截取程序的网络封包（Delphi Hook API）

有时候我们需要对其它应用程序发送和接收的网络数据进行拦截,比如要对IE发送的**头进行分析,得到请求的地址等.这次我们可以用一些例如WPE, Sniffer之类的工具来达到目的.但是工具功能有限,要想实现更强大的功能,还是我们自己动手来DIY吧.

拦截网络数据封包的方法有三种,一是将网卡设为混杂模式,这次就可以监视到局域网上所有的数据包,二是HOOK目标进程的发送和接收的API函数,第三种方法是自己实现一个代理的DLL.在这里我们使用HOOK API的方法,这样易于实现,而且也不会得到大量的无用数据(如第一种方法就会监视到所有的网络数据).

下面是一个尽量简化了的API HOOK的模版,原理是利用消息钩子将DLL中的代码注入到目标进程中,再用GetProcAddress得到API函数入口地址,将函数入口址改为自己定义的函数入口,这样就得到了API函数的相应参数,处理完后,再改回真实API函数入口地址,并调用它.
HOOK.DLL的代码:

library Hook; 

uses 
SysUtils, 
windows, 
Messages, 
APIHook in 'APIHook.pas'; 

type 
PData = ^TData; 
TData = record 
Hook: THandle; 
Hooked: Boolean; 
end; 

var 
DLLData: PData; 

{------------------------------------} 
{过程名:HookProc 
{过程功能:HOOK过程 
{过程参数:nCode, wParam, lParam消息的相 
{ 关参数 
{------------------------------------} 
procedure HookProc(nCode, wParam, lParam: LongWORD);stdcall; 
begin 
if not DLLData^.Hooked then 
begin 
HookAPI; 
DLLData^.Hooked := True; 
end; 
//调用下一个Hook 
CallNextHookEx(DLLData^.Hook, nCode, wParam, lParam); 
end; 


{------------------------------------} 
{函数名:InstallHook 
{函数功能:在指定窗口上安装HOOK 
{函数参数:sWindow:要安装HOOK的窗口 
{返回值:成功返回TRUE,失败返回FALSE 
{------------------------------------} 
function InstallHook(SWindow: LongWORD):Boolean;stdcall; 
var 
ThreadID: LongWORD; 
begin 
Result := False; 
DLLData^.Hook := 0; 
ThreadID := GetWindowThreadProcessId(sWindow, nil); 
//给指定窗口挂上钩子 
DLLData^.Hook := SetWindowsHookEx(WH_GETMESSAGE, @HookProc, Hinstance, ThreadID); 
if DLLData^.Hook > 0 then 
Result := True //是否成功HOOK 
else 
exit; 
end; 

{------------------------------------} 
{过程名:UnHook 
{过程功能:卸载HOOK 
{过程参数:无 
{------------------------------------} 
procedure UnHook;stdcall; 
begin 
UnHookAPI; 
//卸载Hook 
UnhookWindowsHookEx(DLLData^.Hook); 
end; 

{------------------------------------} 
{过程名:DLL入口函数 
{过程功能:进行DLL初始化,释放等 
{过程参数:DLL状态 
{------------------------------------} 
procedure MyDLLHandler(Reason: Integer); 
var 
FHandle: LongWORD; 
begin 
case Reason of 
DLL_PROCESS_ATTACH: 
begin //建立文件映射,以实现DLL中的全局变量 
FHandle := CreateFileMapping($FFFFFFFF, nil, PAGE_READWRITE, 0, $ffff, 'MYDLLDATA'); 
if FHandle = 0 then 
if GetLastError = ERROR_ALREADY_EXISTS then 
begin 
FHandle := OpenFileMapping(FILE_MAP_ALL_ACCESS, False, 'MYDLLDATA'); 
if FHandle = 0 then Exit; 
end else Exit; 
DLLData := MapViewOfFile(FHandle, FILE_MAP_ALL_ACCESS, 0, 0, 0); 
if DLLData = nil then 
CloseHandle(FHandle); 
end; 
DLL_PROCESS_DETACH: 
begin 
if Assigned(DLLData) then 
begin 
UnmapViewOfFile(DLLData); 
DLLData := nil; 
end; 
end; 
end; 
end; 

{$R *.res} 
exports 
InstallHook, UnHook, HookProc; 

begin 
DLLProc := @MyDLLHandler; 
MyDLLhandler(DLL_PROCESS_ATTACH); 
DLLData^.Hooked := False; 
end. 

