Function mediatek_find_hash

util/cbfstool/platform_fixups.c:232–281

#define MEDIATEK_BOOTBLOCK_HEADER_SIZE	2048
#define MEDIATEK_BOOTBLOCK_GFH_SIZE	176
static void *mediatek_find_hash(struct buffer *bootblock, struct vb2_hash *real_hash)
{
	struct buffer buffer;
	size_t data_size;
	const char emmc_magic[] = "EMMC_BOOT";
	const char sf_magic[] = "SF_BOOT";
	const char brlyt_magic[] = "BRLYT";
	const size_t brlyt_offset = 512;

	buffer_clone(&buffer, bootblock);

	/* Doesn't seem to be MediaTek image */
	if (buffer_size(&buffer) <
	    MEDIATEK_BOOTBLOCK_HEADER_SIZE + MEDIATEK_BOOTBLOCK_GFH_SIZE)
		return NULL;

	/* Check header magic */
	if (!buffer_check_magic(&buffer, emmc_magic, strlen(emmc_magic)) &&
	    !buffer_check_magic(&buffer, sf_magic, strlen(sf_magic)))
		return NULL;

	/* Check "BRLYT" */
	buffer_seek(&buffer, brlyt_offset);
	if (!buffer_check_magic(&buffer, brlyt_magic, strlen(brlyt_magic)))
		return NULL;

	buffer_seek(&buffer, MEDIATEK_BOOTBLOCK_HEADER_SIZE - brlyt_offset);
	data_size = read_le32(buffer_get(&buffer) + 32);
	if (data_size <= MEDIATEK_BOOTBLOCK_GFH_SIZE + VB2_SHA256_DIGEST_SIZE) {
		ERROR("fixups: MediaTek: data size too small: %zu\n", data_size);
		return NULL;
	}
	data_size -= MEDIATEK_BOOTBLOCK_GFH_SIZE + VB2_SHA256_DIGEST_SIZE;

	if (buffer_size(&buffer) <
	    MEDIATEK_BOOTBLOCK_GFH_SIZE + data_size + VB2_SHA256_DIGEST_SIZE) {
		ERROR("fixups: MediaTek: not enough data: %zu\n", buffer_size(&buffer));
		return NULL;
	}

	if (vb2_hash_calculate(false, buffer_get(&buffer),
			       MEDIATEK_BOOTBLOCK_GFH_SIZE + data_size,
			       VB2_HASH_SHA256, real_hash)) {
		ERROR("fixups: MediaTek: vboot digest error\n");
		return NULL;
	}

	buffer_seek(&buffer, MEDIATEK_BOOTBLOCK_GFH_SIZE + data_size);
	return buffer_get(&buffer);
}

static bool mediatek_probe(struct buffer *buffer)
{