RAS Security DLL Authentication Transaction

The Windows NT RAS server calls the security DLL's RasSecurityDialogBegin function to begin an authentication of a remote user. The RAS server is blocked and cannot accept any other calls until RasSecurityDialogBegin returns. For this reason, RasSecurityDialogBegin should copy the input parameters, create a thread to perform the authentication, and return as quickly as possible.

The thread created by the security DLL uses the RasSecurityDialogSend and RasSecurityDialogReceive functions to communicate with the remote computer. These functions are not available for static import from any library. Instead, the security DLL must use the LoadLibrary and GetProcAddress functions to dynamically link to these functions in RASMAN.DLL.

During an authentication transaction, the RAS connection manager on the remote computer displays a terminal window. The thread of the security DLL calls RasSecurityDialogSend to send a message to display in the terminal window. The thread then calls RasSecurityDialogReceive to receive the input that the remote user types in the terminal window. The thread can make any number of RasSecurityDialogSend calls, with each call followed by a RasSecurityDialogReceive call. After each call to RasSecurityDialogReceive, the thread must call one of the wait functions, such as WaitForSingleObject, to wait for the asynchronous send and receive operations to be completed. The RAS server signals an event object when the receive operation has been completed or when an optional time-out interval has elapsed.

When the thread has finished authenticating the remote user, it calls the RasSecurityDialogComplete function. This call passes a SECURITY_MESSAGE structure containing the results of the authentication transaction to the RAS server. The RAS server then performs a cleanup sequence that includes a call to the DLL's RasSecurityDialogEnd function. This gives the security DLL an opportunity to perform any necessary cleanup.

The security DLL can call the RasSecurityDialogGetInfo function to retrieve information about the port associated with an authentication transaction. RasSecurityDialogGetInfo fills in a RAS_SECURITY_INFO structure that indicates the state of the last RasSecurityDialogReceive call for the port