"Access Denied" When an SP5 RRAS Client Access an SP5 RRAS Server with OfferMSCHAP

ID: Q240870

The information in this article applies to:

Microsoft Windows NT Server versions 4.0, 4.0 SP5
Microsoft Windows NT Server, Enterprise Edition versions 4.0, 4.0 SP4, 4.0 SP5

SYMPTOMS

When you attempt to make a Point-to-Point Tunneling Protocol (PPTP) connection from a Windows NT 4.0 Service Pack 5 (SP5) client to a Windows NT 4.0 SP5 PPTP server running Remote Access Services (RAS) or Routing and Remote Access Services (RRAS), the initial authentication attempt may not succeed and may display an "Error 5: Access Denied" error message. This problem can also occur if RRAS is configured to forward Microsoft Challenge-Handshake Authentication Protocol (MS-CHAP) version 2 authentication requests to a Radius server.

CAUSE

This behavior is caused by a problem in Rasrad.dll, in which the challenge from the RRAS server to the client is incorrectly formatted. This problem results in the client rejecting the challenge and disconnecting the session.

RESOLUTION

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next Windows NT 4.0 service pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

The English-language version of this fix should have the following file attributes or later:


   Date      Time    Version      Size    File name     Platform
   -------------------------------------------------------------
   07/27/99  09:28a                41,744 Rasrad.dll    x86
   07/27/99  09:26a                68,368 Rasrad.dll    Alpha

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:

Q189594 RRAS Upgrade for WinNT Server 4.0 Hotfix Pack 3.0 Release Notes

Q189595 Performance and Security Upgrade for WinNT 4.0 Release Notes

Q222060 Err Msg: 'Error 5: Access Denied' When Using PPTP with RAS

To enable MS-CHAP with Radius authentication, you must add the following registry value:

Key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Rasman\PPP\CHAP

Value Name: OfferMSCHAP
Type: DWORD
Data Value: 0x00000001 - Once this is enabled, every incoming Point-to-Point Protocol (PPP) connection is offered MS-CHAP, and MS-CHAP is used to authenticate each PPP user against the Radius server that your RAS server is using.

Additional query words: IAS mschap

Keywords : kbbug4.00 kbfix4.00
Version : winnt:4.0,4.0 SP4,4.0 SP5
Platform : winnt
Issue type : kbbug