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1abb32c623
To do this mount all ESP partitions and check all the binaries there to see if they match any entries in the new dbx. If we applied the update when a hash matched, we would unintentially 'brick' the users machine, as the grub and shim binaries *have* to be updated first. This functionality does reimplement the PE hashing functionality found in sbsigntools and pesign. This was done for 4 main reasons: * There were some memory safety issues found when fuzzing random binaries * Executing the tools hundreds of times was a lot of overhead * Operating from a blob of immutable mmap'd memory is much faster * We only need a very small amount of functionality from both tools
333 lines
9.3 KiB
C
333 lines
9.3 KiB
C
/*
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* Copyright (C) 2020 Richard Hughes <richard@hughsie.com>
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*
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* SPDX-License-Identifier: LGPL-2.1+
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*/
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#include "config.h"
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#include "fu-common.h"
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#include "fu-efi-image.h"
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struct _FuEfiImage {
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GObject parent_instance;
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gchar *checksum;
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};
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typedef struct {
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gsize offset;
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gsize size;
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gchar *name;
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} FuEfiImageRegion;
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typedef struct __attribute__((packed)) {
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guint32 addr;
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guint32 size;
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} FuEfiImageDataDirEntry;
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G_DEFINE_TYPE (FuEfiImage, fu_efi_image, G_TYPE_OBJECT)
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#define _DOS_OFFSET_SIGNATURE 0x00
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#define _DOS_OFFSET_TO_PE_HEADER 0x3c
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#define _PEI_OFFSET_SIGNATURE 0x00
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#define _PEI_OFFSET_MACHINE 0x04
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#define _PEI_OFFSET_NUMBER_OF_SECTIONS 0x06
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#define _PEI_OFFSET_OPTIONAL_HEADER_SIZE 0x14
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#define _PEI_HEADER_SIZE 0x18
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#define _PE_OFFSET_SIZE_OF_HEADERS 0x54
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#define _PE_OFFSET_CHECKSUM 0x58
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#define _PE_OFFSET_DEBUG_TABLE_OFFSET 0x98
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#define _PEP_OFFSET_SIZE_OF_HEADERS 0x54
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#define _PEP_OFFSET_CHECKSUM 0x58
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#define _PEP_OFFSET_DEBUG_TABLE_OFFSET 0xa8
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#define _SECTION_HEADER_OFFSET_NAME 0x0
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#define _SECTION_HEADER_OFFSET_SIZE 0x10
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#define _SECTION_HEADER_OFFSET_PTR 0x14
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#define _SECTION_HEADER_SIZE 0x28
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#define IMAGE_FILE_MACHINE_AMD64 0x8664
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#define IMAGE_FILE_MACHINE_I386 0x014c
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#define IMAGE_FILE_MACHINE_THUMB 0x01c2
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#define IMAGE_FILE_MACHINE_AARCH64 0xaa64
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static gint
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fu_efi_image_region_sort_cb (gconstpointer a, gconstpointer b)
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{
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const FuEfiImageRegion *r1 = *((const FuEfiImageRegion **) a);
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const FuEfiImageRegion *r2 = *((const FuEfiImageRegion **) b);
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if (r1->offset < r2->offset)
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return -1;
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if (r1->offset > r2->offset)
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return 1;
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return 0;
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}
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static FuEfiImageRegion *
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fu_efi_image_add_region (GPtrArray *checksum_regions,
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const gchar *name,
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gsize offset_start,
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gsize offset_end)
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{
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FuEfiImageRegion *r = g_new0 (FuEfiImageRegion, 1);
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r->name = g_strdup (name);
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r->offset = offset_start;
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r->size = offset_end - offset_start;
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g_ptr_array_add (checksum_regions, r);
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return r;
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}
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static void
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fu_efi_image_region_free (FuEfiImageRegion *r)
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{
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g_free (r->name);
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g_free (r);
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}
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FuEfiImage *
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fu_efi_image_new (GBytes *data, GError **error)
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{
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FuEfiImageRegion *r;
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const guint8 *buf;
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gsize bufsz;
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gsize image_bytes = 0;
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gsize checksum_offset;
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gsize data_dir_debug_offset;
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gsize offset_tmp;
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guint16 dos_sig = 0;
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guint16 machine = 0;
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guint16 opthdrsz;
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guint16 sections;
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guint32 baseaddr = 0;
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guint32 cert_table_size;
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guint32 header_size;
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guint32 nt_sig = 0;
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g_autoptr(FuEfiImage) self = g_object_new (FU_TYPE_EFI_IMAGE, NULL);
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g_autoptr(GChecksum) checksum = g_checksum_new (G_CHECKSUM_SHA256);
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g_autoptr(GPtrArray) checksum_regions = NULL;
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/* verify this is a DOS file */
