mirror-ac/driver/integrity.c

#include "integrity.h"

#include "common.h"
#include "driver.h"
#include "modules.h"

#include <bcrypt.h>

typedef struct _INTEGRITY_CHECK_HEADER
{
    INT executable_section_count;
    LONG total_packet_size;

}INTEGRITY_CHECK_HEADER, *PINTEGRITY_CHECK_HEADER;

/*
* note: this can be put into its own function wihtout an IRP as argument then it can be used 
* in both the get driver image ioctl handler and the CopyDriverExecvutableRegions func
*/
NTSTATUS GetDriverImageSize(
    _In_ PIRP Irp
)
{
    NTSTATUS status;
    SYSTEM_MODULES modules = { 0 };
    PRTL_MODULE_EXTENDED_INFO driver_info;

    status = GetSystemModuleInformation( &modules );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "GetSystemModuleInformation failed with status %x", status );
        return status;
    }

    driver_info = FindSystemModuleByName(
        "driver.sys",
        &modules
    );

    Irp->IoStatus.Information = sizeof( ULONG );
    RtlCopyMemory( Irp->AssociatedIrp.SystemBuffer, &driver_info->ImageSize, sizeof( ULONG ) );
    
    if (modules.address )
        ExFreePoolWithTag( modules.address, SYSTEM_MODULES_POOL );

    return status;
}

NTSTATUS GetModuleInformationByName(
    _In_ PRTL_MODULE_EXTENDED_INFO ModuleInfo,
    _In_ LPCSTR ModuleName
)
{
    NTSTATUS status = STATUS_SUCCESS;
    SYSTEM_MODULES modules = { 0 };
    PRTL_MODULE_EXTENDED_INFO driver_info;

    status = GetSystemModuleInformation( &modules );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "GetSystemModuleInformation failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        return status;
    }

    driver_info = FindSystemModuleByName(
        "driver.sys",
        &modules
    );

    ModuleInfo->FileNameOffset = driver_info->FileNameOffset;
    ModuleInfo->ImageBase = driver_info->ImageBase;
    ModuleInfo->ImageSize = driver_info->ImageSize;

    RtlCopyMemory(
        ModuleInfo->FullPathName,
        driver_info->FullPathName,
        sizeof( ModuleInfo->FullPathName )
    );

    if ( modules.address )
        ExFreePoolWithTag( modules.address, SYSTEM_MODULES_POOL );

    return status;
}

NTSTATUS StoreModuleExecutableRegionsInBuffer(
    _In_ PVOID* Buffer,
    _In_ PVOID ModuleBase,
    _In_ SIZE_T ModuleSize,
    _In_ PSIZE_T BytesWritten
)
{
    NTSTATUS status = STATUS_SUCCESS;
    PIMAGE_DOS_HEADER dos_header;
    PLOCAL_NT_HEADER nt_header;
    PIMAGE_SECTION_HEADER section;
    ULONG total_packet_size = 0;
    ULONG num_sections = 0;
    ULONG num_executable_sections = 0;
    UINT64 buffer_base;
    ULONG bytes_returned;
    MM_COPY_ADDRESS address;

    if ( !ModuleBase || !ModuleSize )
        return STATUS_INVALID_PARAMETER;

    /*
    * The reason we allocate a buffer to temporarily hold the section data is that
    * we don't know the total size until after we iterate over the sections meaning
    * we cant set Irp->IoStatus.Information to the size of our reponse until we
    * enumerate and count all executable sections for the file.
    */

    *Buffer = ExAllocatePool2( POOL_FLAG_NON_PAGED, ModuleSize + sizeof( INTEGRITY_CHECK_HEADER ), POOL_TAG_INTEGRITY );

    if ( !*Buffer )
        return STATUS_MEMORY_NOT_ALLOCATED;

    /*
    * Note: Verifier doesn't like it when we map the module so rather then mapping it to our address
    * space we will simply use MmCopyMemory on the module to avoid upsetting verifier :)
    */

    dos_header = ( PIMAGE_DOS_HEADER )ModuleBase;

    /*
    * The IMAGE_DOS_HEADER.e_lfanew stores the offset of the IMAGE_NT_HEADER from the base
    * of the image.
    */
    nt_header = ( struct _IMAGE_NT_HEADERS64* )( ( UINT64 )ModuleBase + dos_header->e_lfanew );

    num_sections = nt_header->FileHeader.NumberOfSections;

