NTSTATUS NTAPI FstubReadHeaderEFI	(	IN PDISK_INFORMATION	Disk,
		IN BOOLEAN	ReadBackupTable,
		PEFI_PARTITION_HEADER	HeaderBuffer
	)
Definition at line 798 of file fstubex.c.
Referenced by FstubReadPartitionTableEFI(), FstubVerifyPartitionTableEFI(), and IoWritePartitionTableEx().
{
    NTSTATUS Status;
    PUCHAR Sector = NULL;
    ULONGLONG StartingSector;
    PEFI_PARTITION_HEADER EFIHeader;
    ULONG i, HeaderCRC32, PreviousCRC32, SectoredPartitionEntriesSize, LonelyPartitions;
    PAGED_CODE();

    ASSERT(Disk);
    ASSERT(IS_VALID_DISK_INFO(Disk));
    ASSERT(HeaderBuffer);

    /* In case we want to read backup table, we read last disk sector */
    if (ReadBackupTable)
    {
        StartingSector = Disk->SectorCount - 1ULL;
    }
    else
    {
        /* Otherwise we start at first sector (as sector 0 is the MBR) */
        StartingSector = 1ULL;
    }

    Status = FstubReadSector(Disk->DeviceObject,
                             Disk->SectorSize,
                             StartingSector,
                             Disk->Buffer);
    if (!NT_SUCCESS(Status))
    {
        DPRINT("EFI::Failed reading header!\n");
        return Status;
    }
    /* Let's use read buffer as EFI_PARTITION_HEADER */
    EFIHeader = (PEFI_PARTITION_HEADER)Disk->Buffer;


    /* First check signature
     * Then, check version (we only support v1)
     * Finally check header size
     */
    if (EFIHeader->Signature != EFI_HEADER_SIGNATURE ||
        EFIHeader->Revision != EFI_HEADER_REVISION_1 ||
        EFIHeader->HeaderSize != sizeof(EFI_PARTITION_HEADER))
    {
        DPRINT("EFI::Wrong signature/version/header size!\n");
        DPRINT("%I64x (expected: %I64x)\n", EFIHeader->Signature, EFI_HEADER_SIGNATURE);
        DPRINT("%03x (expected: %03x)\n", EFIHeader->Revision, EFI_HEADER_REVISION_1);
        DPRINT("%02x (expected: %02x)\n", EFIHeader->HeaderSize, sizeof(EFI_PARTITION_HEADER));
        return STATUS_DISK_CORRUPT_ERROR;
    }

    /* Save current checksum */
    HeaderCRC32 = EFIHeader->HeaderCRC32;
    /* Then zero the one in EFI header. This is needed to compute header checksum */
    EFIHeader->HeaderCRC32 = 0;
    /* Compute header checksum and compare with the one present in partition table */
    if (RtlComputeCrc32(0, (PUCHAR)Disk->Buffer, sizeof(EFI_PARTITION_HEADER)) != HeaderCRC32)
    {
        DPRINT("EFI::Not matching header checksum!\n");
        return STATUS_DISK_CORRUPT_ERROR;
    }
    /* Put back removed checksum in header */
    EFIHeader->HeaderCRC32 = HeaderCRC32;

    /* Check if current LBA is matching with ours */
    if (EFIHeader->MyLBA != StartingSector)
    {
        DPRINT("EFI::Not matching starting sector!\n");
        return STATUS_DISK_CORRUPT_ERROR;
    }

    /* Allocate a buffer to read a sector on the disk */
    Sector = ExAllocatePoolWithTag(NonPagedPool,
                                   Disk->SectorSize,
                                   TAG_FSTUB);
    if (!Sector)
    {
        DPRINT("EFI::Lacking resources!\n");
        return STATUS_INSUFFICIENT_RESOURCES;
    }

    /* Count how much sectors we'll have to read to read the whole partition table */
    SectoredPartitionEntriesSize = (EFIHeader->NumberOfEntries * PARTITION_ENTRY_SIZE) / Disk->SectorSize;
    /* Compute partition table checksum */
    for (i = 0, PreviousCRC32 = 0; i < SectoredPartitionEntriesSize; i++)
    {
        Status = FstubReadSector(Disk->DeviceObject,
                                 Disk->SectorSize,
                                 EFIHeader->PartitionEntryLBA + i,
                                 (PUSHORT)Sector);
        if (!NT_SUCCESS(Status))
        {
            ExFreePoolWithTag(Sector, TAG_FSTUB);
            DPRINT("EFI::Failed reading sector for partition entry!\n");
            return Status;
        }

        PreviousCRC32 = RtlComputeCrc32(PreviousCRC32, Sector, Disk->SectorSize);
    }

    /* Check whether we have a last sector not full of partitions */
    LonelyPartitions = (EFIHeader->NumberOfEntries * PARTITION_ENTRY_SIZE) % Disk->SectorSize;
    /* In such case, we have to complete checksum computation */
    if (LonelyPartitions != 0)
    {
        /* Read the sector that contains those partitions */
        Status = FstubReadSector(Disk->DeviceObject,
                                 Disk->SectorSize,
                                 EFIHeader->PartitionEntryLBA + i,
                                 (PUSHORT)Sector);
        if (!NT_SUCCESS(Status))
        {
            ExFreePoolWithTag(Sector, TAG_FSTUB);
            DPRINT("EFI::Failed reading sector for partition entry!\n");
            return Status;
        }

        /* Then complete checksum by computing on each partition */
        for (i = 0; i < LonelyPartitions; i++)
        {
            PreviousCRC32 = RtlComputeCrc32(PreviousCRC32, Sector + i * PARTITION_ENTRY_SIZE, PARTITION_ENTRY_SIZE);
        }
    }

    /* Finally, release memory */
    ExFreePoolWithTag(Sector, TAG_FSTUB);

    /* Compare checksums */
    if (PreviousCRC32 == EFIHeader->PartitionEntryCRC32)
    {
        /* In case of a success, return read header */
        *HeaderBuffer = *EFIHeader;
        return STATUS_SUCCESS;
    }
    else
    {
        DPRINT("EFI::Not matching partition table checksum!\n");
        DPRINT("EFI::Expected: %x, received: %x\n", EFIHeader->PartitionEntryCRC32, PreviousCRC32);
        return STATUS_DISK_CORRUPT_ERROR;
    }
}
ReactOS Development > Doxygen
