i386/x86_64 Grub as there's a bug in Grub whereby it
> doesn't initialise the boot_params correctly.  The incorrect initialisation
> causes sanitize_boot_params() to be triggered, thereby zapping the secure
> boot flag determined by the EFI boot wrapper.
> 
> A manual page, kernel_lockdown.7, is proposed, to which people will be
> directed by messages in dmesg.  This lists the features that are restricted
> amongst other things.  [Note: I need to update this to mention IMA, so I'll
> reply with that later].

I saw all this pop up in linux-next and got curious.

This changelog didn't uncurious me at all.  The
LOCK_DOWN_IN_EFI_SECURE_BOOT Kconfig help is unilluminating.  A bit of
googling led me to kernel_lockdown.7 (https://lwn.net/Articles/735564/)
which kinda helped.

But still.  This is a big, straggly feature and presumably is still
missing things and presumably will require ongoing maintenance as we
add new kernel capabilities.  What do we get in return for all of this?
What are the usecases for this feature and why would anyone want one? 
What's the value to our users?

Thanks.
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