    /*
    * The IMAGE_FIRST_SECTION macro takes in an IMAGE_NT_HEADER and returns the address of
    * the first section of the PE file.
    */
    section = IMAGE_FIRST_SECTION( nt_header );

    buffer_base = ( UINT64 )*Buffer + sizeof( INTEGRITY_CHECK_HEADER );

    for ( ULONG index = 0; index < num_sections; index++ )
    {
        if ( section->Characteristics & IMAGE_SCN_MEM_EXECUTE )
        {
            /*
            * Note: MmCopyMemory will fail on discardable sections.
            */
            address.VirtualAddress = section;

            status = MmCopyMemory(
                ( UINT64 )buffer_base + total_packet_size,
                address,
                sizeof( IMAGE_SECTION_HEADER ),
                MM_COPY_MEMORY_VIRTUAL,
                &bytes_returned
            );

            if ( !NT_SUCCESS( status ) )
            {
                DEBUG_ERROR( "MmCopyMemory failed with status %x", status );
                ExFreePoolWithTag( *Buffer, POOL_TAG_INTEGRITY );
                *Buffer = NULL;
                //TerminateProtectedProcessOnViolation();
                return status;
            }

            address.VirtualAddress = ( UINT64 )ModuleBase + section->PointerToRawData;

            status = MmCopyMemory(
                ( UINT64 )buffer_base + total_packet_size + sizeof( IMAGE_SECTION_HEADER ),
                address,
                section->SizeOfRawData,
                MM_COPY_MEMORY_VIRTUAL,
                &bytes_returned
            );

            if ( !NT_SUCCESS( status ) )
            {
                DEBUG_ERROR( "MmCopyMemory failed with status %x", status );
                ExFreePoolWithTag( *Buffer, POOL_TAG_INTEGRITY );
                *Buffer = NULL;
                //TerminateProtectedProcessOnViolation();
                return status;
            }

            total_packet_size += section->SizeOfRawData + sizeof( IMAGE_SECTION_HEADER );
            num_executable_sections += 1;
        }

        section++;
    }

    INTEGRITY_CHECK_HEADER header = { 0 };
    header.executable_section_count = num_executable_sections;
    header.total_packet_size = total_packet_size + sizeof( INTEGRITY_CHECK_HEADER );

    RtlCopyMemory(
        *Buffer,
        &header,
        sizeof( INTEGRITY_CHECK_HEADER )
    );

    *BytesWritten = total_packet_size + sizeof( INTEGRITY_CHECK_HEADER );

    return status;
}

NTSTATUS MapDiskImageIntoVirtualAddressSpace(
    _In_ PHANDLE SectionHandle,
    _In_ PVOID* Section,
    _In_ PUNICODE_STRING Path,
    _In_ PSIZE_T Size
)
{
    NTSTATUS status;
    HANDLE file_handle;
    OBJECT_ATTRIBUTES object_attributes;
    PIO_STATUS_BLOCK pio_block;
    UNICODE_STRING path;

    RtlInitUnicodeString( &path, Path->Buffer );

    InitializeObjectAttributes(
        &object_attributes,
        &path,
        OBJ_KERNEL_HANDLE | OBJ_CASE_INSENSITIVE,
        NULL,
        NULL
    );

    status = ZwOpenFile(
        &file_handle,
        FILE_GENERIC_READ,
        &object_attributes,
        &pio_block,
        NULL,
        NULL
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "ZwOpenFile failed with statsu %x", status );
        //TerminateProtectedProcessOnViolation();
        return status;
    }

    object_attributes.ObjectName = NULL;

    /*
    * Its important that we set the SEC_IMAGE flag with the PAGE_READONLY
    * flag as we are mapping an executable image.
    */
    status = ZwCreateSection(
        SectionHandle,
        SECTION_ALL_ACCESS,
        &object_attributes,
        NULL,
        PAGE_READONLY,
        SEC_IMAGE,
        file_handle
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "ZwCreateSection failed with status %x", status );
        ZwClose( file_handle );
        *SectionHandle = NULL;
        //TerminateProtectedProcessOnViolation();
        return status;
    }

