2

In the debugger program OllyDbg, How do I set a breakpoint when the left mouse button is pressed? It doesn't matter what it clicks on, so upon mouse click, the breakpoint stops the debugger.

4

All messages in a gui application passes through the Application Defined Callback WinProc whose prototype is

LRESULT CALLBACK WindowProc(
  _In_ HWND   hwnd,
  _In_ UINT   uMsg,
  _In_ WPARAM wParam,
  _In_ LPARAM lParam
);

so when you have breakpointed on a wndproc

esp    -> return Address
esp+4  -> hwnd 
esp+8  -> uMsg  
.....

** MSDN Doc For List of messages**

to know a windoproc or class proc use alt+w shortcut in ollydbg (opens a list of windows ) right click to open the context menu and follow Either Wndproc or ClassProc for the appropriate window of choice

hit shift+f4 and set a log breakpoint that never pauses and set the function type to be WndProc (Assume Function Of Type DropDown)

see screen shot below enter image description here

and run the app

go to log window and observe you will see a lot of logs like this

00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00010236  hWnd = 00010236, class = CalcFrame, text = Calculator
            00000210  Msg = WM_PARENTNOTIFY
            00000204  Event = WM_RBUTTONDOWN, ID = 0
            00230006  Data = 230006
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00030248  hWnd = 00030248, class = CalcFrame
            00000021  Msg = WM_MOUSEACTIVATE
            00010236  hParent = 00010236, class = CalcFrame, text = Calculator
            02040001  Hittest = HTCLIENT, MouseMsg = WM_RBUTTONDOWN
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00010236  hWnd = 00010236, class = CalcFrame, text = Calculator
            00000021  Msg = WM_MOUSEACTIVATE
            00010236  hParent = 00010236, class = CalcFrame, text = Calculator
            02040001  Hittest = HTCLIENT, MouseMsg = WM_RBUTTONDOWN
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00030248  hWnd = 00030248, class = CalcFrame
            00000020  Msg = WM_SETCURSOR
            00030248  hWnd = 00030248, class = CalcFrame
            02040001  Hittest = HTCLIENT, MouseMsg = WM_RBUTTONDOWN
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00010236  hWnd = 00010236, class = CalcFrame, text = Calculator
            00000020  Msg = WM_SETCURSOR
            00030248  hWnd = 00030248, class = CalcFrame
            02040001  Hittest = HTCLIENT, MouseMsg = WM_RBUTTONDOWN
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00030248  hWnd = 00030248, class = CalcFrame
            00000204  Msg = WM_RBUTTONDOWN
            00000002  Keys = MK_RBUTTON
            00230006  X = 6, Y = 35.
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00030248  hWnd = 00030248, class = CalcFrame
            00000084  Msg = WM_NCHITTEST
            00000000  wParam = 0
            01790207  X = 519., Y = 377.
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00030248  hWnd = 00030248, class = CalcFrame
            00000020  Msg = WM_SETCURSOR
            00030248  hWnd = 00030248, class = CalcFrame
            02050001  Hittest = HTCLIENT, MouseMsg = WM_RBUTTONUP
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00010236  hWnd = 00010236, class = CalcFrame, text = Calculator
            00000020  Msg = WM_SETCURSOR
            00030248  hWnd = 00030248, class = CalcFrame
            02050001  Hittest = HTCLIENT, MouseMsg = WM_RBUTTONUP
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00030248  hWnd = 00030248, class = CalcFrame
            00000205  Msg = WM_RBUTTONUP

now refine the breakpoint to suit your condition
(change from never to on condition
add condition like when uMsg == WM_LBUTTONDOWN ie
[esp+8] == 0x20x..20y (see the stack layout mention earlier
0x200 t0 0x220 are WM_MOUSE EVENT MESSAGES

here is screenshot that shows a possible configuration and result below screen shot enter image description here

00551EDE  INT3: [esp+8] = WM_MOUSEMOVE
00551EDE  INT3: [esp+8] = WM_NCHITTEST
00551EDE  INT3: [esp+8] = WM_PARENTNOTIFY
00551EDE  INT3: [esp+8] = WM_MOUSEACTIVATE
00551EDE  INT3: [esp+8] = WM_MOUSEACTIVATE
00551EDE  INT3: [esp+8] = WM_SETCURSOR
00551EDE  INT3: [esp+8] = WM_SETCURSOR
00551EDE  INT3: [esp+8] = WM_LBUTTONDOWN
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00030248  hWnd = 00030248, class = CalcFrame
            00000201  Msg = WM_LBUTTONDOWN
            00000001  Keys = MK_LBUTTON
            00350004  X = 4, Y = 53.
00551EDE  INT3: [esp+8] = WM_NCHITTEST
00551EDE  INT3: [esp+8] = WM_SETCURSOR
00551EDE  INT3: [esp+8] = WM_SETCURSOR
00551EDE  INT3: [esp+8] = WM_LBUTTONUP
00551EDE  INT3: [esp+8] = WM_NCHITTEST
00551EDE  INT3: [esp+8] = WM_PARENTNOTIFY
00551EDE  INT3: [esp+8] = WM_MOUSEACTIVATE
00551EDE  INT3: [esp+8] = WM_MOUSEACTIVATE
00551EDE  INT3: [esp+8] = WM_SETCURSOR
00551EDE  INT3: [esp+8] = WM_SETCURSOR
00551EDE  INT3: [esp+8] = WM_RBUTTONDOWN
00551EDE  Call to CALC.WndProc from USER32.77B4C4E4
            00030248  hWnd = 00030248, class = CalcFrame
            00000204  Msg = WM_RBUTTONDOWN
            00000002  Keys = MK_RBUTTON
            00350004  X = 4, Y = 53.
00551EDE  INT3: [esp+8] = WM_NCHITTEST
00551EDE  INT3: [esp+8] = WM_SETCURSOR
00551EDE  INT3: [esp+8] = WM_SETCURSOR
00551EDE  INT3: [esp+8] = WM_RBUTTONUP
1

Regardless of operating system, a mouse click represents an event and there is a bunch of event handling plumbing that makes this happen. Some of this can hinge upon certain design choices like how processes are separated in the GUI.

A common pattern is to register a context relative to which events can be processed through an implemented handler. Traditionally under Windows, this is a "Window Class" and practically everything is a window. The definition of that window class includes a function/method that handles the events/messages sent to the target window. To target a specific window with a debugger, you would want to break on a condition where the message/event handling function is called with the event you want (like WM_LBUTTONDOWN on Windows). There are cases where default handling of events can occur as well, a la DefWindowProc().

Doing this in a broader context would require hooking that is facilitated by the operating system, perhaps at the kernel level. There may be other options for you available through Hooks.

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