[PATCH 00/15] Secure boot policy support

[PATCH 00/15] Secure boot policy support

[Matthew Garrett]

Secure boot makes it possible to ensure that the on-disk representation of
the kernel hasn't been modified. This can be sidestepped if the in-memory
representation can be trivially altered. We currently have a large number
of interfaces that permit root to perform effectively arbitrary
modifications to the kernel, so this patchset introduces a new capability
("CAP_COMPROMISE_KERNEL") that controls whether or not these features are
available. The aim is for this to be useful in any other situations where
kernel integrity can be assured by some other mechanism rather than special
casing UEFI.

[PATCH 01/15] Secure boot: Add new capability

[Matthew Garrett]

Secure boot adds certain policy requirements, including that root must not
be able to do anything that could cause the kernel to execute arbitrary code.
The simplest way to handle this would seem to be to add a new capability
and gate various functionality on that. We'll then strip it from the initial
capability set if required.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 include/uapi/linux/capability.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
index ba478fa..7109e650 100644
--- a/include/uapi/linux/capability.h
+++ b/include/uapi/linux/capability.h
@@ -343,7 +343,11 @@ struct vfs_cap_data {
 
 #define CAP_BLOCK_SUSPEND    36
 
-#define CAP_LAST_CAP         CAP_BLOCK_SUSPEND
+/* Allow things that trivially permit root to modify the running kernel */
+
+#define CAP_COMPROMISE_KERNEL  37
+
+#define CAP_LAST_CAP         CAP_COMPROMISE_KERNEL
 
 #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
 
-- 
1.8.0.2

[PATCH 02/15] SELinux: define mapping for new Secure Boot capability

[Matthew Garrett]

From: Josh Boyer <jwboyer@redhat.com>

Add the name of the new Secure Boot capability.  This allows SELinux
policies to properly map CAP_COMPROMISE_KERNEL to the appropriate
capability class.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
---
 security/selinux/include/classmap.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index df2de54..70e2834 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -146,8 +146,8 @@ struct security_class_mapping secclass_map[] = {
 	{ "memprotect", { "mmap_zero", NULL } },
 	{ "peer", { "recv", NULL } },
 	{ "capability2",
-	  { "mac_override", "mac_admin", "syslog", "wake_alarm", "block_suspend",
-	    NULL } },
+	  { "mac_override", "mac_admin", "syslog", "wake_alarm",
+	    "block_suspend", "compromise_kernel", NULL } },
 	{ "kernel_service", { "use_as_override", "create_files_as", NULL } },
 	{ "tun_socket",
 	  { COMMON_SOCK_PERMS, NULL } },
-- 
1.8.0.2

[PATCH 03/15] Secure boot: Add a dummy kernel parameter that will switch on Secure Boot mode

[Matthew Garrett]

From: Josh Boyer <jwboyer@redhat.com>

This forcibly drops CAP_COMPROMISE_KERNEL from both cap_permitted and cap_bset
in the init_cred struct, which everything else inherits from.  This works on
any machine and can be used to develop even if the box doesn't have UEFI.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
---
 Documentation/kernel-parameters.txt |  7 +++++++
 kernel/cred.c                       | 17 +++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 363e348..832b39b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2654,6 +2654,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Note: increases power consumption, thus should only be
 			enabled if running jitter sensitive (HPC/RT) workloads.
 
+	secureboot_enable=
+			[KNL] Enables an emulated UEFI Secure Boot mode.  This
+			locks down various aspects of the kernel guarded by the
+			CAP_COMPROMISE_KERNEL capability.  This includes things
+			like /dev/mem, IO port access, and other areas.  It can
+			be used on non-UEFI machines for testing purposes.
+
 	security=	[SECURITY] Choose a security module to enable at boot.
 			If this boot parameter is not specified, only the first
 			security module asking for security registration will be
diff --git a/kernel/cred.c b/kernel/cred.c
index e0573a4..c3f4e3e 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -565,6 +565,23 @@ void __init cred_init(void)
 				     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 }
 
+void __init secureboot_enable()
+{
+	pr_info("Secure boot enabled\n");
+	cap_lower((&init_cred)->cap_bset, CAP_COMPROMISE_KERNEL);
+	cap_lower((&init_cred)->cap_permitted, CAP_COMPROMISE_KERNEL);
+}
+
+/* Dummy Secure Boot enable option to fake out UEFI SB=1 */
+static int __init secureboot_enable_opt(char *str)
+{
+	int sb_enable = !!simple_strtol(str, NULL, 0);
+	if (sb_enable)
+		secureboot_enable();
+	return 1;
+}
+__setup("secureboot_enable=", secureboot_enable_opt);
+
 /**
  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
  * @daemon: A userspace daemon to be used as a reference
-- 
1.8.0.2

[PATCH 04/15] efi: Enable secure boot lockdown automatically when enabled in firmware

[Matthew Garrett]

