Windows NT Driver >> Assembly >> File

IRP


參考資訊:
1. Four-F
2. Source Code

基本上,驅動程式(韌體)的基本功能就是當作User Application(軟體)和硬體的溝通橋樑,軟體可以透過很多種方式和驅動程式溝通,而最常用的溝通方式就是把驅動程式當做是一個檔案在操作,軟體可以透過檔案讀寫的方式和驅動程式做資料傳遞的動作,驅動程式最後再把資料輸出到硬體裝置上,而在Windows系統上,可以使用CreateFile(檔案開啟)、ReadFile(讀取檔案)、WriteFile(寫入檔案)、CloseHandle(關閉檔案)等檔案操作的Win32 API,而驅動程式如何跟軟體串接起來呢?驅動程式必須在DriverEntry()設定IRP_MJ_CREATE(CreateFile)、IRP_MJ_READ(ReadFile)、IRP_MJ_WRITE(WriteFile)、IRP_MJ_CLOSE(CloseHandle)的Callback副程式,這樣I/O Manager才會知道如何串起這條溝通管道。

基本的步驟如下:
1. 安裝驅動程式時,驅動程式註冊自己的名字、註冊檔案的Callback副程式
2. 軟體開啟檔案(使用驅動程式的名字(GUID或者Symbolic)),I/O Manager呼叫驅動程式的IRP_MJ_CREATE
3. 軟體讀寫檔案,I/O Manager呼叫驅動程式的IRP_MJ_READ、IRP_MJ_WRITE
4. 軟體關閉檔案,I/O Manager呼叫驅動程式的IRP_MJ_CLOSE

當然,使用者可能也很好奇,為何軟體不直接跟硬體溝通就好,還要透過一個這麼複雜的驅動程式當作溝通橋樑?當軟體可以直接溝通硬體時,會造成太多衝突,以及優先順序問題,而因為可以直接控制硬體,因此,寫出一個非惡意但具有破壞性的軟體時,是間接可以把一個系統搞壞掉,這也是為何要在Win98之後,架構出一個驅動程式的原因,至少有一個溝通和協調的機制,當然隨著系統的發展,規定就會變成越來嚴格,這也是Microsoft致力於保護系統的最好方式!

對應的溝通管道

Win32 API Kernel IRP
CreateFile() IRP_MJ_CREATE
ReadFile() IRP_MJ_READ
WriteFile() IRP_MJ_WRITE
CloseHandle() IRP_MJ_CLOSE

接著司徒將介紹如何在驅動程式做檔案的基本操作

main.asm

.386p
.model flat, stdcall
option casemap:none
 
include c:\masm32\include\w2k\ntstatus.inc
include c:\masm32\include\w2k\ntddk.inc
include c:\masm32\include\w2k\ntoskrnl.inc
include c:\masm32\include\w2k\ntddkbd.inc
include c:\masm32\Macros\Strings.mac
includelib c:\masm32\lib\wxp\i386\ntoskrnl.lib
 
public DriverEntry

.const
DEV_NAME word "\","D","e","v","i","c","e","\","M","y","D","r","i","v","e","r",0
SYM_NAME word "\","D","o","s","D","e","v","i","c","e","s","\","M","y","D","r","i","v","e","r",0
  
.code
IrpFile proc pOurDevice:PDEVICE_OBJECT, pIrp:PIRP
  IoGetCurrentIrpStackLocation pIrp
  movzx eax, (IO_STACK_LOCATION PTR [eax]).MajorFunction

  .if eax == IRP_MJ_CREATE
    invoke DbgPrint, $CTA0("IRP_MJ_CREATE")
  .elseif eax == IRP_MJ_READ
    invoke DbgPrint, $CTA0("IRP_MJ_READ")
  .elseif eax == IRP_MJ_WRITE
    invoke DbgPrint, $CTA0("IRP_MJ_WRITE")
  .elseif eax == IRP_MJ_CLOSE
    invoke DbgPrint, $CTA0("IRP_MJ_CLOSE")
  .endif

  mov eax, pIrp
  and (_IRP PTR [eax]).IoStatus.Information, 0
  mov (_IRP PTR [eax]).IoStatus.Status, STATUS_SUCCESS
  fastcall IofCompleteRequest, pIrp, IO_NO_INCREMENT
  mov eax, STATUS_SUCCESS
  ret
IrpFile endp

