Reversing Ntdll.dll and Hardcoding Syscalls directly from c++.
In this tutorial I will show you how to reverse Ntdll.dll functions and find the System call then hardcoded it and use it in your c++ project to bypass Userland hooks.
1 – reverse NtCreateFile and NtWriteFile functions and find the system call.
2 – Create function prototype
3 – Hardcode the function system call.
4 – Use the function in main and All done.
So lets start ,
first open your IDA and drag and drop the Ntdll.dll from c:\windows\syswow64\ntdll.dll
then make sure you import idb file .
the next step go to Exports tap and search for Ntcreatefile function .
Now we see :
move eax,55h 55 is the system call number for NtCreateFile function ,
and becouse we are in 64bit system and our application is 86bit so we need to switch to wow64bit ,
so we need to make some changes to this asm code , what we ganna do is make switch to syswow64 manualy using call dword ptr fs :[0xC0]
so the code will be like this :
now we have our asm code for NtcreateFile , now do the same for NtwriteFile function.
Ok we are done save the asm code to text file any were in your disk and close IDA.
Go to visual studio create new c++ empty project and follow me .
What we need now is define the typedef of our functions and ofcurse we need to define others structs and STRING , UNICODE , functions like RtlAnsiStringToUnicodeString to convert the char to string then string to unicode with less code and liss missing.
and becouse we are using Nt functions and we are hardcoding every thing we need to pay attention to the file path we want to write to it.
if we use Winapi and need to create file using CreateFileA Or CreateFileW the path will be like this . c:\users\mose3c\Desktop\my.jpg
and the winapi function will make every thing for you like converting the path to Nt Path . you can see this closely if you open ApiMonotring and trace the CreateFile function you will know what this function do for you and how much make your life easy.
now our Nt path will be like this : \\??\\c:\\users\\mose3c\\Desktop\\my.jpg
other wise will not work.
ok lets define our functions prototype and others .
now lets write our inline asm code .
ok done.whats next , lets go to to our main function.
and pass the address of WIN10_64_NtCreateFile = to NtCreateFile and WIN10_64_NtWriteFile to NtWriteFile
like this
ok . and now we will define attributes and others args but its not our tutorial will skip it and if you need any help just replay and i will try to help you .
now Its bingo we have done build the project and test it if you need to run it in windows 7 you need to reverse the ntdll.dll for windows 7
becouse its wow64 you can't find alot of content and you have to done it by your self
i realy want to make more tutorials what do you like the next tutorial to be about .?
its up to you let me know in replay pleas .
In this tutorial I will show you how to reverse Ntdll.dll functions and find the System call then hardcoded it and use it in your c++ project to bypass Userland hooks.
1 – reverse NtCreateFile and NtWriteFile functions and find the system call.
2 – Create function prototype
3 – Hardcode the function system call.
4 – Use the function in main and All done.
So lets start ,
first open your IDA and drag and drop the Ntdll.dll from c:\windows\syswow64\ntdll.dll
then make sure you import idb file .
the next step go to Exports tap and search for Ntcreatefile function .
Now we see :
Код:
mov eax, 55h ; 'U' ; NtCreateFile
mov edx, offset _Wow64SystemServiceCall@0 ; Wow64SystemServiceCall()
call edx ; Wow64SystemServiceCall() ; Wow64SystemServiceCall()
retn 2Ch; ','move eax,55h 55 is the system call number for NtCreateFile function ,
and becouse we are in 64bit system and our application is 86bit so we need to switch to wow64bit ,
so we need to make some changes to this asm code , what we ganna do is make switch to syswow64 manualy using call dword ptr fs :[0xC0]
so the code will be like this :
Код:
mov eax,55h
call dword ptr fs:[0xC0] ; wow64cpu.dll!X86SwitchTo64BitMode
retn 2ChOk we are done save the asm code to text file any were in your disk and close IDA.
Go to visual studio create new c++ empty project and follow me .