    /*
    * Mapping a section with the flag SEC_IMAGE (see function above) tells the os we 
    * are mapping an executable image. This then allows the OS to take care of parsing
    * the PE header and dealing with all relocations for us, meaning the mapped image
    * will be identical to the in memory image.
    */
    status = ZwMapViewOfSection(
        *SectionHandle,
        ZwCurrentProcess(),
        Section,
        NULL,
        NULL,
        NULL,
        Size,
        ViewUnmap,
        MEM_TOP_DOWN,
        PAGE_READONLY
    );

    if ( !NT_SUCCESS( status ) )
    {
        /*
        * It is of utmost importants to mark SectionHandle as null after closing the
        * handle from inside this function since an error has occured. The reason this is
        * so important is because we are not responsible for freeing the function if it succeeds
        * and even if it fails, we still allocate a value to the handle via ZwCreateSection.
        * Meaning when the caller goes to check if the handle is null, it will not be null
        * and will cause a double free. 
        */
        DEBUG_ERROR( "ZwMapViewOfSection failed with status %x", status );
        ZwClose( file_handle );
        ZwClose( *SectionHandle );
        *SectionHandle = NULL;
        //TerminateProtectedProcessOnViolation();
        return status;
    }

    ZwClose( file_handle );
    return status;
}

NTSTATUS ComputeHashOfBuffer(
    _In_ PVOID Buffer,
    _In_ ULONG BufferSize,
    _In_ PVOID* HashResult,
    _In_ PULONG HashResultSize
)
{
    /*
    * Since the windows documentation for the BCrypt functions contain the worst variable naming scheme 
    * in existence, I will try to explain what they do. (for my sake and any readers who also aren't smart 
    * enough to understand their otherworldy naming convention)
    * 
    * algo_handle: handle to our BCrypt algorithm
    * hash_handle: handle to our BCrypt hash
    * bytes_copied: number of bytes that were copied to the output buffer when using BCryptGetProperty
    * resulting_hash_size: this is the size of the final buffer hash, it should be equal to 32 (sizeof SHA256 hash)
    * hash_object_size: the size of the buffer that will temporarily store our hash object
    * hash_object: pointer to the buffer storing our hash object which is used to hash our buffer
    * resulting_hash: pointer to the buffer that stores the resulting hash of our buffer, this is what we care about
    */

    NTSTATUS status;
    BCRYPT_ALG_HANDLE algo_handle = NULL;
    BCRYPT_HASH_HANDLE hash_handle = NULL;
    ULONG bytes_copied = 0;
    ULONG resulting_hash_size = 0;
    ULONG hash_object_size = 0;
    PCHAR hash_object = NULL;
    PCHAR resulting_hash = NULL;

    status = BCryptOpenAlgorithmProvider(
        &algo_handle,
        BCRYPT_SHA256_ALGORITHM,
        NULL,
        NULL
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "BCryptOpenAlogrithmProvider failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    /*
    * Request the size of the hash object buffer, this is different then the buffer that
    * will store the resulting hash, instead this will be used to store the hash object
    * used to create the hash.
    */
    status = BCryptGetProperty(
        algo_handle,
        BCRYPT_OBJECT_LENGTH,
        ( PCHAR )&hash_object_size,
        sizeof( ULONG ),
        &bytes_copied,
        NULL
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "BCryptGetProperty failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    hash_object = ExAllocatePool2( POOL_FLAG_NON_PAGED, hash_object_size, POOL_TAG_INTEGRITY );

    if ( !hash_object )
    {
        status = STATUS_MEMORY_NOT_ALLOCATED;
        goto end;
    }

    /*
    * This call gets the size of the resulting hash, which we will use to allocate the
    * resulting hash buffer.
    */
    status = BCryptGetProperty(
        algo_handle,
        BCRYPT_HASH_LENGTH,
        ( PCHAR )&resulting_hash_size,
        sizeof( ULONG ),
        &bytes_copied,
        NULL
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "BCryptGetProperty failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    resulting_hash = ExAllocatePool2( POOL_FLAG_NON_PAGED, resulting_hash_size, POOL_TAG_INTEGRITY );

    if ( !resulting_hash )
    {
        status = STATUS_MEMORY_NOT_ALLOCATED;
        goto end;
    }

