Delphi Winsock Hooking Example by Aphex

{

http://www.iamaphex.cjb.net

unremote@knology.net

This example shows you how to hook winsock functions

of a target process and control incomming and outgoing

data. It is based on send and recv but it will work the

same way applied to sendto and recvfrom.

The output file is a CPL (Control Panel Extension) which

is simply a special DLL that is loaded when it is double

clicked. This saves us from having to write a seperate

loader for the hook library.

The example shows how to hook the needed functions and

perform some simple manipulation of the data, using two

different methods of accessing the data. The second, which

uses pointers, is more flexible but also more complex.

}

library Project1;

uses

Windows,

Winsock,

SysUtils,

madCodeHook;

{$R *.RES}

{$E CPL}

var

sendNextHook: function(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall;

recvNextHook: function(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall;

DataSocket: TSocket;

const

szTargetExe: string = 'GAME.EXE';

function ConvertDataToAscii(Buffer: pointer; Length: Word): string;

var

Iterator: integer;

AsciiBuffer: string;

begin

AsciiBuffer := '';

for Iterator := 0 to Length - 1 do

begin

if char(pointer(integer(Buffer) + Iterator)^) in [#32..#127] then

AsciiBuffer := AsciiBuffer + ' ' + char(pointer(integer(Buffer) + Iterator)^) + ' '

else

AsciiBuffer := AsciiBuffer + ' . ';

end;

Result := AsciiBuffer;

end;

function ConvertDataToHex(Buffer: pointer; Length: Word): string;

var

Iterator: integer;

HexBuffer: string;

begin

HexBuffer := '';

for Iterator := 0 to Length - 1 do

begin

HexBuffer := HexBuffer + IntToHex(Ord(char(pointer(integer(Buffer) + Iterator)^)), 2) + ' ';

end;

Result := HexBuffer;

end;

function recvHookProc(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall;

var

AsciiBuffer: string;

HexBuffer: string;

DataBuffer: pchar;

begin

//call the real winsock function

Result := recvNextHook(s, Buf, len, flags);

//allocate memory for our copy of the data

GetMem(DataBuffer, Result);

try

//get our copy of the data

CopyMemory(DataBuffer, @Buf, Result);

//using the data as a byte array

DataBuffer[0] := chr(10); //changing first byte

DataBuffer[1] := chr(20); //changing second byte

DataBuffer[2] := chr(30); //changing thrid byte

//using the data as a pointer to other data sizes

word(pointer(DataBuffer)^) := 10; //changing first 2 bytes

dword(pointer(integer(DataBuffer) + 2)^) := 20; //changing next 4 bytes

word(pointer(integer(DataBuffer) + 6)^) := 30; //changing next 2 bytes

//overwrite the original data with our new data

CopyMemory(@Buf, DataBuffer, Result);

finally

FreeMem(DataBuffer);

end;

//convert data to readable ascii suitable for logging

AsciiBuffer := ConvertDataToAscii(@Buf, Result);

//convert data to readable hex suitable for logging

HexBuffer := ConvertDataToHex(@Buf, Result);

end;

function sendHookProc(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall;

var

AsciiBuffer: string;

HexBuffer: string;

DataBuffer: pchar;

begin

Result := 0;

//save the socket so we can send data too

DataSocket := s;

//allocate memory for our copy of the data

GetMem(DataBuffer, Result);

try

//get our copy of the data

CopyMemory(DataBuffer, @Buf, Result);

//using the data as a byte array

DataBuffer[0] := chr(10); //changing first byte

DataBuffer[1] := chr(20); //changing second byte

DataBuffer[2] := chr(30); //changing thrid byte

//using the data as a pointer to other data sizes

word(pointer(DataBuffer)^) := 10; //changing first 2 bytes

dword(pointer(integer(DataBuffer) + 2)^) := 20; //changing next 4 bytes

word(pointer(integer(DataBuffer) + 6)^) := 30; //changing next 2 bytes

//overwrite the original data with our new data

CopyMemory(@Buf, DataBuffer, Result);

finally

FreeMem(DataBuffer);

end;

//convert data to readable ascii suitable for logging

AsciiBuffer := ConvertDataToAscii(@Buf, Result);

//convert data to readable hex suitable for logging

HexBuffer := ConvertDataToHex(@Buf, Result);

//call the real winsock function

Result := sendNextHook(s, Buf, len, flags);

end;

procedure EntryPoint(Reason: dword); stdcall;

var

lpFileName: array [0..MAX_PATH - 1] of char;

StartInfo: TStartupInfo;

ProcInfo: TProcessInformation;

begin

if Reason = DLL_PROCESS_ATTACH then

begin

//check if we are injected inside the target

if lstrcmpi(pchar(Copy(ParamStr(0), Length(ParamStr(0)) - Length(szTargetExe) + 1, Length(szTargetExe))), pchar(szTargetExe)) = 0 then

begin

//if we are then we hook the needed functions

DataSocket := 0;

HookCode(@send, @sendHookProc, @sendNextHook);

HookCode(@recv, @recvHookProc, @recvNextHook);

end

else

begin

//if not then load the target and inject ourself

GetModuleFileName(hInstance, @lpFileName, MAX_PATH);

ZeroMemory(@StartInfo, SizeOf(TStartupInfo));

ZeroMemory(@ProcInfo, SizeOf(TProcessInformation));

StartInfo.dwFlags := STARTF_USESHOWWINDOW;

StartInfo.wShowWindow := SW_SHOW;

CreateProcess(PChar(ExtractFilePath(lpFileName) + szTargetExe), nil, nil, nil, False, 0, nil, nil, StartInfo, ProcInfo);

Sleep(3000);

InjectLibrary(ProcInfo.hProcess, lpFileName);

end;

begin

DLLProc := @EntryPoint;

EntryPoint(DLL_PROCESS_ATTACH);

end.