Microsoft KB Archive/237691

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Windows 98 Dial-Up Networking Security Upgrade Release Notes (July 1999)

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Q237691

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The information in this article applies to:


 * Microsoft Windows 95
 * Microsoft Windows 95 OEM Service Release, versions 1.0, 2.0, 2.1, 2.5
 * Microsoft Windows 98

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SUMMARY
This article contains a copy of the information in the Windows 98 Dial-Up Networking Security Upgrade Release Notes (Dun40.doc) included with the virtual private network Update for Microsoft Windows 98 and Dialup Networking 1.3 that was released in July, 1999.

For additional information about this release, please see the following article in the Microsoft Knowledge Base:

"Q191540 VPN Update for Microsoft Windows 98 and Dialup Networking 1.3 Available" NOTE: This document includes several updates to the original version that was included in the Windows 98 Dial-up Networking Security Upgrade that was released in August, 1998.

For additional information about this release, please see the following article in the Microsoft Knowledge Base:

"Q189771 Windows 98 Dial-Up Networking Security Upgrade Release Notes (August 1998)"

1. Introduction
This security upgrade for Windows 98 Dial-up Networking is designed to enhance the protection of both dial-up and VPN connections by strengthening several aspects of password management and data encryption.

1.1 Installation Notes
Execute the Install file and follow the instructions it displays. At the end of the installation process you will be required to reboot your PC.

1.2 MSCHAP V2
A new MSCHAP secure mode (MSCHAP V2) has been implemented, providing mutual authentication, stronger initial data encryption keys, and different encryption keys for the transmit and receive paths.

To minimize the risk of password compromise during MSCHAP exchanges, MSCHAP V2 drops support for the MSCHAP password change V1, and will not transmit the LM password response.

For VPN connections, a Windows NT 4.0 server (updated as described below) will negotiate MSCHAP V2 before negotiating the original MSCHAP. An updated Windows 98 client will accept this offer and use MSCHAPV2 as the authentication method. To ensure that no VPN clients authenticate using MSCHAP, the server can be set to require MSCHAP V2. This will prevent legacy clients from presenting their credentials in an MSCHAP or PAP or CHAP exchange, and is a likely configuration for networks that require the most secure authentication method.

1.3 Secure VPN Mode
If there are special circumstances in which you wish to ensure that your PC uses only the new MSCHAP V2 for all VPN connection attempts, a new client-side registry flag, SecureVPN, can be used to force this behavior. When this flag is set, your PC will only accept MSCHAP V2 authentication for any VPN connections. In addition, this flag will require data encryption for all VPN connections. Dial-up connections are not affected.

"NOTE: Most users will not need to use the Secure VPN flag. This flag should be used with care because it will affect the behavior of all VPN connections from your machine. In general, the required use of MSCHAP V2 and data encryption can be enforced more easily on the server."

The registry setting which will force a Windows 98 client to use only the new MSCHAP V2 secure mode and require data encryption for PPTP connections is defined below. By default, this registry variable is absent, meaning "do not force secure mode on PPTP connections". The value of this variable is checked just before a connection is attempted.

HKLM\System\CurrentControlSet\Services\RemoteAccess

Default: 0x00000000

DWORD: SecureVPN

Value: 0x00000001 == Force secure mode (MSCHAP V2 plus data encryption) on all PPTP connections

Value: 0x00000000 == Do not force secure mode on PPTP connections

1.4 LM Response Suppression
This release also provides a new registry variable which prevents the client from sending the LM response to a legacy MSCHAP challenge, as defined below. By default, this variable is absent, meaning that the client should send the LM response (in order to maintain compatibility with legacy servers). This variable affects both dial-up and VPN connections; its value is checked just before a connection is attempted.

"NOTE: Most users will not need to use this registry variable. The new secure mode MSCHAP V2 will not send the LMHash response, so this registry value is most useful when connecting to older access servers which use the original MSCHAP. Setting this variable on a Windows 98 client will prevent the client from connecting to a Windows 95 or Windows 98 server."