The firmware has a set of flags that indicate whether secure boot is enabled
and enforcing. Use them to indicate whether the kernel should lock itself
down.  We also indicate the machine is in secure boot mode by adding the
EFI_SECURE_BOOT bit for use with efi_enabled.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: Josh Boyer <jwboyer@redhat.com>
---
 Documentation/x86/zero-page.txt       |  2 ++
 arch/x86/boot/compressed/eboot.c      | 32 ++++++++++++++++++++++++++++++++
 arch/x86/include/uapi/asm/bootparam.h |  3 ++-
 arch/x86/kernel/setup.c               |  5 +++++
 include/linux/cred.h                  |  2 ++
 include/linux/efi.h                   |  1 +
 6 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/Documentation/x86/zero-page.txt b/Documentation/x86/zero-page.txt
index cf5437d..7f9ed48 100644
--- a/Documentation/x86/zero-page.txt
+++ b/Documentation/x86/zero-page.txt
@@ -27,6 +27,8 @@ Offset	Proto	Name		Meaning
 1E9/001	ALL	eddbuf_entries	Number of entries in eddbuf (below)
 1EA/001	ALL	edd_mbr_sig_buf_entries	Number of entries in edd_mbr_sig_buffer
 				(below)
+1EB/001	ALL	kbd_status	Numlock is enabled
+1EC/001	ALL	secure_boot	Kernel should enable secure boot lockdowns
 290/040	ALL	edd_mbr_sig_buffer EDD MBR signatures
 2D0/A00	ALL	e820_map	E820 memory map table
 				(array of struct e820entry)
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 18e329c..f44adce 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -848,6 +848,36 @@ fail:
 	return status;
 }
 
+static int get_secure_boot(efi_system_table_t *_table)
+{
+	u8 sb, setup;
+	unsigned long datasize = sizeof(sb);
+	efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
+	efi_status_t status;
+
+	status = efi_call_phys5(sys_table->runtime->get_variable,
+				L"SecureBoot", &var_guid, NULL, &datasize, &sb);
+
+	if (status != EFI_SUCCESS)
+		return 0;
+
+	if (sb == 0)
+		return 0;
+
+
+	status = efi_call_phys5(sys_table->runtime->get_variable,
+				L"SetupMode", &var_guid, NULL, &datasize,
+				&setup);
+
+	if (status != EFI_SUCCESS)
+		return 0;
+
+	if (setup == 1)
+		return 0;
+
+	return 1;
+}
+
 /*
  * Because the x86 boot code expects to be passed a boot_params we
  * need to create one ourselves (usually the bootloader would create
@@ -1142,6 +1172,8 @@ struct boot_params *efi_main(void *handle, efi_system_table_t *_table,
 	if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
 		goto fail;
 
+	boot_params->secure_boot = get_secure_boot(sys_table);
+
 	setup_graphics(boot_params);
 
 	setup_efi_pci(boot_params);
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index 92862cd..422e056 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -115,7 +115,8 @@ struct boot_params {
 	__u8  eddbuf_entries;				/* 0x1e9 */
 	__u8  edd_mbr_sig_buf_entries;			/* 0x1ea */
 	__u8  kbd_status;				/* 0x1eb */
-	__u8  _pad6[5];					/* 0x1ec */
+	__u8  secure_boot;				/* 0x1ec */
+	__u8  _pad6[4];					/* 0x1ed */
 	struct setup_header hdr;    /* setup header */	/* 0x1f1 */
 	__u8  _pad7[0x290-0x1f1-sizeof(struct setup_header)];
 	__u32 edd_mbr_sig_buffer[EDD_MBR_SIG_MAX];	/* 0x290 */
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 8b24289..5355a54 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1042,6 +1042,11 @@ void __init setup_arch(char **cmdline_p)
 
 	io_delay_init();
 
+	if (boot_params.secure_boot) {
+		set_bit(EFI_SECURE_BOOT, &x86_efi_facility);
+		secureboot_enable();
+	}
+
 	/*
 	 * Parse the ACPI tables for possible boot-time SMP configuration.
 	 */
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 04421e8..9e69542 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -156,6 +156,8 @@ extern int set_security_override_from_ctx(struct cred *, const char *);
 extern int set_create_files_as(struct cred *, struct inode *);
 extern void __init cred_init(void);
 
+extern void secureboot_enable(void);
+
 /*
  * check for validity of credentials
  */
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 7a9498a..1ae16b6 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -627,6 +627,7 @@ extern int __init efi_setup_pcdp_console(char *);
 #define EFI_RUNTIME_SERVICES	3	/* Can we use runtime services? */
 #define EFI_MEMMAP		4	/* Can we use EFI memory map? */
 #define EFI_64BIT		5	/* Is the firmware 64-bit? */
+#define EFI_SECURE_BOOT	6	/* Are we in Secure Boot mode? */
 
 #ifdef CONFIG_EFI
 # ifdef CONFIG_X86
-- 
1.8.0.2

[PATCH 05/15] PCI: Lock down BAR access in secure boot environments

[Matthew Garrett]

