Hi all. I am using the MS Detours to intercept 4 API functions, DrawText, DrawTextEx, TextOut and ExtTextOut. This is all occurring in a small Unmanaged C++ Dll that I put together (after much Google time, C++ not my forte). From the intercepted functions I call a function that puts together a small COPYDATASTRUCT and ships it off the my main, originating VB.Net app. In the VB.Net app I am retrieving the struct, interpreting and obtaining all text that passes through the target app.
Everything seems to work like a charm for the two DrawText APIs but not for the two TextOut APIs. First off, whenever I close the VB.Net app (WinForm exe) the target app (ANY app, I have tested on countless programs) crashes whenever I hook the TextOut functions. Secondly, all text retrieved from these functions is completely jumbled. Text is perfect from the DrawText functions, and they do not cause errors or crashes (with the TextOut hooks commented out.
Can anybody please direct me to what I may be doing wrong? Any help/advice is greatly appreciated as I have spent weeks scouring Google and the web for an answer.
Code snippets below. Please ask and I will happily provide more info/code.
TIA
C++ code:
VB.Net code:Code:enum Win32API
{
API_TextOut = 1,
API_ExtTextOut = 2,
API_DrawText = 3,
API_DrawTextEx = 4
};
void TransmitToGUI(int Len, LPCWSTR szText, Win32API sourceAPI)
{
HWND hWnd = ::FindWindow(NULL, L"AutoERP::");
if (!hWnd)
{
return;
}
else
{
if(!szText)
return;
wchar_t Text[255];
wcscpy_s(Text, szText);
COPYDATASTRUCT cds;
::ZeroMemory(&cds, sizeof(COPYDATASTRUCT));
cds.dwData = sourceAPI;
cds.cbData = (Len+1)*2;
cds.lpData = &Text;
::SendMessage(hWnd, WM_COPYDATA, NULL, (LPARAM)&cds);
}
}
BOOL (WINAPI * Real_TextOut)(HDC a0, int a1, int a2, LPCWSTR a3, int a4) = TextOutW;
BOOL (WINAPI * Real_ExtTextOut)(HDC a0, int a1, int a2, UINT a3, CONST RECT* a4, LPCWSTR a5, UINT a6, CONST INT* a7) = ExtTextOutW;
int (WINAPI * Real_DrawText)(HDC a0, LPCWSTR a1, int a2, LPRECT a3, UINT a4) = DrawTextW;
int (WINAPI * Real_DrawTextEx)(HDC a0, LPWSTR a1, int a2, LPRECT a3, UINT a4, LPDRAWTEXTPARAMS a5) = DrawTextExW;
BOOL WINAPI Mine_TextOut(HDC hdc,int X,int Y,LPCWSTR text,int textLen)
{
BOOL rv = Real_TextOut(hdc, X, Y, text, textLen);
if (text)
{
TransmitToGUI(textLen, text, API_TextOut);
}
return rv;
}
BOOL WINAPI Mine_ExtTextOut(HDC hdc, int X, int Y, UINT options, RECT* lprc, LPCWSTR text, UINT cbCount, INT* lpSpacingValues)
{
BOOL rv = Real_ExtTextOut(hdc, X, Y, options, lprc, text, cbCount, lpSpacingValues);
if (text)
{
TransmitToGUI(cbCount, text, API_ExtTextOut);
}
return rv;
}
int WINAPI Mine_DrawText(HDC hdc, LPCWSTR text, int nCount, LPRECT lpRect, UINT uOptions)
{
int rv = Real_DrawText(hdc, text, nCount, lpRect, uOptions);
if (text)
{
TransmitToGUI(nCount, text, API_DrawText);
}
return rv;
}
int WINAPI Mine_DrawTextEx(HDC hdc, LPWSTR text, int textLength, LPRECT lpRect, UINT uFormat, LPDRAWTEXTPARAMS lpParams)
{
int rv = Real_DrawTextEx(hdc, text, textLength, lpRect, uFormat, lpParams);
if (text)
{
TransmitToGUI(textLength, text, API_DrawTextEx);
}
return rv;
}
Code:Public Structure COPYDATASTRUCT
Public dwData As Integer
Public cbData As Integer
Public lpData As IntPtr
End Structure
Friend Enum Win32API
API_TextOut = 1
API_ExtTextOut = 2
API_DrawText = 3
API_DrawTextEx = 4
End Enum
<System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
Protected Overrides Sub WndProc(ByRef m As Message)
Select Case (m.Msg)
Case WM_HOTKEY '// hotkey detected, install hook
SetCBTHook()
Case WM_COPYDATA '// data coming from [API] hook(s)
DataReceived(m)
Case Else
MyBase.WndProc(m)
End Select
End Sub
Private Sub DataReceived(ByRef m As Message)
Try
'// marshal and extract COPYDATASTRUCT from pointer
Dim cds As New COPYDATASTRUCT()
cds = DirectCast(Marshal.PtrToStructure(m.LParam, GetType(COPYDATASTRUCT)), COPYDATASTRUCT)
'// if our call, process data
If ((cds.dwData >= 1) AndAlso (cds.dwData <= 4)) Then
'// marshal and extract string from pointer
Dim tms As String = Marshal.PtrToStringAuto(cds.lpData, cds.cbData)
'// display text (if present)
If (tms.Replace(" ", String.Empty).Length > 0) Then
If ((cds.dwData = 1) OrElse (cds.dwData = 2)) Then
ListBox1.Items.Add([Enum].GetName(GetType(Win32API), cds.dwData) & ": " & tms)
ListBox1.SelectedIndex = ListBox1.Items.Count - 1
Else
ListBox2.Items.Add([Enum].GetName(GetType(Win32API), cds.dwData) & ": " & tms)
ListBox2.SelectedIndex = ListBox2.Items.Count - 1
End If
End If
Else
MyBase.WndProc(m)
End If
Catch ex As Exception
'MsgBox(ex.Message)
End Try
End Sub
