12:24 p.m.
From: Matthew Garrett <matthew.garrett(a)nebula.com>
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 enforces this automatically when enabled.
Signed-off-by: Matthew Garrett <matthew.garrett(a)nebula.com>
---
Documentation/x86/zero-page.txt | 2 ++
arch/x86/Kconfig | 11 ++++++
arch/x86/boot/compressed/eboot.c | 66 +++++++++++++++++++++++++++++++++++
arch/x86/include/uapi/asm/bootparam.h | 3 +-
arch/x86/kernel/setup.c | 6 ++++
include/linux/module.h | 6 ++++
kernel/module.c | 7 ++++
7 files changed, 100 insertions(+), 1 deletion(-)
diff --git a/Documentation/x86/zero-page.txt b/Documentation/x86/zero-page.txt
index 95a4d34af3fd..b8527c6b7646 100644
--- a/Documentation/x86/zero-page.txt
+++ b/Documentation/x86/zero-page.txt
@@ -31,6 +31,8 @@ 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 Secure boot is enabled in the firmware
1EF/001 ALL sentinel Used to detect broken bootloaders
290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
2D0/A00 ALL e820_map E820 memory map table
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index bada636d1065..d666ef8b616c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1786,6 +1786,17 @@ config EFI_MIXED
If unsure, say N.
+config EFI_SECURE_BOOT_SIG_ENFORCE
+ def_bool n
+ depends on EFI
+ prompt "Force module signing when UEFI Secure Boot is enabled"
+ ---help---
+ 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.
+ Say Y here to automatically enable module signature enforcement
+ when a system boots with UEFI Secure Boot enabled.
+
config SECCOMP
def_bool y
prompt "Enable seccomp to safely compute untrusted bytecode"
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index cc69e37548db..ebc85c1eefd6 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -12,6 +12,7 @@
#include <asm/efi.h>
#include <asm/setup.h>
#include <asm/desc.h>
+#include <asm/bootparam_utils.h>
#include "../string.h"
#include "eboot.h"
@@ -537,6 +538,67 @@ static void setup_efi_pci(struct boot_params *params)
efi_call_early(free_pool, pci_handle);
}
+static int get_secure_boot(void)
+{
+ u8 sb, setup;
+ unsigned long datasize = sizeof(sb);
+ efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
+ efi_status_t status;
+
+ status = efi_early->call((unsigned long)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_early->call((unsigned long)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;
+}
+
+
+/*
+ * See if we have Graphics Output Protocol
+ */
+static efi_status_t setup_gop(struct screen_info *si, efi_guid_t *proto,
+ unsigned long size)
+{
+ efi_status_t status;
+ void **gop_handle = NULL;
+
+ status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
+ size, (void **)&gop_handle);
+ if (status != EFI_SUCCESS)
+ return status;
+
+ status = efi_call_early(locate_handle,
+ EFI_LOCATE_BY_PROTOCOL,
+ proto, NULL, &size, gop_handle);
+ if (status != EFI_SUCCESS)
+ goto free_handle;
+
+ if (efi_early->is64)
+ status = setup_gop64(si, proto, size, gop_handle);
+ else
+ status = setup_gop32(si, proto, size, gop_handle);
+
+free_handle:
+ efi_call_early(free_pool, gop_handle);
+ return status;
+}
+
static efi_status_t
setup_uga32(void **uga_handle, unsigned long size, u32 *width, u32 *height)
{
@@ -1094,6 +1156,10 @@ struct boot_params *efi_main(struct efi_config *c,
else
setup_boot_services32(efi_early);
+ sanitize_boot_params(boot_params);
+
+ boot_params->secure_boot = get_secure_boot();
+
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 c18ce67495fa..2b3e5427097b 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -134,7 +134,8 @@ struct boot_params {
__u8 eddbuf_entries; /* 0x1e9 */
__u8 edd_mbr_sig_buf_entries; /* 0x1ea */
__u8 kbd_status; /* 0x1eb */
- __u8 _pad5[3]; /* 0x1ec */
+ __u8 secure_boot; /* 0x1ec */
+ __u8 _pad5[2]; /* 0x1ed */
/*
* The sentinel is set to a nonzero value (0xff) in header.S.
*
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index bbfbca5fea0c..d40e961753c9 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1160,6 +1160,12 @@ void __init setup_arch(char **cmdline_p)
io_delay_init();
+#ifdef CONFIG_EFI_SECURE_BOOT_SIG_ENFORCE
+ if (boot_params.secure_boot) {
+ enforce_signed_modules();
+ }
+#endif
+
/*
* Parse the ACPI tables for possible boot-time SMP configuration.
*/
diff --git a/include/linux/module.h b/include/linux/module.h
index 05bd6c989a0c..32327704e18d 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -260,6 +260,12 @@ extern const typeof(name) __mod_##type##__##name##_device_table \
struct notifier_block;
+#ifdef CONFIG_MODULE_SIG
+extern void enforce_signed_modules(void);
+#else
+static inline void enforce_signed_modules(void) {};
+#endif
+
#ifdef CONFIG_MODULES
extern int modules_disabled; /* for sysctl */
diff --git a/kernel/module.c b/kernel/module.c
index cb864505d020..cb1f1da69bf4 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -4285,6 +4285,13 @@ void module_layout(struct module *mod,
EXPORT_SYMBOL(module_layout);
#endif
+#ifdef CONFIG_MODULE_SIG
+void enforce_signed_modules(void)
+{
+ sig_enforce = true;
+}
+#endif
+
bool secure_modules(void)
{
#ifdef CONFIG_MODULE_SIG
--
2.9.3