Any hardware that can potentially generate DMA has to be locked down from
userspace in order to avoid it being possible for an attacker to cause
arbitrary kernel behaviour. Default to paranoid - in future we can
potentially relax this for sufficiently IOMMU-isolated devices.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 drivers/pci/pci-sysfs.c | 9 +++++++++
 drivers/pci/proc.c      | 8 +++++++-
 drivers/pci/syscall.c   | 2 +-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 9c6e9bb..b966089 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -622,6 +622,9 @@ pci_write_config(struct file* filp, struct kobject *kobj,
 	loff_t init_off = off;
 	u8 *data = (u8*) buf;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	if (off > dev->cfg_size)
 		return 0;
 	if (off + count > dev->cfg_size) {
@@ -928,6 +931,9 @@ pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
 	resource_size_t start, end;
 	int i;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	for (i = 0; i < PCI_ROM_RESOURCE; i++)
 		if (res == &pdev->resource[i])
 			break;
@@ -1035,6 +1041,9 @@ pci_write_resource_io(struct file *filp, struct kobject *kobj,
 		      struct bin_attribute *attr, char *buf,
 		      loff_t off, size_t count)
 {
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		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 9b8505c..35580bc 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -139,6 +139,9 @@ proc_bus_pci_write(struct file *file, const char __user *buf, size_t nbytes, lof
 	int size = dp->size;
 	int cnt;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	if (pos >= size)
 		return 0;
 	if (nbytes >= size)
@@ -219,6 +222,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 #endif /* HAVE_PCI_MMAP */
 	int ret = 0;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	switch (cmd) {
 	case PCIIOC_CONTROLLER:
 		ret = pci_domain_nr(dev->bus);
@@ -259,7 +265,7 @@ 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;
 
-	if (!capable(CAP_SYS_RAWIO))
+	if (!capable(CAP_SYS_RAWIO) || !capable(CAP_COMPROMISE_KERNEL))
 		return -EPERM;
 
 	/* Make sure the caller is mapping a real resource for this device */
diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index e1c1ec5..97e785f 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -92,7 +92,7 @@ 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) || !capable(CAP_COMPROMISE_KERNEL))
 		return -EPERM;
 
 	dev = pci_get_bus_and_slot(bus, dfn);
-- 
1.8.0.2

[PATCH 06/15] x86: Lock down IO port access in secure boot environments

[Matthew Garrett]

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.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 arch/x86/kernel/ioport.c | 4 ++--
 drivers/char/mem.c       | 3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 8c96897..a2578c4 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -28,7 +28,7 @@ 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) || !capable(CAP_COMPROMISE_KERNEL)))
 		return -EPERM;
 
 	/*
@@ -102,7 +102,7 @@ long sys_iopl(unsigned int level, struct pt_regs *regs)
 		return -EINVAL;
 	/* Trying to gain more privileges? */
 	if (level > old) {
-		if (!capable(CAP_SYS_RAWIO))
+		if (!capable(CAP_SYS_RAWIO) || !capable(CAP_COMPROMISE_KERNEL))
 			return -EPERM;
 	}
 	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index c6fa3bc..fc28099 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -597,6 +597,9 @@ static ssize_t write_port(struct file *file, const char __user *buf,
 	unsigned long i = *ppos;
 	const char __user * tmp = buf;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	if (!access_ok(VERIFY_READ, buf, count))
 		return -EFAULT;
 	while (count-- > 0 && i < 65536) {
-- 
1.8.0.2

[PATCH 07/15] ACPI: Limit access to custom_method

[Matthew Garrett]

It must be impossible for even root to get code executed in kernel context
under a secure boot environment. custom_method effectively allows arbitrary
access to system memory, so it needs to have a capability check here.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 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 5d42c24..247d58b 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 (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	if (!(*ppos)) {
 		/* parse the table header to get the table length */
 		if (count <= sizeof(struct acpi_table_header))
-- 
1.8.0.2

[PATCH 08/15] asus-wmi: Restrict debugfs interface

[Matthew Garrett]

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. Add a capability check to prevent that.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 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 f80ae4d..059195f 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1521,6 +1521,9 @@ static int show_dsts(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval);
 
 	if (err < 0)
@@ -1537,6 +1540,9 @@ static int show_devs(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param,
 				    &retval);
 
@@ -1561,6 +1567,9 @@ static int show_call(struct seq_file *m, void *data)
 	union acpi_object *obj;
 	acpi_status status;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID,
 				     1, asus->debug.method_id,
 				     &input, &output);
-- 
1.8.0.2

[PATCH 09/15] Restrict /dev/mem and /dev/kmem in secure boot setups

[Matthew Garrett]

Allowing users to write to address space makes it possible for the kernel
to be subverted. Restrict this when we need to protect the kernel.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 drivers/char/mem.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index fc28099..b5df7a8 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -158,6 +158,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
 	unsigned long copied;
 	void *ptr;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	if (!valid_phys_addr_range(p, count))
 		return -EFAULT;
 
@@ -530,6 +533,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
 	char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 	int err = 0;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	if (p < (unsigned long) high_memory) {
 		unsigned long to_write = min_t(unsigned long, count,
 					       (unsigned long)high_memory - p);
-- 
1.8.0.2