    /*
    * Here we create our hash object and store it in the hash_object buffer.
    */
    status = BCryptCreateHash(
        algo_handle,
        &hash_handle,
        hash_object,
        hash_object_size,
        NULL,
        NULL,
        NULL
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "BCryptCreateHash failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    /*
    * This function hashes the buffer, but does NOT store it in our resulting buffer yet, 
    * we need to call BCryptFinishHash to retrieve the final hash.
    */
    status = BCryptHashData(
        hash_handle,
        Buffer,
        BufferSize,
        NULL
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "BCryptHashData failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    /*
    * As said in the previous comment, this is where we retrieve the final hash and store
    * it in our output buffer.
    */
    status = BCryptFinishHash(
        hash_handle,
        resulting_hash,
        resulting_hash_size,
        NULL
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "BCryptFinishHash failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        return status;
    }

    *HashResult = resulting_hash;
    *HashResultSize = resulting_hash_size;

end:

    if ( algo_handle )
        BCryptCloseAlgorithmProvider( algo_handle, NULL );

    if ( hash_handle )
        BCryptDestroyHash( hash_handle );

    if ( hash_object )
        ExFreePoolWithTag( hash_object, POOL_TAG_INTEGRITY );

    return status;
}

/*
* 1. map driver to memory
* 2. store executable sections in buffer
* 3. do the same with the in-memory module
* 4. hash both buffers 
* 5. compare
*/
NTSTATUS VerifyInMemoryImageVsDiskImage(
    //_In_ PIRP Irp
)
{
    NTSTATUS status;
    UNICODE_STRING path = { 0 };
    HANDLE section_handle = NULL;
    PVOID section = NULL;
    SIZE_T section_size = NULL;
    SIZE_T bytes_written = NULL;
    PVOID disk_buffer = NULL;
    PVOID in_memory_buffer = NULL;
    RTL_MODULE_EXTENDED_INFO module_info = { 0 };
    UINT64 disk_base = NULL;
    UINT64 memory_base = NULL;
    PIMAGE_SECTION_HEADER disk_text_header = NULL;
    PIMAGE_SECTION_HEADER memory_text_header = NULL;
    PVOID disk_text_hash = NULL;
    PVOID memory_text_hash = NULL;
    ULONG disk_text_hash_size = NULL;
    ULONG memory_text_hash_size = NULL;
    SIZE_T result = NULL;

    GetDriverPath( &path );

    status = MapDiskImageIntoVirtualAddressSpace(
        &section_handle,
        &section,
        &path,
        &section_size
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "MapDiskImageIntoVirtualAddressSpace failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        return status;
    }

    status = StoreModuleExecutableRegionsInBuffer(
        &disk_buffer,
        section,
        section_size,
        &bytes_written
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "StoreModuleExecutableRegionsInBuffer failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    /*
    * Parse the in-memory module
    */
    status = GetModuleInformationByName(
        &module_info,
        "driver.sys"
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "GetModuleInformationByName failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    status = StoreModuleExecutableRegionsInBuffer(
        &in_memory_buffer,
        module_info.ImageBase,
        module_info.ImageSize,
        &bytes_written
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "StoreModuleExecutableRegionsInBuffe failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    disk_base = ( UINT64 )( ( UINT64 )disk_buffer + sizeof( INTEGRITY_CHECK_HEADER ) + sizeof( IMAGE_SECTION_HEADER ) );
    memory_base = ( UINT64 )( ( UINT64 )in_memory_buffer + sizeof( INTEGRITY_CHECK_HEADER ) + sizeof( IMAGE_SECTION_HEADER ) );

    disk_text_header = ( PIMAGE_SECTION_HEADER )( ( UINT64 )disk_buffer + sizeof( INTEGRITY_CHECK_HEADER ) );
    memory_text_header = ( PIMAGE_SECTION_HEADER )( ( UINT64 )in_memory_buffer + sizeof( INTEGRITY_CHECK_HEADER ) );

    if ( !disk_base || !memory_base || !disk_buffer || !in_memory_buffer )
    {
        DEBUG_ERROR( "buffers are null lmao" );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    if ( disk_text_header->SizeOfRawData != memory_text_header->SizeOfRawData )
    {
        /* report or bug check etc. */
        DEBUG_LOG( "Executable section size differs, LOL" );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    status = ComputeHashOfBuffer(
        disk_base,
        disk_text_header->SizeOfRawData,
        &disk_text_hash,
        &disk_text_hash_size
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "ComputeHashOfBuffer failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    status = ComputeHashOfBuffer(
        memory_base,
        memory_text_header->SizeOfRawData,
        &memory_text_hash,
        &memory_text_hash_size
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "ComputeHashOfBuffer failed with status %x", status );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    if ( memory_text_hash_size != disk_text_hash_size )
    {
        DEBUG_ERROR( "Error with the hash algorithm, hash sizes are different." );
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    result = RtlCompareMemory( 
        memory_text_hash, 
        disk_text_hash, 
        memory_text_hash_size 
    );