Unload proc pOurDriver:PDRIVER_OBJECT
  local szSymName:UNICODE_STRING
  
  invoke RtlInitUnicodeString, addr szSymName, offset SYM_NAME
  invoke IoDeleteSymbolicLink, addr szSymName
  
  mov eax, pOurDriver
  invoke IoDeleteDevice, (DRIVER_OBJECT PTR [eax]).DeviceObject
  ret
Unload endp

DriverEntry proc pOurDriver:PDRIVER_OBJECT, pOurRegistry:PUNICODE_STRING
  local pOurDevice:PDEVICE_OBJECT
  local suDevName:UNICODE_STRING
  local szSymName:UNICODE_STRING
  
  mov eax, pOurDriver
  mov (DRIVER_OBJECT PTR [eax]).MajorFunction[IRP_MJ_CREATE * (sizeof PVOID)], offset IrpFile
  mov (DRIVER_OBJECT PTR [eax]).MajorFunction[IRP_MJ_CLOSE  * (sizeof PVOID)], offset IrpFile
  mov (DRIVER_OBJECT PTR [eax]).MajorFunction[IRP_MJ_WRITE  * (sizeof PVOID)], offset IrpFile
  mov (DRIVER_OBJECT PTR [eax]).MajorFunction[IRP_MJ_READ   * (sizeof PVOID)], offset IrpFile
  mov (DRIVER_OBJECT PTR [eax]).DriverUnload, offset Unload
  
  invoke RtlInitUnicodeString, addr suDevName, offset DEV_NAME
  invoke RtlInitUnicodeString, addr szSymName, offset SYM_NAME
  invoke IoCreateDevice, pOurDriver, NULL, addr suDevName, FILE_DEVICE_UNKNOWN, 0, FALSE, addr pOurDevice
  .if eax == STATUS_SUCCESS
    mov eax, pOurDevice
    or (DEVICE_OBJECT PTR [eax]).Flags, DO_BUFFERED_IO
    and (DEVICE_OBJECT PTR [eax]).Flags, not DO_DEVICE_INITIALIZING
    invoke IoCreateSymbolicLink, addr szSymName, addr suDevName
  .endif
  ret
DriverEntry endp
end DriverEntry
.end

IrpFile()處理檔案相關的IRP,目前只列印IRP資訊,其餘不處理。

為了測試驅動程式的檔案讀寫IRP,我們需要一個User Application做測試(app.asm)

.386p
.model flat, stdcall
option casemap:none

include c:\masm32\include\windows.inc
include c:\masm32\include\masm32.inc
include c:\masm32\include\user32.inc
include c:\masm32\include\msvcrt.inc
include c:\masm32\include\kernel32.inc

includelib c:\masm32\lib\user32.lib
includelib c:\masm32\lib\masm32.lib
includelib c:\masm32\lib\msvcrt.lib
includelib c:\masm32\lib\kernel32.lib

.const
DEVNAME db "\\.\MyDriver",0
ERR_MSG db "failed to open mydriver",0

.data?
hFile    dd ?
dwRet    dd ?
szBuffer db 255 dup(?)

.code
start:
  invoke CreateFile, offset DEVNAME, GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0
  .if eax == INVALID_HANDLE_VALUE
    invoke crt_printf, offset ERR_MSG
    invoke ExitProcess, -1
  .endif

  mov hFile, eax
  invoke WriteFile, hFile, offset szBuffer, 255, offset dwRet, 0
  invoke ReadFile, hFile, offset szBuffer, 255, offset dwRet, 0
  invoke CloseHandle, hFile
  invoke ExitProcess, 0
  
end start

編譯App:

c:\masm32\bin\ml /c /coff /Cp /Zi /Zd "app.asm"
c:\masm32\bin\link /SUBSYSTEM:CONSOLE /DEBUG /VERSION:4.0 /OUT:"app.exe" "app.obj"

接著執行該User Application就可以看到結果

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