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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. |
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