    if (result != memory_text_hash_size)
    {
        /* report etc. bug check etc. */
        DEBUG_ERROR( "Text sections are different from each other!!");
        //TerminateProtectedProcessOnViolation();
        goto end;
    }

    DEBUG_LOG( "Text sections are fine, integrity check complete." );

end:

    if ( section_handle != NULL )
        ZwClose( section_handle );

    if ( section )
        ZwUnmapViewOfSection( ZwCurrentProcess(), section );

    if ( disk_buffer )
        ExFreePoolWithTag( disk_buffer, POOL_TAG_INTEGRITY );

    if ( in_memory_buffer )
        ExFreePoolWithTag( in_memory_buffer, POOL_TAG_INTEGRITY );

    if ( memory_text_hash )
        ExFreePoolWithTag( memory_text_hash, POOL_TAG_INTEGRITY );

    if ( disk_text_hash )
        ExFreePoolWithTag( disk_text_hash, POOL_TAG_INTEGRITY );

    return status;
}

NTSTATUS RetrieveInMemoryModuleExecutableSections(
    _In_ PIRP Irp
)
{
    NTSTATUS status;
    SIZE_T bytes_written = NULL;
    PVOID buffer = NULL;
    RTL_MODULE_EXTENDED_INFO module_info = { 0 };

    status = GetModuleInformationByName(
        &module_info,
        "driver.sys"
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "GetModuleInformationByName failed with status %x", status );
        return status;
    }

    status = StoreModuleExecutableRegionsInBuffer(
        &buffer,
        module_info.ImageBase,
        module_info.ImageSize,
        &bytes_written
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "StoreModuleExecutableRegionsInBuffe failed with status %x", status );
        return status;
    }

    Irp->IoStatus.Information = bytes_written;

    RtlCopyMemory(
        Irp->AssociatedIrp.SystemBuffer,
        buffer,
        bytes_written
    );

    if ( buffer )
        ExFreePoolWithTag( buffer, POOL_TAG_INTEGRITY );

    return status;
}

/*
* From line 727 in the SMBIOS Specification: 
* 
*    727 <EFBFBD> Each structure shall be terminated by a double-null (0000h), either directly following the
*    728   formatted area (if no strings are present) or directly following the last string. This includes
*    729   system- and OEM-specific structures and allows upper-level software to easily traverse the
*    730   structure table. (See structure-termination examples later in this clause.) 
* 
* TLDR is that if the first two characters proceeding the structure are null terminators, then there are no strings,
* otherwise to find the end of the string section simply iterate until there is a double null terminator.
* 
* source: https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_2.7.1.pdf
*/
VOID GetNextSMBIOSStructureInTable(
    _In_ PSMBIOS_TABLE_HEADER* CurrentStructure
)
{
    PCHAR string_section_start = ( PCHAR )( ( UINT64 )*CurrentStructure + ( *CurrentStructure )->Length );
    PCHAR current_char_in_strings = string_section_start;
    PCHAR next_char_in_strings = string_section_start + 1;

    for ( ;; )
    {
        if ( *current_char_in_strings == NULL_TERMINATOR && *next_char_in_strings == NULL_TERMINATOR )
        {
            *CurrentStructure = ( PSMBIOS_TABLE_HEADER )( ( UINT64 )next_char_in_strings + 1 );
            return;
        }

