Understanding Trust Relationships

What are trust relationships

In the Windows NT domain model, domains had to be bound together through trust relationships, simply because the SAM databases used in those domains could not be joined. What this meant was that where a domain trusted another Windows NT domain, the members of the domain could access network resources located in the other domain. Defining trust relationships between domains eliminates the need for an Administrator to configure user accounts in multiple domains.

In a trust relationship, the two domains are referred to as the trusting domain and the trusted domain. The trusted domain is the domain where the trust relationship is created. The trusting domain is the other domain specified in the trust, that is, the one wherein network resources can to be accessed. The trusting domain in this case recognizes the logon authentications of the trusted domain. The logon trust relationship is supported by the NT LanMan Challenge Response. This allows pass-through authentication of users from the trusted domain. One of the shortfalls of Windows NT trust relationships is that trusts between domains were one-way and nontransitive. This meant that the defined trust relationship ended with the two domains between which the particular trust was created. The rights implicit in the trust relationship also flowed only in one single direction. Because of this, defining and managing trust relationships in the Windows NT domain structure was a cumbersome and labour intensive task. The Windows NT domain worked well in small enterprises where one domain typically existed in the enterprise. In those larger enterprises that have multiple domains, Administrators have to define trust relationships between the domains in order for a user in one domain to access resources in another domain.

In Windows 2000 and Windows 2003, Active Directory is built on the concept of trust relationships between domains. Although the actual concept of trust relationships is not new in Windows Server 2003, there are new trust capabilities and trust types available for Windows Server 2003 Active Directory domains.

In Windows Server 2003, authentication of users or applications occurs through the use of one of the following trust protocols:

The characteristics of Windows Server 2003 trusts are outlined below:

Window Server 2003 Active Directory Forest Trust Capability

Forest trust is a new feature introduced with Windows Server 2003 Active Directory. To better understand the feature, lets first look at how forest trust was established in the Windows NT and Windows 2000 domain structures. In these domain structures, when users located in one forest needed to access resources located in a different forest, an external trust relationship had to be defined between the two domains. External trusts are one-way and nontransitive in nature. This in turn increases the Administrative effort required to create and maintain the external trusts needed to enable forest trust in the Windows NT and Windows 2000 domain structures. Forest trust on the other hand enables you to create two-way trust relationships between all domains in two forests. The number of external trusts that has to be configured in Windows NT and Windows 2000 domain structures is reduced in Windows Server 2003 Active Directory domains. The trust between the Active Directory forests is transitive in nature.

Types of Active Directory Trust Relationships

The types of trust relationships that can be created and configured for Active Directory domains are discussed in this section. As an Administrator for Active Directory Windows Server 2003 domains, it is important to understand the different types of trust that are supported in Windows Server 2003, and to know which trust relationship to create for the different network resource access requirements that exist within your organization.

Planning Considerations for Trust Relationships

Tree-root trust and Parent-child trust is implicitly created by Active Directory when new domains are created. What this means is that you do not need to explicitly create these trusts, nor do you have to perform any configuration or management tasks for the trust relationships.

Shortcut trust, Realm trust, External trust and Forest trust differ to Tree-root and Parent-child trust, in that the former four trusts have to be explicitly created and managed. Because of the different types of trust relationships that can be created, you need to plan which type of trust relationship to create for the domains within your Active Directory environment.

Shortcut Trust

Before you can create any shortcut trusts, you must be a member of the Enterprise Admin or Domain Admin groups in each domain in the forest. Another requirement is that the domains you are creating shortcut trust for, are Windows Server 2003 domains that reside in the same forest. As mentioned earlier, Shortcut trust is usually created to speed up authentication between two domains in different trees but within the same forest. Shortcut trust can be one-way transitive trust, or two-way transitive trust. What shortcut trust essentially does is it shortens the trust path traversed for authentication requests made between domains of different trees. Shortcut trust is typically configured in an intricate forest where users continually need to access resources of domains belonging to different trees. Shortcut trust improves query response performance as well.