---------------------------------------------------------------------------------------- 
APIHook.Pas的代码: 

unit APIHook; 

interface 

uses 
SysUtils, 
Windows, WinSock; 

type 
//要HOOK的API函数定义 
TSockProc = function (s: TSocket; var Buf; len, flags: Integer): Integer; stdcall; 

PJmpCode = ^TJmpCode; 
TJmpCode = packed record 
JmpCode: BYTE; 
Address: TSockProc; 
MovEAX: Array [0..2] of BYTE; 
end; 

//--------------------函数声明--------------------------- 
procedure HookAPI; 
procedure UnHookAPI; 

var 
OldSend, OldRecv: TSockProc; //原来的API地址 
JmpCode: TJmpCode; 
OldProc: array [0..1] of TJmpCode; 
AddSend, AddRecv: pointer; //API地址 
TmpJmp: TJmpCode; 
ProcessHandle: THandle; 
implementation 

{---------------------------------------} 
{函数功能:Send函数的HOOK 
{函数参数:同Send 
{函数返回值:integer 
{---------------------------------------} 
function MySend(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall; 
var 
dwSize: cardinal; 
begin 
//这儿进行发送的数据处理 
MessageBeep(1000); //简单的响一声 
//调用直正的Send函数 
WriteProcessMemory(ProcessHandle, AddSend, @OldProc[0], 8, dwSize); 
Result := OldSend(S, Buf, len, flags); 
JmpCode.Address := @MySend; 
WriteProcessMemory(ProcessHandle, AddSend, @JmpCode, 8, dwSize); 
end; 

{---------------------------------------} 
{函数功能:Recv函数的HOOK 
{函数参数:同Recv 
{函数返回值:integer 
{---------------------------------------} 
function MyRecv(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall; 
var 
dwSize: cardinal; 
begin 
//这儿进行接收的数据处理 
MessageBeep(1000); //简单的响一声 
//调用直正的Recv函数 
WriteProcessMemory(ProcessHandle, AddRecv, @OldProc[1], 8, dwSize); 
Result := OldRecv(S, Buf, len, flags); 
JmpCode.Address := @MyRecv; 
WriteProcessMemory(ProcessHandle, AddRecv, @JmpCode, 8, dwSize); 
end; 

{------------------------------------} 
{过程功能:HookAPI 
{过程参数:无 
{------------------------------------} 
procedure HookAPI; 
var 
DLLModule: THandle; 
dwSize: cardinal; 
begin 
ProcessHandle := GetCurrentProcess; 
DLLModule := LoadLibrary('ws2_32.dll'); 
AddSend := GetProcAddress(DLLModule, 'send'); //取得API地址 
AddRecv := GetProcAddress(DLLModule, 'recv'); 
JmpCode.JmpCode := $B8; 
JmpCode.MovEAX[0] := $FF; 
JmpCode.MovEAX[1] := $E0; 
JmpCode.MovEAX[2] := 0; 
ReadProcessMemory(ProcessHandle, AddSend, @OldProc[0], 8, dwSize); 
JmpCode.Address := @MySend; 
WriteProcessMemory(ProcessHandle, AddSend, @JmpCode, 8, dwSize); //修改Send入口 
ReadProcessMemory(ProcessHandle, AddRecv, @OldProc[1], 8, dwSize); 
JmpCode.Address := @MyRecv; 
WriteProcessMemory(ProcessHandle, AddRecv, @JmpCode, 8, dwSize); //修改Recv入口 
OldSend := AddSend; 
OldRecv := AddRecv; 
end; 

{------------------------------------} 
{过程功能:取消HOOKAPI 
{过程参数:无 
{------------------------------------} 
procedure UnHookAPI; 
var 
dwSize: Cardinal; 
begin 
WriteProcessMemory(ProcessHandle, AddSend, @OldProc[0], 8, dwSize); 
WriteProcessMemory(ProcessHandle, AddRecv, @OldProc[1], 8, dwSize); 
end; 

end. 

 

---------------------------------------------------------------------------------------------
编译这个DLL后,再新建一个程序调用这个DLL的InstallHook并传入目标进程的主窗口句柄就可:

unit fmMain; 

interface 

uses 
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, 
Dialogs, StdCtrls; 

type 
TForm1 = class(TForm) 
Button1: TButton; 
Button2: TButton; 
Edit1: TEdit; 
procedure Button1Click(Sender: TObject); 
procedure Button2Click(Sender: TObject); 
private 
{ Private declarations } 
public 
{ Public declarations } 
end; 

var 
Form1: TForm1; 
InstallHook: function (SWindow: THandle):Boolean;stdcall; 
UnHook: procedure;stdcall; 
implementation 

{$R *.dfm} 

procedure TForm1.Button1Click(Sender: TObject); 
var 
ModuleHandle: THandle; 
TmpWndHandle: THandle; 
begin 
TmpWndHandle := 0; 
TmpWndHandle := FindWindow(nil, '目标窗口的标题'); 
if not isWindow(TmpWndHandle) then 
begin 
MessageBox(self.Handle, '没有找到窗口', '!!!', MB_OK); 
exit; 
end; 
ModuleHandle := LoadLibrary('Hook.dll'); 
@InstallHook := GetProcAddress(ModuleHandle, 'InstallHook'); 
@UnHook := GetProcAddress(ModuleHandle, 'UnHook'); 
if InstallHook(FindWindow(nil, 'Untitled')) then 
ShowMessage('Hook OK'); 
end; 

procedure TForm1.Button2Click(Sender: TObject); 
begin 
UnHook 
end; 

end.