        current_char_in_strings++;
        next_char_in_strings++;
    }
}

/*
* Remember that the string index does not start from the beginning of the struct. For example, lets take 
* RAW_SMBIOS_TABLE_02: the first string is NOT "Type" at index 0, the first string is Manufacturer. So if we
* want to find the SerialNumber, the string index would be 4, as the previous 3 values (after the header) are
* all strings. So remember, the index is into the number of strings that exist for the given table, NOT the 
* size of the structure or a values index into the struct.
* 
* Here we count the number of strings by incrementing the string_count each time we pass a null terminator
* so we know when we're at the beginning of the target string.
*/
NTSTATUS GetStringAtIndexFromSMBIOSTable(
    _In_ PSMBIOS_TABLE_HEADER Table,
    _In_ INT Index,
    _In_ PVOID Buffer,
    _In_ SIZE_T BufferSize
)
{
    INT current_string_char_index = 0;
    INT string_count = 0;
    PCHAR current_string_char = ( PCHAR )( ( UINT64 )Table + Table->Length );
    PCHAR next_string_char = current_string_char + 1;

    for ( ;; )
    {
        if ( *current_string_char == NULL_TERMINATOR && *next_string_char == NULL_TERMINATOR )
            return STATUS_NOT_FOUND;

        if ( current_string_char_index >= BufferSize )
            return STATUS_BUFFER_TOO_SMALL;

        if ( string_count + 1 == Index )
        {
            if ( *current_string_char == NULL_TERMINATOR )
                return STATUS_SUCCESS;

            RtlCopyMemory( ( UINT64 )Buffer + current_string_char_index, current_string_char, sizeof( CHAR ) );
            current_string_char_index++;
            goto increment;
        }

        if ( *current_string_char == NULL_TERMINATOR )
        {
            current_string_char_index = 0;
            string_count++;
        }

    increment:

        current_string_char++;
        next_string_char++;
    }

    return STATUS_NOT_FOUND;
}

NTSTATUS ParseSMBIOSTable(
    _In_ PVOID ConfigMotherboardSerialNumber,
    _In_ SIZE_T ConfigMotherboardSerialNumberMaxSize
)
{
    NTSTATUS status;
    PVOID firmware_table_buffer;
    ULONG firmware_table_buffer_size = NULL;
    ULONG bytes_returned;
    PRAW_SMBIOS_DATA smbios_data;
    PSMBIOS_TABLE_HEADER smbios_table_header;
    PRAW_SMBIOS_TABLE_01 smbios_baseboard_information;

    status = ExGetSystemFirmwareTable(
        SMBIOS_TABLE,
        NULL,
        NULL,
        NULL,
        &firmware_table_buffer_size
    );

    /*
    * Because we pass a null buffer here, the NTSTATUS result will be a BUFFER_TOO_SMALL error, so to validate
    * this function call we check the return bytes returned (which indicate required buffer size) is above 0.
    */
    if ( firmware_table_buffer_size == NULL )
    {
        DEBUG_ERROR( "ExGetSystemFirmwareTable call 1 failed to get required buffer size." );
        return STATUS_BUFFER_TOO_SMALL;
    }

    firmware_table_buffer = ExAllocatePool2( POOL_FLAG_NON_PAGED, firmware_table_buffer_size, POOL_TAG_INTEGRITY );

    if ( !firmware_table_buffer )
        return STATUS_MEMORY_NOT_ALLOCATED;

    status = ExGetSystemFirmwareTable(
        SMBIOS_TABLE,
        NULL,
        firmware_table_buffer,
        firmware_table_buffer_size,
        &bytes_returned
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "ExGetSystemFirmwareTable call 2 failed with status %x", status );
        goto end;
    }

    smbios_data = ( PRAW_SMBIOS_DATA )firmware_table_buffer;
    smbios_table_header = ( PSMBIOS_TABLE_HEADER )(&smbios_data->SMBIOSTableData[0] );

    /*
    * The System Information table is equal to Type == 2 and contains the serial number of the motherboard
    * in the computer among various other things.
    * 
    * source: https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_2.7.1.pdf line 823
    */
    while ( smbios_table_header->Type != VMWARE_SMBIOS_TABLE )
        GetNextSMBIOSStructureInTable( &smbios_table_header );

    status = GetStringAtIndexFromSMBIOSTable(
        smbios_table_header,
        VMWARE_SMBIOS_TABLE_INDEX,
        ConfigMotherboardSerialNumber,
        ConfigMotherboardSerialNumberMaxSize
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "GetStringAtIndexFromSMBIOSTable failed with status %x", status );
        goto end;
    }

end:

    if ( firmware_table_buffer )
        ExFreePoolWithTag( firmware_table_buffer, POOL_TAG_INTEGRITY );