The Active Directory tool that you use to create shortcut trust is the Active Directory Domains and Trusts console. The console enables you to specify selective authentication for incoming shortcut trust and outgoing shortcut trust. What this means is that you can set authentication differently for the two forms of trust. When you set selective authentication for incoming shortcut trust, you would need to specify permissions for every resource that users in the other domain should be able to access. If domain wide authentication is specified on the incoming shortcut trust, users in the other domain and users in the local domain have the identical permissions to network resources.

Realm Trust

In order to create realm trust, you should have Enterprise Admin or Domain Admin permissions for the Windows Server 2003 domain, and you should have the permissions required for the non-Windows Kerberos version 5 realm. You would typically create realm trust to enable trust between a Windows Server 2003 domain and a MIT or UNIX v5 Kerberos realm. You can create Realm trust as either transitive or nontransitive trust, and as either be one-way trust or two-way.

External Trust

You need to be a member of Enterprise Admins or Domain Admins of the Windows Server 2003 domain and you need to be a member Enterprise Admins or Domain Admins of the other domain, to create one-way External trust or two-way External trust.

Recall from an earlier discussion, that External trust is always nontransitive in nature, and is typically used to enable trust between an Active Directory domain and a down-level Windows NT 4 domain. When the External trust is created, security principals (Users, Groups, Computers) from the external domain are able to access network resources in the internal domain (Windows Server 2003 domain). The foreign security principals can be examined in the Active Directory Users And Computers console. The only requirement is that Advanced Features are enabled. You can explicitly define different authentication for incoming External trusts and outgoing External trusts.

Forest Trust

You need to belong to the Enterprise Admins groups in each forest that you want to create forest trust between. In addition to this, the domains within each forest and each particular forest have to be raised to the Windows Server 2003 functional level.

Forest trust is typically created when enterprises merge or takeovers occur, and each company within the enterprise still needs to maintain some form of administrative independence. This trust relationship enables users to access Active Directory objects between all domains impacted by the particular forest trust relationship. Forest trust is transitive, and can be one-way or two-way trust. You would create one-way Forest trusts when users in the trusted forest need to access Active Directory objects in the trusting forest, but those users in the trusting forest do not need to access resources in the trusted forest. You would create two-way Forest trust in cases where users in either one of the forests need to access resources hosted in the other forest.

How to create Shortcut trust using Active Directory Domains and Trusts

  1. Open the Active Directory Domains and Trusts console.
  2. In the console tree, locate and right-click the domain for which you want to configure Shortcut trust, and click Properties from the shortcut menu.
  3. When the Properties dialog box of the domain you chose opens, click the Trusts tab
  4. Click the New Trust button at the bottom of the dialog box.
  5. This action starts the New Trust Wizard.
  6. Click Next on the Welcome To The New Trust Wizard page.
  7. When the Trust Name page opens, enter the DNS name of the other domain that you want to create trust with. Click Next.
  8. On the Direction Of Trust page, you can select one of the following options:
    • Two-Way: Click this option if you want to define two-way Shortcut trust. This would mean that users in each domain would be able to access resources in both domains.
    • One-Way: Incoming: This option should be enabled if you only want users of this particular domain to be able to access resources in the other domain.
    • One-Way: Outgoing: This option should be selected if you want users of the other domain to be able to access resources in this particular domain.

    Click Next.

  9. When the Sides Of Trust page opens, you can select one of these options:
    • This Domain Only: Selecting this option creates the Shortcut trust in the local domain.
    • " Both This Domain And The Specified Domain: Selecting this option creates the Shortcut trust in the local domain and in the other domain that you indicated.

