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fu-efi-signature-list.c
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fu-efi-signature-list.c
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/*
* Copyright (C) 2020 Richard Hughes <richard@hughsie.com>
*
* SPDX-License-Identifier: LGPL-2.1+
*/
#define G_LOG_DOMAIN "FuEfiSignatureList"
#include "config.h"
#include <fwupd.h>
#include <string.h>
#include "fu-byte-array.h"
#include "fu-common.h"
#include "fu-efi-signature-list.h"
#include "fu-efi-signature-private.h"
#include "fu-mem.h"
/**
* FuEfiSignatureList:
*
* A UEFI signature list typically found in the `PK` and `KEK` keys.
*
* See also: [class@FuFirmware]
*/
struct _FuEfiSignatureList {
FuFirmware parent_instance;
};
G_DEFINE_TYPE(FuEfiSignatureList, fu_efi_signature_list, FU_TYPE_FIRMWARE)
const guint8 FU_EFI_SIGLIST_HEADER_MAGIC[] = {0x26, 0x16, 0xC4, 0xC1, 0x4C};
static gboolean
fu_efi_signature_list_parse_item(FuEfiSignatureList *self,
FuEfiSignatureKind sig_kind,
const guint8 *buf,
gsize bufsz,
gsize offset,
guint32 sig_size,
GError **error)
{
fwupd_guid_t guid;
gsize sig_datasz;
g_autofree gchar *sig_owner = NULL;
g_autofree guint8 *sig_data = NULL;
g_autoptr(FuEfiSignature) sig = NULL;
g_autoptr(GBytes) data = NULL;
/* allocate data buf */
if (sig_size <= sizeof(fwupd_guid_t)) {
g_set_error(error,
G_IO_ERROR,
G_IO_ERROR_FAILED,
"SignatureSize invalid: 0x%x",
(guint)sig_size);
return FALSE;
}
sig_datasz = sig_size - sizeof(fwupd_guid_t);
sig_data = g_malloc0(sig_datasz);
/* read both blocks of data */
if (!fu_memcpy_safe((guint8 *)&guid,
sizeof(guid),
0x0, /* dst */
buf,
bufsz,
offset, /* src */
sizeof(guid),
error)) {
g_prefix_error(error, "failed to read signature GUID: ");
return FALSE;
}
if (!fu_memcpy_safe(sig_data,
sig_datasz,
0x0, /* dst */
buf,
bufsz,
offset + sizeof(fwupd_guid_t), /* src */
sig_datasz,
error)) {
g_prefix_error(error, "failed to read signature data: ");
return FALSE;
}
/* create item */
sig_owner = fwupd_guid_to_string(&guid, FWUPD_GUID_FLAG_MIXED_ENDIAN);
data = g_bytes_new(sig_data, sig_datasz);
sig = fu_efi_signature_new(sig_kind, sig_owner);
fu_firmware_set_bytes(FU_FIRMWARE(sig), data);
fu_firmware_add_image(FU_FIRMWARE(self), FU_FIRMWARE(sig));
return TRUE;
}
static gboolean
fu_efi_signature_list_parse_list(FuEfiSignatureList *self,
const guint8 *buf,
gsize bufsz,
gsize *offset,
GError **error)
{
FuEfiSignatureKind sig_kind = FU_EFI_SIGNATURE_KIND_UNKNOWN;
fwupd_guid_t guid;
gsize offset_tmp;
guint32 sig_header_size = 0;
guint32 sig_list_size = 0;
guint32 sig_size = 0;
g_autofree gchar *sig_type = NULL;
/* read EFI_SIGNATURE_LIST */
if (!fu_memcpy_safe((guint8 *)&guid,
sizeof(guid),
0x0, /* dst */
buf,
bufsz,
*offset, /* src */
sizeof(guid),
error)) {
g_prefix_error(error, "failed to read GUID header: ");
return FALSE;
}
sig_type = fwupd_guid_to_string(&guid, FWUPD_GUID_FLAG_MIXED_ENDIAN);
if (g_strcmp0(sig_type, "c1c41626-504c-4092-aca9-41f936934328") == 0) {
sig_kind = FU_EFI_SIGNATURE_KIND_SHA256;
} else if (g_strcmp0(sig_type, "a5c059a1-94e4-4aa7-87b5-ab155c2bf072") == 0) {
sig_kind = FU_EFI_SIGNATURE_KIND_X509;
}
if (!fu_memread_uint32_safe(buf,
bufsz,
*offset + 0x10,
&sig_list_size,
G_LITTLE_ENDIAN,
error))
return FALSE;
if (sig_list_size < 0x1c || sig_list_size > 1024 * 1024) {
g_set_error(error,
G_IO_ERROR,
G_IO_ERROR_FAILED,
"SignatureListSize invalid: 0x%x",
sig_list_size);
return FALSE;
}
if (!fu_memread_uint32_safe(buf,
bufsz,
*offset + 0x14,
&sig_header_size,
G_LITTLE_ENDIAN,