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buf = g_bytes_get_data (data, &bufsz);
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if (!fu_common_read_uint16_safe (buf, bufsz,
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_DOS_OFFSET_SIGNATURE,
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&dos_sig, G_LITTLE_ENDIAN, error))
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return NULL;
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if (dos_sig != 0x5a4d) {
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g_set_error (error,
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G_IO_ERROR,
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G_IO_ERROR_NOT_SUPPORTED,
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"Invalid DOS header magic %04x", dos_sig);
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return NULL;
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}
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/* verify the PE signature */
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if (!fu_common_read_uint32_safe (buf, bufsz,
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_DOS_OFFSET_TO_PE_HEADER,
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&baseaddr, G_LITTLE_ENDIAN, error))
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return NULL;
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if (!fu_common_read_uint32_safe (buf, bufsz,
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baseaddr + _PEI_OFFSET_SIGNATURE,
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&nt_sig, G_LITTLE_ENDIAN, error))
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return NULL;
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if (nt_sig != 0x4550) {
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g_set_error (error,
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G_IO_ERROR,
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G_IO_ERROR_NOT_SUPPORTED,
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"Invalid PE header signature %08x", nt_sig);
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return NULL;
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}
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/* which machine type are we reading */
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if (!fu_common_read_uint16_safe (buf, bufsz,
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baseaddr + _PEI_OFFSET_MACHINE,
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&machine, G_LITTLE_ENDIAN, error))
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return NULL;
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if (machine == IMAGE_FILE_MACHINE_AMD64 ||
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machine == IMAGE_FILE_MACHINE_AARCH64) {
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/* a.out header directly follows PE header */
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if (!fu_common_read_uint16_safe (buf, bufsz,
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baseaddr + _PEI_HEADER_SIZE,
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&machine, G_LITTLE_ENDIAN, error))
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return NULL;
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if (machine != 0x020b) {
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g_set_error (error,
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G_IO_ERROR,
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G_IO_ERROR_NOT_SUPPORTED,
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"Invalid a.out machine type %04x", machine);
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return NULL;
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}
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if (!fu_common_read_uint32_safe (buf, bufsz,
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baseaddr + _PEP_OFFSET_SIZE_OF_HEADERS,
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&header_size, G_LITTLE_ENDIAN, error))
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return NULL;
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checksum_offset = baseaddr + _PEP_OFFSET_CHECKSUM;
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/* now, this is odd. sbsigntools seems to think that we're
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* skipping the CertificateTable -- but we actually seems to be
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* ignoring Debug instead */
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data_dir_debug_offset = baseaddr + _PEP_OFFSET_DEBUG_TABLE_OFFSET;
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} else if (machine == IMAGE_FILE_MACHINE_I386 ||
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machine == IMAGE_FILE_MACHINE_THUMB) {
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/* a.out header directly follows PE header */
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if (!fu_common_read_uint16_safe (buf, bufsz,
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baseaddr + _PEI_HEADER_SIZE,
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&machine, G_LITTLE_ENDIAN, error))
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return NULL;
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if (machine != 0x010b) {
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g_set_error (error,
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G_IO_ERROR,
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G_IO_ERROR_NOT_SUPPORTED,
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"Invalid a.out machine type %04x", machine);
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return NULL;
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}
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if (!fu_common_read_uint32_safe (buf, bufsz,
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baseaddr + _PE_OFFSET_SIZE_OF_HEADERS,
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&header_size, G_LITTLE_ENDIAN, error))
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return NULL;
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checksum_offset = baseaddr + _PE_OFFSET_CHECKSUM;
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data_dir_debug_offset = baseaddr + _PE_OFFSET_DEBUG_TABLE_OFFSET;
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} else {
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g_set_error (error,
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G_IO_ERROR,
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G_IO_ERROR_NOT_SUPPORTED,
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"Invalid PE header machine %04x", machine);
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return NULL;
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}
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/* get sections */
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if (!fu_common_read_uint32_safe (buf, bufsz,
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data_dir_debug_offset + sizeof(guint32),
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&cert_table_size, G_LITTLE_ENDIAN, error))
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return NULL;
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if (!fu_common_read_uint16_safe (buf, bufsz,
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baseaddr + _PEI_OFFSET_NUMBER_OF_SECTIONS,
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§ions, G_LITTLE_ENDIAN, error))
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return NULL;
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g_debug ("number_of_sections: %u", sections);
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/* get header size */
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if (!fu_common_read_uint16_safe (buf, bufsz,
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baseaddr + _PEI_OFFSET_OPTIONAL_HEADER_SIZE,
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&opthdrsz, G_LITTLE_ENDIAN, error))
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return NULL;
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g_debug ("optional_header_size: 0x%x", opthdrsz);