What we need now is define the typedef of our functions and ofcurse we need to define others structs and STRING , UNICODE , functions like RtlAnsiStringToUnicodeString to convert the char to string then string to unicode with less code and liss missing.
and becouse we are using Nt functions and we are hardcoding every thing we need to pay attention to the file path we want to write to it.
if we use Winapi and need to create file using CreateFileA Or CreateFileW the path will be like this . c:\users\mose3c\Desktop\my.jpg
and the winapi function will make every thing for you like converting the path to Nt Path . you can see this closely if you open ApiMonotring and trace the CreateFile function you will know what this function do for you and how much make your life easy.
now our Nt path will be like this : \\??\\c:\\users\\mose3c\\Desktop\\my.jpg
other wise will not work.
ok lets define our functions prototype and others .
Код:
typedef _Return_type_success_(return >= 0) LONG NTSTATUS;
typedef struct _STRING { USHORT Length; USHORT MaximumLength; PCHAR Buffer; } STRING;
typedef STRING * PSTRING;
typedef STRING ANSI_STRING;
typedef PSTRING PANSI_STRING;
typedef struct _UNICODE_STRING
{
USHORT Length;
USHORT MaximumLength;
PWSTR Buffer;
} UNICODE_STRING, * PUNICODE_STRING;
typedef struct _OBJECT_ATTRIBUTES
{
ULONG Length;
HANDLE RootDirectory;
PUNICODE_STRING ObjectName;
ULONG Attributes;
PVOID SecurityDescriptor;
PVOID SecurityQualityOfService;
} OBJECT_ATTRIBUTES, * POBJECT_ATTRIBUTES;
typedef struct _IO_STATUS_BLOCK
{
union
{
NTSTATUS Status;
VOID* Pointer;
};
ULONG_PTR Information;
} IO_STATUS_BLOCK, * PIO_STATUS_BLOCK;
typedef NTSTATUS(NTAPI* _RtlGetVersion)(PRTL_OSVERSIONINFOW lpVersionInformation);
typedef void (NTAPI* _RtlInitUnicodeString)(PUNICODE_STRING DestinationString, PCWSTR SourceString);
typedef DWORD(NTAPI* _RtlAnsiStringToUnicodeString)(PUNICODE_STRING, PANSI_STRING, BOOL);
typedef VOID(NTAPI* _RtlInitString)(PSTRING DestinationString, char* SourceString);
_RtlAnsiStringToUnicodeString RtlAnsiStringToUnicodeString = (_RtlAnsiStringToUnicodeString)GetProcAddress(GetModuleHandleA("ntdll.dll"), "RtlAnsiStringToUnicodeString");
_RtlInitUnicodeString RtlInitUnicodeString = (_RtlInitUnicodeString)GetProcAddress(GetModuleHandleA("ntdll.dll"), "RtlInitUnicodeString");
_RtlInitString RtlInitString = (_RtlInitString)GetProcAddress(GetModuleHandleA("ntdll.dll"), "RtlInitString");
typedef VOID(NTAPI* PIO_APC_ROUTINE)(_In_ PVOID ApcContext, _In_ PIO_STATUS_BLOCK IoStatusBlock, _In_ ULONG Reserved);
/******* functions *******/
typedef NTSTATUS(NTAPI* _NtCreateFile)(PHANDLE FileHandle, ACCESS_MASK DesiredAccess, POBJECT_ATTRIBUTES ObjectAttributes, PIO_STATUS_BLOCK IoStatusBlock, PLARGE_INTEGER AllocationSize OPTIONAL, ULONG FileAttributes, ULONG ShareAccess, ULONG CreateDisposition, ULONG CreateOptions, PVOID EaBuffer OPTIONAL, ULONG EaLength);