error))
return FALSE;
if (sig_header_size > 1024 * 1024) {
g_set_error(error,
G_IO_ERROR,
G_IO_ERROR_FAILED,
"SignatureHeaderSize invalid: 0x%x",
sig_size);
return FALSE;
}
if (!fu_memread_uint32_safe(buf, bufsz, *offset + 0x18, &sig_size, G_LITTLE_ENDIAN, error))
return FALSE;
if (sig_size < sizeof(fwupd_guid_t) || sig_size > 1024 * 1024) {
g_set_error(error,
G_IO_ERROR,
G_IO_ERROR_FAILED,
"SignatureSize invalid: 0x%x",
sig_size);
return FALSE;
}
/* header is typically unused */
offset_tmp = *offset + 0x1c + sig_header_size;
for (guint i = 0; i < (sig_list_size - 0x1c) / sig_size; i++) {
if (!fu_efi_signature_list_parse_item(self,
sig_kind,
buf,
bufsz,
offset_tmp,
sig_size,
error))
return FALSE;
offset_tmp += sig_size;
}
*offset += sig_list_size;
return TRUE;
}
static gchar *
fu_efi_signature_list_get_version(FuEfiSignatureList *self)
{
guint csum_cnt = 0;
const gchar *valid_owners[] = {FU_EFI_SIGNATURE_GUID_MICROSOFT, NULL};
g_autofree gchar *checksum_last = NULL;
g_autoptr(GPtrArray) sigs = NULL;
struct {
const gchar *checksum;
guint version;
} known_checksums[] = {
/* DBXUpdate-20100307.x64.bin */
{"5391c3a2fb112102a6aa1edc25ae77e19f5d6f09cd09eeb2509922bfcd5992ea", 9},
/* DBXUpdate-20140413.x64.bin */
{"90fbe70e69d633408d3e170c6832dbb2d209e0272527dfb63d49d29572a6f44c", 13},
/* DBXUpdate-20160809.x64.bin */
{"45c7c8ae750acfbb48fc37527d6412dd644daed8913ccd8a24c94d856967df8e", 77},
/* DBXUpdate-20200729.x64.bin */
{"540801dd345dc1c33ef431b35bf4c0e68bd319b577b9abe1a9cff1cbc39f548f", 190},
/* DBXUpdate-20200729.aa64.bin */
{"8c8183ad9b96fe1f3c74dedb8087469227b642afe2e80f8fd22e0137c11c7d90", 19},
/* DBXUpdate-20200729.ia32.bin */
{"a7dfcc3a8d6ab30f93f31748dbc8ea38415cf52bb9ad8085672cd9ab8938d5de", 41},
/* DBXUpdate-20210429.x64.bin */
{"af79b14064601bc0987d4747af1e914a228c05d622ceda03b7a4f67014fee767", 211},
/* DBXUpdate-20210429.aa64.bin */
{"b133de42a37376f5d91439af3d61d38201f10377c36dacd9c2610f52aa124a91", 21},
/* DBXUpdate-20210429.ia32.bin */
{"a8a3300e33a0a2692839ccba84803c5e742d12501b6d58c46eb87f32017f2cff", 55},
/* DBXUpdate-20220812.x64.bin */
{"90aec5c4995674a849c1d1384463f3b02b5aa625a5c320fc4fe7d9bb58a62398", 217},
/* DBXUpdate-20220812.aa64.bin - only X509 certificates removed */
/* DBXUpdate-20220812.ia32.bin - only X509 certificates removed */
{NULL, 0}};
sigs = fu_firmware_get_images(FU_FIRMWARE(self));
for (guint i = 0; i < sigs->len; i++) {
FuEfiSignature *sig = g_ptr_array_index(sigs, i);
if (fu_efi_signature_get_kind(sig) != FU_EFI_SIGNATURE_KIND_SHA256) {
if (g_getenv("FWUPD_EFI_SIGNATURE_VERBOSE") != NULL)
g_debug("ignoring dbx certificate");
continue;
}
if (!g_strv_contains(valid_owners, fu_efi_signature_get_owner(sig))) {
if (g_getenv("FWUPD_EFI_SIGNATURE_VERBOSE") != NULL) {
g_debug("ignoring non-Microsoft dbx hash: %s",
fu_efi_signature_get_owner(sig));
}
continue;
}
/* save the last hash in the list */
if (i == sigs->len - 1) {
g_autoptr(GError) error_local = NULL;
checksum_last = fu_firmware_get_checksum(FU_FIRMWARE(sig),
G_CHECKSUM_SHA256,
&error_local);
if (checksum_last == NULL) {
g_warning("failed to get checksum for signature %u: %s",
i,
error_local->message);
}
}
csum_cnt++;
}
/*
* Microsoft seems to actually remove checksums in UEFI dbx updates, which I'm guessing is
* a result from OEM pressure about SPI usage -- but local dbx updates are append-only.
*
* That means that if you remove hashes then you can have a different set of dbx checksums
* on your machine depending on whether you went A->B->C->D or A->D...