[PATCH 10/15] acpi: Ignore acpi_rsdp kernel parameter in a secure boot environment

[Matthew Garrett]

From: Josh Boyer <jwboyer@redhat.com>

This option allows userspace to pass the RSDP address to the kernel.  This
could potentially be used to circumvent the secure boot trust model.
We ignore the setting if we don't have the CAP_COMPROMISE_KERNEL capability.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
---
 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 bd22f86..88251d2 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -246,7 +246,7 @@ early_param("acpi_rsdp", setup_acpi_rsdp);
 acpi_physical_address __init acpi_os_get_root_pointer(void)
 {
 #ifdef CONFIG_KEXEC
-	if (acpi_rsdp)
+	if (acpi_rsdp && capable(CAP_COMPROMISE_KERNEL))
 		return acpi_rsdp;
 #endif
 
-- 
1.8.0.2

[PATCH 11/15] Add EFI signature data types

[Matthew Garrett]

From: Dave Howells <dhowells@redhat.com>

Add the data types that are used for containing hashes, keys and certificates
for cryptographic verification.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 include/linux/efi.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 1ae16b6..de7021d 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -388,6 +388,12 @@ typedef efi_status_t efi_query_capsule_caps_t(efi_capsule_header_t **capsules,
 #define EFI_FILE_SYSTEM_GUID \
     EFI_GUID(  0x964e5b22, 0x6459, 0x11d2, 0x8e, 0x39, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b )
 
+#define EFI_CERT_SHA256_GUID \
+    EFI_GUID(  0xc1c41626, 0x504c, 0x4092, 0xac, 0xa9, 0x41, 0xf9, 0x36, 0x93, 0x43, 0x28 )
+
+#define EFI_CERT_X509_GUID \
+    EFI_GUID(  0xa5c059a1, 0x94e4, 0x4aa7, 0x87, 0xb5, 0xab, 0x15, 0x5c, 0x2b, 0xf0, 0x72 )
+
 typedef struct {
 	efi_guid_t guid;
 	u64 table;
@@ -523,6 +529,20 @@ typedef struct {
 
 #define EFI_INVALID_TABLE_ADDR		(~0UL)
 
+typedef struct  {
+	efi_guid_t signature_owner;
+	u8 signature_data[];
+} efi_signature_data_t;
+
+typedef struct {
+	efi_guid_t signature_type;
+	u32 signature_list_size;
+	u32 signature_header_size;
+	u32 signature_size;
+	u8 signature_header[];
+	/* efi_signature_data_t signatures[][] */
+} efi_signature_list_t;
+
 /*
  * All runtime access to EFI goes through this structure:
  */
-- 
1.8.0.2

[PATCH 12/15] Add an EFI signature blob parser and key loader.

[Matthew Garrett]

From: Dave Howells <dhowells@redhat.com>

X.509 certificates are loaded into the specified keyring as asymmetric type
keys.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 crypto/asymmetric_keys/Kconfig      |   8 +++
 crypto/asymmetric_keys/Makefile     |   1 +
 crypto/asymmetric_keys/efi_parser.c | 108 ++++++++++++++++++++++++++++++++++++
 include/linux/efi.h                 |   4 ++
 4 files changed, 121 insertions(+)
 create mode 100644 crypto/asymmetric_keys/efi_parser.c

diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
index 6d2c2ea..ace9c30 100644
--- a/crypto/asymmetric_keys/Kconfig
+++ b/crypto/asymmetric_keys/Kconfig
@@ -35,4 +35,12 @@ config X509_CERTIFICATE_PARSER
 	  data and provides the ability to instantiate a crypto key from a
 	  public key packet found inside the certificate.
 
+config EFI_SIGNATURE_LIST_PARSER
+	bool "EFI signature list parser"
+	depends on EFI
+	select X509_CERTIFICATE_PARSER
+	help
+	  This option provides support for parsing EFI signature lists for
+	  X.509 certificates and turning them into keys.
+
 endif # ASYMMETRIC_KEY_TYPE
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index 0727204..cd8388e 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -8,6 +8,7 @@ asymmetric_keys-y := asymmetric_type.o signature.o
 
 obj-$(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += public_key.o
 obj-$(CONFIG_PUBLIC_KEY_ALGO_RSA) += rsa.o
+obj-$(CONFIG_EFI_SIGNATURE_LIST_PARSER) += efi_parser.o
 
