Re: Doubt on GinaHook for Fingerprint Authentication...

From: Jakub Gwozdz (gwozdziu_at_rpg.pl)
Date: 11/18/04 

Date: Thu, 18 Nov 2004 16:30:31 +0100

Varadharajan. M.V wrote:

> Thanks once again for your reply. I have outlined my understanding here.
> Hope this thread will be useful for others also who implement Fingerprint
> authentication if it is correct:) Please correct me if iam wrong.
> First if the dialog appearing is IDD_WLXDIAPLAYSASNOTICE_DIALOG , i
> would check for sensor and display the dialog, and send
> WlxSASNotify(WLX_SENSOR_FOUND) message to winlogon. As per your message, i
> can expect winlogon to call WlxLoggedOutSAS with the same SAS
> message(WLX_SENSOR_FOUND). Then i can start my sensor activities and
> identify the User in a Thread or as part of some other external dll; In
> WlxLoggedOnSAS i can finish the sensor activities and destroy the dialog.
> One thing which is not clear to me is why WlxSASNotify is required. we
> notify winlogon and again it sends the same SAS message.
>
> Varadha.

You can do the whole authorization in other way:
Override DisplaySASNotice, so it will display some kind of dialog. To
display a dialog, use WlxDialogBox or WlxDialogBoxParam, not standard
WinApi functions.
This dialog may print message "Press C-A-D or put your finger on the
sensor". Then, in DialogProc, check if user puts the finger and validate
it. You can do it by setting a timer and processing WM_TIMER.
If fingerprint passes the validation tests, send
WLX_SAS_TYPE_FINGERPRINT_OKAY by WlxSasNotify and then EndDialog.
Remember to first call WlxSasNotify, and then close the dialog, because
when you send the SAS out of the thread message queue processing (out of
DialogProc), it sometimes is sent two times. I don't know why, but it
is, and several people has had a problem with it (according to google ;-) )
You have to call WlxSASNotify, because gina may log user in only in
WlxLoggedOutSAS, which is called by WinLogon in answer to any SAS, when
no one is logged on.

Then do the processing of WLX_SAS_TYPE_FINGERPRINT_OKAY in
WlxLoggedOutSAS. I.e. by calling MsGina.dll's
WlxLoggedOutSAS(WLX_SAS_TYPE_CTRL_ALT_DEL) and feeding it's dialog with
some username/password.

And one more thing - remember, that when winlogon and gina start, the
drivers and services for fingerprint sensor may not be initialized yet.

Best regards
Jakub Gwozdz

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