Network Security: Allow PKU2U authentication requests to this computer to use online identities

Updated: November 15, 2012

Applies To: Windows 7, Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Vista, Windows XP

This security policy reference topic for the IT professional describes the best practices, location, and values for this policy setting.

Reference

In Windows Server 2008 R2 and Windows 7 the Negotiate Security Support Provider (SSP) supports an extension SSP, Negoexts.dll. This extension SSP is treated as an authentication protocol by the Windows operating system, and it supports SSPs from Microsoft, including PKU2U. You can also develop or add other SSPs.

When computers are configured to accept authentication requests by using online IDs, Negoexts.dll calls the PKU2U SSP on the computer that is used to log on. The PKU2U SSP obtains a local certificate and exchanges the policy between the peer computers. When validated on the peer computer, the certificate within the metadata is sent to the logon peer for validation. It associates the user's certificate to a security token, and then the logon process completes.

This policy is not configured by default on domain-joined computers. This would disallow the online identities to be able to authenticate to the domain-joined computers in Windows 7.

Possible values

• Enabled

  This will allow authentication to successfully complete between the two (or more) computers that have established a peer relationship through the use on online IDs. The PKU2U SSP obtains a local certificate and exchanges the policy between the peer computers. When validated on the peer computer, the certificate within the metadata is sent to the logon peer for validation. It associates the user's certificate to a security token, and then the logon process completes.

• Disabled

  This will prevent online IDs from being used to authenticate the user to another computer in a peer-to-peer relationship.

• Not set. Not configuring this policy prevents online IDs from being used to authenticate the user. This is the default on domain-joined computers.

Best practices

Within a domain, domain accounts should be used for authentication. Set this policy to Disabled or do not configure this policy to exclude online identities from being used to authenticate.

Location

GPO_name**\Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options**

Default values

The following table lists the actual and effective default values for this policy. Default values are also listed on the policy’s property page.

Operating system version differences

This policy was introduced in Windows Server 2008 R2 and Windows 7, and it can be applied to Windows Server operating systems that support the Negotiate Extensions SSP (Negoexts.dll).

Security considerations

This section describes how an attacker might exploit a feature or its configuration, how to implement the countermeasure, and the possible negative consequences of countermeasure implementation.

Vulnerability

Enabling this policy setting allows a user’s account on one computer to be associated with an online identity, such as Windows Live ID, so that account can log on to a peer computer (if the peer computer is likewise configured) without the use of a Windows logon account (domain or local). Although this is beneficial for workgroups or home groups, using this feature in a domain-joined environment might circumvent your established security policies.

Countermeasure

Set this policy to Disabled or do not configure this security policy for domain-joined computers.

Potential impact

If you do not set or disable this policy, the PKU2U protocol will not be used to authenticate between peer computers, which forces users to follow domain defined access control policies. If you enable this policy, you will allow your users to authenticate by using local certificates between systems that are not part of a domain that uses PKU2U. This will allow users to share resources between computers.