 #
 # X.509 Certificate handling
diff --git a/crypto/asymmetric_keys/efi_parser.c b/crypto/asymmetric_keys/efi_parser.c
new file mode 100644
index 0000000..636feb1
--- /dev/null
+++ b/crypto/asymmetric_keys/efi_parser.c
@@ -0,0 +1,108 @@
+/* EFI signature/key/certificate list parser
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#define pr_fmt(fmt) "EFI: "fmt
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/err.h>
+#include <linux/efi.h>
+#include <keys/asymmetric-type.h>
+
+static __initdata efi_guid_t efi_cert_x509_guid = EFI_CERT_X509_GUID;
+
+/**
+ * parse_efi_signature_list - Parse an EFI signature list for certificates
+ * @data: The data blob to parse
+ * @size: The size of the data blob
+ * @keyring: The keyring to add extracted keys to
+ */
+int __init parse_efi_signature_list(const void *data, size_t size, struct key *keyring)
+{
+	unsigned offs = 0;
+	size_t lsize, esize, hsize, elsize;
+
+	pr_devel("-->%s(,%zu)\n", __func__, size);
+
+	while (size > 0) {
+		efi_signature_list_t list;
+		const efi_signature_data_t *elem;
+		key_ref_t key;
+
+		if (size < sizeof(list))
+			return -EBADMSG;
+
+		memcpy(&list, data, sizeof(list));
+		pr_devel("LIST[%04x] guid=%pUl ls=%x hs=%x ss=%x\n",
+			 offs,
+			 list.signature_type.b, list.signature_list_size,
+			 list.signature_header_size, list.signature_size);
+
+		lsize = list.signature_list_size;
+		hsize = list.signature_header_size;
+		esize = list.signature_size;
+		elsize = lsize - sizeof(list) - hsize;
+
+		if (lsize > size) {
+			pr_devel("<--%s() = -EBADMSG [overrun @%x]\n",
+				 __func__, offs);
+			return -EBADMSG;
+		}
+		if (lsize < sizeof(list) ||
+		    lsize - sizeof(list) < hsize ||
+		    esize < sizeof(*elem) ||
+		    elsize < esize ||
+		    elsize % esize != 0) {
+			pr_devel("- bad size combo @%x\n", offs);
+			return -EBADMSG;
+		}
+
+		if (efi_guidcmp(list.signature_type, efi_cert_x509_guid) != 0) {
+			data += lsize;
+			size -= lsize;
+			offs += lsize;
+			continue;
+		}
+
+		data += sizeof(list) + hsize;
+		size -= sizeof(list) + hsize;
+		offs += sizeof(list) + hsize;
+
+		for (; elsize > 0; elsize -= esize) {
+			elem = data;
+
+			pr_devel("ELEM[%04x]\n", offs);
+
+			key = key_create_or_update(
+				make_key_ref(keyring, 1),
+				"asymmetric",
+				NULL,
+				&elem->signature_data,
+				esize - sizeof(*elem),
+				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				KEY_USR_VIEW,
+				KEY_ALLOC_NOT_IN_QUOTA);
+
+			if (IS_ERR(key))
+				pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
+				       PTR_ERR(key));
+			else
+				pr_notice("Loaded cert '%s' linked to '%s'\n",
+					  key_ref_to_ptr(key)->description,
+					  keyring->description);
+
+			data += esize;
+			size -= esize;
+			offs += esize;
+		}
+	}
+
+	return 0;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index de7021d..64b3e55 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -612,6 +612,10 @@ extern int efi_set_rtc_mmss(unsigned long nowtime);
 extern void efi_reserve_boot_services(void);
 extern struct efi_memory_map memmap;
 
+struct key;
+extern int __init parse_efi_signature_list(const void *data, size_t size,
+					   struct key *keyring);
+
 /**
  * efi_range_is_wc - check the WC bit on an address range
  * @start: starting kvirt address
-- 
1.8.0.2

[PATCH 13/15] MODSIGN: Add module certificate blacklist keyring

[Matthew Garrett]

From: Josh Boyer <jwboyer@redhat.com>

This adds an additional keyring that is used to store certificates that
are blacklisted.  This keyring is searched first when loading signed modules
and if the module's certificate is found, it will refuse to load.  This is
useful in cases where third party certificates are used for module signing.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
---
 init/Kconfig             |  8 ++++++++
 kernel/modsign_pubkey.c  | 14 ++++++++++++++
 kernel/module-internal.h |  3 +++
 kernel/module_signing.c  | 12 ++++++++++++
 4 files changed, 37 insertions(+)

diff --git a/init/Kconfig b/init/Kconfig
index be8b7f5..d972b77 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1665,6 +1665,14 @@ config MODULE_SIG_FORCE
 	  Reject unsigned modules or signed modules for which we don't have a
 	  key.  Without this, such modules will simply taint the kernel.
 
+config MODULE_SIG_BLACKLIST
+	bool "Support for blacklisting module signature certificates"
+	depends on MODULE_SIG
+	help
+	  This adds support for keeping a blacklist of certificates that
+	  should not pass module signature verification.  If a module is
+	  signed with something in this keyring, the load will be rejected.
+
 choice
 	prompt "Which hash algorithm should modules be signed with?"
 	depends on MODULE_SIG
diff --git a/kernel/modsign_pubkey.c b/kernel/modsign_pubkey.c
index 2b6e699..4cd408d 100644
--- a/kernel/modsign_pubkey.c
+++ b/kernel/modsign_pubkey.c
@@ -17,6 +17,9 @@
 #include "module-internal.h"
 
 struct key *modsign_keyring;
+#ifdef CONFIG_MODULE_SIG_BLACKLIST
+struct key *modsign_blacklist;
+#endif
 
 extern __initdata const u8 modsign_certificate_list[];
 extern __initdata const u8 modsign_certificate_list_end[];
@@ -43,6 +46,17 @@ static __init int module_verify_init(void)
 	if (IS_ERR(modsign_keyring))
 		panic("Can't allocate module signing keyring\n");
 
