FindWindow fails for MessageBox displayed at Winlogon
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From: dc2000 on 13 Nov 2006 18:43 Hi everyone: I have a tricky situation. My app displays a message box using MB_SERVICE_NOTIFICATION flag like this: ::MessageBox(NULL, message, title, MB_OK | MB_ICONINFORMATION | MB_SERVICE_NOTIFICATION); I'm using MB_SERVICE_NOTIFICATION since I need this message to be displayed over screen-saver, or Winlogon as well. When the window is shown on the screen I use WM_TIMER message and FindWindow() to get the handle of the Message Box and later update text displayed in it. HWND hMsgBxWnd = ::FindWindow("#32770", title); //Get handle to the static window in the Message Box if(::GetDlgItem(hMsgBxWnd, 0xffff)) { //Got it, now can update it ::SetDlgItemText(hMsgBxWnd, 0xffff, message_str); } Everything works fine when user's desktop is shown. If I go into Winlogon by clicking Start -> Log Off -> Switch User (see picture here: http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), the message is displayed but FindWindow() returns NULL. I tried EnumWindows() and it failed as well. I heard that one solution would be to use CBT_HOOK but for that I will need a separate DLL module (for global hook), which I'd really like to avoid. Does anyone know how to get a handle to this message box during Winlogon? FYI. The currently active Terminal Session is still the same as when the message is shown during Winlogon.
From: anton bassov on 13 Nov 2006 22:59 Hi mate > Everything works fine when user's desktop is shown. If I go into Winlogon by > clicking Start -> Log Off -> Switch User (see picture here: > http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), the > message is displayed but FindWindow() returns NULL. I tried EnumWindows() and > it failed as well. When you specify MB_SERVICE_NOTIFICATION flag, message box is displayed as ZwRaiseHardError() call, so that it is owned by csrss.exe, rather than by caller, and,as a result, it gets displayed on currently active desktop. However, it does not mean that the caller has an access to this destop. In general, under Windows, desktop is a security boundary. Therefore, FindWindow() and EnumWindows() are able to find and enumerate only those windows that belong to the desktop the caller is associated with > I heard that one solution would be to use CBT_HOOK but for that I will need > a separate DLL module (for global hook), It is not going to work either - Windows hooks are of desktop-level scope > Does anyone know how to get a handle to this message box during Winlogon? You cannot do it in your application's context - no one, apart from Winlogon.exe, has an access to "Winlogon" desktop. If you are Admin, you may assign yourself privileges of LocalSystem account, so that you are able to open a handle to Winlogon.exe and inject a DLL into it Anton Bassov dc2000 wrote: > Hi everyone: > > > I have a tricky situation. My app displays a message box using > MB_SERVICE_NOTIFICATION flag like this: > > ::MessageBox(NULL, message, title, MB_OK | MB_ICONINFORMATION | > MB_SERVICE_NOTIFICATION); > > I'm using MB_SERVICE_NOTIFICATION since I need this message to be displayed > over screen-saver, or Winlogon as well. > > > When the window is shown on the screen I use WM_TIMER message and > FindWindow() to get the handle of the Message Box and later update text > displayed in it. > > HWND hMsgBxWnd = ::FindWindow("#32770", title); > > //Get handle to the static window in the Message Box > if(::GetDlgItem(hMsgBxWnd, 0xffff)) > { > //Got it, now can update it > ::SetDlgItemText(hMsgBxWnd, 0xffff, message_str); > } > > Everything works fine when user's desktop is shown. If I go into Winlogon by > clicking Start -> Log Off -> Switch User (see picture here: > http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), the > message is displayed but FindWindow() returns NULL. I tried EnumWindows() and > it failed as well. > > I heard that one solution would be to use CBT_HOOK but for that I will need > a separate DLL module (for global hook), which I'd really like to avoid. > > Does anyone know how to get a handle to this message box during Winlogon? > > > FYI. The currently active Terminal Session is still the same as when the > message is shown during Winlogon.