    return status;
}

/*
* Because the infrastructure has already been setup to validate modules in the driver, that
* is how I will validate the usermode modules as well. Another reason is that the win32 api
* makes it very easy to take a snapshot of the modules and enumerate them with easy to use 
* functions and macros.
* 
* 1. Take a snapshot of the modules in the process from our dll
* 2. pass the image base, image size and the image path to our driver via an IRP
* 3. from our driver, to first verify the in memory module, attach to our protected process
*    and using the base + size simply use StoreModuleExecutableRegionsInBuffer()
* 4. Next we use the path to map the image on disk into memory, and pass the image to
*    StoreModuleExecutableRegionsInBuffer() just as we did before.
* 5. With the 2 buffers that contain both images executable regions, we hash them and compare
*    for anomalies.
*/
NTSTATUS ValidateProcessLoadedModule(
    _In_ PIRP Irp
)
{
    NTSTATUS status;
    BOOLEAN bstatus;
    PROCESS_MODULE_VALIDATION_RESULT validation_result;
    PPROCESS_MODULE_INFORMATION module_info;
    PKPROCESS process;
    KAPC_STATE apc_state;
    PVOID in_memory_buffer = NULL;
    PVOID disk_buffer = NULL;
    PVOID in_memory_hash = NULL;
    PVOID disk_hash = NULL;
    ULONG in_memory_hash_size = NULL;
    ULONG disk_hash_size = NULL;
    SIZE_T bytes_written = NULL;
    UNICODE_STRING module_path;
    HANDLE section_handle = NULL;
    PVOID section = NULL;
    ULONG section_size = NULL;

    module_info = ( PPROCESS_MODULE_INFORMATION )Irp->AssociatedIrp.SystemBuffer;

    GetProtectedProcessEProcess( &process );

    /*
    * Attach because the offsets given are from the process' context.
    */
    KeStackAttachProcess( process, &apc_state );

    status = StoreModuleExecutableRegionsInBuffer(
        &in_memory_buffer,
        module_info->module_base,
        module_info->module_size,
        &bytes_written
    );

    KeUnstackDetachProcess( &apc_state );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "StoreModuleExecutableRegionsInBuffer failed with status %x", status );
        goto end;
    }

    status = ComputeHashOfBuffer(
        in_memory_buffer,
        bytes_written,
        &in_memory_hash,
        &in_memory_hash_size
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "ComputeHashOfBuffer failed with status %x:", status );
        goto end;
    }

    RtlInitUnicodeString( &module_path, &module_info->module_path );

    status = MapDiskImageIntoVirtualAddressSpace(
        &section_handle,
        &section,
        &module_path,
        &section_size
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "MapDiskImageIntoVirtualAddressSpace failed with status %x", status );
        goto end;
    }

    status = StoreModuleExecutableRegionsInBuffer(
        &disk_buffer,
        section,
        section_size,
        &bytes_written
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "StoreModuleExecutableRegionsInbuffer 2 failed with status %x", status );
        goto end;
    }

    status = ComputeHashOfBuffer(
        disk_buffer,
        bytes_written,
        &disk_hash,
        &disk_hash_size
    );

    if ( !NT_SUCCESS( status ) )
    {
        DEBUG_ERROR( "ComputeHashOfBuffer 2 failed with status %x", status );
        goto end;
    }

    if ( !in_memory_hash || !disk_hash )
        goto end;

    bstatus = RtlEqualMemory( in_memory_hash, disk_hash, in_memory_hash_size );

    /*
    * Because each module is passed per IRP we don't need to send any reports
    * to the queue we can simply pass it back to usermode via the same IRP.
    * We also don't need to send any module information since usermode has everything
    * needed to file the report.
    */
    validation_result.is_module_valid = bstatus;

    Irp->IoStatus.Information = sizeof( PROCESS_MODULE_VALIDATION_RESULT );