+#ifdef CONFIG_MODULE_SIG_BLACKLIST
+	modsign_blacklist = keyring_alloc(".modsign_blacklist",
+				    KUIDT_INIT(0), KGIDT_INIT(0),
+				    current_cred(),
+				    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				    KEY_USR_VIEW | KEY_USR_READ,
+				    KEY_ALLOC_NOT_IN_QUOTA, NULL);
+	if (IS_ERR(modsign_blacklist))
+		panic("Can't allocate module signing blacklist keyring\n");
+#endif
+
 	return 0;
 }
 
diff --git a/kernel/module-internal.h b/kernel/module-internal.h
index 24f9247..51a8380 100644
--- a/kernel/module-internal.h
+++ b/kernel/module-internal.h
@@ -10,5 +10,8 @@
  */
 
 extern struct key *modsign_keyring;
+#ifdef CONFIG_MODULE_SIG_BLACKLIST
+extern struct key *modsign_blacklist;
+#endif
 
 extern int mod_verify_sig(const void *mod, unsigned long *_modlen);
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index f2970bd..5423195 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -157,6 +157,18 @@ static struct key *request_asymmetric_key(const char *signer, size_t signer_len,
 
 	pr_debug("Look up: \"%s\"\n", id);
 
+#ifdef CONFIG_MODULE_SIG_BLACKLIST
+	key = keyring_search(make_key_ref(modsign_blacklist, 1),
+				   &key_type_asymmetric, id);
+	if (!IS_ERR(key)) {
+		/* module is signed with a cert in the blacklist.  reject */
+		pr_err("Module key '%s' is in blacklist\n", id);
+		key_ref_put(key);
+		kfree(id);
+		return ERR_PTR(-EKEYREJECTED);
+	}
+#endif
+
 	key = keyring_search(make_key_ref(modsign_keyring, 1),
 			     &key_type_asymmetric, id);
 	if (IS_ERR(key))
-- 
1.8.0.2

[PATCH 14/15] MODSIGN: Import certificates from UEFI Secure Boot

[Matthew Garrett]

From: Josh Boyer <jwboyer@redhat.com>

Secure Boot stores a list of allowed certificates in the 'db' variable.
This imports those certificates into the module signing keyring.  This
allows for a third party signing certificate to be used in conjunction
with signed modules.  By importing the public certificate into the 'db'
variable, a user can allow a module signed with that certificate to
load.  The shim UEFI bootloader has a similar certificate list stored
in the 'MokListRT' variable.  We import those as well.

In the opposite case, Secure Boot maintains a list of disallowed
certificates in the 'dbx' variable.  We load those certificates into
the newly introduced module blacklist keyring and forbid any module
signed with those from loading.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
---
 include/linux/efi.h   |  6 ++++
 init/Kconfig          |  9 ++++++
 kernel/Makefile       |  3 ++
 kernel/modsign_uefi.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 108 insertions(+)
 create mode 100644 kernel/modsign_uefi.c

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 64b3e55..76fe526 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -394,6 +394,12 @@ typedef efi_status_t efi_query_capsule_caps_t(efi_capsule_header_t **capsules,
 #define EFI_CERT_X509_GUID \
     EFI_GUID(  0xa5c059a1, 0x94e4, 0x4aa7, 0x87, 0xb5, 0xab, 0x15, 0x5c, 0x2b, 0xf0, 0x72 )
 
+#define EFI_IMAGE_SECURITY_DATABASE_GUID \
+    EFI_GUID(  0xd719b2cb, 0x3d3a, 0x4596, 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f )
+
+#define EFI_SHIM_LOCK_GUID \
+    EFI_GUID(  0x605dab50, 0xe046, 0x4300, 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23 )
+
 typedef struct {
 	efi_guid_t guid;
 	u64 table;
diff --git a/init/Kconfig b/init/Kconfig
index d972b77..27e3a82 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1673,6 +1673,15 @@ config MODULE_SIG_BLACKLIST
 	  should not pass module signature verification.  If a module is
 	  signed with something in this keyring, the load will be rejected.
 