    Click Next

  10. The New Trust Wizard displays different pages next, based on what you have selected in the previous two steps.
  11. Where Two-Way or One-Way: Outgoing was selected in Step 8, and This Domain Only was selected in Step 9, the wizard displays the Outgoing Trust Authentication Level page. You can select either Domain Wide Authentication or Selective Authentication. Choosing Domain Wide Authentication results in the automatic authentication of users in the other domain for network resources in the local domain. If you select Selective Authentication, the users in the other domain are not automatically authenticated for resources in the local domain. Click Next. The wizard then displays the Trust Password page. This is where you have to set the password for the trust. Click Next.
  12. Where One-Way: Incoming was selected in Step 8, and This Domain Only was selected in Step 9, the wizard displays the Trust Password page. Enter the password for the trust in the boxes. Click Next.
  13. Where Both This Domain And The Specified Domain was selected in Step 9, the wizard displays the User Name And Password page. You have to provide the user name and password of an Administrator account that has the necessary rights in the other domain. Click Next.
  14. The Trust Selections Complete page is displayed next. All the settings that you previously specified are shown on this page. After checking that the configuration settings are correct, click Next.
  15. The New Trust Wizard now creates the shortcut trust relationship.
  16. When the Trust Creation Complete page appears, click Next.
  17. The Confirm Outgoing Trust page allows you to verify outgoing trust. Click Yes, Confirm The Outgoing Trust or click No, Do Not Confirm The Outgoing Trust. Click Next.
  18. The Confirm Incoming Trust page allows you to verify incoming trust. Click Yes, Confirm The Incoming Trust or click No, Do Not Confirm The Incoming Trust. Click Next.
  19. Click Finish when the Completing The New Trust Wizard page is displayed.

How to create Realm trust using Active Directory Domains and Trusts

  1. Open the Active Directory Domains and Trusts console.
  2. In the console tree, locate and right-click the domain for which you want to configure Realm trust, and click Properties from the shortcut menu.
  3. When the Properties dialog box of the domain opens, click the Trusts tab
  4. Click the New Trust button at the bottom of the dialog box.
  5. Click Next on the Welcome To The New Trust Wizard page.
  6. When the Trust Name page opens, enter the DNS name of the other domain for the realm trust. Click Next.
  7. The Trust Type page appears next. Select Realm Trust. Click Next.
  8. When the Transitivity Of Trust page opens, select one of the following options:
    • Nontransitive: Select this option if the Realm trust should end with the two domains between which it is created.
    • Transitive: Select this option if you want this particular domain and all other trusted domains to create trust with the realm and other trusted realms.

    Click Next

  9. On the Direction Of Trust page, you can select one of the following options:
    • Two-Way: Click this option if you want to define two-way Realm trust. This would mean that users in the domain and realm would be able to access resources in both the domain and realm.
    • One-Way: Incoming: This option should be enabled if you only want users of this particular domain to be able to access resources in the realm.
    • One-Way: Outgoing: This option should be selected if you only want users of realm to be able to access resources in this particular domain.

    Click Next

  10. The wizard displays the Trust Password page next. Enter the password for the trust in the boxes. Click Next.
  11. The Trust Selections Complete page is displayed next. All the settings that you previously specified are shown on this page. After checking that the configuration settings are correct, click Next.
  12. The New Trust Wizard creates the Realm trust relationship.
  13. Click Finish on the Completing The New Trust Wizard page.

How to create External trust using Active Directory Domains and Trusts

You first have to specify a DNS forwarder for each of the DNS servers that are authoritative for the trusting forests.

You use the DNS Administration tool to configure DNS forwarders,

  1. Click Start, click Administrative Tools, and click DNS.
  2. Right-click the DNS server, and click Properties from the shortcut menu.
  3. When Properties dialog box of the DNS server opens, click the Forwarders tab.
  4. Click New, and enter the DNS domain name that needs queries to be forwarded.
  5. In the Selected Domain's IP Address List, enter the IP addresses of the servers to which these queries are forwarded.
  6. Click Add
  7. Click OK
  8. Open the Active Directory Domains and Trusts console.
  9. In the console tree, locate and right-click the domain in the initial forest which you want to configure External trust, and click Properties from the shortcut menu.
  10. When the Properties dialog box of the domain opens, click the Trusts tab
  11. Click the New Trust button at the bottom of the dialog box.
  12. Click Next on the Welcome To The New Trust Wizard page.
  13. When the Trust Name page opens, enter the DNS name of the domain in the other forest. Click Next.
  14. The Trust Type page appears next if the forest functional level is raised to Windows Server 2003 forest functional level. Select the External Trust option. Click Next.
  15. The Direction Of Trust page is displayed straight after the Trust Name page if the forest functional level is not raised to Windows Server 2003. You can select one of the following options:
    • Two-Way: Click this option if you want to define two-way External trust. This would mean that users in each domain would be able to access resources in both domains.
    • One-Way: Incoming: This option should be enabled if you only want users of this particular domain to be able to access resources in the other domain.
    • One-Way: Outgoing: This option should be selected if you only want users of the other domain to be able to access resources in this particular domain.

