From de8cb458625c164bb3f93c4e415e479afce8fa9d Mon Sep 17 00:00:00 2001 From: David Howells Date: Mon, 6 Feb 2017 11:22:43 +0000 Subject: efi: Get and store the secure boot status Get the firmware's secure-boot status in the kernel boot wrapper and stash it somewhere that the main kernel image can find. The efi_get_secureboot() function is extracted from the ARM stub and (a) generalised so that it can be called from x86 and (b) made to use efi_call_runtime() so that it can be run in mixed-mode. For x86, it is stored in boot_params and can be overridden by the boot loader or kexec. This allows secure-boot mode to be passed on to a new kernel. Suggested-by: Lukas Wunner Signed-off-by: David Howells Signed-off-by: Ard Biesheuvel Cc: Linus Torvalds Cc: Matt Fleming Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1486380166-31868-5-git-send-email-ard.biesheuvel@linaro.org [ Small readability edits. ] Signed-off-by: Ingo Molnar --- drivers/firmware/efi/libstub/Makefile | 2 +- drivers/firmware/efi/libstub/arm-stub.c | 63 +++---------------------------- drivers/firmware/efi/libstub/secureboot.c | 61 ++++++++++++++++++++++++++++++ 3 files changed, 68 insertions(+), 58 deletions(-) create mode 100644 drivers/firmware/efi/libstub/secureboot.c (limited to 'drivers/firmware') diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 33e0e2f1a730..f7425960f6a5 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -28,7 +28,7 @@ OBJECT_FILES_NON_STANDARD := y # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. KCOV_INSTRUMENT := n -lib-y := efi-stub-helper.o gop.o +lib-y := efi-stub-helper.o gop.o secureboot.o # include the stub's generic dependencies from lib/ when building for ARM/arm64 arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c index 6fca48c9e054..d4056c6be1ec 100644 --- a/drivers/firmware/efi/libstub/arm-stub.c +++ b/drivers/firmware/efi/libstub/arm-stub.c @@ -20,52 +20,6 @@ bool __nokaslr; -static int efi_get_secureboot(efi_system_table_t *sys_table_arg) -{ - static efi_char16_t const sb_var_name[] = { - 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 }; - static efi_char16_t const sm_var_name[] = { - 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 }; - - efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID; - efi_get_variable_t *f_getvar = sys_table_arg->runtime->get_variable; - u8 val; - unsigned long size = sizeof(val); - efi_status_t status; - - status = f_getvar((efi_char16_t *)sb_var_name, (efi_guid_t *)&var_guid, - NULL, &size, &val); - - if (status != EFI_SUCCESS) - goto out_efi_err; - - if (val == 0) - return 0; - - status = f_getvar((efi_char16_t *)sm_var_name, (efi_guid_t *)&var_guid, - NULL, &size, &val); - - if (status != EFI_SUCCESS) - goto out_efi_err; - - if (val == 1) - return 0; - - return 1; - -out_efi_err: - switch (status) { - case EFI_NOT_FOUND: - return 0; - case EFI_DEVICE_ERROR: - return -EIO; - case EFI_SECURITY_VIOLATION: - return -EACCES; - default: - return -EINVAL; - } -} - efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg, void *__image, void **__fh) { @@ -157,7 +111,7 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID; unsigned long reserve_addr = 0; unsigned long reserve_size = 0; - int secure_boot = 0; + enum efi_secureboot_mode secure_boot; struct screen_info *si; /* Check if we were booted by the EFI firmware */ @@ -227,19 +181,14 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, pr_efi_err(sys_table, "Failed to parse EFI cmdline options\n"); secure_boot = efi_get_secureboot(sys_table); - if (secure_boot > 0) - pr_efi(sys_table, "UEFI Secure Boot is enabled.\n"); - - if (secure_boot < 0) { - pr_efi_err(sys_table, - "could not determine UEFI Secure Boot status.\n"); - } /* - * Unauthenticated device tree data is a security hazard, so - * ignore 'dtb=' unless UEFI Secure Boot is disabled. + * Unauthenticated device tree data is a security hazard, so ignore + * 'dtb=' unless UEFI Secure Boot is disabled. We assume that secure + * boot is enabled if we can't determine its state. */ - if (secure_boot != 0 && strstr(cmdline_ptr, "dtb=")) { + if (secure_boot != efi_secureboot_mode_disabled && + strstr(cmdline_ptr, "dtb=")) { pr_efi(sys_table, "Ignoring DTB from command line.\n"); } else { status = handle_cmdline_files(sys_table, image, cmdline_ptr, diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c new file mode 100644 index 000000000000..b20b8b460d77 --- /dev/null +++ b/drivers/firmware/efi/libstub/secureboot.c @@ -0,0 +1,61 @@ +/* + * Secure boot handling. + * + * Copyright (C) 2013,2014 Linaro Limited + * Roy Franz + * + * This file is part of the Linux kernel, and is made available under the + * terms of the GNU General Public License version 2. + */ +#include +#include + +/* BIOS variables */ +static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID; +static const efi_char16_t const efi_SecureBoot_name[] = { + 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 +}; +static const efi_char16_t const efi_SetupMode_name[] = { + 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 +}; + +#define get_efi_var(name, vendor, ...) \ + efi_call_runtime(get_variable, \ + (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ + __VA_ARGS__); + +/* + * Determine whether we're in secure boot mode. + */ +enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg) +{ + u8 secboot, setupmode; + unsigned long size; + efi_status_t status; + + size = sizeof(secboot); + status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid, + NULL, &size, &secboot); + 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; + + pr_efi(sys_table_arg, "UEFI Secure Boot is enabled.\n"); + return efi_secureboot_mode_enabled; + +out_efi_err: + pr_efi_err(sys_table_arg, "Could not determine UEFI Secure Boot status.\n"); + if (status == EFI_NOT_FOUND) + return efi_secureboot_mode_disabled; + return efi_secureboot_mode_unknown; +} -- cgit v1.2.3-59-g8ed1b