+config MODULE_SIG_UEFI
+	bool "Allow modules signed with certs stored in UEFI"
+	depends on MODULE_SIG && MODULE_SIG_BLACKLIST && EFI
+	select EFI_SIGNATURE_LIST_PARSER
+	help
+	  This will import certificates stored in UEFI and allow modules
+	  signed with those to be loaded.  It will also disallow loading
+	  of modules stored in the UEFI dbx variable.
+
 choice
 	prompt "Which hash algorithm should modules be signed with?"
 	depends on MODULE_SIG
diff --git a/kernel/Makefile b/kernel/Makefile
index 6c072b6..8848829 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -55,6 +55,7 @@ obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
 obj-$(CONFIG_UID16) += uid16.o
 obj-$(CONFIG_MODULES) += module.o
 obj-$(CONFIG_MODULE_SIG) += module_signing.o modsign_pubkey.o modsign_certificate.o
+obj-$(CONFIG_MODULE_SIG_UEFI) += modsign_uefi.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o
@@ -114,6 +115,8 @@ obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
 
 $(obj)/configs.o: $(obj)/config_data.h
 
+$(obj)/modsign_uefi.o: KBUILD_CFLAGS += -fshort-wchar
+
 # config_data.h contains the same information as ikconfig.h but gzipped.
 # Info from config_data can be extracted from /proc/config*
 targets += config_data.gz
diff --git a/kernel/modsign_uefi.c b/kernel/modsign_uefi.c
new file mode 100644
index 0000000..b9237d7
--- /dev/null
+++ b/kernel/modsign_uefi.c
@@ -0,0 +1,90 @@
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/cred.h>
+#include <linux/err.h>
+#include <linux/efi.h>
+#include <keys/asymmetric-type.h>
+#include "module-internal.h"
+
+static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, unsigned long *size)
+{
+	efi_status_t status;
+	unsigned long lsize = 4;
+	unsigned long tmpdb[4];
+	void *db = NULL;
+
+	status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
+	if (status != EFI_BUFFER_TOO_SMALL) {
+		pr_err("Couldn't get size: 0x%lx\n", status);
+		return NULL;
+	}
+
+	db = kmalloc(lsize, GFP_KERNEL);
+	if (!db) {
+		pr_err("Couldn't allocate memory for uefi cert list\n");
+		goto out;
+	}
+
+	status = efi.get_variable(name, guid, NULL, &lsize, db);
+	if (status != EFI_SUCCESS) {
+		kfree(db);
+		db = NULL;
+		pr_err("Error reading db var: 0x%lx\n", status);
+	}
+out:
+	*size = lsize;
+	return db;
+}
+
+/*
+ *  * Load the certs contained in the UEFI databases
+ *   */
+static int __init load_uefi_certs(void)
+{
+	efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
+	efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
+	void *db = NULL, *dbx = NULL, *mok = NULL;
+	unsigned long dbsize = 0, dbxsize = 0, moksize = 0;
+	int rc = 0;
+
+	/* Check if SB is enabled and just return if not */
+	if (!efi_enabled(EFI_SECURE_BOOT))
+		return 0;
+
+	/* Get db, MokListRT, and dbx.  They might not exist, so it isn't
+	 * an error if we can't get them.
+	 */
+	db = get_cert_list(L"db", &secure_var, &dbsize);
+	if (!db) {
+		pr_err("MODSIGN: Couldn't get UEFI db list\n");
+	} else {
+		rc = parse_efi_signature_list(db, dbsize, modsign_keyring);
+		if (rc)
+			pr_err("Couldn't parse db signatures: %d\n", rc);
+		kfree(db);
+	}
+
+	mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
+	if (!mok) {
+		pr_info("MODSIGN: Couldn't get UEFI MokListRT\n");
+	} else {
+		rc = parse_efi_signature_list(mok, moksize, modsign_keyring);
+		if (rc)
+			pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
+		kfree(mok);
+	}
+
+	dbx = get_cert_list(L"dbx", &secure_var, &dbxsize);
+	if (!dbx) {
+		pr_info("MODSIGN: Couldn't get UEFI dbx list\n");
+	} else {
+		rc = parse_efi_signature_list(dbx, dbxsize,
+			modsign_blacklist);
+		if (rc)
+			pr_err("Couldn't parse dbx signatures: %d\n", rc);
+		kfree(dbx);
+	}
+
+	return rc;
+}
+late_initcall(load_uefi_certs);
-- 
1.8.0.2

[PATCH 15/15] MODSIGN: Always enforce module signing in a Secure Boot environment

[Matthew Garrett]

From: Josh Boyer <jwboyer@redhat.com>

If a machine is booted into a Secure Boot environment, we need to
protect the trust model.  This requires that all modules be signed
with a key that is in the kernel's _modsign keyring.  The checks for
this are already done via the 'sig_enforce' module parameter.  Make
this visible within the kernel and force it to be true.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
---
 kernel/cred.c   | 8 ++++++++
 kernel/module.c | 4 ++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index c3f4e3e..c5554e0 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -565,11 +565,19 @@ void __init cred_init(void)
 				     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 }
 
+#ifdef CONFIG_MODULE_SIG
+extern bool sig_enforce;
+#endif
+
 void __init secureboot_enable()
 {
 	pr_info("Secure boot enabled\n");
 	cap_lower((&init_cred)->cap_bset, CAP_COMPROMISE_KERNEL);
 	cap_lower((&init_cred)->cap_permitted, CAP_COMPROMISE_KERNEL);
+#ifdef CONFIG_MODULE_SIG
+	/* Enable module signature enforcing */
+	sig_enforce = true;
+#endif
 }
 
