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efi: generalize efi_get_secureboot

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Generalize the efi_get_secureboot() function so not only efistub but also
other subsystems can use it.

Note that the MokSbState handling is not factored out: the variable is
boot time only, and so it cannot be parameterized as easily. Also, the
IMA code will switch to this version in a future patch, and it does not
incorporate the MokSbState exception in the first place.

Note that the new efi_get_secureboot_mode() helper treats any failures
to read SetupMode as setup mode being disabled.

Co-developed-by: Chester Lin <clin@suse.com>
Signed-off-by: Chester Lin <clin@suse.com>
Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Chester Lin 2020-10-30 14:08:38 +08:00 committed by Ard Biesheuvel
parent 6edcf9dc2e
commit e1ac4b2406
4 changed files with 40 additions and 28 deletions
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2
arch/x86/boot/compressed/Makefile
View File

@ -35,7 +35,7 @@ cflags-$(CONFIG_X86_32) := -march=i386
cflags-$(CONFIG_X86_64) := -mcmodel=small -mno-red-zone
KBUILD_CFLAGS += $(cflags-y)
KBUILD_CFLAGS += -mno-mmx -mno-sse
KBUILD_CFLAGS += -ffreestanding
KBUILD_CFLAGS += -ffreestanding -fshort-wchar
KBUILD_CFLAGS += -fno-stack-protector
KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
KBUILD_CFLAGS += $(call cc-disable-warning, gnu)

2
drivers/firmware/efi/libstub/efistub.h
View File

@ -848,4 +848,6 @@ asmlinkage void __noreturn efi_enter_kernel(unsigned long entrypoint,
void efi_handle_post_ebs_state(void);
enum efi_secureboot_mode efi_get_secureboot(void);
#endif

41
drivers/firmware/efi/libstub/secureboot.c
View File

@ -12,15 +12,16 @@
#include "efistub.h"
/* BIOS variables */
static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
static const efi_char16_t efi_SecureBoot_name[] = L"SecureBoot";
static const efi_char16_t efi_SetupMode_name[] = L"SetupMode";
/* SHIM variables */
static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
static const efi_char16_t shim_MokSBState_name[] = L"MokSBState";
static efi_status_t get_var(efi_char16_t *name, efi_guid_t *vendor, u32 *attr,
unsigned long *data_size, void *data)
{
return get_efi_var(name, vendor, attr, data_size, data);
}
/*
* Determine whether we're in secure boot mode.
*
@ -30,26 +31,18 @@ static const efi_char16_t shim_MokSBState_name[] = L"MokSBState";
enum efi_secureboot_mode efi_get_secureboot(void)
{
u32 attr;
u8 secboot, setupmode, moksbstate;
unsigned long size;
enum efi_secureboot_mode mode;
efi_status_t status;
u8 moksbstate;
size = sizeof(secboot);
status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
NULL, &size, &secboot);
if (status == EFI_NOT_FOUND)
return efi_secureboot_mode_disabled;
if (status != EFI_SUCCESS)
goto out_efi_err;
size = sizeof(setupmode);
status = get_efi_var(efi_SetupMode_name, &efi_variable_guid,
NULL, &size, &setupmode);
if (status != EFI_SUCCESS)
goto out_efi_err;
if (secboot == 0 || setupmode == 1)
return efi_secureboot_mode_disabled;
mode = efi_get_secureboot_mode(get_var);
if (mode == efi_secureboot_mode_unknown) {
efi_err("Could not determine UEFI Secure Boot status.\n");
return efi_secureboot_mode_unknown;
}
if (mode != efi_secureboot_mode_enabled)
return mode;
/*
* See if a user has put the shim into insecure mode. If so, and if the
@ -69,8 +62,4 @@ enum efi_secureboot_mode efi_get_secureboot(void)
secure_boot_enabled:
efi_info("UEFI Secure Boot is enabled.\n");
return efi_secureboot_mode_enabled;
out_efi_err:
efi_err("Could not determine UEFI Secure Boot status.\n");
return efi_secureboot_mode_unknown;
}

23
include/linux/efi.h
View File

@ -1089,7 +1089,28 @@ enum efi_secureboot_mode {
efi_secureboot_mode_disabled,
efi_secureboot_mode_enabled,
};
enum efi_secureboot_mode efi_get_secureboot(void);
static inline
enum efi_secureboot_mode efi_get_secureboot_mode(efi_get_variable_t *get_var)
{
u8 secboot, setupmode = 0;
efi_status_t status;
unsigned long size;
size = sizeof(secboot);
status = get_var(L"SecureBoot", &EFI_GLOBAL_VARIABLE_GUID, NULL, &size,
&secboot);
if (status == EFI_NOT_FOUND)
return efi_secureboot_mode_disabled;
if (status != EFI_SUCCESS)
return efi_secureboot_mode_unknown;
size = sizeof(setupmode);
get_var(L"SetupMode", &EFI_GLOBAL_VARIABLE_GUID, NULL, &size, &setupmode);
if (secboot == 0 || setupmode == 1)
return efi_secureboot_mode_disabled;
return efi_secureboot_mode_enabled;
}
#ifdef CONFIG_RESET_ATTACK_MITIGATION
void efi_enable_reset_attack_mitigation(void);