    Click Next

  16. When the Sides Of Trust opens, you can select one of these options:
    • This Domain Only: Selecting this option creates the trust in the local domain
    • Both This Domain And The Specified Domain: Selecting this option creates the trust in the local domain and in the other domain.

    Click Next

  17. The New Trust Wizard displays different pages next, based on what you selected in the previous two steps.
  18. Where Two-Way or One-Way: Outgoing was selected in Step 8, and This Domain Only was selected in Step 9, the wizard displays the Outgoing Trust Authentication Level page. You can select either Domain Wide Authentication or Selective Authentication. Choosing Domain Wide Authentication results in the automatic authentication of users in the other domain for network resources in the local domain. If you select Selective Authentication, the users in the other domain are not automatically authenticated for resources in the local domain. Click Next. The wizard then displays the Trust Password page. This is where you have to set the password for the trust. Click Next.
  19. Where One-Way: Incoming was selected in Step 8, and This Domain Only was selected in Step 9, the wizard displays the Trust Password page. Enter the password for the trust. Click Next.
  20. Where Both This Domain And The Specified Domain was selected in Step 9, the wizard displays the User Name And Password page. You have to provide the user name and password of an Administrator account that has the necessary rights. Click Next.
  21. When the Trust Selections Complete page is displayed, the settings that you previously specified are shown. After checking that the configuration settings are correct, click Next.
  22. The New Trust Wizard now creates the External trust.
  23. When the Trust Creation Complete page appears, click Next.
  24. The Confirm Outgoing Trust page allows you to verify outgoing trust. Click Yes, Confirm The Outgoing Trust or click No, Do Not Confirm The Outgoing Trust. Click Next.
  25. The Confirm Incoming Trust page allows you to verify incoming trust. Click Yes, Confirm The Incoming Trust or click No, Do Not Confirm The Incoming Trust. Click Next.
  26. Click Finish.

How to create Forest trust using Active Directory Domains and Trusts

You first have to specify a DNS forwarder for each of the DNS servers that are authoritative for the trusting forests before you can use the Active Directory Domains and Trusts console to create Forest trust relationships. Use the DNS Administration Tool to configure the necessary DNS forwarder. In addition to this, ensure that the forest functional level for each forest is set to Windows Server 2003 forest functional level.

  1. Open the Active Directory Domains and Trusts console.
  2. In the console tree, locate and right-click the domain in the initial forest which you want to configure Forest trust for, and click Properties from the shortcut menu.
  3. When the Properties dialog box of the domain opens, click the Trusts tab and then click the New Trust button.
  4. In the Welcome To The New Trust Wizard page, click Next
  5. Enter the DNS name of the domain in the other forest on the Trust Name page. Click Next.
  6. In the Trust Type page, select the Forest Trust option. Click Next.
  7. On the Direction Of Trust page select one of the following options:
    • Two-Way: Click this option if you want to define two-way Forest trust. This would mean that users in each forest would be able to access resources in both forests.
    • One-Way: Incoming: This option should be enabled if you only want users of this particular forest to be able to access resources in the other forest.
    • One-Way: Outgoing: This option should be selected if you only want users of the other forest to be able to access resources in this particular forest.

    Click Next

  8. When the Sides Of Trust opens, you can select one of these options:
    • This Domain Only: Selecting this option creates the trust in the local forest.
    • Both This Domain And The Specified Domain: Selecting this option creates the trust in the local forest and in the other forest.