HKLM\System\CurrentControlSet\Services\RemoteAccess

DWORD: UseLmPassword

Default: 0x00000001

0x00000000 = Do not send LM challenge response (send only NT challenge response)

0x00000001 = Send LM challenge response

1.5 Forcing Strong Encryption
Windows 98 Dial-up Networking already supports a checkbox to require encryption for a specific connection. Clients which support 128-bit encryption will accept any level of encryption (128-bit or 40-bit) offered by the server. This upgrade provides a new registry flag, ForceStrongEncryption. When set, this flag will require 128-bit encryption for any connection which has already been set to require encryption. (In other words, setting the new registry flag essentially changes the meaning of the existing checkbox from "require encryption" to "require strong encryption".)

"NOTE: As originally installed, Windows 98 Dial-up Networking supports 40-bit encryption. An optional upgrade will be available to users in North America which adds the ability to support 128-bit encryption as well."

The registry flag which forces strong encryption is defined below. By default, the flag is absent. The value of this flag is checked just before a connection is attempted.

HKLM\System\CurrentControlSet\Services\RemoteAccess

DWORD: ForceStrongEncryption

Default: 0x00000000

0x00000000 = No effect; does not force strong encryption

0x00000001 = Requires 128-bit encryption for any connection which already requires encryption

1.6 Server Updates
This upgrade is fully compatible with legacy Dial-up and PPTP systems. However, in order to benefit from MSCHAP V2, both the client and server must support this new mode. Server support for MSCHAPV2 will be included in Windows NT 4.0 Service Pack 4. For installations which require these features before general availability of Service Pack 4, a hotfix for Service Pack 3 has been created. This can be found on the Microsoft FTP site at ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/hotfixes-postSP3/pptp3-fix. Servers running the Routing and Remote Access Upgrade should first apply the above, and then also apply rras30-fix from the same location.

"NOTE: RAS and PPTP servers must be maintained to current Windows NT Service Pack levels. A Windows 98 client machine may not connect to a Windows NT Server that has not been updated to Service Pack 3 or above."

1.7 Other Changes
The details section of the connection status display has been modified to identify the specific form of CHAP that was used in the connection. Standard CHAP is displayed as "Challenge Authentication Protocol"; legacy MSCHAP is displayed as "Microsoft Challenge Authentication Protocol"; and MSCHAP V2 is displayed as "Microsoft Mutual Challenge Authentication Protocol".

1.8 Removing this Update
This security upgrade does not provide its own uninstall program. If you wish to remove the upgrade, you can accomplish this by removing and re-installing Dial-up Networking as a whole. If you installed Windows 98 as an upgrade, this process may ask for your original Windows 98 CD. If you have defined connections in the Dial-up Networking folder, these will not be lost. However, all information regarding ISDN devices (including switch type and spid) will be lost, so you should record this information before proceeding. (ISDN information can be created or reviewed by running the ISDN Setup Wizard which can be found in the Start -> Programs -> Accessories -> Communications menu.) To uninstall Dial-up Networking, use the Windows Setup tab of the "Add/Remove Programs" application in the control panel. Select Communications, then click on the Details button to see individual components. Note the communications features which had previously been enabled so that you can restore them later. Deselect Dial-up Networking and click on OK for this dialog and the Windows Setup dialog. You may receive a warning that removing Dial-up Networking will also remove other features which depend on it. Make a note of these features for later use, and click OK. To reinstall the original Windows 98 Dial-up Networking without this security upgrade, return to the Windows Setup tab of the "Add/Remove Programs" application in the control panel. Select Communications, and again click on the Details. Select Dial-up Networking and each of the communications features which had previously been enabled. Then click OK to this dialog and the Windows Setup dialog.

"NOTE: As Windows restores Dial-up Networking and the associated components, you will receive warnings that the installer has found that that a file which it is about to write is older than the one already present on your machine. In most situations, you would keep the newer file. However, in this case, the correct response is to write the older file to your PC." Additional query words:

Keywords : kbreadme kbtool dun osr2 win95 win98

Issue type : kbinfo

Technology : kbWin95search kbWin98search kbOPKSearch kbWin95 kbWin98 kbWin95OPKOSR25 kbWin95OPKOSR210