*
* If we use the metric of "count the number of SHA256 checksums from MS" then we might
* overcount (due to the now-removed entries) -- in some cases enough to not actually apply
* the new update at all.
*
* In these cases look at the *last* dbx checksum and compare to the set we know to see if
* we need to artificially lower the reported version. This isn't helped by having *zero*
* visibility in the reason that entries were removed or added.
*
* This also fixes the DBX update 20200729 which added 4 duplicate entries, which should be
* rectified during the SetVariable(), so they're only really a problem for transactional
* size limits. But we all noticed that load-bearing *should* word there, didn't we.
*/
for (guint i = 0; checksum_last != NULL && known_checksums[i].checksum != NULL; i++) {
if (g_strcmp0(checksum_last, known_checksums[i].checksum) == 0) {
if (csum_cnt != known_checksums[i].version) {
g_debug("fixing signature list version from %u to %u as "
"last dbx checksum was %s",
csum_cnt,
known_checksums[i].version,
checksum_last);
csum_cnt = known_checksums[i].version;
}
break;
}
}
return g_strdup_printf("%u", csum_cnt);
}
static gboolean
fu_efi_signature_list_check_magic(FuFirmware *firmware, GBytes *fw, gsize offset, GError **error)
{
fwupd_guid_t guid = {0x0};
g_autofree gchar *sig_type = NULL;
/* read EFI_SIGNATURE_LIST */
if (!fu_memcpy_safe((guint8 *)&guid,
sizeof(guid),
0x0, /* dst */
g_bytes_get_data(fw, NULL),
g_bytes_get_size(fw),
offset, /* src */
sizeof(guid),
error)) {
g_prefix_error(error, "failed to read magic: ");
return FALSE;
}
sig_type = fwupd_guid_to_string(&guid, FWUPD_GUID_FLAG_MIXED_ENDIAN);
if (g_strcmp0(sig_type, "c1c41626-504c-4092-aca9-41f936934328") != 0 &&
g_strcmp0(sig_type, "a5c059a1-94e4-4aa7-87b5-ab155c2bf072") != 0) {
g_set_error_literal(error,
FWUPD_ERROR,
FWUPD_ERROR_INVALID_FILE,
"invalid magic for file");
return FALSE;
}
/* success */
return TRUE;
}
static gboolean
fu_efi_signature_list_parse(FuFirmware *firmware,
GBytes *fw,
gsize offset,
FwupdInstallFlags flags,
GError **error)
{
FuEfiSignatureList *self = FU_EFI_SIGNATURE_LIST(firmware);
gsize bufsz = 0;
const guint8 *buf = g_bytes_get_data(fw, &bufsz);
g_autofree gchar *version_str = NULL;
/* parse each EFI_SIGNATURE_LIST */
while (offset < bufsz) {
if (!fu_efi_signature_list_parse_list(self, buf, bufsz, &offset, error))
return FALSE;
}
/* set version */
version_str = fu_efi_signature_list_get_version(self);
if (version_str != NULL)
fu_firmware_set_version(firmware, version_str);
/* success */
return TRUE;
}
static GBytes *
fu_efi_signature_list_write(FuFirmware *firmware, GError **error)
{
GByteArray *buf = g_byte_array_new();
/* SignatureType */
for (guint i = 0; i < 16; i++)
fu_byte_array_append_uint8(buf, 0x0);
/* SignatureListSize */
fu_byte_array_append_uint32(buf, 16 + 4 + 4 + 4 + 16 + 32, G_LITTLE_ENDIAN);
/* SignatureHeaderSize */
fu_byte_array_append_uint32(buf, 0, G_LITTLE_ENDIAN);
/* SignatureSize */
fu_byte_array_append_uint32(buf, 16 + 32, G_LITTLE_ENDIAN);
/* SignatureOwner */
for (guint i = 0; i < 16; i++)
fu_byte_array_append_uint8(buf, '1');
/* SignatureData */
for (guint i = 0; i < 16; i++)
fu_byte_array_append_uint8(buf, '2');
return g_byte_array_free_to_bytes(buf);
}
/**
* fu_efi_signature_list_new:
*
* Creates a new #FuFirmware that can parse an EFI_SIGNATURE_LIST
*
* Since: 1.5.5
**/
FuFirmware *
fu_efi_signature_list_new(void)
{
return g_object_new(FU_TYPE_EFI_SIGNATURE_LIST, NULL);
}
static void
fu_efi_signature_list_class_init(FuEfiSignatureListClass *klass)
{
FuFirmwareClass *klass_firmware = FU_FIRMWARE_CLASS(klass);
klass_firmware->check_magic = fu_efi_signature_list_check_magic;
klass_firmware->parse = fu_efi_signature_list_parse;
klass_firmware->write = fu_efi_signature_list_write;
}
static void
fu_efi_signature_list_init(FuEfiSignatureList *self)
{
fu_firmware_add_flag(FU_FIRMWARE(self), FU_FIRMWARE_FLAG_ALWAYS_SEARCH);
}