typedef NTSTATUS(NTAPI* _NtWriteFile)(HANDLE FileHandle, HANDLE Event, PIO_APC_ROUTINE ApcRoutine, PVOID ApcContext, PIO_STATUS_BLOCK IoStatusBlock, PVOID Buffer, ULONG Length, PLARGE_INTEGER ByteOffset, PULONG Key);
typedef NTSTATUS(NTAPI* _NtResumeThread)(HANDLE ThreadHandle, PULONG SuspendCount);
typedef NTSTATUS(NTAPI* _NtClose)(HANDLE Handle);
_NtCreateFile NtCreateFile;
_NtWriteFile NtWriteFile;
_NtResumeThread NtResumeThread;
_NtClose NtClose;
Код:
_declspec(naked) NTSTATUS _stdcall WIN10_64_NtCreateFile(PHANDLE FileHandle, ACCESS_MASK DesiredAccess, POBJECT_ATTRIBUTES ObjectAttributes, PIO_STATUS_BLOCK IoStatusBlock, PLARGE_INTEGER AllocationSize OPTIONAL, ULONG FileAttributes, ULONG ShareAccess, ULONG CreateDisposition, ULONG CreateOptions, PVOID EaBuffer OPTIONAL, ULONG EaLength)
{
_asm
{
mov eax, 55h
call dword ptr fs : [0xC0]
retn 2Ch
}
}
_declspec(naked) NTSTATUS _stdcall WIN10_64_NtWriteFile(HANDLE FileHandle, HANDLE Event, PIO_APC_ROUTINE ApcRoutine, PVOID ApcContext, PIO_STATUS_BLOCK IoStatusBlock, PVOID Buffer, ULONG Length, PLARGE_INTEGER ByteOffset, PULONG Key)
{
_asm
{
mov eax, 1A0008h
call dword ptr fs : [0xC0]
retn 24h
}
}and pass the address of WIN10_64_NtCreateFile = to NtCreateFile and WIN10_64_NtWriteFile to NtWriteFile
like this
Код:
NtCreateFile = &WIN10_64_NtCreateFile
NtWriteFile = &WIN10_64_NtWriteFile
Код:
NTSTATUS status;
UNICODE_STRING Ustring;
ANSI_STRING as;
HANDLE hFile;
IO_STATUS_BLOCK risb;
OBJECT_ATTRIBUTES robj;
char szDir[MAX_PATH];
strcpy(szDir, "\\??\\c:\users\mose3c\Desktop\my.txt");
as.Buffer = (char*)malloc(strlen(szDir) + 1);
strcpy(as.Buffer, szDir);
as.Length = as.MaximumLength = Ustring.MaximumLength = Ustring.Length = strlen(szDir);
// convert directory name from ANSI to UNICODE
_RtlAnsiStringToUnicodeString RtlAnsiStringToUnicodeString = (_RtlAnsiStringToUnicodeString)GetProcAddress(GetModuleHandleA("ntdll.dll"), "RtlAnsiStringToUnicodeString");
RtlAnsiStringToUnicodeString(&Ustring, &as, TRUE);
RtlFillMemory(&obj, sizeof(OBJECT_ATTRIBUTES), 0);
robj.Length = sizeof(obj);
robj.Attributes = OBJ_CASE_INSENSITIVE;
robj.RootDirectory = NULL;
robj.SecurityDescriptor = NULL;
robj.SecurityQualityOfService = NULL;
robj.ObjectName = &Ustring;
status = NtCreateFile(&hFile, FILE_GENERIC_READ | FILE_GENERIC_WRITE | SYNCHRONIZE, &obj, &risb, 0, FILE_ATTRIBUTE_NORMAL, 0, FILE_OVERWRITE_IF, FILE_SYNCHRONOUS_IO_NONALERT, NULL, 0);
if (!NT_SUCCESS(status))
return 1 ;
IO_STATUS_BLOCK WFISB;
status = NtWriteFile(hFile, NULL, NULL, NULL, &WFISB, /*your Buffer here*/, BufLen, 0, NULL);
if (!NT_SUCCESS(status))
return 1;now Its bingo we have done build the project and test it if you need to run it in windows 7 you need to reverse the ntdll.dll for windows 7
becouse its wow64 you can't find alot of content and you have to done it by your self
i realy want to make more tutorials what do you like the next tutorial to be about .?
its up to you let me know in replay pleas .