    RtlCopyMemory( 
        Irp->AssociatedIrp.SystemBuffer, 
        &validation_result, 
        sizeof( PROCESS_MODULE_VALIDATION_RESULT ) 
    );

end:
    
    if ( section_handle != NULL )
        ZwClose( section_handle );

    if ( section )
        ZwUnmapViewOfSection( ZwCurrentProcess(), section );

    if ( in_memory_buffer )
        ExFreePoolWithTag( in_memory_buffer, POOL_TAG_INTEGRITY );

    if ( in_memory_hash )
        ExFreePoolWithTag( in_memory_hash, POOL_TAG_INTEGRITY );

    if ( disk_buffer )
        ExFreePoolWithTag( disk_buffer, POOL_TAG_INTEGRITY );

    if ( disk_hash )
        ExFreePoolWithTag( disk_hash, POOL_TAG_INTEGRITY );

    return status;
}

/*
* TODO: Query PhysicalDrive%n to get the serial numbers for all harddrives, can use the command
* "wmic diskdrive" check in console.
*/
NTSTATUS GetHardDiskDriveSerialNumber(
    _In_ PVOID ConfigDrive0Serial,
    _In_ SIZE_T ConfigDrive0MaxSize
) 
{
    NTSTATUS status;
    HANDLE handle;
    OBJECT_ATTRIBUTES attributes;
    IO_STATUS_BLOCK status_block;
    STORAGE_PROPERTY_QUERY storage_property = { 0 };
    STORAGE_DESCRIPTOR_HEADER storage_descriptor_header = { 0 };
    PSTORAGE_DEVICE_DESCRIPTOR device_descriptor = NULL;
    UNICODE_STRING physical_drive_path;
    PCHAR serial_number = NULL;
    SIZE_T serial_length = NULL;

    RtlInitUnicodeString( &physical_drive_path, L"\\DosDevices\\PhysicalDrive0" );

    InitializeObjectAttributes( 
        &attributes, 
        &physical_drive_path,
        OBJ_CASE_INSENSITIVE | OBJ_KERNEL_HANDLE, 
        NULL, 
        NULL 
    );

    status = ZwOpenFile(
        &handle,
        GENERIC_READ,
        &attributes,
        &status_block,
        NULL,
        NULL
    );

    if ( !NT_SUCCESS( status ) ) 
    {
        DEBUG_LOG( "ZwOpenFile on PhysicalDrive0 failed with status %x", status);
        goto end;
    }

    storage_property.PropertyId = StorageDeviceProperty;
    storage_property.QueryType = PropertyStandardQuery;

    status = ZwDeviceIoControlFile(
        handle,
        NULL,
        NULL,
        NULL,
        &status_block,
        IOCTL_STORAGE_QUERY_PROPERTY,
        &storage_property,
        sizeof( STORAGE_PROPERTY_QUERY ),
        &storage_descriptor_header,
        sizeof( STORAGE_DESCRIPTOR_HEADER ) 
    );

    if ( !NT_SUCCESS( status ) ) 
    {
        DEBUG_LOG( "ZwDeviceIoControlFile first call failed with status %x", status );
        goto end;
    }

    device_descriptor = ExAllocatePool2( POOL_FLAG_NON_PAGED, storage_descriptor_header.Size, POOL_TAG_INTEGRITY );

    if ( !device_descriptor ) 
    {
        status = STATUS_MEMORY_NOT_ALLOCATED;
        goto end;
    }

    status = ZwDeviceIoControlFile(
        handle,
        NULL,
        NULL,
        NULL,
        &status_block,
        IOCTL_STORAGE_QUERY_PROPERTY,
        &storage_property,
        sizeof( STORAGE_PROPERTY_QUERY ),
        device_descriptor,
        storage_descriptor_header.Size
    );

    if ( !NT_SUCCESS( status )  ) 
    {
        DEBUG_LOG( "ZwDeviceIoControlFile second call failed with status %x", status );
        goto end;
    }

    if ( device_descriptor->SerialNumberOffset > 0 ) 
    {
        serial_number = ( PCHAR )( ( UINT64 )device_descriptor + device_descriptor->SerialNumberOffset );
        serial_length = strnlen_s( serial_number, DEVICE_DRIVE_0_SERIAL_CODE_LENGTH ) + 1;

        if ( serial_length > ConfigDrive0MaxSize )
        {
            DEBUG_ERROR( "Serial length is greater then config drive 0 buffer size" );
            status = STATUS_BUFFER_TOO_SMALL;
            goto end;
        }

        RtlCopyMemory(
            ConfigDrive0Serial,
            serial_number,
            serial_length
        );
    }

end:

    if ( handle )
        ZwClose( handle );

    if ( device_descriptor )
        ExFreePoolWithTag( device_descriptor, POOL_TAG_INTEGRITY );

    return status;
}