From: dc2000 on 13 Nov 2006 23:40 Wow, that sucks. No way out, hah? Thanks anyway. "anton bassov" wrote: > Hi mate > > > Everything works fine when user's desktop is shown. If I go into Winlogon by > > clicking Start -> Log Off -> Switch User (see picture here: > > http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), the > > message is displayed but FindWindow() returns NULL. I tried EnumWindows() and > > it failed as well. > > When you specify MB_SERVICE_NOTIFICATION flag, message box is displayed > as ZwRaiseHardError() call, so that it is owned by csrss.exe, rather > than by caller, and,as a result, it gets displayed on currently active > desktop. However, it does not mean that the caller has an access to > this destop. In general, under Windows, desktop is a security boundary. > Therefore, FindWindow() and EnumWindows() are able to find and > enumerate > only those windows that belong to the desktop the caller is associated > with > > > > > I heard that one solution would be to use CBT_HOOK but for that I will need > > a separate DLL module (for global hook), > > It is not going to work either - Windows hooks are of desktop-level > scope > > > > Does anyone know how to get a handle to this message box during Winlogon? > > You cannot do it in your application's context - no one, apart from > Winlogon.exe, has an access to "Winlogon" desktop. If you are Admin, > you may assign yourself privileges of LocalSystem account, so that you > are able to open a handle to Winlogon.exe and inject a DLL into it > > Anton Bassov > > dc2000 wrote: > > Hi everyone: > > > > > > I have a tricky situation. My app displays a message box using > > MB_SERVICE_NOTIFICATION flag like this: > > > > ::MessageBox(NULL, message, title, MB_OK | MB_ICONINFORMATION | > > MB_SERVICE_NOTIFICATION); > > > > I'm using MB_SERVICE_NOTIFICATION since I need this message to be displayed > > over screen-saver, or Winlogon as well. > > > > > > When the window is shown on the screen I use WM_TIMER message and > > FindWindow() to get the handle of the Message Box and later update text > > displayed in it. > > > > HWND hMsgBxWnd = ::FindWindow("#32770", title); > > > > //Get handle to the static window in the Message Box > > if(::GetDlgItem(hMsgBxWnd, 0xffff)) > > { > > //Got it, now can update it > > ::SetDlgItemText(hMsgBxWnd, 0xffff, message_str); > > } > > > > Everything works fine when user's desktop is shown. If I go into Winlogon by > > clicking Start -> Log Off -> Switch User (see picture here: > > http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), the > > message is displayed but FindWindow() returns NULL. I tried EnumWindows() and > > it failed as well. > > > > I heard that one solution would be to use CBT_HOOK but for that I will need > > a separate DLL module (for global hook), which I'd really like to avoid. > > > > Does anyone know how to get a handle to this message box during Winlogon? > > > > > > FYI. The currently active Terminal Session is still the same as when the > > message is shown during Winlogon. > >
From: dc2000 on 14 Nov 2006 19:36 Hey, it just dawned on me. Is there any way to display my own dialog window during Winlogon? "anton bassov" wrote: > Hi mate > > > Everything works fine when user's desktop is shown. If I go into Winlogon by > > clicking Start -> Log Off -> Switch User (see picture here: > > http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), the > > message is displayed but FindWindow() returns NULL. I tried EnumWindows() and > > it failed as well. > > When you specify MB_SERVICE_NOTIFICATION flag, message box is displayed > as ZwRaiseHardError() call, so that it is owned by csrss.exe, rather > than by caller, and,as a result, it gets displayed on currently active > desktop. However, it does not mean that the caller has an access to > this destop. In general, under Windows, desktop is a security boundary. > Therefore, FindWindow() and EnumWindows() are able to find and > enumerate > only those windows that belong to the desktop the caller is associated > with > > > > > I heard that one solution would be to use CBT_HOOK but for that I will need > > a separate DLL module (for global hook), > > It is not going to work either - Windows hooks are of desktop-level > scope > > > > Does anyone know how to get a handle to this message box during Winlogon? > > You cannot do it in your application's context - no one, apart from > Winlogon.exe, has an access to "Winlogon" desktop. If you are Admin, > you may assign yourself privileges of LocalSystem account, so that you > are able to open a handle to Winlogon.exe and inject a DLL into it > > Anton Bassov > > dc2000 wrote: > > Hi everyone: > > > > > > I have a tricky situation. My app displays a message box using > > MB_SERVICE_NOTIFICATION flag like this: > > > > ::MessageBox(NULL, message, title, MB_OK | MB_ICONINFORMATION | > > MB_SERVICE_NOTIFICATION); > > > > I'm using MB_SERVICE_NOTIFICATION since I need this message to be displayed > > over screen-saver, or Winlogon as well. > > > > > > When the window is shown on the screen I use WM_TIMER message and > > FindWindow() to get the handle of the Message Box and later update text > > displayed in it. > > > > HWND hMsgBxWnd = ::FindWindow("#32770", title); > > > > //Get handle to the static window in the Message Box > > if(::GetDlgItem(hMsgBxWnd, 0xffff)) > > { > > //Got it, now can update it > > ::SetDlgItemText(hMsgBxWnd, 0xffff, message_str); > > } > > > > Everything works fine when user's desktop is shown. If I go into Winlogon by > > clicking Start -> Log Off -> Switch User (see picture here: > > http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), the > > message is displayed but FindWindow() returns NULL. I tried EnumWindows() and > > it failed as well. > > > > I heard that one solution would be to use CBT_HOOK but for that I will need > > a separate DLL module (for global hook), which I'd really like to avoid. > > > > Does anyone know how to get a handle to this message box during Winlogon? > > > > > > FYI. The currently active Terminal Session is still the same as when the > > message is shown during Winlogon. > >
From: Skywing [MVP] on 14 Nov 2006 22:51
WlxDialogBox* from a GINA DLL. Note that GINA DLLs are obsolete and unusable in Windows Vista and future OS releases. -- Ken Johnson (Skywing) Windows SDK MVP http://www.nynaeve.net "dc2000" <dc2000(a)discussions.microsoft.com> wrote in message news:B5021860-82E2-4EB8-BD9B-48B2C7AA6B1F(a)microsoft.com... > Hey, it just dawned on me. Is there any way to display my own dialog > window > during Winlogon? > > > "anton bassov" wrote: > >> Hi mate >> >> > Everything works fine when user's desktop is shown. If I go into >> > Winlogon by >> > clicking Start -> Log Off -> Switch User (see picture here: >> > http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), >> > the >> > message is displayed but FindWindow() returns NULL. I tried >> > EnumWindows() and >> > it failed as well. >> >> When you specify MB_SERVICE_NOTIFICATION flag, message box is displayed >> as ZwRaiseHardError() call, so that it is owned by csrss.exe, rather >> than by caller, and,as a result, it gets displayed on currently active >> desktop. However, it does not mean that the caller has an access to >> this destop. In general, under Windows, desktop is a security boundary. >> Therefore, FindWindow() and EnumWindows() are able to find and >> enumerate >> only those windows that belong to the desktop the caller is associated >> with >> >> >> >> > I heard that one solution would be to use CBT_HOOK but for that I will >> > need >> > a separate DLL module (for global hook), >> >> It is not going to work either - Windows hooks are of desktop-level >> scope >> >> >> > Does anyone know how to get a handle to this message box during >> > Winlogon? >> >> You cannot do it in your application's context - no one, apart from >> Winlogon.exe, has an access to "Winlogon" desktop. If you are Admin, >> you may assign yourself privileges of LocalSystem account, so that you >> are able to open a handle to Winlogon.exe and inject a DLL into it >> >> Anton Bassov >> >> dc2000 wrote: >> > Hi everyone: >> > >> > >> > I have a tricky situation. My app displays a message box using >> > MB_SERVICE_NOTIFICATION flag like this: >> > >> > ::MessageBox(NULL, message, title, MB_OK | MB_ICONINFORMATION | >> > MB_SERVICE_NOTIFICATION); >> > >> > I'm using MB_SERVICE_NOTIFICATION since I need this message to be >> > displayed >> > over screen-saver, or Winlogon as well. >> > >> > >> > When the window is shown on the screen I use WM_TIMER message and >> > FindWindow() to get the handle of the Message Box and later update text >> > displayed in it. >> > >> > HWND hMsgBxWnd = ::FindWindow("#32770", title); >> > >> > //Get handle to the static window in the Message Box >> > if(::GetDlgItem(hMsgBxWnd, 0xffff)) >> > { >> > //Got it, now can update it >> > ::SetDlgItemText(hMsgBxWnd, 0xffff, message_str); >> > } >> > >> > Everything works fine when user's desktop is shown. If I go into >> > Winlogon by >> > clicking Start -> Log Off -> Switch User (see picture here: >> > http://www.codeguru.com/forum/attachment.php?attachmentid=17852&stc=1), >> > the >> > message is displayed but FindWindow() returns NULL. I tried >> > EnumWindows() and >> > it failed as well. >> > >> > I heard that one solution would be to use CBT_HOOK but for that I will >> > need >> > a separate DLL module (for global hook), which I'd really like to >> > avoid. >> > >> > Does anyone know how to get a handle to this message box during >> > Winlogon? >> > >> > >> > FYI. The currently active Terminal Session is still the same as when >> > the >> > message is shown during Winlogon. >> >> |