Notes de mise à jour sur la sécurité réseau à distance de Windows 98 (août 1998)

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Numéro d'article: 189771 - Voir les produits auxquels s'applique cet article
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Résumé

Cet article contient une copie de la distance réseau Notes de sécurité Windows 98 mise à niveau Release à partir du août 1998.

Plus d'informations

Microsoft(r) Windows(r) 98 Dial-Up Networking Security Upgrade
Release Notes

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 Dun40.exe 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 MSCHAP V2 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.

      HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RemoteAccess

      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
                           (default)

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.

      HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RemoteAccess

      DWORD: UseLmPassword
      0x00000001 == Send LM challenge response (default)
      0x00000000 == Do not send LM challenge response (send only NT
                    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.

      HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RemoteAccess

      DWORD: ForceStrongEncryption
      0x00000001 == Requires 128-bit encryption for any connection which
                    already requires encryption
      0x00000000 == No effect; does not force strong encryption (default)

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 MSCHAP V2 is included in
Windows NT 4.0 Service Pack 4. For more information, please see the
following article in the Microsoft Knowledge Base.

   ARTICLE-ID: Q152734
   TITLE     : How to Obtain the Latest Windows NT 4.0 Service Pack

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
========================

IMPORTANT: This section is different from the same section in the Release
Notes that is available with the Windows 98 Dial-Up Networking Security
Upgrade.

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.)

Perform the following steps to uninstall Dial-Up Networking:

1. In Control Panel, double-click the Add/Remove Programs tool, click the
   Windows Setup tab, click Communications (do not click the check box,
   click the word "communications"), and then click Details.

2. Click the Dial-Up Networking check box so that it is no longer selected,
   click OK, and then click OK again. Please note that this removes VPN as
   well.

3. When prompted to restart your computer, click No.

4. Click the Start button, point to Find, click Files or Folders, and then
   click the Name And Location tab.

5. In the Named field, find and delete the following files from the
   Windows\System folder:

      Pppmac.vxd
      Rasapi32.dll
      Rnaapp.exe

6. Close the Find dialog box.

7. In Control Panel, double-click the Add/Remove Programs tool, click the
   Windows Setup tab, click Communications (do not click the check box,
   click the word "communications"), and then click Details.

8. Add Dial-Up Networking and VPN, click OK, and then click OK again.

9. Restart your computer when prompted.
				

Propriétés

Numéro d'article: 189771 - Dernière mise à jour: mardi 23 janvier 2007 - Version: 1.3
Les informations contenues dans cet article s'appliquent au(x) produit(s) suivant(s):
  • Microsoft Windows 98 Standard Edition
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