Customizing Winlogon

Customize Winlogon behavior by implementing a Credential Provider. For information about Credential Providers, see ICredentialProvider Interface.

Windows Server 2003 and Windows XP: Credential Providers are not supported.

The following sections describe ways to customize Winlogon in Windows versions prior to Windows Vista.

• Winlogon Notification Packages
• GINA Stubs
• GINA Hooks

Winlogon Notification Packages

A Winlogon notification package is a DLL that exports functions that handle Winlogon events. For example, when a user logs onto the system, Winlogon calls each notification package to provide information about the event. For more information, see Winlogon Notification Packages.

GINA Stubs

A GINA stub is a custom GINA DLL that uses the export function implementations of a previously installed GINA DLL (typically MsGina.dll). A GINA stub gets pointers to each function exported by the previously installed GINA DLL. Each GINA stub function then uses the appropriate function pointer to call the corresponding function in the previously installed GINA DLL.

A GINA stub function can implement additional functionality in one or more of its export functions. For example, the WlxLoggedOutSAS function of a GINA stub might check the current time before calling the WlxLoggedOutSAS function of the MsGina.dll. If the current time was within a specific range, the stub function could display a message that indicates logon is disallowed during that time period and return WLX_SAS_ACTION_NONE to Winlogon. The WlxLoggedOutSAS function of the MsGina.dll would then be called only during the allowed time period.

The GINA stub application gets a dispatch table to Winlogon support functions through the pWinlogonFunctions parameter of the WlxInitialize function. The GINA stub application can use this dispatch table to call Winlogon support functions. For example, A GINA stub application can call the WlxSasNotify function to cause a secure attention sequence (SAS) event when a smart card is inserted into a reader.

For more information about creating a GINA stub, see the Gina Stubs sample in the \Samples\Security\Gina\GinaStub directory of a Platform Software Development Kit (SDK) installation.

GINA Hooks

A GINA hook is a GINA stub that, in its implementation of the WlxInitialize function, replaces the pointer to the WlxDialogBoxParam support function in the dispatch table with a pointer to its own implementation of the WlxDialogBoxParam function. As a result, each time the previously installed GINA (typically MsGina.dll) calls the WlxDialogBoxParam function, the function implemented by the GINA hook is called.

The WlxDialogBoxParam function implemented by the GINA hook can replace the DialogProc callback procedure that responds to a specific dialog box event.

This gives the GINA hook full control over the appearance and behavior of all of the dialog boxes that MsGina.dll creates.

For more information about creating a GINA hook, see the Gina Hooks sample in the \Samples\Security\Gina\GinaHook directory of a Platform SDK installation.