 /* Dummy Secure Boot enable option to fake out UEFI SB=1 */
diff --git a/kernel/module.c b/kernel/module.c
index eab0827..93a16dc 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -109,9 +109,9 @@ struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */
 
 #ifdef CONFIG_MODULE_SIG
 #ifdef CONFIG_MODULE_SIG_FORCE
-static bool sig_enforce = true;
+bool sig_enforce = true;
 #else
-static bool sig_enforce = false;
+bool sig_enforce = false;
 
 static int param_set_bool_enable_only(const char *val,
 				      const struct kernel_param *kp)
-- 
1.8.0.2

Re: [PATCH 10/15] acpi: Ignore acpi_rsdp kernel parameter in a secure boot environment

[Dave Young]

On Tue, Jan 29, 2013 at 12:42 AM, Matthew Garrett
<matthew.garrett@nebula.com> wrote:
> From: Josh Boyer <jwboyer@redhat.com>
>
> This option allows userspace to pass the RSDP address to the kernel.  This
> could potentially be used to circumvent the secure boot trust model.
> We ignore the setting if we don't have the CAP_COMPROMISE_KERNEL capability.
>
> Signed-off-by: Josh Boyer <jwboyer@redhat.com>
> ---
>  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 bd22f86..88251d2 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -246,7 +246,7 @@ early_param("acpi_rsdp", setup_acpi_rsdp);
>  acpi_physical_address __init acpi_os_get_root_pointer(void)
>  {
>  #ifdef CONFIG_KEXEC
> -       if (acpi_rsdp)
> +       if (acpi_rsdp && capable(CAP_COMPROMISE_KERNEL))


This caused an issue in a kdump test even without secure boot enabled.
Looks like security subsystem init is not initialized yet at this
point.

See redhat bug 906225:
https://bugzilla.redhat.com/show_bug.cgi?id=906225


>                 return acpi_rsdp;
>  #endif
>
> --
> 1.8.0.2
>
> --
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> the body of a message to majordomo@vger.kernel.org
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> Please read the FAQ at  http://www.tux.org/lkml/



-- 
Regards
Dave

Re: [PATCH 00/15] Secure boot policy support

[Yves-Alexis Perez]

[-- Attachment #1: Type: text/plain, Size: 860 bytes --]

On lun., 2013-01-28 at 11:42 -0500, Matthew Garrett wrote:
> Secure boot makes it possible to ensure that the on-disk representation of
> the kernel hasn't been modified. This can be sidestepped if the in-memory
> representation can be trivially altered. We currently have a large number
> of interfaces that permit root to perform effectively arbitrary
> modifications to the kernel, so this patchset introduces a new capability
> ("CAP_COMPROMISE_KERNEL") that controls whether or not these features are
> available. The aim is for this to be useful in any other situations where
> kernel integrity can be assured by some other mechanism rather than special
> casing UEFI.
> 
Wouldn't it make sense to prevent writing to MSRs too? Something like
c903f0456bc69176912dee6dd25c6a66ee1aed00 with CAP_COMPROMISE_KERNEL?

Regards,
-- 
Yves-Alexis

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 490 bytes --]

Re: [PATCH 10/15] acpi: Ignore acpi_rsdp kernel parameter in a secure boot environment

[Josh Boyer]

On Sun, Feb 17, 2013 at 05:00:23PM +0800, Dave Young wrote:
> On Tue, Jan 29, 2013 at 12:42 AM, Matthew Garrett
> <matthew.garrett@nebula.com> wrote:
> > From: Josh Boyer <jwboyer@redhat.com>
> >
> > This option allows userspace to pass the RSDP address to the kernel.  This
> > could potentially be used to circumvent the secure boot trust model.
> > We ignore the setting if we don't have the CAP_COMPROMISE_KERNEL capability.
> >
> > Signed-off-by: Josh Boyer <jwboyer@redhat.com>
> > ---
> >  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 bd22f86..88251d2 100644
> > --- a/drivers/acpi/osl.c
> > +++ b/drivers/acpi/osl.c
> > @@ -246,7 +246,7 @@ early_param("acpi_rsdp", setup_acpi_rsdp);
> >  acpi_physical_address __init acpi_os_get_root_pointer(void)
> >  {
> >  #ifdef CONFIG_KEXEC
> > -       if (acpi_rsdp)
> > +       if (acpi_rsdp && capable(CAP_COMPROMISE_KERNEL))
> 
> 
> This caused an issue in a kdump test even without secure boot enabled.
> Looks like security subsystem init is not initialized yet at this
> point.
> 
> See redhat bug 906225:
> https://bugzilla.redhat.com/show_bug.cgi?id=906225

I've fixed this in a newer revision of the patch.  Basically we can't
rely on capable() working at this point because security_init hasn't
been called yet.  Sigh.

Despite the desire to not sprinkle if (!secure_boot) checks all over,
I'm thinking less and less that using a CAP is going to work.  Maybe
I'll come up with some kind of secure_kernel() function that can be set
per-arch or something and use that instead.  At least that would have
the semantics we're looking for without breaking in various places or
causing unintended side-effects in userspace.

josh