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/* first region: beginning to checksum_offset field */
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checksum_regions = g_ptr_array_new_with_free_func ((GDestroyNotify) fu_efi_image_region_free);
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r = fu_efi_image_add_region (checksum_regions, "begin->cksum", 0x0, checksum_offset);
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image_bytes += r->size + sizeof(guint32);
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/* second region: end of checksum_offset to certificate table entry */
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r = fu_efi_image_add_region (checksum_regions, "cksum->datadir[DEBUG]",
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checksum_offset + sizeof(guint32),
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data_dir_debug_offset);
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image_bytes += r->size + sizeof(FuEfiImageDataDirEntry);
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/* third region: end of checksum_offset to end of headers */
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r = fu_efi_image_add_region (checksum_regions, "datadir[DEBUG]->headers",
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data_dir_debug_offset + sizeof(FuEfiImageDataDirEntry),
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header_size);
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image_bytes += r->size;
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/* add COFF sections */
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offset_tmp = baseaddr + _PEI_HEADER_SIZE + opthdrsz;
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for (guint i = 0; i < sections; i++) {
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guint32 file_offset = 0;
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guint32 file_size = 0;
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gchar name[9] = { '\0' };
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if (!fu_common_read_uint32_safe (buf, bufsz,
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offset_tmp + _SECTION_HEADER_OFFSET_PTR,
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&file_offset, G_LITTLE_ENDIAN, error))
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return NULL;
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if (!fu_common_read_uint32_safe (buf, bufsz,
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offset_tmp + _SECTION_HEADER_OFFSET_SIZE,
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&file_size, G_LITTLE_ENDIAN, error))
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return NULL;
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if (file_size == 0)
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continue;
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if (!fu_memcpy_safe ((guint8 *) name, sizeof(name), 0x0, /* dst */
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buf, bufsz,
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offset_tmp + _SECTION_HEADER_OFFSET_NAME, /* src */
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sizeof(name) - 1, error))
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return NULL;
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r = fu_efi_image_add_region (checksum_regions, name, file_offset, file_offset + file_size);
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image_bytes += r->size;
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if (file_offset + r->size > bufsz) {
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g_set_error (error,
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G_IO_ERROR,
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G_IO_ERROR_INVALID_DATA,
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"file-aligned section %s extends beyond end of file",
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r->name);
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return NULL;
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}
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offset_tmp += _SECTION_HEADER_SIZE;
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}
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/* make sure in order */
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g_ptr_array_sort (checksum_regions, fu_efi_image_region_sort_cb);
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/* for the data at the end of the image */
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if (image_bytes + cert_table_size < bufsz) {
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fu_efi_image_add_region (checksum_regions, "endjunk",
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image_bytes, bufsz - cert_table_size);
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} else if (image_bytes + cert_table_size > bufsz) {
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g_set_error (error,
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G_IO_ERROR,
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G_IO_ERROR_INVALID_DATA,
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"checksum_offset areas outside image size");
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return NULL;
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}
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/* calculate the checksum we would find in the dbx */
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for (guint i = 0; i < checksum_regions->len; i++) {
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r = g_ptr_array_index (checksum_regions, i);
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g_debug ("region %s: 0x%04x -> 0x%04x [0x%04x]",
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r->name,
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(guint) r->offset,
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(guint) (r->offset + r->size - 1),
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(guint) r->size);
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g_checksum_update (checksum,
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(const guchar *) buf + r->offset,
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(gssize) r->size);
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}
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self->checksum = g_strdup (g_checksum_get_string (checksum));
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return g_steal_pointer (&self);
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}
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const gchar *
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fu_efi_image_get_checksum (FuEfiImage *self)
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{
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return self->checksum;
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}
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static void
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fu_efi_image_finalize (GObject *obj)
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{
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FuEfiImage *self = FU_EFI_IMAGE (obj);
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g_free (self->checksum);
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G_OBJECT_CLASS (fu_efi_image_parent_class)->finalize (obj);
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}
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static void
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fu_efi_image_class_init (FuEfiImageClass *klass)
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{
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GObjectClass *object_class = G_OBJECT_CLASS (klass);
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object_class->finalize = fu_efi_image_finalize;
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}
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static void
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fu_efi_image_init (FuEfiImage *self)
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{
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}
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