View Single Post
Old 02-23-2004, 08:28 PM   #4 (permalink)
n0nsensical
Junkie
 
Location: San Francisco
I've screwed around with it trying to inject code into another process on Windows 9x (on NT you can just use VirtualAllocEx and CreateRemoteThread but the latter isn't implemented on 9x), but I couldn't get it working and stopped bothering because I figure everyone should be using 2000 or XP by now anyway. ;-) It is kind of confusing and I'm not sure why I couldn't do it before but some code I just wrote seems to work.

Basically you need a
LRESULT CALLBACK HookProc(int, WPARAM, LPARAM),
called by Windows when the thread(s) you are monitoring get whatever type of message, and then you have to call SetWindowsHookEx with a pointer to that function, the handle to the DLL the function is in if necessary, the type of hook, and which threads. If you want the hook on another process you have to put the callback function in a DLL.

First the driver program, as simple as it gets:
Code:
#include <windows.h>

extern "C" void startKeyMonitoring();
extern "C" void stopKeyMonitoring();

int main()
{
	startKeyMonitoring();
	Sleep(10000);
	stopKeyMonitoring();
	return 0;
}
And now the DLL. The .lib file needs to be linked with the driver program for the start and stop functions. It then loads itself at runtime with the LoadLibrary API because you need the handle for SetWindowsHookEx. For some reason Visual Studio is making me use a .def file even though I have dllexport; if anyone knows why please enlighten me. Passing 0 for the dwThreadId parameter of SetWindowsHookEx monitors all threads in the same desktop.

Code:
#include <windows.h>
#include <sstream>

BOOL __stdcall DllMain(HANDLE, DWORD, LPVOID)
{
	return TRUE;
}

HHOOK g_hhk;

extern "C" __declspec(dllexport)
void startKeyMonitoring()
{
	HMODULE hLib = LoadLibrary("hooklib.dll");
	HOOKPROC proc = (HOOKPROC)GetProcAddress(hLib, "KeyProc");
	g_hhk = SetWindowsHookEx(WH_KEYBOARD, proc, hLib, 0);
}

extern "C" __declspec(dllexport)
void stopKeyMonitoring()
{
	UnhookWindowsHookEx(g_hhk);
}

extern "C" __declspec(dllexport)
LRESULT CALLBACK KeyProc(int nCode, WPARAM wParam, LPARAM lParam)
{
	std::ostringstream oss;
	oss << "Here I am in process " << GetCurrentProcessId() << " with a message for you.";
	MessageBox(NULL, oss.str().c_str(), "Hello", MB_OK);
	return CallNextHookEx(g_hhk, nCode, wParam, lParam);
}
And there you go, you get some message boxes with the PID of whatever process received the keyboard messages.

Last edited by n0nsensical; 02-23-2004 at 08:32 PM..
n0nsensical is offline  
 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360