[PATCH 8/8] efi: Handle secure boot from UEFI-2.6 [ver #5]

From: David Howells
Date: Wed Dec 07 2016 - 08:19:11 EST


UEFI-2.6 adds a new variable, DeployedMode. If it exists, this must be 1
if we're to engage lockdown mode.

Reported-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

drivers/firmware/efi/libstub/secureboot.c | 16 +++++++++++++++-
include/linux/efi.h | 4 ++++
2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
index ba6ef717c66f..333b1594cce4 100644
--- a/drivers/firmware/efi/libstub/secureboot.c
+++ b/drivers/firmware/efi/libstub/secureboot.c
@@ -22,6 +22,9 @@ static const efi_char16_t const efi_SecureBoot_name[] = {
static const efi_char16_t const efi_SetupMode_name[] = {
'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0
};
+static const efi_char16_t const efi_DeployedMode_name[] = {
+ 'D', 'e', 'p', 'l', 'o', 'y', 'e', 'd', 'M', 'o', 'd', 'e', 0
+};

/* SHIM variables */
static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
@@ -40,7 +43,7 @@ static efi_char16_t const shim_MokSBState_name[] = {
enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg)
{
u32 attr;
- u8 secboot, setupmode, moksbstate;
+ u8 secboot, setupmode, deployedmode, moksbstate;
unsigned long size;
efi_status_t status;

@@ -59,6 +62,17 @@ enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg)
if (secboot == 0 || setupmode == 1)
goto secure_boot_disabled;

+ /* UEFI-2.6 requires DeployedMode to be 1. */
+ if (sys_table_arg->hdr.revision >= EFI_2_60_SYSTEM_TABLE_REVISION) {
+ size = sizeof(deployedmode);
+ status = get_efi_var(efi_DeployedMode_name, &efi_variable_guid,
+ NULL, &size, &deployedmode);
+ if (status != EFI_SUCCESS)
+ goto out_efi_err;
+ if (deployedmode == 0)
+ goto secure_boot_disabled;
+ }
+
/* See if a user has put shim into insecure mode. If so, and if the
* variable doesn't have the runtime attribute set, we might as well
* honor that.
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 135ca9c0c0b5..e1893f5002c3 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -645,6 +645,10 @@ typedef struct {

#define EFI_SYSTEM_TABLE_SIGNATURE ((u64)0x5453595320494249ULL)

+#define EFI_2_60_SYSTEM_TABLE_REVISION ((2 << 16) | (60))
+#define EFI_2_50_SYSTEM_TABLE_REVISION ((2 << 16) | (50))
+#define EFI_2_40_SYSTEM_TABLE_REVISION ((2 << 16) | (40))
+#define EFI_2_31_SYSTEM_TABLE_REVISION ((2 << 16) | (31))
#define EFI_2_30_SYSTEM_TABLE_REVISION ((2 << 16) | (30))
#define EFI_2_20_SYSTEM_TABLE_REVISION ((2 << 16) | (20))
#define EFI_2_10_SYSTEM_TABLE_REVISION ((2 << 16) | (10))