    Click Next

  9. Where Two-Way or One-Way: Outgoing was selected in Step 7, and This Domain Only was selected in Step 8, the wizard displays the Outgoing Trust Authentication Level page. You can select either Domain Wide Authentication or Selective Authentication. Choosing Domain Wide Authentication results in the automatic authentication of users in the other forest for network resources in the local forest. If you specify Selective Authentication, the users in the other forest are not automatically authenticated for resources in the local forest. Click Next. The wizard then displays the Trust Password page. This is where you have to set the password for the trust. Click Next.
  10. Where One-Way: Incoming was selected in Step 7, and This Domain Only was selected in Step 8, the wizard displays the Trust Password page. Enter the password for the trust. Click Next.
  11. Where Both This Domain And The Specified Domain was selected in Step 8, the wizard displays the User Name And Password page. You have to provide the user name and password of an Administrator account that has the necessary rights. Click Next.
  12. When the Trust Selections Complete page is displayed, the settings that you previously specified are shown. After checking that the configuration settings are correct, click Next.
  13. The New Trust Wizard now creates the Forest trust.
  14. When the Trust Creation Complete page appears, click Next.
  15. The Confirm Outgoing Trust page allows you to verify outgoing trust. Click Yes, Confirm The Outgoing Trust or click No, Do Not Confirm The Outgoing Trust. Click Next.
  16. The Confirm Incoming Trust page allows you to verify incoming trust. Click Yes, Confirm The Incoming Trust or click No, Do Not Confirm The Incoming Trust. Click Next.
  17. Click Finish on the Completing The New Trust Wizard page.

How to remove existing Active Directory trust relationships

  1. Open the Active Directory Domains And Trusts console.
  2. In the console tree, right-click a domain that is specified in the trust relationship which you want to remove, and select Properties from the shortcut menu.
  3. Click the Trusts tab.
  4. Use the Domains Trusted By This Domain (Outgoing Trusts) box to select the trust you want to remove.
  5. Click the Remove button alongside the box.
  6. If you want to remove the trust from the local domain only, click the No, Remove The Trust From The Local Domain Only option, and click OK
  7. If you want to remove the trust from the local domain and the other domain, click the Yes, Remove The Trust From Both The Local Domain And The Other Domain option. Enter the appropriate user name and password combination in the User Name and Password boxes and click OK.
  8. Click Yes to verify that you want to remove the trust relationship.
  9. Use the Domains That Trust This Domain (Incoming Trusts) box to select the trust you want to remove.
  10. Choose the appropriate option in the Active Directory dialog box, and then click OK
  11. Click Yes to verify that you want to remove the trust relationship.

How to validate existing Active Directory trust relationships

  1. Open the Active Directory Domains And Trusts console
  2. In the console tree, right-click a domain that is defined in the trust relationship which you want to validate, and select Properties from the shortcut menu.
  3. Click the Trusts tab
  4. You can select the trust you want to examine in one of the following boxes:
    • Domains Trusted By This Domain (Outgoing Trusts) box
    • Domains That Trust This Domain (Incoming Trusts) box
  5. After you have selected the trust, click the Properties button.
  6. When the Properties dialog box of the trust opens, click the Validate button.
  7. If you only want to verify outgoing trust, click the No, Do Not Validate The Incoming Trust option and click OK.
  8. If you want to verify incoming trust and outgoing trust, click Yes, Validate The Incoming Trust option. Enter the appropriate user name and password combination in the User Name and Password boxes and click OK
  9. After the trust is validated, a message is displayed indicating this.
  10. Click OK

How to create and manage trust relationships using the Windows Domain Manager Command-line Tool

You can use the Windows Domain Manager command line tool to create and manage Active Directory trusts. Netdom.exe is included with the Windows Support Tools available on the Windows Server 2003 Setup CD-ROM.

The netdom trust command is used to create and manage trusts:

netdom trust TrustingDomainName /d: TrustedDomainName [/ud:[Domain\]User]

[/pd:{Password|*}] [/uo: User] [/po:{Password|*}] [/verify] [/reset] [/passwordt: NewRealmTrustPassword]

[/add [/realm]] [/remove [/force]] [/twoway] [/kerberos] [/transitive[:{YES|NO}]] [/verbose]



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